Some forms of mercury more toxic than others.
An article describing high levels of mercury in the Mackenzie River missed the chance to explain how the metal is connected to human health risks and that one form of mercury is of greater risk than the other.
A June 16 article in the Edmonton Journal describes new research about the levels of mercury in the Mackenzie River, Northwest Territories, Canada.
The article nicely profiles research by University of Alberta scientists who collected water samples from several locations in the river basin to better understand how much mercury the system delivers to the Arctic Ocean. However, reporter Hanneke Brooymans failed to cover how mercury in this river is connected to human health risks or explain how one form of mercury is of greater risk than the other.
The researchers found that the river and its connecting lakes carried a lot more – up to 4 times more – mercury to the ocean than previously thought. This river may be a big source of mercury for the ocean, the fish, marine mammals and the Inuit, who eat these traditional foods.
The article mentions that there is an ongoing concern about human and wildlife exposure to mercury because it is a neurotoxin and can also affect reproduction.
What is missing is a description of the several forms of mercury that exist in the environment. Readers are not told there are several kinds that differ in where they are found, in the effects they have on wildlife and human health, and how one type is more of a health concern than the others. Without this context, it is challenging to understand the links between the research and the concerns over health impacts.
The two main forms of mercury in the environment are an inorganic, less toxic type (elemental or ionic) and an organic, more toxic form (methylmercury). Both were found in the Mackenzie River in this study, but the inorganic form was present at much higher levels. However, the organic form – methylmercury – is of the greatest concern because high exposure can affect our nervous system and fetal development.
What is also not clearly stated in the article is that inorganic mercury is converted to methylmercury by bacteria that are present in lakes and rivers. It is the methylmercury, not all mercury, that concentrates up food chains to high levels in fish, fish-eating birds, other wildlife and people.
The main source of human exposure to methylmercury is through eating fish. Detailed advice on minimizing this risk is available through Health Canada.
