by Martin Mittelstaedt, Globe and Mail
The breast milk of Canadian women contains the second-highest
levels in the world of a compound used as a flame retardant in
computer casings and household furniture, according to a new survey
compiled by Health Canada.
The highest amounts of the contaminants, known as polybrominated
diphenyl ethers, or PBDEs, were detected in the milk of nursing
But women in Canada had levels about five to 10
times those in other advanced industrial countries, such as Japan,
Sweden, and Germany.
The amounts in U.S. women were double those in
Canada, and exceptionally high compared to those elsewhere in
The international comparison was made by Jake Ryan,
a research scientist at Health Canada, who is presenting the finding
later today at a conference in Toronto devoted to the controversial
chemicals, which some scientists fear may be as dangerous as the
polychlorinated biphenyls, or PCBs, that were banned as an environmental
hazard in the 1970s.
Health Canada official Samuel Ben Rejeb said the
department is studying why levels in Canadian women are so much
higher than elsewhere in the world.
Health Canada and Environment Canada recommended last month that
some forms of PBDEs be declared toxic and eliminated from use.
The European Union has already issued restrictions on the substances,
and several U.S. states plan to follow suit.
"This is a poster-child chemical for something
that ought to be zeroed out," says Tom Muir, a researcher
at Environment Canada who has studied PBDEs and is worried they
may be contributing to thyroid disorders and children's health
Although the federal government is proposing restrictions
on PBDEs, Health Canada concluded that human exposure from sources
such as breast milk had not yet reached harmful levels.
But Mr. Muir said PBDE levels in the breast milk
of a small number of women surveyed in North America are approaching
the critical concentrations associated with health impairment
The highest reading in Canada was of one woman
who had 956 parts per billion of PBDEs in the fat of her breast
The highest in the U.S. was just over 1,000 ppb.
The average breastfeeding woman in Canada has concentrations of
about 60 ppb. Samples were taken in all regions of Canada.
PCB concentrations become of concern when they
reach 1,250 ppb, according to Mr. Muir.
Health Canada said confidentiality reasons prevented
it from seeking clues on why concentrations seem to vary so wildly.
Mr. Ryan based his findings on a survey of almost
all of the studies in the world that have analyzed mothers' milk
for the chemical. Scientists have checked milk samples from Sweden
and Japan dating back to the early 1970s, finding almost no PBDEs.
But over the past three decades, increasing amounts
of PBDEs have been added to consumer products such as TV sets,
computers, and the polyurethane foam used in furniture to make
them less likely to burn during a fire.
Levels in human milk have been rising in tandem
with the growing use of the product, and in Canada are now four
times those in the early 1990s. International comparisons made
by Mr. Ryan indicate that breast milk has about 100 times more
PBDEs than samples collected 30 years ago.
Health Canada has been studying the chemical because
of fears it is a new pollutant in the food supply.
"We were interested in PBDEs as a new emerging
class of persistent organic pollutant," said Mr. Ben Rejeb,
who is associate director of Health Canada's bureau of chemical
He said that while levels of most other harmful
industrial chemicals found in breast milk, such as DDT, PCBs,
and dioxin, have been falling in recent surveys, PBDE concentrations
have risen rapidly.
"This is unlike the other persistent organic
Health Canada denied a request from The Globe and
Mail to interview Mr. Ryan about his findings, but had Mr. Ben
Rejeb answer questions about his colleague's work.
It is not known exactly how PBDEs migrate from
consumer products into human tissue. They have been found in household
dust and sewage sludge, in many fatty foods such as meat and fish,
and in wildlife.
Although there is little research on human health
and PBDEs, recent animal experiments with the chemical have linked
it to learning difficulties, memory impairment, and alterations
in thyroid hormone levels.
The similarity of these effects to those of childhood
attention-deficit disorders, and the rising tide of adult thyroid
problems, have led to calls for studies into whether PBDEs and
other pollutants play a role in these ailments.
Mr. Ben Rejeb said Health Canada has been checking
PBDE levels in food to see if there is a link to the breast-milk
The department has found the contaminant is present
at about the same levels in Canadian and European food, suggesting
the high Canadian readings in breast milk are due to some other
Because they're in computers and furniture, PBDEs
are probably found in large numbers of homes and offices.
But they are also present in many manufacturing
companies and recycling centres that deal with high-technology
waste. "It would have to be related to the use of PBDEs,"
Mr. Ben Rejeb said.