Page 399 - Environment: The Science Behind the Stories

Risk Assessment and 1 in 6 Heart disease
Risk Management 1 in 7 Cancer

Policy decisions on whether to ban chemicals or restrict
their use generally follow years of rigorous testing for 1 in 29 Stroke
toxicity. Likewise, strategies for combating disease and
other health threats are based on extensive scientific 1 in 98 Motor vehicle incidents
research. However, policy and management decisions
also incorporate economics and ethics. And all too often, 1 in 109 Intentional self-harm
they are influenced by political pressure from powerful 1 in 126 Accidental poisoning
interests. The steps between the collection and interpreta- 1 in 163 Falls
tion of scientific data and the formulation of policy involve 1 in 321 Assault by firearms
assessing and managing risk. 1 in 1103 Drowning and submersion

1 in 1344 Exposure to smoke, fire, and flames
1 in 7178
We express risk in terms 1 in 97,807 Air and space transport incidents
Earthquakes, landslides, etc.
of probability 1 in 134,906 Lightning

Exposure to an environmental health threat does not invari-
ably produce some given effect. Rather, it causes some prob- Figure 14.17 Our perceptions of risk do not always match the
ability of harm, some statistical chance that damage will reality of risk. Listed here are several leading causes of death in
result. To understand a health threat, a scientist must know the United States, along with a measure of the risk each poses. The
more than just its identity and strength. He or she must also larger the area of the circle in the figure, the greater the risk of dying
know the chance that one will encounter it, the frequency from that cause. Note that the risk of death from motor vehicle inci-
with which one may encounter it, the amount of substance or dents is over 70 times that from air and space transport incidents.
degree of threat to which one is exposed, and one’s sensitiv- Data are for 2008 from Injury Facts, 2012, National Safety Council, Itasca, IL.
ity to the threat. Such factors help determine the overall risk
posed.
Risk can be measured in terms of probability, a quantita- and not exercising—voluntary activities statistically shown to
tive description of the likelihood of a certain outcome. The pose far greater risks to health.
probability that some harmful outcome (for instance, injury,
death, environmental damage, or economic loss) will result
from a given action, event, or substance expresses the risk
posed by that phenomenon. Risk assessment analyzes
risk quantitatively

Our perception of risk may not match reality The quantitative measurement of risk and the comparison of
risks involved in different activities or substances together are
Every action we take and every decision we make involves termed risk assessment. Risk assessment is a way to iden-
some element of risk, some (generally small) probability that tify and outline problems. In environmental health, it helps
things will go wrong. We try in everyday life to behave in ascertain which substances and activities pose health threats
ways that minimize risk, but our perceptions of risk do not to people or wildlife and which are largely safe.
always match statistical reality (Figure 14.17). People often Assessing risk for a chemical substance involves several
worry unduly about negligibly small risks yet happily engage steps. The first steps involve the scientific study of toxicity we
in other activities that pose high risks. For instance, most examined above—determining whether a substance has toxic
people perceive flying in an airplane as a riskier activity than effects and, through dose-response analysis, measuring how
driving a car, but according to a 2012 report by the National effects vary with the degree of exposure. Subsequent steps
Safety Council, a person’s chance of dying from an automo- involve assessing the individual’s or population’s likely extent
bile accident is 73 times higher than from an airplane crash. of exposure to the substance, including the frequency of con-
Psychologists agree that this difference between perception tact, the concentrations likely encountered, and the length of
and reality stems from the fact that we feel more at risk when encounter.
we are not controlling a situation and more safe when we are To assess risk from a widely used substance such as bis-
“at the wheel”—regardless of the actual risk involved. phenol A, teams of scientific experts may be convened to
This psychology may help account for people’s anxi- review hundreds of studies so that regulators and the public
ety over nuclear power, toxic waste, and pesticide residues can benefit from informed summaries. Between 2001 and
on foods—environmental hazards that are invisible or little 2012, the U.S. government sponsored three such panels on
understood and whose presence in our lives is largely outside BPA, and the American Plastics Council, an industry group,
our personal control. In contrast, people are more ready to sponsored two. The 2008 panel, sponsored by the govern-
398 accept and ignore the risks of smoking cigarettes, overeating, ment’s National Toxicology Program of the National Institute

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