In a study in Occupational and Environmental Medicine, researchers found out that women during her mid 30's exposed to petrol products and synthetic fibers could treble the risk of developing breast cancer after menopause.

Occupational exposure to nylon and acrylic fibers as well as to polycyclic aromatic hydrocarbons has higher risk of developing postmenopausal breast cancer, they wrote.

But David Cogon, a professor of occupational and environmental medicine at Britain's Southampton University, expressed caution that such links can be minimized by chance.

These sort of positive associations often occur by chance. They carry a little weight in the lack of stronger evidence during our research.

Canadian scientists may have conceded that it could occur by chance, but they said that they were consistent on the theory that breast tissue is sensitive to harmful chemicals if active breast cells are exposed to it - in other words, before a woman reaches her 40's.

The research by the Occupational Health Research Institute in Montreal, Canada, led by France Labreche, based their study on 1100 women. 556 of whom were diagnosed with breast cancer between 1996 to 1997 when they were aged 50 to 75 and had gone through their menopausal stage.

Compared with the comparison group, they found out that the risk peaked for aged group younger than 36, and increased with each additional decade of exposure before this age.

This meant that women exposed to acrylic fibers runs a seven fold risk of breast cancer, while it doubles for those who were exposed to nylon fibers.

The scientists said that a more detailed study on these chemicals are needed in order to find out more about their role in the development of breast cancer.