About the Branch
Overview
The Occupational and Environmental Epidemiology Branch conducts studies in the United States and abroad to identify and evaluate environmental and workplace exposures that may be associated with cancer risk. Workers often have heavier and more prolonged exposures to hazardous chemicals that also occur in the general environment, but at lower levels. When excess risks are detected from workplace studies, they may provide important leads as to the etiology of cancer in other settings. Occupational studies have identified many chemicals that cause cancer in humans, and they have provided direction for initiatives aimed at reducing or eliminating these carcinogens in the workplace and elsewhere.
The mission of Occupational and Environmental Epidemiology Branch includes interdisciplinary research, resource development, and training. Research projects are designed to identify occupational, environmental, and other factors affecting cancer risk; to characterize exposure response relationships; to elucidate biological mechanisms of action; to identify susceptible populations and gene environment interactions; and to improve research methods for occupational investigations. Projects typically involve sophisticated exposure assessments, biological components for mechanistic evaluations, and intensive collaboration among epidemiologists, industrial hygienists, and molecular biologists. In addition to the major research areas summarized below, emphasis is placed on developing new and innovative approaches for assessing carcinogenic risks from occupational and environmental exposures.
Pesticides and Other Agricultural Exposures
Projects on pesticides and other agricultural exposures include: 1) a prospective study of nearly 90,000 farmers and their spouses in Iowa and North Carolina, which is being carried out in collaboration with the National Institute of Environmental Health Sciences and the Environmental Protection Agency; 2) case control studies of stomach and brain cancer in Nebraska; 3) a biomarker investigation of intermediate outcomes and precursor states among herbicide applicators; 4) studies among migrant agricultural workers; and 5) a study of non Hodgkin's lymphoma risk associated with exposure to pesticides and nitrates.
Industrial Chemicals
Major investigations underway on industrial chemicals include: 1) a study of cancer risk and mechanisms of susceptibility in a cohort of 75,000 benzene-exposed workers in China; 2) a cohort mortality study of 25,000 workers with exposure to acrylonitrile; 3) a case control study of renal cancer in Eastern Europe; 4) a case control study of bladder cancer in Spain; and 5) a case control study of lung cancer in a heavily industrialized region around St. Petersburg, Russia.
Occupational and Environmental Cancer Among Women
Studies aimed at occupational and environmental causes of cancer among women include: 1) a prospective cohort study of 75,000 women in Shanghai, which includes the collection of biologic specimens for evaluating gene environment interactions; 2) investigations in Alaska, Michigan, and Alabama to evaluate breast cancer risk in relation to serum levels of DDT, PCB, PBB, and other organohalide chemicals; 3) a case control study of breast cancer in Poland to evaluate risks associated with chemical exposures and gene environment interactions; and 4) large cohort studies of farmers, dry cleaners, formaldehyde workers, benzene workers, and acrylonitrile workers that include a substantial number of women.
General Environmental Exposures
A number of projects are evaluating cancer risks associated with general environmental exposures, including: 1) studies of non Hodgkin's lymphoma and cancers of the brain, bladder, colon, and stomach in relation to levels of nitrate, arsenic, and chlorination by products in drinking water in Iowa, Minnesota, and Nebraska; 2) a study of non Hodgkin's lymphoma and pesticide exposure associated with domestic use or residential proximity to agricultural land; 3) a study of bladder cancer in relation to arsenic levels in drinking water and other risk factors in high rate areas of the northeastern United States; and 4) a study of non Hodgkin's lymphoma and multiple myeloma and cancers of the prostate, brain, ovary, and uterus among Norwegians in relation to serum levels of organochlorine chemicals.
Other Risk Factors
The examination of dietary, hormonal, and lifestyle factors on cancer risk is included in case-control studies of non Hodgkin's lymphoma, multiple myeloma and cancers of the oropharynx, esophagus, stomach, colon, rectum, pancreas, brain, bladder, kidney, and prostate. Special attention is also being given to dietary and lifestyle factors in three long term prospective studies: 1) the Agricultural Health Study; 2) the Prostate, Lung, Colon and Ovarian (PLCO) Screening Trial; and 3) the Shanghai Women's Cohort. A major new study of renal cell cancer is investigating promising etiologic leads associated with this rapidly increasing tumor.
Methodologic Projects
Methodologic projects are carried out to develop and improve techniques and procedures in occupational epidemiology. Specialized job modules were constructed to obtain information on occupational exposures in case control studies of non Hodgkin's lymphoma and cancers of the brain and bladder. A computerized exposure assessment program, originally developed for an acrylonitrile-exposed cohort, was modified to make it usable for other cohort investigations. An occupational coding system (CodeSearch), which was developed for the personal computer, has lessened the burden of classifying jobs in epidemiologic investigations. In collaboration with the National Institute for Occupational Safety and Health (NIOSH), a Computerized Occupational Referent Population System, which aggregates completed cohort mortality studies conducted by NIOSH and ourselves, was constructed to provide data for referent populations in occupational cohort studies. The utility of remote sensing and geographic information systems in environmental epidemiologic research is being evaluated in studies in Nebraska. These research resources are available to the scientific community.
Collaboration and Training
The breadth of our occupational, environmental, and other risk factor research offers many possibilities for collaboration with investigators at other agencies and institutions, as well as training opportunities for young scientists. Extensive collaborations are underway in epidemiology, exposure assessment, biologic monitoring and biomarker studies. Training opportunities for junior investigators include planning new projects, participating in ongoing investigations, and analyzing data from studies whose field work is completed. Pre-doctoral and postdoctoral fellows are mentored by senior investigators in the Branch.
