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Unit 6: Risk, Exposure, and Health // Section 8: Risk Perception


Expert assessments and public perceptions of risk are not always the same. Decision makers need to understand factors that influence how people understand and interpret risk information for several reasons. First, public concerns may influence research and development priorities, such as which chemicals to analyze in toxicity studies. Second, individual behavior choices are guided by risk avoidance, so if experts want people to avoid certain risks, they need to understand whether the public sees those actions as dangerous. If the public views a risky activity as benign, officials may have to develop public-education campaigns to change those perceptions. Current examples include labels warning about health risks on cigarette packages and alcoholic beverage containers.

Behavioral and social scientists have compared risk perceptions among many different groups, including scientists' views compared to those of laypersons, men compared to women, and differences among diverse ethnic and economic groups. One finding is that the general public overestimates the prevalence of some risks (such as those lying above the straight line in Fig. 14) and underestimates others (those lying below the line).

Relationship between judged frequency and actual number of deaths per year

Figure 14. Relationship between judged frequency and actual number of deaths per year
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Source: Scope Report 27 - Climate impact assessment, Chapter 16, Figure 16.5, ed. by RW Kates, JH Ausubel, and M Berberian. J Wiley & Sons Ltd, UK (1985). Adapted from: Slovic et al. Rating the risks. Environment, 21(3) 14-39 (1979).

Laypeople judge risks differently from technical experts because they give greater weight to factors such as the potential for catastrophic damage, the likelihood of threats to future generations, and their own sense of whether they can control the risk. This can be seen in Table 4, which shows how technical experts and several sets of laypeople ranked the risk from a list of activities and technologies. Note, for example, that the expert group was much less worried about nuclear power but more worried about x-rays than laypeople. Both involve radiation exposure, but x-rays may have seemed less risky to the non-specialists because the scale of an x-ray is much smaller than a nuclear reactor accident and because people usually have a choice about whether to undergo x-rays.

Table 4. Perceived risk for 30 activities and technologies Source: Source: Paul Slovic et al., "Rating the Risks," Environment, vol. 21, no. 3 (1979).
Activity or technology League of Women Voters College students Active club members Experts
Nuclear power 1 1 8 20
Motor vehicles 2 5 3 1
Handguns 3 2 1 4
Smoking 4 3 4 2
Motorcycles 5 6 2 6
Alcoholic beverages 6 7 5 3
General (private) aviation 7 15 11 12
Police work 8 8 7 17
Pesticides 9 4 15 8
Surgery 10 11 9 5
Firefighting 11 10 6 18
Large construction 12 14 13 13
Hunting 13 18 10 23
Spray cans 14 13 23 26
Mountain climbing 15 22 12 29
Bicycles 16 24 14 15
Commercial aviation 17 16 18 16
Electric power (nonnuclear) 18 19 19 9
Swimming 19 30 17 10
Contraceptives 20 9 22 11
Skiing 21 25 16 30
X-rays 22 17 24 7
High school/college football 23 26 21 27
Railroads 24 23 29 19
Food preservatives 25 12 28 14
Food coloring 26 20 30 21
Power mowers 27 28 25 28
Prescription antibiotics 28 21 26 24
Home appliances 29 27 27 22
Vaccinations 30 29 29 25

Other factors can influence how both experts and laypeople perceive risks. Paul Slovic and other behavioral researchers have found that many Americans stigmatize certain industries, especially nuclear power and chemicals, which are widely viewed as repellent, disruptive, and dangerous. Conversely, scientists who work for industry tend to see chemicals as less threatening than do government and academic researchers (a phenomenon called affiliation bias). Ultimately, they argue, all groups bring their own assumptions to bear on discussions of risk.

Communicating risk information to the public is an important part of risk management. In the early decades of environmental regulation, public communication often took what critics called the "decide, announce, defend" approach: agencies developed policies and released their final results to the public and regulated industries. But since risk analysis involves many uncertainties, assumptions, and judgments, it requires policy makers to explain clearly how decisions are reached—especially if the issue involves risks that laypeople perceive differently from scientific experts.

Often effective risk communication means involving the public in the decision process, not just informing people at the end. Public involvement in risk decisions can take many forms. In early planning stages, it can help regulators identify the issues that citizens care most about, how much risk they will tolerate, and what they view as acceptable mitigation costs. Stakeholders may also take part in implementing decisions. For example, the Defense and Energy Departments have formed community advisory boards to help make decisions about cleaning up contaminated military bases and nuclear weapons production sites.

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