The pill has been linked to the rise in prostate cancer
Increasing use of the contraceptive pill is being linked with the rise of prostate cancer in men.
The researchers believe oestrogen by-products in the urine of pill-users may be entering food and drinking water. The hormone is known to feed the growth of certain cancers.
Regions where the oral contraceptive was commonplace had higher incidents of cancer, the research found.
Using data from 87 countries, researchers found that where the proportion of women using the contraceptive pill is higher, rates of prostate cancer are higher.
The findings were not affected by a nation's wealth.
Other contraceptives such as intrauterine devices or condoms were not linked to higher incidence of prostate cancer.
The authors stress that their research is speculative and say their findings do not confirm cause and effect.
"It must be considered hypthesis generating and thought-provoking," they say in their BMJ Open report.
They said more investigations are needed and recommend close monitoring of environmental levels of oral contraceptive by-products or endocrine disruptive compounds.