Evaluation and Use of Epidemiological Evidence for Environmental Health Risk Assessment: WHO Guideline Document
Environmental health risk assessment is increasingly being used in the development of environmental health policies, public health decision making, the establishment of environmental regulations, and research planning. The credibility of risk assessment depends, to a large extent, on the strength of the scientific evidence on which it is based. It is, therefore, imperative that the processes and methods used to evaluate the evidence and estimate health risks are clear, explicit, and based on valid epidemiological theory and practice. Epidemiological Evidence for Environmental Health Risk Assessment is a World Health Organization (WHO) guideline document. The primary target audiences of the guidelines are expert review groups that WHO (or other organizations) might convene in the future to evaluate epidemiological evidence on the health effects of environmental factors. These guidelines identify a set of processes and general approaches to assess available epidemiological information in a clear, consistent, and explicit manner. The guidelines should also help in the evaluation of epidemiological studies with respect to their ability to support risk assessment and, consequently, risk management. Conducting expert reviews according to such explicit guidelines would make health risk assessment and subsequent risk management and risk communication processes more readily understood and likely to be accepted by policymakers and the public. It would also make the conclusions reached by reviews more readily acceptable as a basis for future WHO guidelines and other recommendations, and would provide a more rational basis for setting priorities for future research. Key words: environmental health, environmental health risk assessment, guidelines, international cooperation, World Health Organization. Environ Health Perspect 108:997-1002 (2000). [Online 11 September 2000]
Environmental health risk assessment contributes increasingly to policy development, public health decision making, the establishment of environmental regulations, and research planning. It also often plays an important role in cost-benefit analysis and risk communication. Its credibility depends, to a large extent, on the strength of the scientific evidence on which it is based. Epidemiology, toxicology, clinical medicine, and environmental exposure assessment all contribute information for risk assessment.
However, epidemiological studies play a unique role in the assessment of the health risk of environmental factors. Unlike laboratory experiments, epidemiology provides evidence based on studies of human populations under real-world conditions. It largely avoids the extrapolations across species and levels of exposure required for the use of data from animal experiments, which contribute large uncertainties. In addition, epidemiology has often contributed to the recognition of new hazards, thereby stimulating new research and identifying new areas for public health action. The contribution of epidemiology to health risk assessment has been widely discussed (1-5). However, epidemiological studies that report associations between measures of the health of populations and the presence of hazardous factors in the environment are frequently difficult to interpret (6,7). Therefore, a careful evaluation of all existing epidemiological evidence is necessary as part of the risk assessment process.
To provide authoritative assessments of environmental epidemiology research, public health and regulatory agencies may rely on expert review groups to evaluate the evidence, draw conclusions on the existence of hazard to health, and estimate the magnitude of associated health risks. These expert reviews may then be used to support actions that are difficult and expensive. It is, therefore, imperative that the processes and methods used to evaluate the evidence and estimate health risks are clear, explicit, and based on valid epidemiological theory and practice. …