Improving the regulation of carcinogens by expediting cancer potency estimation

Learning from the law to address uncertainty in the precautionary principle

Environmentalists have advocated the Precautionary Principle (PP) to help guide public and private decisions about the environment. By contrast, industry and its spokesmen have opposed this. There is not one principle, but many that have been recommendedfor this purpose. Despite the attractiveness of a core idea in all versions of the principle--that decision-makers should take some precautionary steps to ensure that threats of serious and irreversible damage to the environment and public health do not materialize into harm--even one of the most widely endorsed principles needs considerable specification and refinement before it can be used. Moreover, the PP is an approach or guide to utilizing scientific evidence in social or legal decision-making contexts. In this it does not differ in kind from other approaches to using factual information such as in the law. The law provides some models for different strategies to guide decision-making under uncertainty when factual issues cannot be resolved with certainty. These in turn can help guide the formulation of different versions of PP and help clarify some presuppositions of the principle. Once some plausible versions of PP are articulated, I suggest some applications to existing environmental problems.

Potency equivalency factors for some polycyclic aromatic hydrocarbons and polycyclic aromatic hydrocarbon derivatives

Potency equivalency factors (PEFs) for cancer induction relative to benzo[a]pyrene have been derived for 21 polycyclic aromatic hydrocarbons (PAHs) and PAH derivatives based on a data preference scheme. PEFs have been derived only for PAHs with demonstrated carcinogenicity in bioassays. Cancer potency values and inhalation unit risks are presented for four additional carcinogenic PAHs based on expedited risk assessments conducted for California's Proposition 65. A much larger number of PAHs and PAH derivatives are considered mutagenic or genotoxic and may have limited evidence for carcinogenicity, but these compounds are not considered in this evaluation. New cancer bioassay data and possibly structure-activity analysis may indicate that additional PAHs are carcinogenic. Thus, additional PAHs may be identified as potential human carcinogens when such data become available. However, until that time the PEFs proposed for use in risk assessment were estimated only for PAHs currently classified as carcinogens.

Eggshell skulls and loss of hair from fright: some moral and legal principles that protect susceptible subpopulations

Some of the legislation authorizing the Environmental Protection Agency's (EPA) regulation of toxic substances, principles deeply embedded in our legal system, and some moral principles tend to support the claim that all of us, even the most susceptible, have equal standing to be protected from harms from toxic substances. Information about susceptible subpopulations should be part of risk assessment, either as default considerations or as a result of empirical research. Risk assessment is the step in a regulatory process where higher risks to sensitive subpopulations should be recognized regardless of the statute authorizing agency action. If we do not acknowledge susceptible subpopulations in risk assessment, this suggests that they do not have sufficient standing to be protected. Such a view would be unacceptable. However, because full protection for susceptible subpopulations might be costly, risk managers may have to be imaginative in finding regulatory options to provide these protections.