Polluted Children, Toxic Nation: A Report on Pollution in Canadian Families

This report by Environmental Defence is a follow-up on the first Toxic Nation report, released in 2005, which examined the levels of 88 different chemicals in the blood and urine of 11 Canadian adults. This follow-up report assesses pollution levels in children, and the difference between the chemical body burdens of adults with their children. Five Canadian families were selected from Vancouver, Toronto, Sarnia, Montreal, and Quispamsis (New Brunswick). Six adults (two men and four women) and seven children (five girls and two boys), aged 10 to 66 years, were included in this analysis. Blood and urine samples were collected from the volunteers and tested for 68 chemicals which were grouped according to five main health effects: carcinogens, hormone disruptors, respiratory toxins, neurotoxins, and reproductive/developmental toxins. The chemicals selected for analysis fell into one of six major chemical families: PFCs (perfluorinated chemicals), PBDEs (polybrominated diphenyl ethers), PCBs (polychlorinated biphenyls), organochlorine pesticides, organophosphate insecticide metabolites, and heavy metals.

Laboratory analysis of the blood and urine samples detected 46 of the 68 selected chemicals in the 13 subjects. The 46 chemicals detected were comprised of 5 PBDEs, 13 PCBs, 5 PFCs, 9 organochlorine pesticides, 4 organophosphate insecticide metabolites, 5 PAHs, and 5 heavy metals. Each of these chemicals were related to a specific health effect group except for 3 of the PFCs for which there was no data on health effects. An average of 32 chemicals were detected in each adult volunteer, and an average of 23 were detected in each child. Several of the compounds included in the report, such as PCBs and some of the organochlorine pesticides, were banned in Canada before the child volunteers were born, yet these chemicals were detected in all of the subjects. On average, 11 PCBs and 8 organochlorine pesticides were detected in the adults, compared to 7 PCBs and 4 organochlorine pesticides in the children. The median total plasma concentration of PCBs (0.574 µg/L, range: <0.01 – 0.76µ/L) and organochlorine pesticides (0.286µg/L, range: <0.005-0.48µ/L) in children was lower then the median levels of PCBs (1.934ug/L, range <0.01-2.6µ/L) and organochlorine pesticides (0.787µg/L, range <0.005 – 1.5µ/L ) in the adults. For several of the chemicals which are still in use, the median levels were higher in the children as compared to the parents. The median concentration for 2 of the 5 PBDEs, and 3 of the 5 PFCs that were detected were higher in the children then the median concentration of these chemicals in the adults. It should be considered that due to the small number of subjects tested (7 children, and 6 adults) the median levels reported are not robust measures. Therefore, reliable inferences concerning the differences in contaminant levels between the adults and children cannot be made.

Despite the limitations in the generalizability and quantitative interpretation of the results presented, this report highlights the importance of considering the difference in exposure patterns between adults and children when evaluating the potential health risks associated with known or suspected toxins. Children may be exposed to some chemicals at a greater extent due to their behavioural patterns, such as putting contaminated objects in their mouth, spending more time outdoors, and playing close to the ground. In addition, per kilogram of body weight, children eat more, drink more, and breath more then adults. These behavioural patterns may be particularly important when considering exposure to chemicals such as PFOA, a suspected carcinogen, which is used in non-stick cookware and as a stain repellent on furniture and carpeting, and PBDEs which are commonly used as flame retardants and are expected to have carcinogenic and endocrine disrupting characteristics.

The detection of PCBs and organochlorine substances in children, suggests that these chemicals have persisted in the environment long after they had been banned from use in Canada. The authors state that because the total number and concentration of these substances were lower in children the ban appears to have been effective in reducing human exposure to these substances. These results need to be replicated in a large, randomly selected population before this type of speculation can be made.

Although the test results obtained from this small sample of non-randomly selected individuals can not be generalized to the general Canadian public, this report provides some insight about the type of chemicals which Canadians may be exposed to, and illustrates potentially important differences in exposure between adults and children. However, it is not clear how these findings translate to human health risk. Although the main health outcome of most of the chemicals can be predicted from observations in animal models, the extrapolation of these predictions to humans is complicated by many factors. More information is required to establish the effects of low-dose long term exposure, the way individual lifestyle and genetic variables influence health outcomes following chemical exposure, and the consequence of concurrent exposure to many chemicals at once. It is also important to identify critical periods of exposure for specific chemicals, as individuals may be more susceptible to adverse health outcomes based on their stage of development at the time of exposure. For example, children and adolescents may be most susceptible to endocrine disrupting hormones during this period of key endocrine system and reproductive organ maturation.

It must be considered that the data presented in this report were not obtained through a well-designed, peer-reviewed scientific study. There are several limitations which prevent the extrapolation of these results to a broader population. The non-random selection of participants raises the possibility that some form of selection bias may influence the results presented. This problem is further exacerbated by the small sample size of only 13 subjects. Statistically reliable measures can not be obtained from a sample of this size, especially considering the numerous individual biological and lifestyle factors which can influence the extent of exposure to environmental pollutants. The authors state that the detection of a large number of chemicals in each volunteer is a cause for concern; however, it is not clear if the presence of these chemicals at the amounts detected are reflective of the exposure experiences of the general population or actually pose a risk to human health. Further studies are required to examine how the levels of chemicals found in the volunteers relate to the actual manifestation of the suspected health outcomes. Larger population based bio-monitoring studies are needed to establish more reliable estimations of the average body burden of these chemicals, and to identify the most susceptible sub-populations. Longitudinal studies which assess the levels of certain chemicals in the same group of subjects at several time intervals would provide valuable insight into the variation of exposure over time, as well as a further understanding of the persistence of environmental pollutants in the body. The report concluded by making recommendations to protect children’s health related to the upcoming review of the Canadian Environmental Protection Act (CEPA). A research report on this topic prepared by the McLaughlin Centre for Population Health Risk Assessment at the University of Ottawa is available at: www.mclaughlincentre.ca.