76 CHAPTER 4 Risk Analysis and Environmental Health HazardsPercentYear102030400
1990 1995 2000 2005 2010Current smoking males
Current smoking femalesBased on data from Centers for Disease Control and Prevention 2011© Scott Camazine/Alamy a
bThere are several explanations for this type of think-
ing. One is that most of the decisions we make about risks
are based on habit and culture, not analysis. Indeed, it
would take far too much time and effort to apply anal-
ysis to all risk decisions. Fortunately, culture can shift
peoples’ habits over time. For example, the number of
adolescents in the United States who smoke has dropped
over the past two decades (Figure 4.3b).
Several factors determine which risks we are con-
cerned about. One is trust in institutions—when people
believe that business and government are managing risks,
they are less concerned about them. Another is that we
find some risks—such as dying from cancer—to be more
dreadful than others—such as car accidents. We worry
more about risks that we dread, even when analysis sug-
gests they are less common. Similarly, we are more con-
cerned about risks that are unfamiliar and those that we
don’t feel we can control.- What are risk and risk assessment?
- What are the four steps of risk assessment?
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a. Cancer was diagnosed in the right lung of this 73-year-old
woman (shown by the red areas) after years of heavy smoking,
a high-risk behavior. b. Data suggest that smoking is on the
decline among younger people, although the poor and some
minority groups have disproportionately high smoking rates.
Percentage of U.S. students (grades 9–12) who smoked
cigarettes on at least 1 or 2 of the past 30 days (CDCP 2011).containing traces of the cancer-causing chemical trichlo-
roethylene (in amounts permitted under Environmental
Protection Agency [EPA] limits). Without knowledge of
risk assessment, this person might buy bottled water in
an attempt to reduce his or her chances of getting can-
cer. Based on risk assessment calculations, the annual
risk of death from smoking is 0.00059, or 5.9 10 ^4 ,
whereas the annual risk from drinking water with EPA-
accepted levels of trichloroethylene is 0.000000002, or
2.0 10 ^9. This means that this person is almost 300,000
times more likely to get cancer from smoking than to get
it from ingesting such low levels of trichloroethylene
( Figure 4.3a). Knowing this, the person in our example
would, we hope, stop smoking.
A dilemma that makes risk management a chal-
lenge is that risk experts and nonexperts often dis-
agree about which risks are most worrisome. Experts
are often surprised when people seem to be far more
concerned about small risks, such as those from exposure
to small doses of a chemical, than about large risks, like
those associated with obesity and smoking. We know, for
example, that the average life expectancy of smokers is
more than eight years less than that of nonsmokers, and
almost one-third of all smokers die from diseases created
or exacerbated by tobacco smoke.Interpreting Data
In what year did smoking peak
among males? Among females?