Food Scientists Estimate Contaminants in Canadian Diet
 You
will never hear the phrase "ignorance is bliss," in
the laboratories of the Food Research Division, Bureau of Chemical
Safety at Health Canada. Our scientists and researchers prefer "better
safe than sorry" when it comes to measuring the levels of
contaminants -- such as lead, mercury, cadmium, PCBs and pesticides
-- that Canadians are exposed to through the food supply.
Some compounds, present at certain levels in food, may have harmful
effects on health. So it's essential to figure out the total
exposure of Canadians to contaminants.
Since 1969, the Food Research Division has conducted Total Diet
Studies (TDS) at five different times. These studies estimate the
dietary intakes of contaminants and nutrients for Canadians of different
age and sex groups.
Each study is conducted in several major Canadian cities, normally
one city per year. In each city, over 200 individual food items
are purchased from four different supermarkets. The selection of
sample items aims to reflect the different dietary habits of Canadians.
The food samples are then sent to Kemptville College where they
are heated up, cooked or processed the way they would be by the
average Canadian. In this way, the Total Diet Study differs from
other food monitoring studies which analyse only raw produce.
Dr. Samuel Ben Rejeb, Director of the Bureau of Chemical Safety,
says this is important because contaminants can be affected through
food processing. For example, some contaminants are formed through
processing, while other contaminants may decompose.
"People don't eat their fish raw, unless they're
having sushi," he said. "They eat it cooked, so we prepare
it and analyse it the way Canadians eat it."
The food is then analysed for toxic and nutritionally important
chemicals. Combined with information on average food consumption
levels, this data provides us with estimates of dietary intakes
of these chemicals for Canadians.
While the levels of contaminants are generally far below regulatory
limits, Dr. Ben Rejeb says that if they don't check regularly,
they will never know if the levels change. As well, he points out
that a low level may mean there are no acute effects, but that doesn't
rule out possible long-term health effects.
"The study is not simply a routine activity. Sometimes
a specific incident will push us to investigate certain issues further," he added.
He cited a case in 1993, when unusually high levels of lead were
found in raisins imported from Turkey. An investigation by Health
Canada, in collaboration with Turkish scientists, led us to discover
that a fungicide sprayed on the crops was contaminated with lead.
Further work with Turkish authorities helped lower lead levels and
improve quality control methods for exports.
"We need to be proactive," he said. "The
study is not conducted to simply give us peace of mind, but also
to ensure that our food supply is safe."
The data from the Total Diet Study are also used by other national
and international regulatory agencies. The results from the Canadian
study are compared to those of other countries to interpret differences
and trends.
"The program feeds our own needs as well as the international
need for data on the exposure of humans to contaminants through
the food supply," explains Dr. Ben Rejeb.
This year the team is finishing a five-year cycle of five cities.
They will be performing analyses to determine if the current design
of the Total Diet Study meets Health Canada's risk assessment
needs. Dr. Ben Rejeb predicts an expansion in the number of classes
of contaminants and food composites to better reflect habits of
the Canadian population.
The study is an evolutionary process," he said. "It changes
as our society changes."
This work is supported by the Nutrition Research and Evaluation
Divisions, the Regional Laboratories of the Health Products and
Food Branch, and the Pest Management Regulatory Agency of Health
Canada, as well as the Canadian Food Inspection Agency.
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