US Environmental Protection Agency

Using Contaminant Information in Evaluating Water Contamination Threats and Incidents U.S. Environmental Protection Agency 1 • This course is divided into ten parts Course Overview – Part 1: Course Goals and Definitions – Part 2: Contaminants of Concern and Overview of Toxicology, (Primarily as related to Chemical Contaminants) – Part 3: Characteristics and Properties of Chemicals as they Relate to Water Systems Contamination – Part 4: Properties and Characteristics: Pathogens – Part 5: Properties and Characteristics: Radiochemical Agents – Part 6: Gathering and Managing Contaminant Information – Part 7: Data Use for Consequence Analysis – Part 8: Example Contamination Scenario – Part 9: Action Items and Learning Tools – Part 10: Appendix (Example Scenarios for other Contaminants) • Please click on the links above to go to that part of the presentation 2 Part 1: Course Goals and Definitions Return to Course Overview Slide 3 Course Goal • Integrate existing water security knowledge, information, resources and tools into a training to provide for a more effective and efficient response to contamination threats and incidents Return to Course Overview Slide 4 Course Goal • Gain a basic understanding of the following: – Basic toxicology – Contaminants of concern – Types of contaminant properties / characteristics • Understand the process involved in researching and analyzing contaminants of concern, including: – Identifying appropriate sources of information – Using data to assess potential threat and consequences to public health Return to Course Overview Slide 5 Definitions • Routine Threats and Incidents – An actual occurrence in which hazards or threats result in a harmful, dangerous, or otherwise unwanted outcome • • • • Hoaxes Security breaches September 11, 2001 Anthrax-contaminated mail • National Special Security Events (NSSE) – A significant event or designated special event requiring security • Presidential Inauguration • • • • State of the Union Address National conventions Olympics International summit conferences Return to Course Overview Slide 6 Part 2: Contaminants of Concern and Overview of Toxicology (Primarily as Related to Chemical Contaminants) Return to Course Overview Slide 7 What are the Priority Drinking Water Contaminants? • More than 200 contaminants identified as posing a threat to drinking water systems, based on: – Health effects (toxicity or infectivity) – Ability to be dispersed through distribution system • Six main categories of contaminants – Inorganic chemicals (e.g., cyanide) – Organic chemicals (e.g., pesticides) – Schedule 1 Chemical Warfare Agents (e.g., sulfur mustard) – Biotoxins (e.g., ricin) – Pathogens (e.g., Bacillus anthracis [Anthrax]) – Radiochemicals (e.g., Cesium-137) Return to Course Overview Slide 8 Toxicity Data • What is it? – A measure of the degree to which a substance can elicit a deleterious effect (including death) in a given organism • Why is it important? – Toxicity is directly related to the public health outcome of a threat – Many chemicals are more toxic via exposure routes other than ingestion – The public can be exposed to drinking water contaminants via showering (inhalation), bathing (dermal contact), as well as ingestion – Different types (acute, chronic) depending on chemical, concentration, and exposure route Basic tenet of toxicology: “Dosis facit venenum” The dose makes the poison (Paracelus) Return to Course Overview Slide 9 Basic Toxicology • Acute, Sub-Acute – Immediate or almost immediate adverse health effects from exposure to a substance (for water contaminants, usually within a day) • Chronic, Sub-Chronic – Adverse health effects resulting from long-term or repeated (chronic, >10% of lifespan) exposure to a substance over a period of time – Can occur at low levels that have no ACUTE effects – Chronic health effects can be as severe as acute effects, but take much longer to manifest • Lethal, Sub-Lethal – Causes death immediately or over a short period of time – Sub-lethal is not quite lethal; less than lethal Return to Course Overview Slide 10 Exposure Routes • Definition – The route through which a chemical, physical, or biological agent may enter the body • Dermal Route – Agent is absorbed directly through the skin • Inhalation Route – Agent enters through the respiratory tract or lungs • Oral Ingestion Route – Agent enters through the mouth and digestive system Return to Course Overview Slide 11 Exposure Routes (cont.) • Other Routes – Ocular (through the eyes) – Mucous membranes – Direct entry into the bloodstream through cuts or open sores Return to Course Overview Slide 12 Drinking Water and Exposure Routes • Drinking water use provides opportunities for exposure through all of these routes • Drinking and Cooking – Ingestion – Dermal • Bathing and Showering – Inhalation – Ocular – Mucus membranes –Direct entry through cuts or open sores –Inadvertent ingestion –Dermal • Maintenance and Recreation – Inhalation (Watering vegetable gardens) – Dermal, Inadvertent ingestion (Swimming and wading pools) Return to Course Overview Slide 13 Toxicity Measures • Some toxicity measurements are more applicable than others in assessing the concentration at which a contaminant will have acute or immediate impacts, while others will have more chronic, long-term impacts • Assessing acute or immediate impacts of contaminant: – Lethal dose 50 (LD50), infectious dose 50 (ID50), or lethal concentration 50 (LC50) – No observed adverse effect level (NOAEL) – Lowest observed adverse effect level (LOAEL) • Assessing chronic, or long-term impacts of contaminant: – Maximum contaminant level (MCL) – Maximum contaminant level goal (MCLG) Return to Course Overview Slide 14 Toxicity Measures (cont.) • Impacts will vary and may be based on acute or chronic levels – Health advisory (HA) – Reference dose (RfD) Return to Course Overview Slide 15 MCLs and MCLGs • Maximum Contaminant Level (MCL) – The highest level of a contaminant that is allowed in drinking water – Only established for regulated contaminants – Enforceable standards – Based on lifetime exposure risk (typically for an end point, such as cancer) • Maximum Contaminant Level Goals (MCLGs) – Level of a contaminant in drinking water below which there is no known or expected risk to health – Allow for a margin of safety and are non-enforceable public health goals – The MCLG for some contaminants is zero, which means there is no safe level for the contaminant Return to Course Overview Slide 16 Drinking Water Health Advisories (HAs) • Estimate of acceptable drinking water levels for a chemical substance based on health effects information • HAs are not a legally enforceable Federal standard, but serve as technical guidance to assist federal, state, and local officials • Developed for specific exposure durations • Developed by EPA’s Office of Water to provide guidance on non-regulated water contaminants and for emergency contamination events Return to Course Overview Slide 17 Drinking Water Health Advisories (HAs) (cont.) • 1-Day HA – The concentration of a chemical in drinking water that is not expected to cause any adverse noncarcinogenic effects for up to 1 day of exposure. The 1-day HA is normally designed to protect a 10-kg child consuming 1 L of water per day • 10-Day HA – The concentration of a chemical in drinking water that is not expected to cause any adverse noncarcinogenic effects for up to 10 days of exposure. The 10-day HA is also normally designed to protect a 10-kg child consuming 1 L of water per day Return to Course Overview Slide 18 Drinking Water Health Advisories (HAs) (cont.) • Lifetime HA – The concentration of a chemical in drinking water that is not expected to cause any adverse noncarcinogenic effects for a lifetime of exposure – Based on exposure of a 70-kg adult consuming 2L of water per day – The Lifetime HA for Group C carcinogens (i.e., possible human carcinogen) includes an adjustment for possible carcinogenicity • HAs are a concentration – They can be compared to the concentration of what was found in the contaminated water • HAs function as benchmark – If a contaminant is found in the water at a concentration higher than the HA, then people might suffer adverse health effects from drinking the contaminated water Return to Course Overview Slide 19 Effect Levels • No Observable Adverse Effect Level (NOAEL) – Highest exposure level at which there are no biologically significant increases in the frequency or severity of adverse effect between the exposed population and its appropriate control – Some effects may be produced at this level, but they are not considered adverse or precursors of adverse effects – In short — concentrations below the NOAEL are generally considered safe, even when exposure is chronic • Lowest Observable Adverse Effect Level (LOAEL) – Lowest exposure level at which there are biologically significant increases in frequency or severity of adverse effects between the exposed population and its appropriate control group Return to Course Overview Slide 20 Reference Dose (RfD) • Estimate of a daily exposure to the human population that is likely to be without an appreciable risk of deleterious effects during a lifetime. – Uncertainty may span an order of magnitude – Generally expressed in units of milligrams per kilogram of body weight per day (mg/kg/day) • Useful as a reference point from which to gauge the potential effects of the chemical at other doses. • Doses less than the RfD are not likely to be associated with adverse health risks Return to Course Overview Slide 21 Reference Dose (RfD) (cont.) • As the frequency and/or magnitude of the exposures exceeding the RfD increase, the probability of adverse effects in a human population increases • However, all doses below the RfD may not be ―acceptable‖ (or risk-free) and all doses in excess of the RfD may not be ―unacceptable‖ (or result in adverse effects) Return to Course Overview Slide 22 LD50, LC50, and ID50 • Lethal dose 50 (LD50) – Dose of a chemical required to kill 50% of the experimental subjects (e.g., rats, mice, cockroaches) – Standard measurement of acute toxicity for chemicals stated in milligrams (mg) of contaminant per kilogram (kg) of body weight – Applies to ingestion and dermal exposure routes Return to Course Overview Slide 23 LD50, LC50, and ID50 (cont.) • Lethal concentration 50 (LC50) – Two types, depending on situation: • Human inhalation (also called LCt) measured in milligrams per cubic meter of air in a given time period (t) • Environmental exposure by aquatic organisms, measured in mg/L of water • Often human data are not available, and animal models are used • Infectious dose 50 (ID50) – Number of infectious pathogens required to produce infection or disease in 50% of the experimental subjects Return to Course Overview Slide 24 LD50, LC50, and ID50 (cont.) • The lower the dose or concentration, the more toxic or infectious the contaminant • A contaminant with an LD50 value of 10 mg/kg is 10 times more toxic than one with an LD50 of 100 mg/kg • One limitation of animal models in determining what LD50, LC50, or ID50 of a human population may be that different animal species may have significantly different susceptibilities to certain contaminants than humans Return to Course Overview Slide 25 LD50, LC50, and ID50 (cont.) • LD50, LC50, or ID50 are published for a variety of exposure routes, and only values for the same route are comparable • It is important to remember that the public can be exposed through all these routes (e.g. via showering (inhalation), bathing (dermal contact), as well as ingestion) Return to Course Overview Slide 26 Related Acute Toxicity Measures • Other Lethal Doses (LDs) – Amount at which the contaminant is an LD to X percent of the population (e.g., LD10) – Lethal DoseLO (LDLO): The lowest published lethal dose of a chemical via a particular exposure route • The dose may greatly exceed the true lethal dose because it is often determined from a single individual and circumstance (e.g., an individual commits suicide by ingesting an entire can of poison; the LDLO is based on what they consumed, not the MINIMUM lethal dose) Return to Course Overview Slide 27 Other Toxicity Measurements • Cell Death 50 (CD50) – The dose of a contaminant required to produce death in 50% of cells in study • Convulsive Dose 50 (CD50) – Median convulsive dose • Chronic Dose 50 (CD50) – Chronic dose resulting in chronic effects within 50% of the test population • Minimal Risk Levels (MRLs) – Estimate of the daily human exposure to a hazardous substance that is likely to be without appreciable risk of adverse non-cancer health effects over a specified duration of exposure Return to Course Overview Slide 28 Toxicity Calculations • MCLs and MCLGs can be compared directly to drinking water concentrations to determine if there will be NO potential effect – The reverse is not necessarily true – Complex risk calculations are required to determine the extent of any potential effect • For other toxicity values, calculations must be performed to determine if the concentration level in water poses a threat Return to Course Overview Slide 29 Toxicity Calculations (cont.) • Example: Comparison of an oral LD50 with the concentration of the contaminant in water: • C = concentration (activity for radionuclides) of contaminant in water • V = average volume of water consumed by an individual • W = average weight of individual consuming water • D = individual’s contaminant dose – The contaminant dose can be compared to the LD50 • If the calculated dose is higher than the LD50, health effects in the population could be severe and widespread • If the calculated does is lower than the LD50, comparisons to LOAEL and NOAEL should be made to determine if some effects may still occur; these risk calculations may be complex Return to Course Overview Slide 30 Toxicity Measurements • Many assumptions about exposure are made when performing these types of calculations that may limit their usefulness – Average volume consumed may not reflect volumes actually consumed by an individual – Average weights do not reflect actual individual weights in a population; may be necessary to do calculations at multiple weights – Even if concentrations are below LD50; some adverse effects may occur – Common practice is to assume the exposure is to a 70kg human – May need to do perform calculations for sensitive populations (e.g. daycare center, or retirement facility, or hospital) Return to Course Overview Slide 31 Part 3: Characteristics and Properties of Chemicals as they Relate to Water Systems Contamination Return to Course Overview Slide 32 Chemical Contaminants Overview • Many potential chemical contaminants are widely available and vary greatly in their health effects (e.g., their acute toxicity) • Detecting some of these contaminants in water presents special challenges; detection of others is routine • Drinking water distribution systems may spread the contaminant over vast distances, although changes to the contaminated water may occur within the distribution system • Various physical and chemical properties of the contaminants affect their ability to efficiently contaminate and persist in water systems Return to Course Overview Slide 33 Chemical Contaminants Overview (cont.) • Generally grouped into the following categories: – Inorganic chemicals (e.g., cyanide) – Organic chemicals (e.g., pesticides) – Schedule 1 Chemical Weapons (e.g., sulfur mustard) – Biotoxins (e.g., ricin) – Radiochemicals (e.g., Cesium-137) Return to Course Overview Slide 34 Chemical Contaminants Overview (cont.) • Chemical Weapons (CW): defined in the Chemical Weapons Convention (www.cwc.gov); includes toxic chemicals covered by a listing known as Schedules, including their precursors – Schedule 1 contains chemicals that have been developed, produced, stockpiled, or used as CW or chemicals that are precursors (any chemical reactant that takes part at any stage in the production of a toxic chemical regardless of method); Schedule 1 chemicals have no large-scale industrial purpose – Schedule 2 contains chemicals that pose a significant risk to the objectives of the CWC or are CW precursors, and have no legitimate industrial use – Schedule 3 contains "dual-use" chemicals—chemicals that have been developed, produced, stockpiled, or used as CW or are CW precursors, but are produced in large quantities for legitimate (non-CW) uses Return to Course Overview Slide 35 Chemical Contaminants Overview (cont.) – CW are popularly grouped into five categories: • Nerve (e.g., VX, Sarin) • • • • Blister (e.g., distilled mustard, nitrogen mustard, sulfur mustard) Choking (e.g., chlorine) Blood (e.g., hydrogen cyanide) Vomiting (e.g., adamsite) – Some generalities can be made: • Many are not stable in water • Many are difficult to obtain • Many are gases Return to Course Overview Slide 36 Chemical Contaminants Overview (cont.) – Several Schedule 3 chemicals are found in water as a result of disinfection (e.g., chloropicrin, cyanogen chloride, etc.) – Water may not be the best delivery mechanism for CWs – Properties of CWs are evaluated like other chemicals Return to Course Overview Slide 37 Chemical Contaminants Overview (cont.) • Biotoxin: A toxin naturally produced by a microorganism, plant, or animal – Examples: • Ricin – toxin that is derived from castor plant beans, Ricinus communis • Microcystins – toxins produced by blue-green algae – Some have very low lethal dose relative to most contaminants; however, some are less toxic than more common man-made organic chemicals – Although biotoxins may be used in an aerosol attack, they also represent a concern for food and water contamination – Properties evaluated like other chemicals – Biotoxins are also organic chemicals Return to Course Overview Slide 38 Chemical Identity • Chemicals can be uniquely identified by their Chemical Abstract Registry Number, often called ―CAS‖ – In finding properties of chemicals, the CAS is often helpful because many chemicals go by a lot of other names • CAS numbers can be in chemical catalogs, databases, and Material Safety Data Sheets (MSDS) • Illustration: The CAS for glyphosate is 1071-83-6 Return to Course Overview Slide 39 Chemical Detection • The ability to detect a chemical contaminant in water is often an important step in the investigation of contamination • As used here, detection falls into two categories: – Sensory Perception – Chemical Analysis Return to Course Overview Slide 40 Chemical Detection (cont.) • Sensory perception: usually occurs when the drinking water customer complains that the water looks, smells, and/or tastes unusual, but may or may not prevent the customer from drinking the water – Some contaminants may have distinctive odors or tastes, although perception of these by customers can vary dramatically – Is not always a sign of intentional contamination because some water systems are prone to complaints, particularly at certain times of year – NEVER INTENTIONALLY SMELL or TASTE a suspected sample – Example: A customer complains of an almond smell to the water • Hydrogen cyanide may smell like almonds • On closer inspection, the odor is determined to be a new almond scented shampoo Return to Course Overview Slide 41 Chemical Detection (cont.) • Compliance monitoring for regulated chemical contaminants will most likely not detect the presence of many of the potential chemical agents; compliance monitoring for some chemicals is sometimes only required a few times a year • Water quality laboratories are often capable of analyzing water for many regulated chemicals of concern. Special techniques are required for confirming some Schedule 1 CW and biotoxins. • Early warning or rapid field detection is not available for many contaminants of concern • Changes in baseline water quality parameters (e.g., pH, turbidity, residual chlorine) may or may not indicate the presence of a chemical contaminant Return to Course Overview Slide 42 Fate and Transport of a Chemical within a Drinking Water System • The fate of a chemical as it moves through a water system to the tap depends on the nature of the particular water system and also on properties of the contaminant • Predictions are often complicated and rely on: - Accuracy of physical and chemical property data in the literature - Knowledge of the individual drinking water system Return to Course Overview Slide 43 Drinking Water System Return to Course Overview Slide 44 Portion of Drinking Water Distribution System • Understanding the behavior or water and contaminants in a distribution system is a complex task Return to Course Overview Slide 45 Contaminant Properties • The next few slides will describe several contaminants properties: – – – – Solubility Detectability (of the contaminant in water) Treatability (at the water treatment plant) Stability (of the contaminant in the distribution system) • Along with a description of property, we’ll look at: – How does the property help assess the threat – What limitations about the property may be important – Illustration about the property’s relevance to a water system Return to Course Overview Slide 46 Contaminant Property: Solubility • What is solubility? – The ability of a certain amount of chemical to dissolve in a certain amount of a given solvent – For example, one gram of sodium chloride dissolves in 2.8 mL of water at room temperature • How does this information help assess the threat? – Solubility must be compared to the concentration of concern in water (i.e., a highly toxic, less soluble chemical may be soluble enough to pose a health threat); low solubility does not automatically imply low threat – Some chemicals, which are soluble in water, need to be dispersed (e.g., by stirring) in order to dissolve – Some insoluble chemicals can still be effectively dispersed in water, although it presents a greater technical challenge (e.g., insoluble metals may need to be dissolved in acid and then added to water) Return to Course Overview Slide 47 Contaminant Property: Solubility (cont.) • What limitations in solubility information should you be aware of? – Solubility data are based on pure chemicals and sometimes solubility is described using words such as ―very‖, ―sparingly‖, ―slightly‖, which is not very helpful, especially for highly toxic chemicals – Factors influenced by conditions in the distribution system affect solubility (e.g., temperature, pH, TDS concentration) – For contaminants added at high concentrations that exceed solubility, a layer of contaminant may be found on top or at the bottom of the water depending if the contaminant’s density (mass per unit volume) is less or more than water (e.g., oil floats on water) – The absence of a contaminant film on top (or bottom) of the water does not necessarily mean that no contamination is present, but that the contaminant is present but below its solubility limit Return to Course Overview Slide 48 Contaminant Property: Solubility (cont.) • Illustration – Someone adds a 10 kg (10,000,000 mg) of a contaminant to a 1,000,000 L water tank • The LC50 of the liquid is 2000 mg/L to a water tank • Solubility data indicates the solubility is 0.1 mg/L • Where will the contaminant be (in the water or at the bottom of the tank)? – One source for solubility data says that a particular contaminant is ―practically insoluble‖ • The LC50 of the contaminant is 30 mg/L • How does the toxicity compare with the solubility? Return to Course Overview Slide 49 Contaminant Property: Treatability • What is treatability? – Ability of water treatment technologies (e.g., chlorination, sand filtration, activated carbon, etc.) to remove a contaminant or reduce its concentration in the water • How does this information help assess the threat? – The existing plant may be treating the water in such a way that contamination is removed or mitigated rapidly, resulting in fewer long term consequences – Also relevant to remediation in the case of contamination Return to Course Overview Slide 50 Contaminant Property: Treatability (cont.) • What limitations in this information should you be aware of? – Efficacy of a particular process for a particular contaminant depends on the treatment technologies conditions at the plant – Treatment data may be unavailable for many contaminants – Literature has inconsistent data for some contaminants-possibly due to difference in treatment conditions – Applies generally to contamination added to the system before the treatment plant. However, water treatment plants add residual disinfectant before the water leaves the plant and enters the distribution system • Illustration: – Someone adds a quantity of a particular pesticide to the source water of the treatment plant – The treatment plant uses activated carbon, which the literature indicates effectively removes the contaminant Return to Course Overview Slide 51 Contaminant Property: Stability • What is stability? – The ability of a contaminant to withstand degradation, which can reduce the toxicity or infectivity of a contaminant – With the distribution system, primarily a function of processes such as hydrolysis, volatilization, reactivity, adsorption – Biodegradation (degradation of the contaminant by microorganisms) may be important in the source water • How does this information help assess the threat? – When available, degradation rate data may be used to estimate the half-life of a contaminant in a water system; half-life is the time is takes for half of the contaminant to degrade – A chemical with a short half-life in a drinking water system may not persist long enough to have significant effects on the public – A chemical with a longer half-life in a drinking water system may persist for sufficient time to have significant effects on the public Return to Course Overview Slide 52 Contaminant Properties: Stability (cont.) • What limitations in this information should you be aware of? – Stability data are based on pure chemicals, and depending on the stability process, the data may not be available for the chemical dissolved in water. • For instance, reactivity data are sometimes given for the undissolved compound, which can differ markedly from the compounds behavior in water – Estimates of half-life are not available for some contaminants – Environmental fate and transport predictions rely on the accuracy of physical and chemical property data in the literature – Due to the complexity of drinking water distribution systems, the amount of time that contaminated water can remain in the distribution system varies tremendously by location, even within the same distribution system; it can be an extremely complex task to apply degradation rates when trying to estimate how much contaminant the public has been exposed to Return to Course Overview Slide 53 Stability Related Process: Hydrolysis • What is hydrolysis? – A reaction that occurs between a chemical and the water itself, often resulting in permanent degradation of the original chemical • How does this information help assess the threat? – Hydrolysis may produce byproducts that are less toxic than the parent chemical, thus, hydrolysis sometimes, but not always, greatly reduces the toxicity of contaminated water – Contaminants, especially highly toxic ones, that are resistant to hydrolysis may be of greater concern due to their persistence in water • What limitations in this information should you be aware of? – Hydrolysis rate is pH and temperature dependent – Hydrolysis rate data are not available for all contaminants or are not available for pH’s and temperatures of interest Return to Course Overview Slide 54 Stability Related Properties: Hydrolysis (cont.) • Illustration – The half-life of a certain pesticide is listed as 2 days • This means that after two days, the concentration of the contaminant will by 1/2, but will still be present – The half-life of a particular chemical weapon is around 8 minutes at room temperature • Within an hour or two, the concentration is reduced to essentially zero Return to Course Overview Slide 55 Stability Related Process: Volatilization • What is volatilization from water? – The process through which a contaminant dissolved in the water enters the gas phase (i.e., the air above the water) – Henry’s Law constants are essentially determined from the equilibrium ratio of the concentration in the air to the concentration in the water – Vapor density is the density of a gas relative to air • How does this information help assess the threat? – Henry’s Law constants provide an indication of whether the chemical is likely to move from an aqueous phase into gas phase (e.g., contaminated water to the air) – Vapor density provides an indication of how quickly a contaminant could dissipate – May help predict risk due to inhalation Return to Course Overview Slide 56 Stability Related Properties: Volatilization (cont.) • What limitations in this information should you be aware of? – Henry’s Law Constant assume equilibrium conditions, but volatilization is not an equilibrium process – Applies to small concentrations – Temperature dependent – In water under specific conditions (e.g., pH), some contaminants may co-exist in both volatile and non-volatile forms, which affects the amount of volatile contaminant • Illustration – The dimensionless Henry’s Law constant for benzene is 0.25 • This means that concentration in the water is 4 times in the air. – At drinking water pH’s, sodium cyanide is present as hydrogen cyanide, which can volatilize from the water Return to Course Overview Slide 57 Stability Related Process: Reactivity • What is reactivity? – Reaction between a contaminant and another substance – For water systems, a principal reaction of interest occurs between an oxidant and the contaminant of concern – One oxidant frequently found in finished drinking water is chlorine • How does this information help assess the threat? – The oxidation of a chemical contaminant frequently, but not always, decreases the toxicity of the water – Reaction rates for different contaminants can vary dramatically from instantaneous to nearly imperceptible • What limitations in this information should you be aware of? – Oxidation is dependent on temperature and pH – The presence and concentration of other substances in the water may significantly affect the oxidation rate Return to Course Overview Slide 58 • Illustration Stability Related Process: Reactivity (cont.) – A certain pesticide is known to react rapidly with chlorine • You measure the chlorine residual at a tap and find there is a large one • It is less likely that the pesticide is present at that tap – Contamination with a chlorine sensitive contaminant is suspected, so you measure the chlorine residual at a tap • You find very little • Does this indicate contamination? • Maybe not—some parts of the distribution system have far less residual than was added at the plant due to natural chlorine decay – In arsenic treatment of water systems, oxidation changes the chemical form of arsenic, and is known to frequently reduce toxicity and ease of removal Return to Course Overview Slide 59 Stability Related Properties: Adsorption • What is adsorption? – A measure of the tendency of a chemical to partition out of the water into a substance with an organic-like phase (e.g., certain sediments, some water system pipes and components, etc.) – The octanol-water partition coefficient (KOW ) may be an indicator. KOW is the concentration of the contaminant in octanol divided by the concentration in water after the contaminant equilibrates between the two solvents • How does this information help assess the threat? – Related to the fate of a chemical in the water system – May provide an indication of the chemical’s persistence in the water system (e.g., need for remediation of the system) – A compound with a higher KOW may be more likely to persistently contaminate drinking water system components than a contaminant with a lower one. A slow release of the contaminant from the water system components could taint the water until enough water has passed through for sufficient desorption of the contaminant. 60 Stability Related Properties: Adsorption (cont.) • What limitations in this information should you be aware of? – The reliability of KOW as a predictor is highly dependent on both the chemical and the material to which the chemical is partitioning. Not all materials have an organic-like phase that behaves like octanol. – This dependency may be unknown (e.g., given the wide variety of pipe materials in use) – Temperature-dependent – Valid only under equilibrium conditions • Illustration – Hydrogen cyanide has a KOW of 0.5. An organic pesticide has a KOW of 1.3. Which is more likely to persist in the pipes, leading to a slow release in the water over time? • Information gathered revealed that the pipes in that part of town were made of a material to which neither contaminant measurably adsorbed. 61 Part 4: Properties and Characteristics: Pathogens Return to Course Overview Slide 62 Pathogens Overview • Disease-causing organisms that may result in illness or death • May be referred to as bioterrorism agents, replicating agents, select agents, pathogens, microorganisms, microbes • Large quantities may be grown from small initial cultures • Unique ability to multiply in the body over time and increase their effect • May be referred to by disease or by organism name: – Salmonella typhi is the causative agent for typhoid fever – Vibrio cholerae is the causative agent for cholera – Yersinia pestis is the causative agent for plague Return to Course Overview Slide 63 Pathogens Overview (cont.) • Classified (for our purposes) into three categories – Bacteria (including rickettsia and rickettsia-like organisms) – Viruses – Protozoa Escherichia coli bacteria Return to Course Overview Slide 64 Bacteria • Single-celled, prokaryotic (non-nucleated) • Relatively easy to grow, may not require host cells for growth; growth media often simple • 0.1 - 10Fm in size • Some are easily disinfected by chlorination, certain species produce spores that are stable in some environmental matrices for weeks or longer; also some may propagate in a water system Return to Course Overview Slide 65 Bacteria (cont.) • Organisms may be susceptible to antibiotics • Examples – – – – Bacillus anthracis (anthrax) Burkholderia pseudomallei (melioidosis) Yersinia pestis (plague) E. coli O157:H7 (hemorrhagic colitis) Return to Course Overview Slide Bacillus anthracis 66 Viruses • Obligate intracellular parasites containing either DNA or RNA with a protein coat. May also have a lipid envelope • Unable to replicate or metabolize without a host cell • Grown in cell cultures, embryonated eggs, or animals • 0.01 - 0.1Fm in size • Stability is estimated at less than a day to weeks for some, unknown for others • Antibiotics have no effect • Examples: – Variola (smallpox) – Caliciviruses (e.g., Norwalkvirus) – Hepatitis viruses (e.g., Hepatitis A) Calicivirus Return to Course Overview Slide 67 Protozoa • Single-celled, eukaryotic (containing a nucleus), organisms; 0.8 - 70Fm in size • Protozoa of concern are parasites. There are other nonprotozoan parasites, some of which may be of concern • Some produce cysts (or oocysts) that are very stable • May be susceptible to specialized antibiotics (e.g., Nitazoxanide) • Examples: – Cryptosporidium parvum (cryptosporidiosis) – Toxoplasma gondii (toxoplasmosis) – Entamoeba histolytica (amebic dysentery) Return to Course Overview Slide Cryptosporidium 68 Fate and Transport and Health Effects • Fate and Transport – Many pathogens are stable in water long enough to pose a threat – In suspension in water, rather than in solution – Exposure routes may include: ingestion, inhalation, and/or dermal contact • Health Effects – Small volumes of infectious material can potentially infect large numbers of people – May not cause immediate symptoms due to incubation period in host – Symptoms may be vague/ambiguous (e.g., ―flu-like symptoms‖), delaying diagnosis Return to Course Overview Slide 69 Other Properties: Infectivity • What is infectivity? – A measure of the ability of a microorganism to establish itself in a host species and begin to multiply – May be expressed as an ID50 value (the number of organisms needed to infect 50 percent of the exposed hosts in a given time period) • How does this information help assess the threat? – Introduction of pathogen with a low ID50 value may be a significant threat, even when low levels or concentrations are present – Introduction of pathogen with very high ID50 value may require high concentration of organisms to have the same impact Return to Course Overview Slide 70 Other Properties: Infectivity (cont.) • What are the limitations of infectious dose information? – Knowledge of the source of the estimate is crucial to understanding the significance of this number • ID50 values may be derived from estimates made at outbreaks, or from animal models (rather than human dosing studies). • Variation in reported and actual ID50 may also arise from strain, culture conditions, host factors, etc. • ID50 values should include information on the route of infection. ID50 values for ingestion and inhalation may differ by several orders of magnitude • Doses lower than the ID50 may cause illness, and this relationship may not be linear – Some studies report the ―Minimum Infectious Dose‖, which may vary greatly from the ID50 – Many pathogen detection methods do not provide information on infectivity Return to Course Overview Slide 71 Other Properties: Incubation Period • What is incubation period? – The time between exposure and the appearance of symptoms • How does this information help assess the threat? – Pathogens with longer incubation times may no longer be viable or present in the water system at or after the onset of symptoms – If there is a continuous source of a pathogen, then a longer incubation period may allow more individuals to be exposed • What limitations in this information should you be aware of? – Actual incubation period will depend on the following conditions: • Initial dose • Virulence of the organism (severity of disease produced) • Rate of replication of the organism • Health of the host (e.g., immunocompromised) Return to Course Overview Slide 72 Other Properties: Virulence • What is virulence? – Virulence is a measure of the ability of an organism to cause severe disease or death – One measure of virulence is the mortality rate. This is generally calculated as the number of deaths per thousand. • How does this information help assess the threat? – Diseases with higher mortality rates may be of greater consequence to homeland security • What limitations in this information should you be aware of? – Medical treatment may affect the mortality rate, so mortality may be reported with both treated and untreated rates – Mortality rates are dependant on correctly identifying underlying cases, so the case definition used in generating the mortality rate will be highly significant Return to Course Overview Slide 73 Other Properties: Communicability • What is communicability? – Transmission of disease from person to person; the property of being contagious • How does this information help assess the threat? – Even though ―stop-use‖ notices to public may prevent new infections for non-communicable diseases, new infections may continue to occur for communicable pathogens via secondary transmission • What limitations in this information should you be aware of? – Degree of communicability may depend on the strain of organism released • Good sanitation practices can prevent the spread of many communicable diseases Return to Course Overview Slide 74 Other Properties: Stability • What is stability? – An assessment of the organism’s susceptibility to various environmental factors while in the distribution system, including: • Temperature, pH • Osmotic pressure caused by differences in chemical concentrations inside and outside the pathogen • Residual chlorine • How does this information help assess the threat? – Stable organisms with environmentally resistant life stages (such as anthrax spores and Cryptosporidium spp. oocysts) may survive longer in the distribution system – Some organisms may be more susceptible to residual chlorine levels or osmotic pressure, reducing the possibility of transmission Return to Course Overview Slide 75 Other Properties: Stability (cont.) • What limitations in this information should you be aware of? – Data on organism stability may result from studies using different organism strains or system conditions than are present any specific distribution system Salmonella typhi Return to Course Overview Slide 76 Other Properties: Treatability • What is treatability? – Assessment of removal or inactivation of an organism by various treatment processes • How does this information help assess the threat? – Determination of effectiveness of treatment at the water treatment plant during event if organism is added to source water – Determination of chlorine residual effectiveness in distribution system during event if organism is added after treatment – Evaluate the effectiveness of various options to decontaminate the system • What limitations in this information should you be aware of? – Data on organism treatability may result from studies using different strains or conditions Return to Course Overview Slide 77 Challenges for Detection • Most pathogens of concern will not be detected during monitoring for routine contaminants or indicators (e.g., total coliforms) • Analytical results may not be indicative of virulence or infectivity • Water concentration techniques can be used prior to analysis but overall analytical sensitivity may be below the concentration of concern for some contaminants • Most onsite drinking water utility laboratories are currently capable of monitoring for indicator organisms, some of these laboratories can conduct assays for some common waterborne pathogens; however, capability and capacity for many specific pathogens must be expanded Return to Course Overview Slide 78 Challenges for Detection (cont.) • The Select Agent Program (SAP) limits confirmatory analysis for a list of ―Select Agent‖ pathogens (e.g., Bacillus anthracis) to approved labs. Failure to comply with the SAP can result in lengthy jail terms or heavy fines. • Many of the SAP approved labs conducting confirmatory testing of Select Agent samples are part of Laboratory Response Network (LRN) Return to Course Overview Slide 79 Part 5: Properties and Characteristics: Radiochemical Agents Return to Course Overview Slide 80 Radiochemical Agents Overview • Two general types – Naturally occurring (e.g., radium, uranium and thorium) – Man-made; produced exclusively by nuclear reactors, accelerators, cyclotrons, or nuclear weapons • Neutron capture products in nuclear fuel rod assemblies, such as plutonium-239 (239 Pu) and americium-241 (241Am) • Fission products that accumulate in fuel rod assemblies or produced by nuclear detonations, such as cesium-137 (137Cs), and strontium-90 (90Sr) or corrosion/wear product activation such as cobalt-60 (60Co) • Accelerator produced medical radioisotopes, such as iodine-123 (123I) or cobalt-57 (57Co) Return to Course Overview Slide 81 Radiochemical Agents Overview (cont.) • Can be categorized by the type of radiation an unstable isotope emits – Alpha radiation: Particle emitted from the nucleus of an atom consisting of two neutrons and two protons (same as a helium atom nucleus) – Beta radiation: Particle emitted from the nucleus of an atom consisting of an electron or positron – Gamma radiation: Emission from the nucleus of an atom consisting of a high energy photon (gamma photon) Return to Course Overview Slide 82 Radiochemical Agents Overview (cont.) • Radiochemical agents may fall into one or multiple radiation categories: – – – 90Sr is a beta emitter 137Cs and 60Co are both beta and gamma emitters 235U and 239Pu are both alpha and gamma emitters • Sources of radiochemical agents: – Oil exploration equipment – Mining and milling sites for uranium, and rare earth ores – Power generation equipment – Weapons production, maintenance and disposal – Food and medical irradiators – Industrial radiography Return to Course Overview Slide 83 Radiochemical Agents Overview (cont.) • Small quantities widely used in many activities: – Medical – Food industry – Laboratory/scientific research Return to Course Overview Slide 84 Fate and Transport and Health Effects • Fate and transport: – Most will remain in solution – Many are highly absorbable into biologic systems (e.g., 90Sr, uranium, tritium) – Concentrations will likely be uniform in the distribution system • Health effects: – If exposure is at low levels but for a long duration, or is at a high, but non-fatal level for a short duration, the general longterm health effect is induction of cancers – However, extremely high doses in short-term exposure events cause cellular damage that may be significant enough to result in death Return to Course Overview Slide 85 Fate and Transport and Health Effects (cont.) • Health effects, cont.: – Many radioactive agents are organ-specific • Iodine-129 [129I] uptake in the thyroid gland • Uranium uptake and toxicity in kidneys – For contaminated water, the most significant health risk is ingestion; water can significantly attenuate (shield) alpha and beta radiation (but only minimally attenuate gamma radiation), reducing the threat of direct exposure Return to Course Overview Slide 86 Other Properties: Toxicity • What is toxicity? – How poisonous or harmful a substance is in specified amounts • How does this information help assess the threat? – Some radioisotopes may result in both chemical- and radiation-induced toxicity – Chemical toxicity often is of greater concern (e.g., uranium) – LD50 much higher than MCLs (for the regulated analytes) – However, a single alpha particle may induce a mutational event • What limitations in this information should you be aware of? – Toxicity studies for radiochemical contaminants may not cover all chemical species – Most radiation exposure limits are based on dosimetric models combined with radiation dose-response models, rather than empirical studies Return to Course Overview Slide 87 Other Properties: Speciation • What is speciation? – The types of chemical compounds in which a radioactive contaminant may occur, such as a salt, oxide, hydroxide, or organometallic complex, etc. • How does this information help assess the threat? – Can identify forms of radioactive species that may be in solution – Different species will have different properties relevant to chemical fate and transport and health effects • What limitations in this information should you be aware of? – Can be used only to estimate the actual threat of the contaminant of concern Return to Course Overview Slide 88 Other Properties: Solubility • What is solubility? – The amount of a solid that can be dissolved in a solvent (water) • How does this information help assess the threat? – Can be used to assess the exposure risk – Radiochemical compounds with relatively high solubility may be more of a threat (but low solubility does not equate to low threat) – The species of the radioactive material of interest may be changed from one with a low solubility (metal) to one with a high solubility (metallic salt) Return to Course Overview Slide 89 Other Properties: Solubility (cont.) • What limitations in this information should you be aware of? – Solubility of radiochemicals depends on pH and oxidizing potential (Eh) of the water – Solubility also influenced by the dominant anionic coordinating species present in the water (e.g., sulfates, nitrates, carbonates, chlorides) – Many radiochemicals used in sealed sources for medical and industry applications are in insoluble forms (e.g., impregnated ceramics) Return to Course Overview Slide 90 Other Properties: Reactivity • What is reactivity? – Ability of the radiochemical agent to undergo a chemical reaction with other constituents in the matrix (e.g., finished drinking water) • How does this information help assess the threat? – Can affect solubility – Important factor for fate and transport assessment and treatability assessment – Water drawn from the bottom of a storage tank may have higher concentrations of the radioactive contaminant if mixing and turnover only minimally affects the storage facilities in the distribution system Return to Course Overview Slide 91 Other Properties: Reactivity (cont.) • What limitations in this information should you be aware of? – Reactivity may be influenced by pH, redox potential, residual chlorine, and other chemical properties of water in the distribution system – Properties in distribution may not be the same as for the reference reactivity of the radiochemical Return to Course Overview Slide 92 Other Properties: Specific Activity • What is specific activity? – Measure of radioactivity per unit weight of the contaminant • How does this information help assess the threat? – Used to determine the radioactive intensity of the contaminant – The more radioactive the contaminant (the higher specific activity), and the greater the potential health effect • What limitations in this information should you be aware of? – Values usually provided for pure solids – Information will need to be adjusted for dilution effects if in water Return to Course Overview Slide 93 Other Properties: Half-Life • What is half-life? – The elapsed time required for one-half of the radioactive material present to undergo radioactive decay • How does this information help assess the threat? – Can be used in calculating specific activities – Specific activity used to assess the intensity of radioactivity present in drinking water – Also used to evaluate persistence in the environment • What limitations in this information should you be aware of? – No significant limitations – physical constants have been determined experimentally – Potency of daughter products must also be considered Return to Course Overview Slide 94 Other Properties: Principal Daughter Products • What are principal daughter products? – The stable or radioactive isotopes formed when a specific radioisotope (the ―parent radioisotope‖) decays • How does this information help assess the threat? – Can be used to identify other radioisotopes present from the decay of the listed radioactive contaminant – May have different stability/toxicity/solubility, etc., compared to parent; must evaluate risk of daughters independently • What limitations in this information should you be aware of? – No significant limitations – Physical constants have been determined experimentally Return to Course Overview Slide 95 Challenges for Detection • Radiochemical contaminants in water generally cannot be identified by a change in most physical properties of the water • Determining contaminant properties is useful primarily in assessing radiation exposure risks after agent is identified – not identifying the presence of the contaminant itself • There are many advanced environmental radiochemistry labs, however, capability and capacity at drinking water utilities should be enhanced Return to Course Overview Slide 96 Challenges for Detection (cont.) • While it is possible to screen for specific types of radioactivity, no method is available for field screening for all types radioactivity in water • Current GM probes can detect gamma activity in water; however, alpha and beta radiations are shielded to a large extent by the water and thus present a challenge in the area of rapid detection • Geiger counter screening is limited for water screening – Can identify only gross beta/gamma radioactivity – Limited ability to screen for alpha emitters • High-efficiency gamma detectors (scintillation detectors) – Can identify fission products that are often beta/gamma emitters – Cannot identify pure beta emitters, such as Sr-90, or I-129, or the presence of alpha emitting contaminants, such as Pu-238/239 Return to Course Overview Slide 97 Part 6: Gathering and Managing Contaminant Information Return to Course Overview Slide 98 Gathering the Data: Organizations • Agency for Toxic Substances and Disease Registry (ATSDR) – http://www.atsdr.cdc.gov/atsdrhome.html – 1-888-422-8737 • Centers for Disease Control and Prevention (CDC) – http://www.bt.cdc.gov/ – 1-888-246-2675 • Environmental Protection Agency (EPA) – http://www.epa.gov – Integrated Risk Information Hotline, 1-202-566-4676 – National Response Center, 1-800-424-8802 • National Institute for Occupational Safety and Health (NIOSH) – http://www.cdc.gov/niosh/homepage.html – 1-800-35-NIOSH • Occupational Safety and Health Administration (OSHA) – http://www.osha.gov/SLTC/emergencypreparedness/index.html – 800-321-OSHA Return to Course Overview Slide 99 Gathering the Data: Databases • EPA’s Water Contaminant Information Tool – Will contain peer reviewed information on contaminants that are of concern to drinking water – Will contain information on health effects, properties, fate and transport, and drinking water treatment – Currently exists as a prototype populated with 9 contaminants – Currently being revised and further populated – A partially populated version will be available on a secure Web site by early 2005 Return to Course Overview Slide 100 Gathering the Data: Databases • Hazardous Substances Databank (HSDB) – A cluster of databases on toxicology, hazardous chemicals, and related areas – http://toxnet.nlm.nih.gov/ • Integrated Risk Information System (IRIS) – A database of human health effects that may result from exposure to various substances found in the environment – http://www.epa.gov/iris/ – Integrated Risk Information Hotline: 202-566-4676 • NIOSH Emergency Response Cards – http://www.cdc.gov/niosh/topics/emres/chemagent.html • NIOSH Pocket Guide to Hazardous Substances – http://www.cdc.gov/niosh/npg/npg.html Return to Course Overview Slide 101 Gathering the Data: Databases (cont.) • CHEMFATE – A data value file containing 25 categories of environmental fate and physical/chemical property information on commercially important chemical compounds – http://www.syrres.com/esc/chemfate.htm • PHYSPROP – Online interactive demo of physical property data about 25,000 compounds – http://www.syrres.com/esc/physdemo.htm • ATSDR HazDat Database – Provides access to information on the release of hazardous substances from Superfund sites or from emergency events and on the effects of hazardous substances on the health of human populations – http://www.atsdr.cdc.gov/hazdat.html Return to Course Overview Slide 102 Gathering the Data: Databases (cont.) • Food and Drug Administration (FDA) Bad Bug Book – Handbook providing basic facts regarding food-borne pathogenic microorganisms and natural toxins; consolidates information from FDA, CDC, USDA, and the National Institutes of Health – http://vm.cfsan.fda.gov/~mow/intro.html • United Kingdom Water Industry Research (UKWIR) Contaminant Database – Available through WaterISAC for a fee – EPA Regions should have access to WaterISAC, and thus the UKWIR database – http://www.waterisac.org Return to Course Overview Slide 103 Gathering the Data: Scientific Literature • The following information sources have a fee associated with them, but check within your local office, as you may currently have access or have a subscription: – Ovid Biomedical Journal Database – FirstSearch (Worldcat) – Science Citation Index (Web of Science) – ProQuest – Biological Abstracts – STN Online (Chemical Abstracts and more than 140 other scientific databases) – DIALOG – American Chemical Society journal publications online Return to Course Overview Slide 104 Gathering the Data: Scientific Literature (cont.) • The following sources are available on-line at no cost: – American Society for Microbiology journal publications on line • http://www.asm.org/ • Abstracts and full text articles are available at no cost from 1994 through November 2003 – National Institutes of Health, National Library of Medicine • http://www.nlm.nih.gov/ • Abstracts and full text articles are available at no cost from 1992 Return to Course Overview Slide 105 Gathering the Data: Subject Matter Experts • Government – EPA Water Security Division • Expertise on overall threat analysis, response, NSSEs, contaminant evaluation • 202-564-3779 (not for emergencies) • During emergency situations call: 202-564-3850 – EPA National Homeland Security Research Center • NHSRC Red Team • Expertise on monitoring and detection of contaminants and contaminant properties • Hotline: 513-569-7990 – CDC Emergency Response Hotline • Expertise on biological, chemical, and radiological contaminants • 770-488-7100 (24 hours) Return to Course Overview Slide 106 Gathering the Data: Subject Matter Experts (cont.) • Associations – American Water Works Association • Authoritative scientific and technological knowledge geared to the drinking water community • http://www.awwa.org/ • 1-800-926-7337 – Water Information Sharing and Analysis Center (WaterISAC) • Gathers, analyzes and disseminates threat information that is specific to the drinking water and wastewater community. • http://www.waterisac.org/ • Universities and colleges Return to Course Overview Slide 107 Contaminant Characterization and Transport Worksheet • Comprehensive data worksheet for broad range of reported and researched information • Example provided in Module 5 of Response Protocol Toolbox • Designed to capture most likely information provided and gathered for threat assessment • Can be modified or expanded to manage additional information Return to Course Overview Slide 108 Contaminant Information Captured by the Worksheet • Properties reported from the field, when available – – – – Physical form and description Taste and odor (if reported) Environmental indicators of contamination Amount of contaminant introduced • • • • • Consumer complaints or feedback Witness accounts Site characterization information Reported changes in water quality parameters Results of field tests conducted in response to the incident Return to Course Overview Slide 109 Contaminant Information Captured by the Worksheet (cont.) • Details on lab analyses conducted in response to the incident – Critical for verifying the identity of the contaminant – May be limited by detectability issues with some contaminants • Potential information to record and evaluate – Analytical results – Method used – Sensitivity of method (minimum reporting limit (MRL) or minimum level (ML)), if available – Other data quality information critical to assessing reliability of results (precision, recovery, positive and negative controls, blanks, etc.) – Other information reported by the laboratory that may help verify the identity of the contaminant or nature of the threat Return to Course Overview Slide 110 Contaminant Information Captured by the Worksheet (cont.) • Contaminant properties – – – – Solubility Stability Reactivity Effect on water quality parameters • Contaminant health effects – – – – Exposure routes Toxicity Onset of symptoms Available preventive measures or treatments • Contaminant treatability Return to Course Overview Slide 111 Part 7: Data Use for Consequence Analysis Return to Course Overview Slide 112 What Now? Fate and Transport Individual contaminant properties are simply individual values in a larger equation for the potential public health consequences of the contamination Physical Data Infectivity Data ? Toxicity Data Chemical Data Exposure Potential Return to Course Overview Slide 113 Consequence Analysis • During the initial assessment of the contaminant, much of the information collected serves to respond to the two primary consequence analysis components: • The fate and transport of the contaminant – Will the contaminant reach members of the population? – If so, how many individuals will it potentially affect? • The overall health effect of the contaminant – If the contaminant does reach members of the population, will the exposure cause an effect? – What will the severity of the health effects be? Return to Course Overview Slide 114 Fate and Transport • Fate and transport of the contaminant can be assessed using information collected for contaminant properties, such as: – Solubility – Reactivity – Hydrolysis – Stability – Volatility – Adsorbtivity • Other incident information is combined with the information collected on contaminant properties to assess contaminant fate and transport, including: – Location of introduction – Initial concentration of contaminant – Public water system hydraulics and operation Return to Course Overview Slide 115 Fate and Transport (cont.) • Modeling tools to estimate spread of a contaminant – Contaminant properties, incident, and operational information can be used to drive modeling tools such as PipelineNet • Simpler alternatives to estimate spread of a contaminant – Using operational information potentially maintained by the water utility, such as typical travel times from key nodes in a system to large population centers or critical customers Return to Course Overview Slide 116 Fate and Transport (cont.) • Contaminant properties and operational information – Can be used to determine whether the contamination may be mitigated altogether by current treatment operations or conditions in the distribution system • After the area impacted by the spread of contamination has been estimated the number of individuals potentially affected must be determined Return to Course Overview Slide 117 Health Effects • Fate and transport assessment is used with the health effects assessment to complete the initial consequence analysis • Health effects of the contaminant can be assessed using information collected for contaminant properties, such as: – Formulation, species, or strain – Toxicity or infectivity – Severity of health effects – Likely exposure routes – Communicability Infection-causing Cryptosporidium sporozoites – Medical intervention Return to Course Overview Slide 118 Health Effects (cont.) • Toxicity properties – MCL or LD50 are combined with the estimated concentration of the contaminant at the tap to determine the likelihood of health effects • Communicability information for pathogens – Can be used to determine whether the health threat will end with a do-not-drink order or continue even after this exposure route is eliminated • Treatability properties – Combined with operational information to determine whether contaminants, such as pathogens, will be inactivated or neutralized Return to Course Overview Slide 119 Health Effects (cont.) • Information on subpopulations – Combined with the health effect information to assess whether these populations will be affected, even if the majority of consumers are not • If sufficient information is not available, or there isn’t sufficient time to find the information, it is best to make a conservative estimate that severe public health impacts are possible Return to Course Overview Slide 120 NO Collect more information Are witness reports, lab analyses, or other properties known? YES Consult with experts or use available tools to reduce list of potential contaminants NO T AR Has ST contaminant been positively identified? YES Contaminant Research Prioritization Tree for Consequence Analysis NO Research health effects Has the public been exposed? Research fate and transport properties YES NO Are health effects consistent with symptoms? YES Work with health agency to determine actions Can the contaminant be contained before public exposure? NO Research health effects YES Will contaminant reach tap at adverse public health levels? Work with water utility to determine action NO YES 121 Return to Course Overview Slide Potential Outcomes of Consequence Analysis • Example 1: – Contaminant is introduced at levels that would cause severe health effects – Degrades or is diluted to levels below concern before reaching any consumers – Work primarily with water utility to determine action • Example 2: – Contaminant introduced at levels that would cause severe health effects – Reaches segments of the population at levels of concern – Consumer use is not consistent with effective exposure routes – Work with both health agency and water utility to determine actions Return to Course Overview Slide 122 Potential Outcomes of Consequence Analysis (cont.) • Example 3: – Contaminant reaches segments of the population at levels that cause severe health effects – Consumers will be exposed – Work with both health agency and water utility to determine actions • Example 4: – Contaminant is introduced at levels that would not cause severe health effects – Decontamination results in long-term remediation, disruption in service for extended periods of time – Work primarily with water utility to determine actions Return to Course Overview Slide 123 Secondary Consequence Analysis Issues • Contaminant properties also will help respond to secondary questions – Remediation options for contaminant after initial response – Assessment of impacts on the water system and consumers • Contaminant properties also will help in identifying the contaminant, if this is unknown – Physical properties reported during the incident (taste, odor, appearance) – Potential for contaminant to affect water quality parameters – Symptoms reported by health agencies Return to Course Overview Slide 124 Part 8: Example Contamination Scenario (Other Examples Provided in Appendix) Return to Course Overview Slide 125 Example: Cyanide • A sensor located in a distribution system indicated a dramatic drop in residual chlorine • Tests confirmed the presence of cyanide in the drinking water distribution system – Samples collected from taps and throughout distribution system – Positive samples, up to ½ -mile upstream at the distribution system pump station, and up to 1- mile downstream near a residential area • Hydrogen cyanide concentration in the water system = 40 mg/L • The previously measured speed of water travel through the distribution system is 10 ft/sec • Summary of symptoms of those exposed: difficulty breathing; flushed skin; nausea; vomiting Return to Course Overview Slide 126 Critical Questions • The following critical questions regarding cyanide properties need to be answered: – What methods, both field and laboratory, are available to measure cyanide? – Are current cyanide levels toxic enough to pose a threat to public health? – Which routes of exposure pose a threat to consumers? – What is the fate and transport of cyanide through a drinking water distribution system? – What is the anticipated residence time of cyanide through the treatment and the distribution system? – Which treatment technologies can remove or detoxify cyanide? – What reaction products of cyanide in finished drinking water pose significant public health risks? Return to Course Overview Slide 127 Sources of Information Identified • The following potential sources were identified to collect information on cyanide properties to support consequence analysis: – Material Safety Data Sheet for cyanide • http://chppm-www.apgea.army.mil/dts/docs/detac.pdf – National Institutes of Health TOXNET database • http://toxnet.nlm.nih.gov/ – Centers for Disease Control and Prevention • http://www.bt.cdc.gov/agent/cyanide/index.asp – NIOSH Emergency Response Cards • http://www.bt.cdc.gov/agent/cyanide/erc74-90-8.asp – Subject Matter Experts from USEPA WSD and NHSRC Return to Course Overview Slide 128 Information from First Source • The Material Safety Data Sheet for cyanide was consulted first, and the following information collected: • Molecular weight: 27.03 • Vapor Pressure (mm Hg): 742 @ 25°C • Boiling point: 25.7°C • Adverse Health Effects – Rapid acting, potentially deadly – Prevents the cells of the body from using oxygen – Exposure by inhalation, ingestion, or skin contact may result in symptoms such as reddening of the eyes, flushing of the skin, nausea Return to Course Overview Slide 129 Information from First Source (cont.) • Toxicity – – – – – LCt (inhalation, 0.5 min) = 2.000 mg-min/m3 LCt (inhalation, 30 min) = 20,600 mg-min/m3 NOAEL (inhalation) = 670 mg-min/m3 RfD (ingestion) = 0.750 mg/L (liquid) LD50 (dermal) = 100 mg/kg (liquid) • This information was entered on the Contaminant Characterization and Transport Worksheet • Additional information on fate and transport was needed, and a second source consulted Return to Course Overview Slide 130 Information from Second Source • On the TOXNET site, a search for ―cyanide‖ was conducted by first selecting the ―HSDB full record‖ option • The following information was gathered from this source: • Solubility – Highly soluble in water, but stable • Stability – – Forms equilibrium in water between CN- and HCN (aqueous) Unstable with heat, alkaline materials Return to Course Overview Slide 131 Information from Second Source (cont.) • Persistence – – Open system: Cyanide is highly volatile, and in the gaseous state, it dissipates quickly in the air Closed system: Does not dissipate in a pressurized pipe • Reactivity – – – – May react with chlorine to form CNCl, which is very toxic via multiple exposure routes Cyanide reactions sensitive to pH changes May react violently with strong mineral acids Polymerizes when heated and forms a potentially explosive solid Return to Course Overview Slide 132 Information from Second Source (cont.) • Other properties – – – – – – – – – ―Bitter almond‖ or pepper-like odor; not always detectable Molecular weight: 27.03 Vapor Pressure (mm Hg): 742 @ 25°C Volatilization half lives: Rivers: 3 days; Lakes: 3 days Log Kow: -0.25 Henry’s Law constant: 1.33X10-4 atm-cu m/mol @ 25 deg C Density: 0.7 g/cu cm Water solubility = 1,000,000 mg/L @ 25°C pKa of 9.2 Return to Course Overview Slide 133 Information from Second Source (cont.) • Toxicity – – – – – – LC50 inhalation (rat) 142 ppm/30 min LC50 inhalation (dog) 300 ppm/3 min LC50 subcutaneous (groundhog) 100 ug/kg LC50 ip (intraperitoneal) (mouse) 2990 ug/kg LC50 im (intramuscular) (mouse) 2700 ug/kg LC50 iv (intravenous) (mouse) 990 ug/kg • No LD50 for ingestion of cyanide was found • This information also conflicted with the information found on the MSDS Return to Course Overview Slide 134 Information from Second Source (cont.) • Additional toxicity information – Determined from rat chronic oral – NOAEL: 10.8 mg/kg/day cyanide converted to 11.2 mg/kg/day of hydrogen cyanide • Adverse Health Effects – Rapid acting, potentially deadly – Prevents the cells of the body from using oxygen – Exposure by inhalation, ingestion, or skin contact may result in symptoms such as reddening of the eyes, flushing of the skin, nausea – The human body can de-toxify cyanide, so exposure to a lethal dose would need to occur over a relatively short time period • This information was entered on the Contaminant Characterization and Transport Worksheet Return to Course Overview Slide 135 Information from Other Sources • The Centers for Disease Control and Prevention site was consulted, but no LD50 for cyanide ingestion was found • EPA Subject Matter Expert contacted – According to subject matter expert, the LD50 for cyanide ingestion was approximately ~1.5 mg/kg • NIOSH Emergency Response Card for hydrogen cyanide evaluated for additional health effects descriptions Return to Course Overview Slide 136 Use of Information Collected • Health effect information was considered important – Needed to determine worst consequence exposure route – Needed to prepare for medical response • The toxicity information was considered important – Needed to confirm consequences of exposure and determine concentration levels at which adverse effects are not likely to occur • The solubility, fate, and reactivity information was considered important for developing a treatment strategy • Information on treatability was considered important – Needed to determine a treatment method to eliminate the cyanide Return to Course Overview Slide 137 Use of Information Collected (cont.) • Other physio-chemical property information may prove useful for planning the response and treatment • Water Solubility – Cyanide is water soluble and stable – In a drinking water system, there is no place for HCN to go, so it will stay in the water – The higher the water solubility, the more likely the contaminant will be available (soluble) in the water in both a closed and open system Return to Course Overview Slide 138 Use of Information Collected (cont.) • Fate – Estimated volatilization half-lives for open systems: shows cyanide can exist for up to 3 days in an open system – Closed system: Expected to exist in a nearly equilibrium state between CN- and HCN; especially in a pressurized pipe • Could be dangerous if pipe pressure increases • Possible explosion hazard as cyanide is trapped in the pressurized distribution pipes • Upon exit, may be further trapped in shower stalls, closed bathrooms, containers, etc • Reactivity – Cyanide may react with treatment chemicals such as chlorine, but the the product, CNCl is highly toxic. Return to Course Overview Slide 139 Use of Information Collected (cont.) • Log KOW – Low – In water, hydrogen cyanide is not expected to adsorb to suspended solids and sediment in water • Henry’s Law constant – High – Volatilization from water surfaces is expected to be an important fate process; the contaminant will have a tendency to go into air once exiting the closed system • Density – Cyanide gas is less dense than air, so it will rise Return to Course Overview Slide 140 Use of Information Collected (cont.) • Health Effects and Toxicity Information Selected – Health Effects Descriptions (NIOSH emergency response cards, CDC Bioterrorism provide the most succinct descriptions of adverse health effects) – The toxicity values collected varied widely; in this case, the lowest (or most conservative value) was selected to ensure public safety – LD50 (ingestion) = ~1.5 mg/kg (from EPA subject matter expert) was most recent peer-reviewed data, the lowest LD50 value, and the value is consistent with other data Return to Course Overview Slide 141 Other Relevant Information • Any breaches in security • Additional operational information • Affected population information Return to Course Overview Slide 142 Consequence Analysis • Toxicity Evaluation – Based on the LD50 of 1.5 mg/kg, it was calculated that a concentration of 50 mg/L would be needed to adversely affect an infant drinking one 4 oz bottle of cyanide-contaminated water – The cyanide concentration found in the water was 40 mg/L, which does not exceed this 50 mg/L concentration, but adverse effects are being reported indicating low level exposure Return to Course Overview Slide 143 Consequence Analysis (cont.) • Total Estimated Exposure – Because the water travels at 10 ft/sec and contamination was discovered only 1 mile downstream of the affected population, it was assumed that contamination was discovered quickly after occurrence and no more than 200 homes were affected before the system was shut off • Health Consequences – Hydrogen cyanide is absorbed well by inhalation (showering) and can produce death within minutes; therefore, immediate action should be taken to treat victims for cyanide exposure – Cyanide exposure is not contagious but persons whose clothing or skin is contaminated with cyanide-containing solutions can secondarily contaminate response personnel by direct contact or through off-gassing vapor; secondary exposure should be avoided by following emergency response guidance Return to Course Overview Slide 144 Consequence Analysis (cont.) • Emergency Action – Shut off distribution system – Evacuation of the premises – Immediately treat exposed victims • Recommended treatment options: – Flush the system to a holding tank for subsequent treatment – Chlorination at elevated pH levels will mineralize cyanide Return to Course Overview Slide 145 Part 9: Action Items and Learning Tools Return to Course Overview Slide 146 Take Home Assignments • Identify potential contaminant information resources and subject matter experts in your home office. Make arrangements for accessing these resources. • Research information on one contaminant of each of the major categories (pathogens, chemical agents, radiochemical agents), using the data collection worksheet • Research one contaminant to understand those properties that would impact fate and transport in a distribution system Return to Course Overview Slide 147 Take Home Assignments (cont.) • Evaluate the health effects if one of the contaminants reached the consumer’s tap at a concentration of 10 percent of the LD50 • Integrate the above into a consequence analysis for the contaminant under a hypothetical scenario Return to Course Overview Slide 148 Acknowledgments • USEPA would like to thank the individuals who contributed to their time and expertise to the development, review and presentation of this training – – – – – – – – – Steve Allgeier Michael Boykin Alan Lindquist Matthew Magnuson Neal Nelson Grace Robiou Irwin Silverstein, AAAS Fellow Ashley M. Smith Stanley States, Pittsburgh Water and Sewer Authority 149 Part 10: Appendix: Example Scenarios for Other Contaminants Return to Course Overview Slide 150 Example: Bacillus anthracis • Caller threatened to dump 55 gallons of anthrax into the reservoir used as the source water for the surface water treatment plant • The utility uses a multiple barrier treatment process including coagulation/flocculation, sedimentation and high rate granular media filtration • The measured distribution system travel time through the treatment process is 12 hours and between nearby node and population center is 4 hours Return to Course Overview Slide 151 Critical Questions • Based on the information provided, the following critical questions regarding Bacillus anthracis properties need to be answered: – Are there immediate health and safety risks to first responders and water utility staff if anthrax is present in the source water and were to enter the treatment plant? – What is the anticipated fate and transport of Bacillus anthracis through treatment and the distribution system? – Are utility treatment practices sufficient to remove or inactivate Bacillus anthracis to mitigate or minimize the risk to drinking water customers? – What concentration levels of Bacillus anthracis in finished drinking water pose significant public health risks? Return to Course Overview Slide 152 Information Gathering: Bacillus anthracis • The following outside sources were consulted to characterize the contaminant and answer these questions: – Centers for Disease Control and Prevention http://www.bt.cdc.gov/agent/anthrax/index.asp • HOTLINE: 888.246.2675 – The Journal of the American Medical Association • http://jama.ama-assn.org/ – Subject matter experts from USEPA (WSD and NHSRC) Return to Course Overview Slide 153 Information From First Source • From the CDC Web site, the following information was gathered: • Health effects – Symptoms and incubation period vary by route of exposure – Lethality varies by route of exposure (inhalation most severe) – If exposure or potential exposure is identified early, antibiotics or vaccination can be used to prevent disease or lessen severity of symptoms • Size – Spore size is approximately 1 µm x 2 µm Return to Course Overview Slide 154 Information From First Source (cont.) • This information was entered on the Contaminant Characterization and Transport Worksheet • However, no information on fate and transport, stability, or toxicity was found from this source, but the Web site pointed to JAMA Web site for additional public health information Return to Course Overview Slide 155 Information From Second Source • From the JAMA Web site, the following information was gathered: • Health Effects – Inhalational anthrax is expected to account for most morbidity and essentially all mortality following the use of anthrax as an aerosolized biological weapon • Virulence – Estimate for humans: LD50 2500 to 55,000 inhaled anthrax spores (based on primate data) • This information was entered on the Contaminant Characterization and Transport Worksheet • However, no information on fate and transport or stability was found from this source, so additional sources were consulted Return to Course Overview Slide 156 Information From Third Source • From the EPA subject matter experts, the following information was gathered: • Stability – Likely to be stable in water long enough to pose a threat – Spores will survive longer and are more resistant to chlorine than are vegetative cells • Toxicity – Vegetative cells are more infective than spores via ingestion Return to Course Overview Slide 157 Information From Third Source (cont.) • This information was entered on the Contaminant Characterization and Transport Worksheet • Although additional information was still needed, it was clear that actions needed to be taken and a consequence analysis was performed using the data that had been gathered Return to Course Overview Slide 158 Use of Information Collected • Information collected from three sources was then evaluated based on the two components of consequence analysis, fate and transport and health effects • Properties related to fate and transport – Stability: Spores will survive longer and are more resistant than vegetative cells to chlorine – Size: Spores are smaller than many filters: 1 µm x 2 µm Return to Course Overview Slide 159 Use of Information Collected (cont.) • Properties related to health effects – Exposure and severity • Symptoms and incubation period vary by route of exposure • Lethality varies by route of exposure (inhalation most severe) • If exposure or potential exposure is identified early, antibiotics or vaccination can be used to prevent disease or lessen severity of symptoms – Virulence • Infective dose: 6,000 inhaled anthrax spores • LD50 2500 to 55,000 inhaled anthrax spores (based on primate data) • Vegetative cells are more infective than spores via ingestion Return to Course Overview Slide 160 Other Relevant Information • Information from the incident • Additional operational information • Affected population information Return to Course Overview Slide 161 Consequence Analysis • Sampling, analysis and additional information about the threat confirmed that anthrax was introduced into the source water and it is estimated that up to 500 million spores entered the treatment plant • The utility could expect a 3-log removal based on existing treatment processes using conventional filtration • The estimated quantity of anthrax spores released into the distribution system would be 500,000 spores Return to Course Overview Slide 162 Consequence Analysis (cont.) • Laboratory results for samples taken at various points along the suspected travel route of the slug of anthrax will help to confirm the concentration of the contaminant • The drinking water utility should continue to work closely with public health officials Return to Course Overview Slide 163 Example: Sulfur Mustard • Based on information in the incident report, an estimated 10 kg of sulfur mustard was thought to be introduced into a primary storage tank of a water treatment plant based on information provided about the incident • The tank contains 4 million liters of water • The water temperature in the tank is approximately 70° F • The water in the tank will take 12 hours to reach the nearest consumer tap • The sampling results indicated: – No measurable amounts of sulfur mustard were found in the storage tank – Sulfur mustard was not detected downstream in the distribution system; thioglycol concentrations were detected – MDL of method used was reported as 50 µ/L Return to Course Overview Slide 164 Critical Questions • Based on the information provided, the following critical questions regarding sulfur mustard properties need to be answered: – Are sulfur mustard levels at the tap likely to be toxic enough to issue a ―stop-use‖ order? – Where would the sulfur mustard be within the distribution system? – Will water treatment technologies currently in use be effective at detoxifying or degrading mustard gas? Return to Course Overview Slide 165 Sources of Information Identified • The following potential sources are identified to collect information on sulfur mustard properties to support consequence analysis if the contaminant is introduced into the system: – U.S. Army Chemical Materials Agency • http://www.cma.army.mil/home.aspx – Agency for Toxic Substances and Disease Registry (ATSDR) • http://www.atsdr.cdc.gov/tfactsd3.html – Centers for Disease Control and Prevention (CDC) • http://www.bt.cdc.gov/agent/sulfurmustard/index.asp Return to Course Overview Slide 166 Information from First Source • Information on the U.S. Army Chemical Materials Agency site was evaluated, but the information provided on the Web site was very general • However, a point of contact was provided for additional information • The point of contact was able to provide information on who to contact at the nearby Army facility for further action • This information was entered on a Contaminant Characterization and Transport Worksheet • Additional sources were consulted to find information on health effects and fate and transport Return to Course Overview Slide 167 Information from Second Source • On the ATSDR Web site, a lengthy toxicological profile of sulfur mustard was identified and reviewed, providing information on many of the properties of interest • Color and Odor – Pure liquid is colorless and odorless – Appears brown and has a garlic-like smell when mixed with other chemicals • Solubility – Limited in water • 920 mg/L at 22°C • 684 mg/L at 25°C – Dissolves easily in oils, fats, and other solvents Return to Course Overview Slide 168 Information from Second Source (cont.) • Henry’s law constant – 1.87 x 10-5 or 2.4 x 10-5 atm-m3/mol • Hydrolysis of sulfur mustard is relatively rapid in water once dissolved – Hydrolysis half-life ranges from 1.5 minutes at 40°C to 158 minutes at 6°C – Primary hydrolysis products include mustard chlorohydrin, thiodiglycol, and hydrochloric acid – Mustard chlorohydrin hydrolyses faster than sulfur mustard – Thiodiglycol is not susceptible to hydrolysis – Although not well documented, it has been reported that sulfur mustard immersed in water has been found to be active and toxic; this may be the result of a protective oxidative coating forming on the outside of microscopic particles of sulfur mustard Return to Course Overview Slide 169 Information from Second Source (cont.) • Oxidation – Mustard gas is oxidized in aqueous solution to mustard sulfoxide and mustard sulfone by agents such as hydrogen peroxide and ozone as well as chlorine and hypochlorites – Mustard sulfoxide is extremely stable, and not prone to hydrolysis; it is slightly toxic • Reactivity – Bleaching-powder and chloramines react violently and form nonpoisonous oxidation products – On contact with acid or acid vapors, it emits highly toxic fumes of vapors of sulfur and chlorine Return to Course Overview Slide 170 Information from Second Source (cont.) • Toxicity Values – MRL of 0.0005 mg/kg/day for acute-duration exposure (14 days or less) – Inhalation LCt50 for humans is 900 mg-minute/m3 for 10-minute exposure • Estimated for humans by Army’s Chemical Defense Equipment Process Action Team by averaging toxicity data from several animal species – LD50 for skin exposure is 100 mg/kg • Value provided by Army without details on how it was derived – Oral LD50 of 0.7 mg/kg • Estimated for humans by the Army but no information was provided on how it was derived Return to Course Overview Slide 171 Information from Second Source (cont.) • Health Effects – Skin absorption will result in skin burns and blisters – Eye contact may make the eyes burn and eyelids swell – Inhalation may result in coughing, bronchitis, and long-term respiratory disease • Hoarseness and irritation of the nasal mucus may develop 12 hours to 2 days after exposure to 12-70 mg-minute/m3; recovery may occur after approximately 2 weeks • Exposure to 1,000 mg-minute/m3 may result in injuries progressing to edema in the pharynx and tracheobronchial tree, followed by death due to severe edema, secondary infection or necrotic bronchopneumonia – Symptoms may not occur for 2 to 24 hours – Symptoms that occur get progressively worse – Effects of long term or repeated exposure: second/third degree burns, scarring, chronic respiratory disease, permanent blindness, death • This information was entered or updated on the Contaminant Characterization and Transport Worksheet • Additional information was desired for oxidation and reactivity Return to Course Overview Slide 172 Information from Third Source • The CDC Bioterrorism Web site was accessed, and the information reviewed • It was found that much of the same information found in ATSDR was also posted on this site, with no new information on oxidation or reactivity • Although additional information was still needed, a consequence analysis was performed using the data that had been gathered Return to Course Overview Slide 173 Use of Information Gathered • MRLs and other toxicity values were considered important – Needed for comparison to the measured values in the storage tank and distribution system – Assessment of the effect of the contaminant at the concentration the population potentially would be exposed to it • Health effect information was considered important – Determine if any health effects seen in the public are a result of the contamination event – Determine likely adverse effects if concentrations were high – Prepare for medical response if necessary Return to Course Overview Slide 174 Use of Information Gathered (cont.) • Information on hydrolysis was considered important to determine how quickly sulfur mustard would break down, if it was introduced – The hydrolysis half-life of 1.5 to 158 minutes indicates the hydrolysis of sulfur mustard takes place quickly once it is dissolved – Because the breakdown product, thiodiglycol, is not susceptible to hydrolysis, this was identified as a potential analyte for monitoring of the system • The solubility in water was considered important because hydrolysis will not take place until sulfur mustard dissolved Return to Course Overview Slide 175 Use of Information Gathered (cont.) • Because the sulfur mustard may be colorless and odorless, color and odor were not considered useful for determining whether a contamination event had occurred • Henry’s law constant, used to determine volatilization, was not considered useful due to the closed storage tank, which had little headspace, and distribution system in this situation Return to Course Overview Slide 176 Other Relevant Information • Information from the incident • Additional operational information • Affected populations Return to Course Overview Slide 177 Consequence Analysis • If 10 kg of sulfur mustard were introduced into 4 million liters of water: – 10 kg/(4x106 L) = 2.5 x 10-6 kg/L = 2.5 x 10-3 g/L = 2.5 mg/L • This is well below the solubility of sulfur mustard in the system of approximately 1000 mg/L • All of the sulfur mustard will have dissolved in the tank and entered the distribution system Return to Course Overview Slide 178 Consequence Analysis (cont.) • The oral LD50 for sulfur mustard of 0.7 mg/kg translates to 49 mg total dose for an average, 70 kg person • 20 L of contaminated water would need to be ingested to get the LD50 • Although this is not likely, toxicity is not linear with concentration, so drinking 1 L containing 2.5 mg/L might still kill some portion of the population, but not 50 percent Return to Course Overview Slide 179 Consequence Analysis (cont.) • Due to the hydrolysis, even this dose is unlikely to reach the public • If the half-life due to hydrolysis is approximately 60 minutes at the temperature in the system, the contaminant would undergo 12 halflives in 12 hours • This equates to 2.5/122 = 0.0006 mg/L = 0.6 Fg/L sulfur mustard at the nearest consumer’s tap • Health effects due to sulfur mustard, if any, should be mild • Sulfur mustard in chlorine water will cause oxidation which results in mustard sulfoxide; mustard sulfoxide is extremely stable to hydrolysis and slightly toxic. Additional toxicity and health effects data should be collected. • Thiodiglycol is a precursor for sulfur mustards and is completely soluble in water; inhalation and skin contact are the primary routes of exposure. Based on single exposure animal tests, thiodiglycol is considered non-toxic if swallowed, slightly irritating to eyes, and practically non-irritating to skin. Return to Course Overview Slide 180 Example: Ricin • An approximate concentration of 100 mg/L of Ricin is detected in public drinking water • Summary of victim symptoms include nausea, diarrhea, and weight loss, and reports of coughing and difficulty breathing in the shower • Drinking water distribution map noted locations of incidents • The rate of water moving through the distribution system was used to determine the spread of contamination • Sensitive population is served by municipal water utility Return to Course Overview Slide 181 Critical Questions • Based on the preliminary results, the following questions regarding ricin properties need to be answered: – How serious are the consequences of ricin exposure? – What is the anticipated fate and transport of ricin in the distribution system? – Because ricin has already reached the public via finished water, what additional water treatment can the utility use to mitigate further exposure? Return to Course Overview Slide 182 Sources of Information Identified • The following potential sources are identified to collect information on ricin properties to support consequence analysis if the contaminant is introduced into the system: – Centers for Disease Control and Prevention http://www.bt.cdc.gov/agent/ricin/index.asp – National Institutes of Health TOXNET database http://toxnet.nlm.nih.gov/ – Subject mater experts from USEPA (WSD and NHSRC) Return to Course Overview Slide 183 Information from First Source • On the CDC Web site, several resources were available on ricin’s health impacts and toxicity • Health Effects – Symptoms occur within 4 to 12 hours if inhaled or swallowed – Symptoms following ingestion include abdominal pain, vomiting, and diarrhea (sometimes bloody) – Symptoms following inhalation would be respiratory distress (difficulty breathing), fever, cough, nausea, convulsions, paralysis – Potential exposure to lethal doses through cuts in the skin, bleeding gums, etc. Return to Course Overview Slide 184 Information from First Source (cont.) • Toxicity – Inhalation and intravenous injection are the most lethal (5–10 µg/kg); not well absorbed through the digestive tract or through the skin – LD50: 5 mg/kg – Possibility for 1 mg to kill an adult via direct injection Return to Course Overview Slide 185 Information from First Source (cont.) • CDC’s Web site provided only general information on physical properties of ricin • Fate and Transport – Powder form disperses readily into all media • Stability – Stable in ambient conditions and temperature extremes in water – Resistant to chlorine • Solubility – Freely soluble in water (20°C) and dilute acetic acid – Soluble: 10 percent NaCl solution • This information was entered on the Contaminant Characterization and Transport Worksheet Return to Course Overview Slide 186 Information from Second Source • The TOXNET database provided more information on toxicity and adverse health effects • Adverse Health effects: – Symptoms of Ricin exposure: weight loss, diarrhea, convulsions, alternating periods of paralysis, then death – Exposure routes: Toxic by ingestion, small particle in cut or abrasion may prove fatal • Toxicity – Probable oral human lethal dose: a taste (less than 7 drops) for a 70 kg person (150 lbs) Return to Course Overview Slide 187 Information from Second Source (cont.) • TOXNET provided much the same information on physical properties, such as stability, and solubility found on CDC’s Web site • Additional sources were consulted to find information on fate and transport and other physical properties Return to Course Overview Slide 188 Information from Third Source • EPA subject matter expert knowledge was sought out to provide confirmation of data found and fill gaps • Toxicity – Oral LD50 values can be as low as 1 mg/kg • Other Physical Properties: very little is known – – – – Boiling Point: Decomposes Vapor Pressure (20°C): Negligible Volatility: Negligible Solubility: In an acid and a base Return to Course Overview Slide 189 Information from Third Source (cont.) • Treatability – Ricin is detoxified in 10 minutes at 176°F (80°C), and in 1 hour at 122°F (50°C) • This information was entered on the Contaminant Characterization and Transport Worksheet • Although additional information was still needed, and a consequence analysis was performed using the data that had been gathered Return to Course Overview Slide 190 Use of Information Gathered • Health effect information was considered important – Needed to determine worst consequence exposure route – Needed to prepare for medical response • The toxicity information was considered important – Needed to confirm consequences of exposure • The solubility in water was considered important – Needed to confirm whether ricin remains stable in water Return to Course Overview Slide 191 Use of Information Gathered (cont.) • Information on treatability was considered important – Needed to determine whether standard water treatment would significantly degrade ricin – Needed to understand potential drawbacks of emergency water treatment such as boiling and its increase in potential exposure (aerosols) • Half-life in water and other information would have been useful but not available Return to Course Overview Slide 192 Other Relevant Information • 166 mg/L concentration (calculated using 5 mg/kg lethal dose) is what would have to be found to be a lethal concentration for an average 70 kg person in the drinking water • Operational Information • Affected Population Information Return to Course Overview Slide 193 Consequence Analysis: Ricin • Health consequences – The concentration found doesn’t exceed the fatal concentration – People are suffering adverse affects – Because the tested concentration is in the same order of magnitude as LD50, it could be potentially fatal – Issuing a ―boil water‖ advisory could expose the public to toxic vapors before the ricin is decomposed • Fate and transport – The extent of contamination reached a sensitive population area • Treatability – Chlorine levels in the finished water do not reduce ricin toxicity – Effects of other treatment technologies on ricin are not known Return to Course Overview Slide 194 Example: Cesium-137 • A white crystalline powder was introduced into an opened entry port at a remote pump station • Initial radioactivity screening of the area with Geiger counters indicated the white powder was radioactive, with high levels of beta/gamma activity • Screens for microbial or chemical contaminants were negative • The previously measured distribution system travel time between the inlet used to add the contaminant and the nearest population center is 180 minutes Return to Course Overview Slide 195 Example: Cesium-137 (cont.) • Follow-up field screening of the white powder and bags with a portable gamma detector initially detected gamma activity. Laboratory analysis results positively identified the substance as Cs-137. – Four water samples taken from sampling points with increasing distance from the site of the contamination were further characterized on an expedited basis at a radiochemistry laboratory certified for gross beta, Cs-137, and gamma screen analyses – These measurements indicate the majority of beta radiation from the sample is from Cs-137 at a concentration level of 130 + 13 pCi/L Return to Course Overview Slide 196 Critical Questions • Based on the information provided, the following critical questions regarding Cs-137 properties need to be answered: – What concentration levels of Cs-137 in finished drinking water can be tolerated before public health is endangered and a stop-use order must be issued? – What are the short- and long-term health effects of the consumption of Cs-137 contaminated drinking water? – Will it decay away in sufficient time so not to require treatment? – What is the anticipated fate and transport of the radionuclide in the distribution system? Return to Course Overview Slide 197 Sources of Information Identified • The following potential sources were consulted to characterize the contaminant and answer these questions: – EPA Radionuclides Fact Sheets and Contaminants MCLs • http://www.epa.gov/radiation/radionuclides/cesium.htm • http://www.epa.gov/safewater/mcl.html#mcls – Agency for Toxic Substances and Disease Registry (ATSDR) • http://www.atsdr.cdc.gov/toxprofiles/tp157.html – CDC Radiation Emergency Page • http://www.bt.cdc.gov/radiation/index.asp Return to Course Overview Slide 198 Information from First Source • At the EPA Web site, the following information was found: • General properties – A soft malleable silver-white metal – A liquid near room temperatures (83oF) • Health effects of Cs-137 exposure – At low exposure levels, increases in cancer rates are observed – At high exposure levels, burns and deaths can result • Half-life of Cs-137 – 30 years Return to Course Overview Slide 199 Information from First Source (cont.) • Fate and transport information – Moves easily through the environment – No specific information was found • MCL of 4 mRem/yr • This information was entered on a Contaminant Characterization and Transport Worksheet • Because no specific fate and transport data or information on chemical or physical properties was found from this source, additional sources were consulted Return to Course Overview Slide 200 Information from Second Source • On the ATSDR Web site, a toxicological profile of cesium was identified and reviewed, providing information on many of the properties of interest • Common chemical forms of Cesium-137 and their chemical properties – Chlorides are the most common forms found – Can also exist as carbonates, hydroxides, or oxides – Chemical and physical data for these chemical forms Return to Course Overview Slide 201 Information from Second Source (cont.) • Environmental Fate and Partitioning – In solution with water, Cs-137 will be present as a Cs1+ ion – Most Cs-137 will be adsorbed onto surfaces of suspended solids, eventually settling – Will bioaccumulate in both terrestrial and aquatic food chains – Waters with a high humic content and potassium levels increase partitioning Cs-137 into the food chains or sediments Return to Course Overview Slide 202 Information from the Second Source (cont.) • Health effects of Cs-137 exposure – Systemic Toxicity • All systems depressed • Higher doses can cause sterility – Cancers often occur in exposed populations due to chromosomal damage – Children are the most susceptible population – Exposure limits reported • EPA MCL for Cs-137 is 4 mRem/yr total body dose, equivalent to an activity concentration of 200 pCi/L of Cs-137 • NOAEL = 200 rads Total Body Dose • LOAEL = 350 rads Total Body Dose Return to Course Overview Slide 203 Information from the Second Source (cont.) • Types of radioactivity emitted by Cs-137 – Can emit beta particles with two different energies • 0.1734 and 0.4346 MeV – Gamma particle with an energy of 661.67 keV emitted when one immediate daughter, Ba-137m, decays to a stable form; Ba-137 • This information was entered or updated on the Contaminant Characterization and Transport Worksheet • Essential information was found in the two references, so the third source was not consulted Return to Course Overview Slide 204 Fate and Transport and Health Effects • Information collected from the two sources was evaluated based on the two components of consequence analysis • Properties related to fate and transport – Solubility • In a chloride form, Cs-137 forms a white, crystalline powder that is highly soluble in water (1.8 kg/L) • Cesium halides dissociate much like sodium and potassium, and exist as Cs+1 ions in solution – Reactivity • As with the other alkali metals, cesium in a water solution is relatively unreactive – Absorptivity • Cs-137 is highly absorbed by mineral surfaces of suspended solids that eventually become sediments Return to Course Overview Slide 205 Fate and Transport and Health Effects (cont.) • Properties related to health effects – Half-life • 30.17 years – Exposure and severity • Short term chronic external exposure can cause burns, acute radiation sickness, and even death • NOAEL is 200 rads, and LOAEL is 350 rads • Risks at lower levels still exist, including increased cancer risks – Emergency Action Trigger • Water activity concentration limit above which a stop-use order is required is 4 mRem/yr (equivalent to 200 pCi/L) Return to Course Overview Slide 206 Other Relevant Information • Information reported from the incident • Operational information • Affected population information Return to Course Overview Slide 207 Consequence Analysis • Based on flow rate, mixing models for the Cs-137 in water, and the characteristics of the water system, the contaminant will spread to the nearest population center in 180 minutes • Based on the laboratory results, the concentration at the consumer’s tap is likely to be within 10 percent of 130 pCi/L. This level is at least 53 pCi/L below the beta particle activity MCL for Cs-137 • Although no general stop-use order needs to be issued, children should not use the water until the contamination can be remediated Return to Course Overview Slide 208