Incidence of cancers of the brain, the lymphatic tissues, and of leukemia and the use of pesticides among Quebec's rural farm population, 1982-1983.

Massive use of pesticides in agriculture poses risks for the environment and for human health. Pesticides are toxic substances and the suggestion that some may be carcinogenic has been the source of much controversy. In this article we focus on the relation between the use of pesticides in agriculture and the incidence of cancers of the lymphatic tissues, the brain, and of leukemia in the rural farm population in 34 major drainage basins in the province of Quebec (Canada) for the period 1982-1983. The basins were grouped into three categories (low, intermediate and high exposure) based upon the amount of pesticide sold. The study of highly exposed basins shows an excessive incidence of leukemia (SMR = 1.69, p less than or equal to 0.05) for men in rural farm areas in the Yamaska river basin. This specific group's relative risk (RR) of incidence as compared to the urban male population is 2.27 (p less than or equal to 0.05). The RR is also high and statistically significant among the men in municipalities that draw their drinking water from wells (RR = 2.07, p less than or equal to 0.05) as compared to those where water is drawn from rivers. Most municipalities using wells are in the rural farm areas. These results suggest that there may be a relationship between leukemia and the use of pesticides in this drainage basin, and this hypothesis could be verified at the individual level in epidemiological studies.