ANDREY KORCHEVSKIY, PhD, DABT, CIH, is director of research and development at Chemistry and Industrial Hygiene Inc. in Wheat Ridge, Colorado.
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The Safety Threshold: Understanding Risk Tolerances
The “safety threshold”—that is, the limit of our tolerance for risk—is an important determinant of human behavior. We are wired to filter our activities through reasonable frameworks of hazard acceptability. Experience and science show that there is no universal level of risk tolerance, which varies between individuals, groups, and societies.
Our personal safety threshold reveals itself subconsciously. We do not make mathematical calculations to decide how to act when facing risky situations. Some studies suggest that the propensity for risky behavior is embedded deeply in the human brain and might even be inherited; training can change it only to an extent. Other studies have convincingly shown that risky behaviors in the workplace are often driven by the environment, outside stimuli, and the culture of the organization.
Several years ago when I presented a risk assessment class at AIHce, I used a questionnaire to estimate each student’s safety threshold. Amazingly, the threshold was highest for people sitting in the first row and decreased according to distance from the presenter, with those at the furthest tables having the lowest thresholds. During our discussion of these results, it was suggested that cautious participants would choose seats that were less “exposed,” while more adventurous students would sit in the first row. Another theory was that people with higher safety thresholds would come to the class at the last minute, when only front-row seats were available. In any case, the safety threshold seems to be a useful metric for anticipating the outcomes of activities in various situations.
SOCIETY AND RISK A group of people may have a collective safety threshold that is greater or lesser than the thresholds of individual group members. For example, the risk of death from COVID-19 apparently reached the level of 1 case per 1,000 per year, but many people seemed to express an elevated tolerance by refusing the obvious protective measures. In such circumstances, society would benefit from better informing individuals about the probability of disease so they can self-regulate their own risk thresholds.
We do not make mathematical calculations to decide how to act when facing risky situations.
Especially dangerous is allowing groups to dictate elevated tolerances for their members and to engage in “risk shaming” of people with lower safety thresholds. OEHS professionals should determine if such pressure exists in the workplace and find ways to overcome this detrimental culture. But attempts to promote complete “intolerance” for risk, with “absolute” safety as a goal, are also ineffective because they may prevent society (and organizations) from correctly assessing and prioritizing hazards.
RISK BENCHMARKS FROM GOVERNMENT AGENCIES The risk benchmarks established by government agencies vary significantly. In the United States, OSHA relies on the Supreme Court’s “benzene decision,” which held that the probability of a fatal disease above one in a thousand in a lifetime should not be tolerated. EPA considers one-in-a-million lifetime risk as “so small as to be negligible” and treats the range from 1 to 100 cases per million as “reasonable risk.” The NIOSH Chemical Carcinogen Policy established a “risk management limit for carcinogens” of 1 in 10,000 cases per lifetime based on exposure during 45 years. The European Union’s REACH policy sets a risk tolerance limit of 1 case per 100,000 for workers and 1 case per million for the general population.
The recommended threshold should be utilized correctly. For example, EPA’s criteria refer to cases of fatal disease (usually cancer) that may occur over a whole lifetime, not in one year. Also, we need not always utilize agency-based recommendations when we establish quantitative safety thresholds. In many cases, baseline rates of disease in the general population can serve as a reasonable tolerance benchmark for disease cases.
THE RIGHT DECISIONS In the future, science will develop new tools for understanding the psychology of safety and measuring safety thresholds. In the meantime, we should become not more tolerant of risk but more knowledgeable and informed to make the right decisions when risks are faced.