Assessing Exposures and Reducing Risks to ... - ACS Publications

Chapter 8

A Reality Fix for Risk Managers 1

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Downloaded by PENNSYLVANIA STATE UNIV on July 5, 2012 | http://pubs.acs.org Publication Date: February 1, 2007 | doi: 10.1021/bk-2007-0951.ch008

John H . Ross , JJeffrey H. Driver , and Robert I. Krieger

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infoscientific.com, Inc., 5233 Marimoore Way, Carmichael, C A 95608 infoscientific.com, Inc., 10009 Wisakon Trail, Manassas, V A 20111 Personal Chemical Exposure Program, Department of Entomology, University of California, Riverside, C A 92521 2

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Human health risk assessment is the process of comparing hazard to exposure. In its quantitative form, human health risk analyses represent the systematic evaluation of the likelihood of an adverse effect arising from exposure within a defined population. Predictive human exposure and health risk analyses include uncertainties and often widely differing degrees of conservative bias. In the absence of the benefit of transparent and quantitative disclosure of variability and uncertainty, risk managers may be faced with making decisions on the basis of risk assessments that are significantly biased by the "Precautionary Principle,." with the philosophy that it is better not to allow the proposed use of a chemical than risk uncertain but possibly very negative consequences. In order to understand the uncertainties and conservative biases, it is useful to compare alternative risk management policies. For example, potential health risks associated with the use of common pharmaceuticals versus those associated with environmental exposures to pesticides indicates that more stringent "acceptable risk standards" are applied to pesticides. To illustrate the impact of conservative biases often applied to pesticides, this chapter summarizes comparisons between predictive models and actual measurements. Numerous variables used in "screening-level" or initial tier risk assessments contribute to overestimations of exposure. Risk managers can gain important perspective by requesting quantitative disclosure of uncertainty and evaluation of © 2007 American Chemical Society

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In Assessing Exposures and Reducing Risks to People from the Use of Pesticides; Krieger, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2007.


112 conservative bias. This process can assure that conservatively— based risk estimates are appropriately qualified, or that "refined assessments" reflect realistic conditions. The Food Quality Protection Act (FQPA) requires quantitative estimation of aggregate pesticide exposure from multiple sources, routes and pathways, and where appropriate cumulative assessments must be developed for chemicals having the same mode of action. There is a continuing need to evaluate the degree of conservatism inherent in "screening-level" risk assessment methods, and thereby critique default assumptions and model uncertainty, to avoid the Precautionary Principle, and to pass the "common sense test."

Introduction The risk assessment paradigm in use today was described in a monograph written by experts from the National Academy of Sciences (/). This paradigm recommended a clear separation of the functions of risk characterization encompassing the areas of hazard identification, dose response and exposure assessment from risk management, in which policy is delineated from the science. To appreciate the decision-making process, risk managers must understand the perspective of regulatory risk assessors in constructing the typical risk assessment (Figure 1). A risk assessor's directive can be summarized by the Hippocratic Oath "...never do harm to anyone". Recognizing sources of uncertainty in a risk assessment, the risk assessor feels that it is imperative not to underestimate risk, i.e., if there is any error, the error must be on the side of safety (2). Even more conservative is the increasingly popular Precautionary Principle with the philosophy that it is better not to allow the proposed use of a chemical than risk uncertain but possibly very negative consequences (5). In contrast to risk assessors, risk managers must deal with the political implications of the risk assessment and act to respond to the conclusions from the risk assessment. To do this, risk managers must know how much the risk may be under- or over-estimated, and balance that risk with possible benefits if the law allows it (e.g., public health protection, new tools to combat evolving


113 resistance, etc.) or foresee real risks created by mitigating theoretical ones. They must also determine if the regulatory decision based on the risk assessment opens their agency to legal liability.


Risk Assessment

Risk Management

Figure L National Academy ofScience Risk Assessment/Management Paradigm.

Discussion To do their job, risk managers must be able to distinguish the possibility of risk from actual risk. Real risks are risks that will likely occur (and are known with medical certainty to have occurred previously in humans, i.e., an incidence in humans with an associated causal and/or dose-response relationship). Theoretical risks are those derived from laboratory animals given high dosages that are unlikely to occur in humans without extraordinary circumstance (high exposure). A good example is the theoretical excess cancer risk from using chlorine to purify water versus the very real risks of water-borne diseases such as cholera, poliomyelitis and a variety of disease-causing coliform bacteria. Pesticides are designed to adversely affect pests, but they may also have adverse effects on humans. To provide perspective on real risk, the risk manager should know that annually in the US, unintentional deathsfromall chemicals is > 14,000 persons (4) (See Table I). This figure does not include the >3,200 persons that die annually from drowning (J), nor the >5,000 persons that die each year from food-borne disease related to microbial contamination in the US (6). A l l of these mortality statistics can be considered chemical-related. And


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Table I. Unintentional Poisoning Deaths by Chemical Class in 2001" Type of Poison Nonopioid analgesics, antipyretics, & antirheumatics (X40) Antiepileptic, sedative-hypnotic, antiparkinson & psychotropic drugs (X41) Narcotics & psychodysleptics (X42) Other drugs acting on the autonomic nervous system (X43) Other & unspecified drugs, medicaments, & biosubstances (X44) Alcohol (45) Organic solvents & halogenated hydrocarbons & their vapors (X46) __ _ Other gases and vapors (X47) Pesticides (X48) Other & unspecified chemical and noxious substances (X49) Total Poisoning Deaths From Reference 4.

All Ages 208 763 6,509 19 5,525 303 63 593 7 88 14,078

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