Our research focuses on interdisciplinary studies to investigate cancer risks associated with environmental and occupational exposures. Both host and environmental risk factors are examined, including possible gene-environment interactions. Studies also include testing and application of innovative methods of exposure assessment.
A series of population based, case control studies of lung cancer among smoking and non smoking women identified a number of new etiologic associations. Using an innovative technique to estimate radon exposure retrospectively, we detected a significant dose response between lung cancer risk and residential radon at levels commonly found in North American and European homes. Environmental tobacco smoke was also found to be a significant risk factor, particularly among half the population with a GSTM1 (null) genotype. In addition, risk of lung cancer was associated with dietary intake of red meat, especially when cooked well done. The heterocyclic aromatic amine, 2-Amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQX), formed in meat cooked at high temperature, was identified as a risk factor. A protective effect was related to regular consumption of fruits and vegetables. Women with pre existing nonmalignant chronic lung disease were at a 40% excess risk of lung cancer. Risks were also significantly elevated among women with a family history of lung cancer. In our Missouri study, we are continuing to examine p53 and other markers of genetic susceptibility to evaluate potential gene-environment interactions. We are working with investigators at Lawrence Livermore Laboratories to study the health effects of heterocyclic aromatic amine exposure from consumption of meats cooked at high temperature.
Carcinogen Exposures in the Agricultural Environment
Studies around the world have observed that farmers and other agricultural workers are at elevated risk of several specific cancers, despite lower overall mortality and, in particular, cancer mortality. In this occupational group, excess risks are observed for Hodgkin's disease, non Hodgkin's lymphoma, leukemia, multiple myeloma, and cancers of the brain, skin, lip, stomach, and prostate. Work-related exposures suspected of contributing to the excesses include pesticides, sunlight, viruses, mycotoxins, well water contaminants, and a variety of other agents encountered in the agricultural environment.
In collaboration with the National Institute of Environmental Health Sciences, the National Institute for Occupational Safety and Health, and the Environmental Protection Agency, we are conducting the Agricultural Health Study to evaluate exposures that may be responsible for the cancer excesses. This prospective cohort study of about 90,000 participants includes licensed private pesticide applicators, their spouses, and commercial pesticide applicators. Cohort members are being followed to collect data on cancer incidence and mortality. An evaluation will also be undertaken on disease risks among spouses and children of farmers. The study includes detailed exposure analyses and assessments of non cancer health outcomes. Epithelial cheek cells are being obtained from cohort members as a source of genomic DNA. Markers of genetic susceptibility will be assessed in a series of nested case control studies. We are collaborating with investigators at the University of Iowa to evaluate pesticide exposures using fluorescent dyes and to study the epidemiology of injury among cohort members.