VIEWS: 8 PAGES: 31 POSTED ON: 8/18/2012
Chemical Hazard Communication Chemistry 550 Be a Scout: Be Prepared Chemical Risk Assessment Process • Identify chemical-using activities • Identify chemicals • Gather hazard information • Evaluate hazards and appropriate controls relative to usage Chemical Risk Assessment Identify Chemical-Using Activities Chemical Risk Assessment Identify Chemicals • Chemical Inventory: Required by CHP Used for compliance with other regulations Source of info during emergency response Identify specific safety & health concerns (monitoring for exposure, time-sensitives) Useful for finding small amounts of a material (waste reduction) Chemical Risk Assessment Gather Hazard Information: Sources • Merck Index: chemical structure, CAS#, technical references, physical data • Sax: chemical formula, toxicity data, safety • Hawley’s Condensed Chemical Dictionary: physical properties, chemical formula, hazards, uses • Material Safety Data Sheet (MSDS) Hazard Evaluation What is my risk? • Factors: Specific activity: heating, increased pressure? Type and amount used Duration & frequency of usage Controls used: engineering, administrative, PPE • Written SOPs have to be thorough and be followed by everybody • Always be looking for a safer way! Material Safety Data Sheet: A Key Hazard Evaluation Tool • Probably the best “one-stop” source for information of all aspects of chemicals. • Hard copy, vendor-specific for every chemical used – use EH&S website to locate • No good unless they are used and interpreted relative to use. • Nuances MSDS Chemical Identity Physical Data Physical & Health Hazards Signs & Symptoms of Exposure Permissible Exposure Limits Procedures for safe handling and use (e.g., PPE, engineering controls, storage, spills) Control Measures Emergency and First Aid Contact Information Hazard Assessment 2 Major Classification Schemes Physical Hazards: flammable/combustible liquids, compressed gases, explosives, organic peroxides, oxidizers, pyrophorics, unstables, water reactives. 14 Bleach 12 Aqueous ammonia 10 Milk of magnesia Borax Baking soda solution 8 Sea water pH Blood Pure Water Milk 6 Black coffee 4 Tomatoes Wine Vinegar 2 Lemon juice Stomach fluids Battery acid 0 100 10-2 10-4 10-6 10-8 10-10 10-12 10-14 Proton or hydronium ion concentration [H3O+] in moles per liter Flashpoint • The minimum temperature at which a liquid gives off a vapor in sufficient concentration to ignite under specific test conditions. • Examples: – gasoline, - 45oF – mineral spirits, 102oF to 110oF Vapor Pressure • Pressure exerted by a saturated vapor above its own liquid in a closed container. • Expressed as pounds per square inch (psig or psia), or millimeters of mercury (mmHg). • Vapor pressure increases with temperature • 1atm = 760mmHg = 29.92”Hg = 14.7psi • The lower the boiling point of a substance, the higher its vapor pressure Table 5. Vapor pressure of select compounds* Material Vapor pressure (mm Hg) parathion (insecticide) 0.00004 sulfuric acid 0.001 Slow evaporation elemental mercury 0.0012 mineral oil mist < 0.5 kerosene 5.0 octane 10.0 Moderate evaporation water 18.6 gasoline 38 - 100 Fast evaporation chlorine 5,200 Gas at standard conditions * at standard (room) temperature and pressure Evaporation Rate • FAST evaporating if greater than 3.0. – Examples: Acetone = 5.6, Hexane = 8.3. • MEDIUM evaporating if 0.8 to 3.0. – Example: 190 proof Ethyl Alcohol = 1.4. • SLOW evaporating if less than 0.8. – Examples: Water = 0.3, Mineral Spirits = 0.1. Stability and Reactivity Data • Incompatibilities – important for usage and storage • Water – important in fire-fighting situations • Heat – relationship with pressure/volume • Oxidizers – non-flammable but make combustion possible or faster Physical Hazards Flammables • Definitions: flammables/ combustibles • Eliminate ignition sources • 10 gallon/40 liter limit • Store away from oxidizers or other incompatibles • Use approved refrigerators • Make sure fire extinguishers are available Physical Hazards Reactives • Explosives, pyrophorics, oxidizers, air/water reactives • Peroxide-formers: date containers; test opened containers every six months; test unopened containers prior to expiration date. Hazard Assessment 2 Major Classification Schemes Health Hazards: carcinogens, corrosives, toxics/highly toxics, reproductive toxins, irritants, sensitizers, target organs Acute & Chronic Health Effects • Acute – immediate, short duration; examples: nausea, dizziness, headache, irritation • Chronic – long term; carcinogenicity, asbestosis • Signs & symptoms of overexposure Dose-Response Curve • Fundamental tenet of toxicology • Key concept to understand for the assessment of health hazards. • “As the dose increases, so does the response” • What kinds of responses? (signs & symptoms of exposure) • Benefits versus risks of chemical exposure - pharmaceuticals Health Hazards Toxic/Highly Toxic LD50 (milligrams toxin per kilogram of body weight). A lower LD50 value means that it is more harmful (toxic). LC50 (milligrams toxin per cubic meter of air or in parts per million). A lower LC50 value means that is more harmful (toxic). Table 3. Probable Lethal Dose for Humans Toxicity Animal LD50 Lethal Dose When Ingested Rating (per kg) by 70-kg (150lb) Human extremely toxic <5mg less than 7 drops highly toxic 5-50mg 7 drops to 1 teaspoonful moderately toxic 50-500mg 1 teaspoonful to 1 ounce slightly toxic 500-5,000mg 1 ounce to 1 pint practically nontoxic above 5,000mg above 1 pint Source: Prudent Practices in the Laboratory, 1995 Table 4. Lethal dose and lethal concentration examples Compound Animal Route LD50/LC50 Ethanol Rat Inhalation 20,000ppm Ascorbic Acid Rat Oral 11,900mg/kg Acetone Rat Oral 5,800mg/kg Acetic Acid Rat Oral 3,310mg/kg Aspirin Rat Injection 1,450mg/kg Formaldehyde Rat Oral 800mg/kg Atrazine (herbicide) Rat Oral 672mg/kg Phenol Rat Oral 317mg/kg Health Hazards Carcinogens • Cause cancer • Designated area • Require prior approval along with materials that are reproductive toxins • Make sure signs are in place Health Hazards Corrosives / Irritants • Wear appropriate PPE that protects eyes and exposed skin – know where emergency equipment is located. • Always add acid to water • Have calcium gluconate gel available when working with HF • Distinction with “irritants”. Health Hazards Sensitizer • Repeated contact with material causes heightened response • Metals, aldehydes Health Hazards Target Organ Effects • Hepatotoxins – liver; carbon tetrachloride • Nephrotoxins – kidneys; halogenated hydrocarbons • Neurotoxins – nerve; mercury • Hematopoietic – blood; CO • Pulmonary – lungs; asbestos • Reproductive (including teratogens) – embryo or fetus; DBCP • Cutaneous – skin; ketones • Eye - acids Exposure Limits Maximum levels considered safe for most people when exposed 8 hr/day, 40 hrs/wk, 50 wks/yr, over a lifetime TWAs • PEL – OSHA (Law) • REL – NIOSH (Guide) • TLV – ACGIH Other designations (Guide) • STEL • Ceiling (C) • "Skin" • IDLH Conducting a Chemical Hazard Evaluation. Next Time!