Public Risks from Chemical Exposures

Chemical exposures are not always private. But the ingredients for optimal private exposure also pertain to public exposure basic knowledge about the effects of exposure on healfh, dissemination of that knowledge, the transaction costs of becoming informed about numerous exposure risks, equity considerations, and struggles between emitters and emittees. This chapter does not repeat the discussions of Chapter 3 but discusses the additional considerations relevant to managing public exposures. 

The main difference between public and private chemical exposures is that the level of public exposures must be equal for all those in the same airshed or watershed. That, of course, eliminates the primary method of reducing conflict associated with private goods individual differences in consumption. 

Although people consume identical amounts of air and water pollution, individuals could differ in their contributions to the collective outcome if an emissions-rights market existed. On the other hand, bureaucratic regulations could attempt to duplicate the results of an emissions markef. Finally, class-action torts could serve as either a substitute or a supplement. 

Public chemical exposures, by definition, cause everyone to consume the same ambient exposure. What should that exposure level be Because the harms from chemical exposure are collectively consumed, the efficient level is that which equates the sum of the marginal harms among those exposed with the marginal benefits of firms thaf emif (Samuelson 1954). Emissions reductions should occur until the abatement costs equal the sum of fhe amounfs that exposed people would pay to avoid (or be willing to accept in compensation for exposure to) a similar known risk in a market setting (Viscusi 1989a Broome 1978). 

The main difficulty with both the too-many and too-few emis-sions-rights scenarios, however, is the collective nature of the benefits. Let us first examine the too-many scenario. 

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Managing Public Risks from Chemical Exposures... 

Refer to the handbook s Glossary. The definitions provided are universally recognized. Many of these terms are not just pertinent to inhalation hazards. It would be remiss not to mention other risks beyond inhalation from chemical exposure in a work environment and to the general public. 

This causes two problems in cancer-risk policy. First, because the public (and, hence, policymakers) worries about small levels of increased cancer risk resulting from chemical exposures, the number of subjects required to differentiate small risks from zero risk is enormous, which makes the studies prohibitively expensive. Second,... 

Because of the ethical and legal restrictions on the exposure of humans to chemicals, and the limitations and uncertainties inherent in using information from available human exposure data, animal experiments are used to characterize the hazard, to determine the toxicity, for most chemicals. This necessity places many toxicologists (scientists who study and assess the risks from chemicals) in a very difficult position, between a rock and a hard place the public expects drugs to be safe and insists on knowing the adverse effects of chemicals to which they may be exposed, and at the same time many people demand an end to experiments on animals. 

This is a philosophical as well as a social issue. At present there may be no socially acceptable risk from chemicals similar to the acceptable risks from food-borne infections, occupational injuries, or injuries incurred around the home. The public often occupies an extremist position - from "It can t hurt you I ve bathed in it," to "I don t care what you say, I don t want any exposure I want zero risk."... 

In some instances ADRs may be more specifically related to drug or chemical exposure some examples of these are shown in Table 2. From this latter table note that there are some very common problems with a relatively lower drug relatedness at the bottom, but these constitute a numerically higher public health risk. 

The TOCDF QRA estimates the risk to the public and workers from accidental releases of chemical agent associated with all activities during storage at DCD and throughout the disposal process at the TOCDF. The HRA, which was conducted by the Utah Division of Solid and Hazardous Waste (Department of Environmental Quality), is a screening analysis to estimate possible off-site human health risks associated with exposure to airborne emissions from the TOCDF under normal and upset conditions. The HRA also estimates risks to wildlife and the environment. 

In many respects, the foundations and framework of the proposed risk-based hazardous waste classification system and the recommended approaches to implementation are intended to be neutral in regard to the degree of conservatism in protecting public health. With respect to calculations of risk or dose in the numerator of the risk index, important examples include (1) the recommendation that best estimates (MLEs) of probability coefficients for stochastic responses should be used for all substances that cause stochastic responses in classifying waste, rather than upper bounds (UCLs) as normally used in risk assessments for chemicals that induce stochastic effects, and (2) the recommended approach to estimating threshold doses of substances that induce deterministic effects in humans based on lower confidence limits of benchmark doses obtained from studies in humans or animals. Similarly, NCRP believes that the allowable (negligible or acceptable) risks or doses in the denominator of the risk index should be consistent with values used in health protection of the public in other routine exposure situations. NCRP does not believe that the allowable risks or doses assumed for purposes of waste classification should include margins of safety that are not applied in other situations. 

Toxicity is the inherent ability of a chemical to cause injury. It is a property of th,e molecule and does not change. Hazard, on the other hand, involves toxicity but also involves exposure. And exposure involves many factors, some of them difficult to quantify. However, it can be said that hazard is the probability that a chemical will cause injury. The distinction between toxicity and hazard is often omitted in public discussions of risk from the use of herbicides in the forest. 

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