Canadian researchers say they have found a possible link between oral contraceptive pill use and rising prostate cancer rates.
Drs David Margel and Neil Fleshner of Toronto University believe oestrogen by-products excreted in the urine of pill-users may have contaminated the food chain and drinking water.
The hormone is known to feed the growth of certain cancers.
The researchers looked at data from 2007 for individual nations and continents worldwide to see if there was any link, the BBC reports.
They found a significant association between contraceptive pill use in the population as a whole with both the number of new cases of, and deaths from, prostate cancer.
They stress that their work merely suggests a link and is not proof.