Women exposed to certain chemicals and pollutants before their mid-30s could have triple the risk of developing cancer after menopause, suggests the lastest study co-authored by Mark Goldberg, Medical Scientist at the MUHC, and France Labreche, of the National Institute of Public Health in Montreal. Their research was recently published in the Bristish Journal, Occupational and Environmental Medicine.
The study suggests that women exposed to synthetic fibres and certain oil byproducts during the course of their work life seem to be most at risk. The results done on more than 1,100 Canadian women aged 50 to 75 showed that 556 (just under half) of them, who had gone through menopause, were diagnosed with breast cancer in 1996 and 1997. The remaining women were diagnosed with a range of other cancers and were intended to act as a comparison group.
Moreover, an expert team of chemists and industrial hygienists then set about investigating the women’s levels of exposure to around 300 different substances throughout their job history. They showed –- after taking account of the other known causes of breast cancer – a link between occupational exposure to several of these substances found in textile factories and other industrials materials.
Compared to the non-breast cancer group, the study showed that the risk of chemical exposure peaked before a woman reaches her 40s – in other words when cells in breast tissues are still active and thought to be more sensitive to harmful chemicals. “Indeed, women occupationally exposed to acrylic fibres ran a seven-fold risk of breast cancer, while the exposure to nylon fibres almost doubled their risk,” explained Dr. Goldberg.
Women, whose cancers responded to oestrogen but not progesterone – both hormones used in breast cancer treatment – were more than twice as likely to have breast cancer for every decade they were exposed to monaromatic hydrocarbons (a byproduct of crude oil) and to acrylic or rayon fibres.
The researchers also found that exposure before the age of 36 to another class of
hydrocarbons – found in petroleum products – tripled the risk for women whose tumours were responsive to both oestrogen and progesterone.
“Our findings are not conclusive but they are consistent in pointing out the fact that breast tissue is more sensitive to chemical toxins in women under 40,” says Dr. Goldberg. The future step is to focus on certain chemical exposures in order to better understand their role in the development of breast cancer.