A new study finds that mercury exposure levels for First Nations populations in Ontario are 1.6 times higher than the national average, with the bulk of the exposure coming from the consumption of traditional foods, especially fish. Yet, the elevated levels present a generally low risk for adverse health effects, say the study’s authors, who say that for both cultural and health purposes, First Nations should actually be eating more fish.
Billed as the first total dietary assessment of mercury exposure for First Nations in the province, the study involved 1429 adults from 18 First Nation communities across Ontario, with participants being interviewed on their daily diet and researchers conducting hair analyses for mercury levels.
The research concluded that although overall exposure risk was higher than for the general population, less than one per cent of those First Nations studied had hair mercury levels higher than six micrograms per gram, which Health Canada has associated with increased health risks for adults. A further 1.3 per cent of women of child-bearing age were found with mercury levels above the Health Canada guideline of two micrograms per gram.
“Although this study noted elevated exposures to methylmercury in First Nations compared to the general Canadian population, both dietary estimates and hair mercury biomonitoring data indicate low population risk for adverse health effects,” say the study’s authors, whose research is published in the journal Environmental Research.
Mercury is naturally present in the environment in trace amounts, but industrial processes such as mining, pulp and paper milling and fossil fuel combustion release further concentrations, some of which gets converted to the more toxic form, methylmercury, which can collect in organisms and become more concentrated as it travels up the food chain.
The consumption of fish and other marine animals is the most common path of methylmercury exposure, which can harm neurological development and result in birth defects. In Canada, some Indigenous populations have been documented to have elevated exposure to environmental mercury, and ongoing biomonitoring of First Nations groups has been conducted since the 1970s, showing an overall decline in exposure over that time period.
The study found that First Nations participants living on reserve consumed on average 112 grams of fish per week, which is below the recommended 200 g by the American Heart Association. As a result, and taking into consideration both rising rates of obesity and cardiovascular disease among First Nations populations and the role that fish have traditionally played in the Indigenous diet and culture, the researchers call for greater consumption of traditional foods including fish.
“The quality of the diet of First Nations is substantially better on days when traditional foods are consumed, as there are significantly lower intakes of saturated fats, sugars, and sodium than on days when only market foods are consumed,” say the researchers.
In Ontario, a history of industrialization has led to mercury contamination problems in some regions. In the 1960s and early 1970s, the Reed Paper company dumped an estimated ten tonnes of inorganic mercury into the English-Wabigoon river system in northwestern Ontario, upstream of the First Nations reserves of Grassy Narrows and Wabaseemong. As a result, over 90 per cent of the population show signs of mercury poisoning.
Last month, the Ontario government pledged $85 million to clean up the English-Wabigoon contamination.