Incorporating the Environmental Context in the Study of Cancer

Summary

The analysis in Section 2 of this chapter presents several lines of evidence that implicate the environment in cancer causation; specifically, findings from wildlife studies, cancer trend reports, immigrant studies, childhood cancer studies and twin studies are reviewed. Having established the general evidentiary basis for the cancer-environment linkage, in Section 3 we turn to a discussion of the current methodological difficulties in incorporating the environmental context in the study of cancer. The particular focus here is on exposure assessment — a key methodological limitation in studying the cancer-environment linkage. It is reasonable to expect that cancer cases arising from point source environmental exposure will tend to cluster geographically. For this reason the role of exposure assessment and other methodological issues in the context of cancer cluster investigations are considered. The case of the Woburn Massachusetts leukaemia cluster is reviewed to illustrate some of the pertinent issues involved. In Section 4, we move to a general discussion of the implications of cancer risk assessment methodologies for cancer policy and intervention. In light of the observational evidence concerning the cancer-environment link (Section 2), as well as the uncertainties involved in assessing the risks associated with environmental carcinogens (Section 3), it is suggested that the precautionary principle be adopted as a guiding principle for cancer policy and intervention. The precautionary principle calls for protective action, even when the evidence of harm remains inconclusive and the adoption of this principle seems warranted under the present technical and policy circumstances. The final section ends the chapter with some recommendations and concluding remarks.