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3. Issues in Human Health Risk Assessment

Various reports have stated concern that EPA's current approaches to risk assessment do not adequately account for cumulative risks arising from complex exposure patterns and human variability due to genetic and other factors. These documents include the National Academy of Sciences (NAS) 1993 report titled, "Pesticides in the Diets of Infants and Children;" the NAS 1994 report on "Science and Judgment in Risk Assessment;" and the 1996 draft report by the President’s Commission on Risk Assessment & Risk Management titled, "Risk Assessment and Risk Management in Regulatory Decision-Making."

Several recent pieces of legislation have mandated the consideration of cumulative risk and variability factors and press for stakeholder involvement in the risk characterization process. Specifically, the Food Quality Protection Act of 1996 (FQPA) directs EPA in its assessments of pesticide safety to focus in part on the cumulative effects of pesticides and other substances that have a common mechanism of toxicity and the aggregate of dietary and non-occupational consumer exposure. These reports and laws point to an emerging body of evidence that suggests person-to-person differences in metabolism, genetic pre-disposition, physical environment, and age (infants, children, and elderly) may place certain groups of individuals at an increased risk from environmental stressors. This can result in decreased quality of life and increased illness and mortality.

The traditional standard default approaches used in risk assessment may underestimate the impact of environmental agents on particular groups of individuals. These approaches do not adequately account for complex exposure patterns involving multiple acute exposures and/or exposures to mixtures of toxic chemicals or for the variability in human biological responses to toxic chemicals. Expanded investigation in these areas will benefit risk assessment by providing the tools to identify and characterize high risk groups and by providing fundamental data to develop predictive approaches and more reliable assessment methods.

FQPA also directs the Federal Government to begin providing consumer right-to-know information related to understanding the risks and benefits of aggregate and cumulative exposure.

Human health risk assessment research is needed in the three areas described below.

3A. Human Health Effects of Complex Exposure Patterns

Research is needed on the influence of complex exposures on the non-cancer human health effects of pesticides and other toxic chemicals in the environment. Exposure of human beings to toxic chemicals arises from multiple sources and via multiple pathways. They also occur in a variety of complex temporal patterns. EPA risk assessments have usually focused on individual environmental agents, often considering chronic exposures from individual sources occuring via individual pathways. EPA would like to shift the emphasis to a more broadly based approach which incorporates multiple sources and pathways of exposure and considers complex exposure patterns such as multiple acute exposures and exposures to mixtures of pesticides and other toxic chemicals. The evaluation of the effects of these complex exposure patterns has been collectively termed cumulative risk assessment.

EPA is interested in sponsoring basic research to develop novel risk that affect human health: (1) who, what, and/or where is/are being affected? (2) what are the stressors? (3) what are the sources? (4) what are the pathways and routes of exposure? (5) what are the relevant timeframes? and (6) what are the assessment endpoints? Approaches might include measurement-based, multipathway human exposure assessment, toxicological studies, mechanistic research, pharmacokinetic and/or dose-response modeling.

Specifically, this research should include:

  • studies to quantify the cumulative exposures resulting from these complex multipathway exposure patterns, including studies utilizing environmental, biological, and/or behavioral data, and
  • toxicological and other studies that investigate the neurological, developmental, reproductive, and other non-cancer human health effects of these exposures, with the aim of developing dose-response relationships.

The exposure patterns used in these studies should have a demonstrated relationship to actual or potential human exposures. Also, the studies should compare acute, episodic, and chronic exposure regimes and/or compare the effects of chemical mixtures with those of the single chemicals in the mixtures.

3B. Variability in Human Responses to Environmental Agents

Research is needed to study the impact of genetic polymorphisms on human susceptibility to the effects of toxic chemicals in the environment. The intent should be to quantify these variabilities within the general population. These studies might also extend to the incorporation of results into dose-response models for use in risk assessment. Of interest would be molecular,epidemiological, and other types of research to examine:

  • The causes and extent of interindividual variability in susceptibility to neurological, developmental, reproductive, and other non-cancer health effects resulting from exposure to toxic chemcials in the environment;
  • Possible relationships between susceptibility and such covariates as age, race, ethnicity, and sex; and
    (3)Approaches for improving the default assumption that individual humans on average have the same susceptibility as populations of humans in epidemiological studies.

3C. Consumer Right-to-Know

The FQPA requires the federal government to provide consumer right-to-know information in a format understandable to a lay person. Such information would be distributed to large retail grocers for public display related to the risks and benefits of pesticide chemical residues in or on food purchased by consumers with recommendations to consumers for reducing dietary exposure to pesticide chemical residues in a manner consistent with maintaining a healthy diet. Therefore, research is needed on how best to communicate the results of these more comprehensive assessments.

Risk communication research is needed: (1) to identify optimal communication strategies and tools with which to disseminate information and educate consumers, and (2) determine what kinds of information consumers will find most useful. Research is needed to explore whether any adjunct or complementary communication strategies (e.g., public information, health information campaign) would contribute to assuring that the public receives accurate, pertinent, and useful information. Factors that could be explored include, but need not be limited to: (1) strategies for increasing comprehensibility and retention of information, (2) strategies to motivate behavioral changes to reduce potential exposures, and (3) identifying factors key to ensuring understanding and cultural acceptability to minorities and potentially susceptible subpopulations.

Funding:

About $5 million is expected to be available in fiscal year 1997 for awards in this program area. The projected award range is $50,000 to $300,000/year for up to three years.

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