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Contaminants will require close scrutiny

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Recently, Ontario’s Ministry of Environment released the 2007-08 Guide To Eating Ontario Sport Fish.





The guide includes consumption advisories for many areas due to concerns about dietary intake of contaminants, particularly by children and women who are or may become pregnant. This started me thinking — it is fortunate we are at the top of the food chain. Obviously, this is good for us, but I am thinking more of a hapless would-be predator.





While we have reason to avoid some foods, such as larger sport fish, the consumption advisories on us would be highly restrictive. With fish, we can generally still eat the smaller ones that have had less time to accumulate toxic chemicals. No such luck for the “homovore.” Sadly, with respect to some chemicals, the little ones are often more toxic than adults.





Several recent studies have found high levels of a variety of chemicals in human blood serum, urine, and breast milk. These studies include the Human Toxome Project (Environmental Working Group), and, of special interest to Canadians, the Toxic Nation Project (Environmental Defence).





In the Toxic Nation studies, a wide variety of organic chemicals and heavy metals linked to adverse health effects were found in participants from across Canada, representing different age groups and occupations. Some historical contaminants that are no longer produced were more concentrated in adults than in their children, suggesting exposure has decreased since production was discontinued. However, some contemporary chemicals are more abundant in children than in their parents.





In these studies, the detected body burdens of individual contaminants were lower than levels considered dangerous by regulatory bodies (at least for contaminants where such levels have been established).





However, none of the volunteers carried a body burden of just one single toxic chemical. Assuming the Toxic Nation volunteers are representative, we in Canada each possess a wide variety of toxicants, some of which may have additive or synergistic effects.





Are we becoming more toxic? Of course we care more from the perspective of our health than the dining options of the homovore.





Probably, we are not, but we are becoming more aware of the extent to which we are contaminated. The nature of health risks will shift as the contaminant profile changes.





When chemicals with commercial value are banned, they are generally replaced by substitutes believed more benign. Some of these are now showing up in human tissues.





It is the unanticipated health effects of these new chemicals, either on their own, or in concert with other contaminants, that will require close scrutiny.





Andrew Laursen is an assistant professor in the department of chemistry and biology at Ryerson University and is a member management program in graduate studies. His research is in the area of ecosystem ecology. Sophia Dore is an environmental scientist with Conestoga-Rovers & Associates, an environmental consulting company. Contact Andrew Laursen at earthtones.metro@gmail.com