Against "individual risk": a sympathetic critique of risk assessment.

• Jurisdiction: United States
• Author: Adler, Matthew D.
• Date: 01 March 2005

INTRODUCTION I. RISK ASSESSMENT: A PRIMER A. History and Structure B. What Is Risk? The Frequentist Answer II. RISK REGULATION AND "INDIVIDUAL RISK": A SURVEY OF GOVERNMENTAL PRACTICE A. "Individual Risk" and Agency Practice: The Environmental Protection Agency 1. Cancer Risk Assessment and "Individual Risk" a. Air pollution (Clean Air Act section 112) b. Water pollution (Clean Water Act and Safe Drinking Water Act) c. Solid waste (RCRA and CERCLA) d. Pesticides (FIFRA and FQPA) e. Toxic Substances Control Act f. Title VI 2. Risk Assessment of Noncarcinogens B. "Individual Risk" and Agency Practice: Other Agencies 1. The Food and Drug Administration 2. The Occupational Safety and Health Administration 3. The Nuclear Regulatory Commission 4. The Consumer Product Safety Commission C. Beyond "Individual Risk": "Population Risk" in Agency Practice III. FREQUENTIST RISK AND WELFARIST CONSEQUENTIALISM A. Welfarist Consequentialism: Some Clarifications B. The Ex Post Question: Does "Individual Risk" Degrade Outcomes? C. The Ex Ante Question: Should Frequentist Risk Play a Role in the Choices of the Welfare-Consequentialist Regulator? IV. FREQUENTIST RISK AND BAYESIAN RISK: ARE THEY REALLY DIFFERENT? V. BEYOND WELFARISM: FREQUENTIST RISK AND NONWELFARIST VIEWS A. Safety-Focused Consequentialism B. Deontological Views C. Contractualist Views D. Democratic Views VI. RISK ASSESSMENT AND POPULATION SIZE CONCLUSION INTRODUCTION

EPA's decision to list a carcinogenic substance as a "hazardous waste," subject to stringent regulation under the Resource Conservation and Recovery Act, depends on the fatality risk that the substance would impose upon highly exposed individuals if discarded in unregulated landfills. If this risk exceeds 1 in 10,000, the substance is listed. (1) EPA's rule for cleanups under the Superfund statute is similarly risk-based: toxic waste dumps are to be remedied so that the lifetime fatality risk to the "maximally exposed individual" from carcinogens in the dump is within the range of 1 in 10,000 to 1 in 1 million. (2) FDA has traditionally used a 1 in 1 million threshold in determining whether carcinogenic food constituents exempt from the Delaney Clause pose a de minimis safety threat to consumers and thus should be permitted to enter or remain in the food supply. (3) OSHA, which is statutorily authorized to regulate workplace toxins that pose "significant" threats to safety, is more permissive than FDA and EPA but also focuses, in part, on individual fatality risks: the agency has generally followed the rule that carcinogens creating more than a 1 in 1000 risk for any worker are "significant," for statutory purposes, and that toxins creating a substantially smaller risk are not. (4)

In all these cases, health and safety agencies have decided to key regulatory choices to the level of "individual risk" (specifically, the "individual risk" to the maximally exposed individual or some similar construct) without any explicit statutory mandate to do so. But such mandates do exist. A salient one: when Congress in 1990 overhauled section 112 of the Clean Air Act, the section covering carcinogens and other "hazardous air pollutants," it put in place a hybrid regulatory regime that first requires polluters to use the best currently available technology for reducing emissions, and then requires EPA to consider promulgating yet more stringent emissions standards if "excess cancer risks to the individual most exposed to emissions ... [exceed] one in one million." (5) The 1 in 1 million risk level is also invoked in another provision of the amended Clean Air Act. (6) And when the legislative regime for pesticide licensing was reworked in 1996 (7)--the ban on certain carcinogenic pesticides was replaced with a "reasonable certainty [of] no harm" (8) standard both for possible carcinogens and for pesticides that might cause other toxic effects--the official House Committee report explained that this new statutory standard ought to be construed as an "individual risk" test:

[T]he Committee expects ... that a [pesticide] tolerance will be considered to provide a 'reasonable certainty of no harm' if any increase in lifetime risk, based on quantitative risk assessment using conservative assumptions, will be no greater than 'negligible.' ... [A] negligible risk [is] a one-in-a-million lifetime risk. (9) In short: individual fatality risk plays a major role in our current system of health and safety regulation. Some examples have just been provided. Many more will be furnished below. In particular, "individual risk" is absolutely central to federal regulation of toxic chemicals. EPA employs an "individual risk"-based approach in administering all of its major statutes: the Clean Air Act (which addresses toxins present in air), the Clean Water Act and Safe Drinking Water Act (toxins in water), the Resource Conservation and Recovery Act and the Comprehensive Environmental Response, Compensation, and Liability Act (toxins that leach into the ground from waste sites), the Federal Insecticide, Fungicide, and Rodenticide Act (toxic pesticides), and the Toxic Substances Control Act (a backup statute authorizing EPA to take measures not authorized by the media-specific statutes). (10) FDA and OSHA follow a similar approach, as we have seen. But the focus on "individual risk" is not limited to toxins, or to federal agencies. For example, the Nuclear Regulatory Commission (NRC) has long taken the position that the ultimate safety goals governing its licensing and regulation of nuclear power plants partly concern the "individual risk" of immediate death, resulting from an accidental release of radiation, incurred by the average person living near a plant. (11) FDA sets acceptable levels of microbial contaminants in foods with reference to the "individual risk" of illness of a high-end consumer. (12) Although OSHA traditionally focuses on aggregate fatalities or lost days of work in regulating workplace conditions that cause injury (as opposed to illness), it has recently begun to consider the "individual risk" of injury--the rate at which workers in particular industries are injured by electric shock, falls, explosions, fires, and other such industrial accidents. (13) And environmental agencies in some states have followed EPA's lead and employ "individual risk" tests in regulating toxins. (14)

What accounts for this regulatory focus on "individual risk"? One answer is tempting, but wrong. The temptation is to say that regulatory agencies inevitably take the maximal level of "individual risk" as the test of safety, at least for substances and activities that cannot be removed from our lives without massive cost. Many, many chemicals cause cancer to animals at large enough doses, and can be predicted to cause some human deaths at actual doses in a sufficiently large group. (15) How else to determine which toxic exposures merit a regulatory response except by setting an "individual risk" threshold which seems very low--say, 1 in 1 million to the maximally exposed individual-and taking that as the trigger for regulatory intervention? But this response overlooks a crucial deficit in "individual risk" tests of this kind: their insensitivity to population size. Compare an isolated toxic waste dump that (under worst-case modeling) leaches contaminants to a radius of ten miles, affecting a population of 10,000; a workplace toxin employed in certain industries, to which one million workers are exposed; and a chemical in drinking water that is consumed by 100 million. For simplicity, assume that in each case every person in the exposed population incurs a 1 in 1 million risk of dying from the hazard. Then in the waste-dump case it is overwhelmingly likely that the hazard will cause no fatalities; in the workplace case it is reasonably likely that the hazard will cause one or more fatalities, with one incremental death the expected outcome; and in the drinking-water case it is overwhelmingly likely that the hazard will cause one or more fatalities, with 100 incremental deaths the expected outcome. (16)

Risk assessors typically distinguish between "individual risk"--the risk of death borne by a particular individual, either a named person or someone identified by her exposure characteristics--and "population risk." (17) "Population risk" (also sometimes called "societal risk") is the total number of fatalities resulting from a toxin, a hazardous activity, or some other threat to human life. To quote a leading textbook on risk assessment:

[Risk assessments typically] include several common measures of individual and societal risk, in particular:

* Individual risk, which is the probability of a specified individual dying prematurely as a result of exposure to the risk agents....

* Individual risk contours show the geographical distribution of individual risk....

* Maximum individual risk is the individual risk to the person experiencing the highest risk in the exposed population....

....

* Various measures of societal risk, such as ... the expected number of fatalities as a function of location or population subgroup.... (18)

Regulatory agencies might use the level of "population risk," rather than the level of "individual risk," as their measure of health and safety. (19) This is true both for agencies operating under statutes that accord high priority to the avoidance of death, illness, and injury, as opposed to other goals, as well as for agencies operating under cost-benefit statutes or other "balancing" statutes that permit a wider array of considerations to trump the goal of physical integrity. (20) Indeed, as we shall see, federal programs concerned with safety rather than health hazards generally seem to focus on "population risk" rather than "individual risk," and even health threats such as toxins, radiation, and pathogens are sometimes regulated with reference to "population risk." (21)

So the question just posed...