Evaluating evidence on environmental health risks.

The assessment of adverse health effects from environmental hazards involves integration of evidence from a variety of sources, including experimental studies, both in animals and humans, in vitro studies, and epidemiological research. It requires an understanding of the sources, nature and levels of exposure to which humans may be subjected, the nature of the health outcome or toxic effect and the mechanisms by which this might occur, the relationship between dose and response, and a knowledge of the variability and susceptibility of potentially exposed populations. After outlining the process of risk assessment, this paper gives an overview of the most relevant human study methods used to investigate environment and health effects and discusses issues such as confounding and effect modification, that are important to consider when interpreting the results from such studies. Future challenges are outlined, such as increasing responsibility required by scientists to the sensitive issue of data protection and confidentiality, and also new opportunities, such as the increasing availability of computerized data, the incorporation of molecular epidemiological methods to aid the investigation of mechanistic pathways and gene-environment interactions, and the development and utilization of sophisticated statistical approaches.