A common chemical used in cosmetics and household plastics doesn’t significantly increase the risk of breast cancer in postmenopausal women, suggests the largest study to date to investigate the impact of phthalates on cancer risk.

Despite finding metabolites of phthalates, which are used as gelling agents or plasticisers, in the urine of more than 1200 postmenopausal women, US researchers have found no significant positive relationship between the chemical and breast cancer risk over 19 years of follow-up.

Participants, with a mean age of 62, were part of the Womens’ Health Initiative prospective cohort and had phthalates measured in at least two urine samples taken at different times.

Mean urinary concentrations of 13 phthalate biomarkers were similar in 419 women who developed invasive breast cancer and 839 who did not, they reported in the Journal of the National Cancer Institute.