Dioxin pollution leads to more baby girls -study

By Jonathan Spicer

TORONTO (Reuters) - More girls than boys are born in some Canadian communities because airborne pollutants called dioxins can alter normal sex ratios, even if the source of the pollution is many kilometers away, researchers say.

Dioxin exposure has been shown elsewhere to lead to both higher cancer rates and the birth of more females.

Researchers at the IntrAmericas Centre for Environment and Health say their findings, released this month, confirm the phenomenon in Canada.

The study also reveals the health risks of living within 25 km (15.5 miles) of sources of pollution -- a greater distance than previously thought, they said.

Normally, 51 percent of births are boys and 49 percent are girls. But the ratio was reversed -- with as few as 46 males born for every 54 females -- in Canadian cities and towns where parents were exposed to pollutants from sources such as oil refineries, paper mills and metal smelters, according to the study.

"If you find an inverted sex ratio, and want to know what causes it, look for sources of dioxin," said James Argo, a medical geographer who headed the study, which was published in a journal of the American Chemical Society.

"In every one of those cities where those industries are found ... there was a higher probability of female births to male births," Argo said in an interview.

Using birth data and an inventory of pollution sources, the study also concluded that early exposure to dioxins -- even at 25 km away from the source -- increased the risk of cancer later in life in a group of 20,000 people surveyed during the 1990s.