Pollutants alter birth sex ratios

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 miles away, according to a study published this month in the journal Environmental Science & Technology.

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