Interview with Constanze Mackenzie

Constanze Mackenzie is currently a 4th year medical student at the University of Ottawa. Prior to pursuing a career in medicine, she completed her undergraduate degree in Toxicology and Environmental Science at the University of Western Ontario and a M.Sc. in Wildlife Toxicology at Trent University. Her interest in the health effects of endocrine disrupting compounds started with her research on changes in sexual differentiation in frogs exposed to endocrine disruptors.

It was this background in wildlife toxicology and serendipity that led her to research changes in the sex ratio of the Aamjiwnaang First Nation community. She plans to pursue a career in medical toxicology.

1. What are the implications of the results of this study?
   
   There is evidence from wildlife and human populations that contaminants can alter the reproductive ability of populations. We have a high index of suspicion that this community has multiple chemical exposures based on their proximity to the industrial plants and contaminant levels on the reserve. The observed sex ratio between the years 1999 to 2003 of 35% boys is outside the range of normal variation, even for a small sample population. Together with the downward trend in sex ratio over the last 10 years, we believe that there is enough evidence that we should be concerned about the effects of contaminants on this community and it warrants further study to determine the cause of the phenomenon. To date this community is not known to have a single high dose exposure to a single chemical compound, rather there have likely been chronic exposures to multiple contaminants over time. If future studies show a role for contaminant exposure in the decline in sex ratio of this community, this would have great implications for our understanding of the effects of chronic exposure to multiple contaminants on reproduction in human populations.
   
   
2. Are there any methodological issues involved in this study which may influence the overall interpretation of the results?
   
   We acknowledge that there are several limitations to this study:
   
   
• Small sample size. This community has a total population just over 850 with approximately 20-40 live births per year.
• Short study period. We studied all available live birth data available for this community, with the full length of record spanning 20 years.
• Unable to eliminate other factors that have been shown to have a small influence on sex ratios such as smoking, parity, and parental age. Although we have tried to account for some of the socioeconomic factors by comparing the sex ratio data with data from another Chippewa First Nation community that is located away from the industrial sites. This "control" Chippewa community did not show any change in sex ratio when compared to expected sex ratio for Canada.
• No known chemical exposure has been documented for this community and we are unable to show cause and effect without exposure data.
  
  
3. Due to the proximity of the community to several large industrial plants it was proposed that endocrine disrupting compounds may be responsible for the observed decline in sex ratio. Could you comment on some of the issues related specifically to the exposure assessment of the community to endocrine disrupting compounds?
   
   The community is located in the centre of a heavily industrial area and there are documented high concentrations of contaminants on the reserve land including persistant organic pollutants such as PCBs, HCB, mirex, PAHs, and metals (copper, nickel, lead, mercury, arsenic, chromium, manganese, iron) (e.g. levels of mercury and lead are 10 x higher that the acceptable lower limit). In addition to this, the surrounding industry has multiple emissions that have been identified as EDCs including phthalates, dioxins and furans, and HCB.
   Although there are multiple potential routes of exposure to contaminants such as endocrine disrupting compounds for this population, we do not have exposure data for this community at this time. Future studies will hopefully clarify the routes and types of exposures that this population has, including air, water, food, and transdermal exposures.
   
   
4. Is it possible to obtain an estimate of individual exposure to endocrine disrupting compounds for residents in this community?
   
   Blood and urine samples are one method to estimate individual exposure to EDCs for this community.
   
   
5. Is there any evidence of declining sex ratios in other communities in the Sarnia-Lambton Chemical Valley region?
   
   Unpublished preliminary results of an assessment of sex ratios in other communities in the area done by another researcher have indicated that there may also be a decline in sex ratio in communities south of Aamjiwnaang, but not north in Sarnia. These results need to be interpreted cautiously since they have been calculated using Statistics Canada sex ratio data for an age cohort of 0-4 instead of live birth sex ratio data as was done in our assessment of Aamjiwnaang First Nation sex ratio. Using a 0-4 age cohort as a data set introduces a number of variables that could influence the sex ratio including perinatal and infant mortality. In addition to this, the Aamjiwnaang First Nation truly has a unique environment with their close proximity to multiple industries that is not the case to the same extent for the other communities in the Sarnia region.
   
   
6. The article mentions that a community health survey is currently under way to collect additional information about the factors that could be contributing to the observed decrease in the proportion of male births in the Aamjiwnaang First Nation community. Could you describe how this information will be used to further assess the observed change in sex ratio.
   
   As part of the community health survey, we are collecting information about miscarriages and stillbirths in the community as well as smoking rate, parity, and length of residency on the reserve land. This information will hopefully allow us to rule out some confounding factors that may be influencing the sex ratio.
   
   
7. What is the significance of community-based participatory research?
   
   Community-based participatory research means that the community plays a large role in deciding the direction that future research will take. This empowers the community to play an active role in understanding the health of their people and the influences on their health.
   
   
8. How have the results been communicated to the participants? What was their reaction? Were the limitations of the study explained?
   The community has been actively involved throughout the process of this study and has been informed of the results and the limitations of the study. The reaction from the community has been understandably mixed. There is a general concern for the health and well being of the community, but there are also strong financial links within the community to the neighbouring industries.