Young women exposed to certain chemicals and pollutants in the workplace before their mid-30s may have a higher risk of developing breast cancer in later life, a study suggests.
Women exposed to petroleum products and to synthetic fibres including acrylic, rayon and nylon appear to be at the highest risk, Canadian researchers have found.
But UK experts said the findings were highly likely to be the result of chance and would need replicating in other studies to be of significance.
The research, published in the journal Occupational and Environmental Medicine, examined more than 500 women in Canada with breast cancer and compared their exposure to about 300 different chemicals with women who did not have cancer.
The results showed that exposure to nylon fibres in the workplace before the age of 36 increased the risk of developing postmenopausal breast cancer by almost double, while exposure to acrylic fibres increased the risk more than seven times. Exposure to chemicals formed during the burning of coal, oil and gas increased the risk of one type of breast cancer threefold.
The researchers admitted their findings could be due to chance alone but said they were consistent with the theory that breast tissue is more sensitive to harmful chemicals if exposure occurs when breast cells are still active – before a woman reaches her 40s.
David Coggon, professor of occupational and environmental medicine at the University of Southampton, said of the findings: "As the authors recognise, in a study of this sort, positive associations often occur simply by chance. They carry little weight in the absence of stronger supportive evidence from other research."
Toxicologist professor Anthony Dayan said: "The conclusions are presented too strongly in relation to the weight of evidence."
He said it was unclear if all factors had been properly taken into account, including smoking and taking the Pill, both of which are linked to breast cancer.
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