A report Toxic Nation: A Report on Pollution in Canadians was recently released by Environmental Defence.

In the report, results of the testing of blood and urine samples of 11 volunteers for a variety of metals and chemicals were described. The chemical groups that were examined included: heavy metals, polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), perfluorinated compounds (PFOs), organochlorine pesticides, organophosphate insecticide metabolites, and volatile organic compounds (VOCs).

Overall, a total of 60 different chemicals were detected out of a total of 88 tested, with an average of 44 chemicals per volunteer. A total of 18 heavy metals, 5 PBDEs, 14 PCBs, 1 PFO, 10 organochlorine pesticides, 5 organphosphate insecticide metabolites, and 7 VOCs were found. Median, minimum, and maximum values were also presented for each chemical group. The results were also presented as classified according to the following recognized or suspected health effect categories: carcinogen (41 detected), hormone disruptor (27 detected), respiratory toxin (21 detected), and reproductive/developmental toxin (53 deteched).

Although the findings represent an important step in understanding the burden of chemical exposure experienced by Canadians, there remain a number of important limitations associated with this study. First, the study examined a non-random sample of 11 volunteers. With such a small sample size, it is not possible to extrapolate the findings to Canadians a whole. Indeed, one of the major conclusions of the report states that levels of PCBs were lower among younger volunteers as compared to older volunteers. In addition, due to the detection of one type of PFO compound among study participants, it was concluded that there is likely widespread PFO contamination in the Canadian population. Due to the limited number of study participants, these conclusions are unjustifiable.

Another major limitation of this report is the link of chemical exposure to human health effects. In the report, each chemical was classified according to recognized or suspected health effect and the number of chemicals in each category was reported. Indeed, it must be recognized that evidence linking specific human health effects for many of the chemicals tested remains unclear. In addition, it remains uncertain at what exposure level human health effects may manifest and how the levels of chemicals found in study volunteers relate. There also exists limited scientific evidence with which to differentiate critical periods of exposure to chemicals for specific human health effects.

Large population-based monitoring programs would help to determine actual levels of chemicals found among Canadians and how those levels may change over time. Further examination of the human health effects associated with exposure to chemicals at the levels found among the general population and if there exists a critical window of exposure would also be helpful to delineate a regulatory strategy.

References

Environmental Defence. Nov 9, 2005. Harmful Toxic Chemicals Pollute Blood of Canadians. http://www.environmentaldefence.ca/pressroom/releases/20051109.htm.

Environmental Defence. 2005. Toxic Nation: A Report on Pollution in Canadians. http://www.environmentaldefence.ca/toxicnation/landing.htm