According to a report by the Associated Press (AP), members of the 850-strong community on the Aamjiwnaang First Nation Reserve made the shocking finding after launching a campaign against a proposed ethanol plant two years ago.
Ada Lockridge banded together with a group of other concerned locals to oppose the Suncor Energy initiative and asked biologist Michael Gilbertson to examine analyses of air, water and soil samples taken from the reserve.
Mr Gilbertson said the data revealed elevated levels of dioxin, PCBs, pesticides and heavy metals including cadmium, arsenic, lead and mercury which had built up in the area after nearly half a century of concentrated petrochemical manufacturing around the reserve.
He asked the group whether anyone had noticed a difference in the number of boys and girls in the community.
“All of a sudden everybody in that room started talking,” Margaret Keith, a staffer for the Occupational Health Clinic for Ontario Workers, told AP.
Baseball teams
Somebody then remarked that the reserve had fielded three girls’ baseball teams in a recent year and only one boys’ team.
Ms Lockridge said she thought about herself and her two sisters, with eight daughters among them and only one son.
“I had been interested in sex ratio as an indicator, a very sensitive indicator of effects going on as a result of exposure to chemicals,” Mr Gilbertson reportedly said, explaining the reasoning behind his unexpected question.
The question opened up a new stream of research within the reserve.
Ms Lockridge co-authored a paper published in the Environmental Health Perspectives scientific journal.
Since 1984, figures indicated that from 1993, the percentage of boys to girls began to slide dramatically.
It is now approaching 30 percent and there is no sign the decline is levelling off.
Typically the sex ratio of newborn babies is within a hair’s breadth of 50-50, with slightly more boys born than girls.
Chemicals investigated
There are very few other cases where such an extreme disparity has occurred, the most notable being the devastating Minamata mercury poisoning outbreak in Japan in the late 1950s.
Statistics in Aamjiwnaang have also shown that one in four of the reserve’s children have learning or behavioural disabilities, and that they suffer from asthma at nearly three times the national rate.
Four out of every 10 women on the reserve have had at least one miscarriage or still birth.
It is known that mercury and other heavy metals can cause the preferential miscarriage of male foetuses, due to the increased sensitivity of their brains in the early stages of development.
But levels of heavy metal exposure in Aamjiwnaang have fallen to below what they were 50 years ago.
This has lead scientists to believe that another chemical or combination of compounds is responsible for the dwindling male birth rate.
Some have suggested that dioxin and PCBs, among other pollutants listed as endocrine disrupters, may be to blame, interfering with the production of hormones which control healthy growth and development.