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Women who already have an above-average risk of breast cancer and who work with organic solvents, such as factory and laboratory workers working with benzene or other such chemicals, may have an even higher risk, researchers reported Friday.
It’s one of the first studies to show a clear link between certain chemicals and breast cancer, but the risks are limited, the researchers report in the journal Cancer Research.
Only some women who handled the chemicals had an added risk, the government researchers found.
Women who worked with organic solvents before they had their first baby had about a 40 percent extra risk for developing breast cancer, and all women who worked in clinical laboratories had about twice the extra risk, said Christine Ekenga of the National Institute of Environmental Health Sciences.
“Our study is an important first step toward understanding how the timing of chemical exposures may impact breast cancer risk,” Ekenga said in a statement. “We hope that our findings will generate additional interest in the possible role of solvents and other chemicals in the etiology of breast cancer.”
Ekenga and colleagues used data on 50,000 women taking part in the Sister Study, an ongoing study of women whose sisters have had breast cancer but who, when they enrolled, did not have breast cancer themselves.
Breast cancer affects more than 200,000 women a year in the United States, and kills more than 40,000.
About one in eight women will be diagnosed with breast cancer at some point. But women who have a sister with breast cancer have about double the risk of developing breast cancer.
Clearly, genes are involved but the researchers are trying to find out what else affects that risk.
Organic solvents are known to cause cancer anyway, and the women in the study answered questions about whether they’d ever used them or been exposed to them and if so, when.
When the group was looked at as a whole, working with solvents did not raise breast cancer risk.
But the women who used them early on in life had a greater risk of breast cancer. “The time between puberty and before first birth is an important period of development when the breast may be more vulnerable to chemical exposures,” said Ekenga.
“We identified several occupations where solvent exposure was associated with an elevated risk for breast cancer,” she added. “These include clinical laboratory technicians, maids and house cleaners, and production [factory] workers.” It was difficult to calculate the risk for house cleaners and factory workers, however.
“All women should be familiar with the chemicals and hazards that are present in their workplace, and use personal protective equipment and minimize exposures when appropriate," Ekenga added.