I n 1981 Doll and Peto reviewed current scientific knowledge regard- ing the environmental causes of human cancer, and they concluded that environmental pollution, in its various forms arising from human activity, could account for only a small fraction of total cancer mortality. 1 Their best estimate for such mortality arising from all forms of pollution, principally affecting air, water, and food, was 2%, within a range of uncertainty extending from Γ΅1% to Β°5%. In contrast, the use of tobacco was judged to account for 30% and dietary factors (excluding food additives) for 35% of cancer deaths.
These relative contributions to the human cancer burden are unlikely to have changed over the past 15 years. Nonetheless, despite this striking contrast in levels of risk, public concern regarding the role of environmental pollutants in causing human cancer remains intense, and for no specific class of potential pollutant is concern more intense than for chemical pesticides.
The increasing level of such concern in Canada (similar to concerns voiced in the U.S.) led the Canadian Cancer Society and the National Cancer Institute of Canada in 1994 to form a Panel to review current scientific knowledge regarding pesticides and cancer. I participated in that Panel's deliberations as one of two members from the U.S.; the Panel's full report is published in this issue of Cancer. 2 Issues regarding pesticides and cancer are complex. Aside from scientific evidence regarding pesticide exposures and the potential importance of certain pesticides for carcinogenesis, one must consider regulatory aspects, socioeconomic implications, and public perceptions. In covering these several topics, the Panel's report concluded that no increase in overall cancer risk has appeared since the 1981 review, that safety regulations and procedures provide a wide margin of safety, and that agricultural uses of pesticides play a substantial role in providing high quality food products, especially fruits and vegetables, that contribute strongly to population health and to the primary prevention of cancer. This is not to say that scientific knowledge is complete, that regulatory systems have no flaws, that current uses of pesticides in agriculture and elsewhere do not need See referenced original article on pages 2019continuous scrutiny, and that alternate pest control approaches may 33, this issue. not be required. Instead, the report calls for continued research to fill gaps in existing knowledge and to assure adequate risk assessment