Human Health &
Environmental Hazards
Chapter 18
Hazards to Human Health
• Environmental risk analysis is the
comparing of the risk of a situation to its
related benefits.
• It is the overall process that allows one to
evaluate and deal with the consequences
of events, based on their probability.
• There are four classes of risk
Classes of Human Health Risks
• High risk – behavior that has
potential life and death
consequences. Ex; smoking or
driving while intoxicated.
• Low risk – infrequent events that
may have large consequences
such as an earthquake on the East
Coast of the US
Classes of Human Health Risks cont.
• Very low risk – events that have
never occurred in recorded history,
such as a major meteor striking the
US.
• Mixed risk – outcomes that
increase in frequency against a
background of occurrences, such
as additional cases of cancer
beyond that normally expected.
Risk Analysis
• Three problems arise in risk analysis:
– Lack of information leads to uncertainty.
– Complexity of the information often leads to
confusion.
– Failure to interpret uncertainty and confusion.
• External influences are factored into
decisions:
– Public concern
– Economic interest
– Legislative actions
Risk Analysis cont.
• Risk analysis is divided into risk assessment
and risk management.
• Risk assessment is an objective estimation of
risk. It includes:
– Identification of hazards
– Dose-response assessment
– Exposure assessment
– Risk characterization
• Risk management is the process of
determining what to do about risk.
Risk Management Strategies
• Market-based – relies on market forces to
provide indirect controls. Usually the
response from industry.
• Hierarchical – relies on explicit controls
and top-down management styles (gov.,
laws, etc.) Response from legislators.
• Sectarian – relies on emotions. Response
from citizens.
• Rational – relies on logic & facts in decision
making. Response from researchers.
Acute and Chronic Effects
• Acute Health Effects:
– Characterized by sudden and sever exposure.
– Normally, a single large exposure is involved.
– Health effects are often reversible
– Ex. Carbon monoxide poisoning
• Chronic Health Effects:
– Characterized by prolonged or repeated
exposures over long time periods.
– Symptoms may not be immediately apparent
– Health effects are often irreversible
– Ex. lead or mercury poisoning, asbestos.
Dose-Response Relationships
• Describe the change in effect on an organism
or a population caused by differing levels of
exposures (doses) to a substance (stressor).
• These may apply to individuals (small amount has
no observable effect; large amount is fatal) or to
populations (how many people are affected at different
levels of exposure).
• These relationships are used to determine
whether various environmental risks are safe
or hazardous. “All substances are poisons: there is none
which is not a poison. The right dose
differentiates a poison and a remedy.”
Paracelsus (1493-1541)
Dose-Response Curve
• A graph that relates
the amount of a
substance given (x-
axis) compared with
the response (y-axis)
• The point where the
response is first
observed is the
threshold dose.
LD50
• The median lethal dose of a pollutant or drug
that kills half the members of a tested
population within fourteen days.
• Usually expressed as the mass of substance
administered per unit mass of test subject,
such as milligrams per milligram of body
weight.
– Allows the relative toxicity of different
substances to be compared
– Normalizes for the variation in the size of
the animals exposed.
LD50 Dose
Air Toxics
• A group of air pollutants that are known or
suspected to cause serious health
problems.
• People exposed to air toxics at sufficient
concentrations and durations may have an
increased chance of developing cancer,
damage to the immune system, neurological
problems, reproductive problems,
developmental problems, and respiratory
problems.
Air Toxics cont.
• Asbestos –
– Breathing asbestos fibers can lead to an
increased risk of:
• Lung cancer
• Mesothelioma – a cancer of the lining of the chest and
the abdominal cavity
• Asbestosis – the lungs become scarred with fibrous
tissue.
– The risk of lung cancer is greater for smokers.
– The symptoms of these diseases do not usually
appear until about twenty to thirty years after
the first exposure.
Air Toxics cont.
• Carbon Monoxide (CO) –
– Enters the bloodstream through the lungs and binds
chemically to hemoglobin (that carries oxygen to cells)
– Causes slower reflexes, confusion, and drowsiness.
– Reduces visual perception and coordination and
decreases the ability to learn.
– People with cardiovascular disease are most at
risk from exposure to CO
• They may experience chest pain and other
cardiovascular symptoms if exposed.
Air Toxics cont.
• Indoor Air Pollutants –
– Health effects may be acute and experienced
soon after exposure or they may be chronic.
– Symptoms may include headaches, dizziness,
fatigue, and irritation of the eyes, nose, and
throat, and are usually short term and treatable.
– Immediate reactions to indoor pollutants depends
on age, preexisting medical conditions, and
individual sensitivity.
– Immediate effects are similar to colds or other
viral diseases.
– Long-term exposure may include some
respiratory diseases, heart disease and cancer.
Air Toxics cont.
• Lead (Pb) –
– Exposure to lead can occur through inhalation of
air and ingestion of lead in food, water, soil, or
dust.
– Excessive lead exposure can cause seizures,
brain and kidney damage, mental retardation,
and/or behavioral disorders.
– Children six and under are most at risk because
their bodies are growing quickly.
Air Toxics cont.
• Nitrogen Dioxide (NO2)
– Symptoms include coughing, wheezing, and
shortness of breath in children and adults with
respiratory disease such as asthma.
– Even short exposures can affect lung function
and may cause permanent structural changes
in the lungs.
Air Toxics cont.
• Ozone (O3) –
– Ozone damages lung tissue, reduces lung
function, and sensitizes the lungs to other irritants.
– Exposure for several hours at relatively low
concentrations has been found to significantly
reduce lung function and induce respiratory
inflammation in normal, healthy people during
exercise.
– Decreased lung function is generally
accompanied by symptoms including chest
pain and pulmonary congestion.
Air Toxics cont.
• PM10 – (suspended particulate matter - <10 μm)
– Can increase susceptibility to respiratory infections
and can aggravate existing respiratory diseases
(such as asthma and chronic bronchitis).
– When exposed, people with existing heart or lung
diseases are at increased risk of premature death.
(Older persons are especially sensitive to exposure).
– Children and people with existing lung disease
may not be able to breath as deeply or
vigorously as they normally would and may
experience symptoms such as coughing and
shortness of breath.
Air Toxics cont.
• Sulfur Dioxide (SO2) –
– High concentrations of sulfur dioxide affect
breathing and may aggravate existing
respiratory and cardiovascular disease.
– Sensitive populations include asthmatics,
individuals with bronchitis or emphysema,
children, and the elderly.
Smoking
• Cigarette smoke contains over 4,700
chemical compounds including 60 known
carcinogens.
• Responsible for more than 85% of lung
cancers and is also associated with cancers
of the mouth, pharynx, larynx, esophagus,
stomach, pancreas, kidney, bladder, and
colon as well as leukemia.
Smoking cont.
• There are links to increased risk of
cardiovascular diseases (including stroke),
sudden death, cardiac arrest, and peripheral
vascular disease.
• Smoke irritates the lining of the respiratory
system resulting in increased bronchial
mucus secretion and chronic decreases in
pulmonary function.
Hazardous Chemicals in the Environment
• A hazardous waste is a waste with properties
that make it dangerous or potentially harmful
to human health or the environment.
• They can be liquids, solids, contained gases,
or sludges.
• The Environmental Protection Agency (EPA)
has separated hazardous wastes into 7
categories.
Hazardous Waste Categories
• Corrosive – are strong acids or strong
bases that are capable of corroding metal
containers, such as storage tanks, drums,
or barrels. Ex. battery acid.
• Discarded Commercial Products –
specific commercial chemical products in an
unused form. Some pesticides and some
pharmaceutical products become
hazardous wastes when discarded.
Hazardous Waste Categories cont.
• Ignitable – can create fires under certain
conditions, are spontaneously
combustible, or have a flash point less
than 140◦F (60◦C).
Ex.- waste oils and used solvents.
• Nonspecific Source – include wastes
from common manufacturing and
industrial processes, such as solvents that
have been used in cleaning or
degreasing operations.
Hazardous Waste Categories cont.
• Reactive – unstable under normal
conditions. They can cause explosions, toxic
fumes, gases, or vapors when heated,
compressed, or mixed with water.
Ex. – lithium batteries and explosives.
• Source Specific – wastes from specific
industries, such as petroleum refining or
pesticide manufacturing. Ex. – sludges
and wastewaters from treatment and
productions processes.
Hazardous Waste Categories cont.
• Toxic – harmful or fatal when ingested or
absorbed. They may contain mercury or
lead for example. When toxic wastes are
land disposed, contaminated liquid may
leach from the waste and pollute
groundwater.
Hazardous Waste Cleanup
Reduction and cleanup of hazardous wastes
can occur by:
• Producing less waste
• Converting the hazardous material to less
hazardous or non-hazardous substances
• Placing the toxic material into perpetual
storage.