Women working in manufacturing industries - as well as bars and casinos - face a higher risk of breast cancer, warn researchers.
Some have double the normal risk of developing the disease, probably due to higher exposure to cancer-causing chemicals.
The risk to employees in bars, casinos and race tracks is blamed on second hand smoke and night work, which has previously been linked to hormonal disruption.
Pesticides are thought to be responsible for a heightened risk for women working in farming, according to a team of researchers from the UK, Canada and the US.
Overall, researchers estimated that women working for 10 years in jobs where they were potentially exposed to a ‘toxic soup’ of chemicals had a 42 per cent higher risk of breast cancer.
The findings come from a study of 1,000 women with breast cancer whose employment history was compared with another 1,147 women who did not have the disease in areas of Canada with extensive manufacturing and agricultural businesses.
However, experts cautioned that the study was relatively small, lack of information about the level of exposure to chemicals weakened the results and there was little supporting evidence from other research.
In the study, researchers collected data on the occupational and reproductive histories of the women and coded their jobs for likely exposure to chemicals known to cause cancer or upset the body’s hormone system.
Overall, researchers estimated that women working for 10 years in jobs where they were potentially exposed to a ¿toxic soup¿ of chemicals had a 42 per cent higher risk of breast cancer.
It found, across all sectors, women in jobs with potentially high exposures to chemicals had a higher risk than normal risk of breast cancer.
Industries with increased risk included agriculture, bar/gambling, automotive plastics manufacturing, food canning and metal-working.
Additional breast cancer risk before the menopause was highest in the automotive plastics and food canning industries.
The risk of developing breast cancer doubled for women working in plastics and food canning, and was almost five times as great for pre-menopausal women.
There was a 73 per cent increased breast cancer risk in the metalworking industries while farming showed a 36 per cent increased risk.
The risk of developing breast cancer doubles for women working in the bar/casino/racing sector, says a report published in the journal Environmental health.
The higher risk may be linked to second-hand smoke exposure and night work which has been found to disrupt the hormone system.
Professor Andrew Watterson, head of the University of Stirling’s Occupational and Environmental Health Research Group and a co-investigator, said: ‘Many workers face multiple exposures to chemicals, not only from their employment, but from their everyday environment.