Dec. 11, 2008 The U.S. Environmental Protection Agency's process of generating risk assessments -- which estimate the potential adverse effects posed by harmful chemicals found in the environment in order to protect public health -- is bogged down by unprecedented challenges, and as a decision-making tool it is often hindered by a disconnect between available scientific data and the information needs of officials, says a new report from the National Research Council. EPA's risk assessment process should be streamlined to ensure the appropriate use of available science, technical accuracy, and tailoring to the specific needs of the problem.
The risk assessment process entails four steps -- hazard identification, exposure assessment, dose-response assessment, and risk characterization -- which were described in a 1983 National Research Council report known as the Red Book. After a risk assessment is complete, officials and regulators use it to decide how to protect the public from exposure to toxic substances. However, the challenges of risk assessment have become increasingly complex. As knowledge of environmental contaminants and potential health impacts advances, EPA must address issues of multiple exposure, multiple risks, and susceptibility of different populations. Recognizing this, the agency asked the Research Council to identify improvements it could make to enhance risk assessment. In turn, the committee that wrote the report presented recommendations and a proposed framework for risk-based decision making to provide a template for risk assessment in EPA and strengthen the scientific basis, credibility, and effectiveness of future risk management decisions.
The committee found that EPA is struggling to keep up with demands for hazard and dose-response information and is challenged by a lack of resources. For example, the risk assessment for trichloroethylene, a chemical that is linked to cancer, has been under development since the 1980s and is not expected until 2010. However, state and federal officials often must continue to make risk management decisions in the absence of completed risk assessments. If this practice continues, the value and credibility of risk assessment will erode, the committee stressed. Perfection in scientific knowledge is unattainable; therefore, risk assessment should incorporate the best available scientific information and reasonably capture uncertainties in information so it is still useful for officials.
EPA should focus more attention on the formative stages of risk assessment, specifically on planning, scoping, and problem formulation, which have been applied inconsistently, the committee said. This includes defining a clear set of options for consideration and involving decision makers, stakeholders, and risk assessors upfront to evaluate whether the design of the assessment will address the problems.
To this end, the committee proposed that EPA adopt an expanded risk assessment framework (outlined in Figure S-1) that has the same core as the Red Book model but differs in its preliminary and final steps. The three-phase framework begins with enhanced problem formulation and scoping, in which risk management options and the types of technical analyses needed to evaluate and discriminate among the options are identified. The second phase involves planning, hazard identification, exposure assessment, risk characterization, and deciding whether the assessment is appropriate and allows discrimination among risk management options. The final phase examines the relative health or environmental benefits of the proposed risk management options for the purpose of reaching a decision.
Under this framework, the questions posed come from early and careful planning and stress the appropriate level of scientific depth that is needed to evaluate the relative options being considered. The goal of the new approach is to assure that risk assessments are focused on the right questions, use the best available science, and address the needs of decision makers.
The committee also recommended that EPA adopt a unified approach for the dose-response step of risk assessment, which estimates the amount of a chemical that would lead to an adverse health effect. Currently, dose-response assessments are conducted differently for chemicals that produce cancerous effects and those that produce other health effects. For carcinogens, EPA assumes that even a low exposure may result in cancer, and scientists estimate the probability of cancer developing in a certain population given different levels of exposure. For chemicals that could produce noncancerous effects, such as asthma or birth defects, scientists currently try to determine a threshold -- the amount below which effects of the chemical are not expected to occur or are extremely unlikely.
However, the current noncancer assessment process, while valuable in certain public-health situations, does not provide decision makers with information on varying estimates of risk at different exposure levels, nor does it allow for adjustment of background exposures and underlying disease that may lead to increased risk. Rather, it provides a distinct line between possible harm and safety for all populations. The committee suggested unifying the cancer and noncancerous dose-response assessment approaches to include assessments of background disease processes and exposures, possible vulnerable populations, and modes of action that may affect a chemical's dose-response relationship in humans. This unified approach would incorporate advances in scientific knowledge and provide clearer estimates of population risk -- information that is most useful for decision making, including informing risk trade-offs or cost-benefit analyses. Moving toward this approach would require new research and development, but the tools are available to do this.
EPA's current institutional structure and level of resources may pose a challenge to implementation of the report's recommendations, which are equivalent to major transformations in the agency's culture, the committee said. It would require a commitment to leadership, cross-program coordination and communication, and training to ensure the requisite expertise. EPA should initiate a senior-level strategic re-examination of its risk-related structures and processes to make sure that it has the institutional capacity and resources to implement the committee's recommendations. In addition, EPA should develop a capacity building plan that includes budget estimates required for implementation.
The report was sponsored by the U.S. Environmental Protection Agency. The National Academy of Sciences, National Academy of Engineering, Institute of Medicine, and National Research Council make up the National Academies. They are private, nonprofit institutions that provide science, technology, and health policy advice under a congressional charter. The Research Council is the principal operating agency of the National Academy of Sciences and the National Academy of Engineering. A committee roster follows.
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