The study involved 1,005 women with breast cancer and 1,147 without the disease and found women who worked in jobs classified as highly exposed to chemicals for 10 years had a 42 percent increased risk of breast cancer.
Study leader Dr. James Brophy and Dr. Margaret Keith, both at the Occupational and Environmental Health Research Group at the University of Stirling in Scotland and the University of Windsor in Ontario, Canada, said women who worked in farming had a 36 percent increased breast cancer risk. Several pesticides act as mammary carcinogens and many are endocrine disrupting chemicals, the researchers said.
In addition, the study published in the journal Environmental Health, found women who worked in food canning had double the risk of breast cancer, but for pre-menopausal, the risk was five times as great.
Women working in metalworking -- tooling, foundries and metal parts manufacturing -- had a statistically significant 73 percent increased breast cancer risk.
The study also found women who worked in bars, casinos and race courses had double the risk of breast cancer -- perhaps due to secondhand smoke, the researchers said.
The risk of developing breast cancer doubled for women working in the Canadian car industry's plastics manufacturing sector; and among those who were pre-menopausal, the risk was almost five times as great.