[Dioxin pollution leads to more baby girls -study
Thu Oct 18, 2007
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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
"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.
Previous studies that linked dioxins with cancer and a gender
imbalance focused on smaller distances, usually about 5 km, Argo said.
= -- = -- = --
Excess female to male births in Canada linked to chronic dioxin exposure
Environmental Science & Technology
Almost 90 Canadian communities have experienced a shift in the normal
51:49 ratio of male to female births, so that more girls than boys are
being born, according to two studies in the Oct. 1 issue of ACS'
Environmental Science & Technology, a semi-monthly journal. James
Argo, who headed the research, attributes this so-called "inverted sex
ratio" of the residents in those communities to dioxin air pollutants
from oil refineries, paper mills, metal smelters and other sources.
The studies analyzed information in the Environmental Quality Database
(EQDB), an inventory of pollution sources, cancer data, and other
factors developed for Canadian government research on how early
exposure to environmental contaminants affects the health of
Canadians. Argo points out that the EQDB enables researchers to
pinpoint the location of 126,000 homes relative to any of about 65 air
pollution sources-types and the occurrence of cancer among residents
of those homes.
Argo focused on air pollutants from those sources and the
corresponding incidence of cancer among more than 20,000 residents and
5,000 controls. He identified inverted male sex ratios, sometimes as
profound as 46:54 in almost all of the communities. The ratio
indicated that more females than males were born, a situation that
Argo attributed to chronic exposure of parents to dioxin, based on
previous studies. The study "may represent one of only a few studies
explicitly designed to identify the impact of carcinogens from
industrial sources on residents at home," Agro stated.
"Chronic Disease and Early Exposure to Air-Borne Mixtures: 1. The
Environmental Quality Database" and "Chronic Disease and Early
Exposure to Air-Borne Mixtures: 2. Exposure Assessment"
James Argo, Ph.D.
IntrAmericas Centre for Environment and Health