Mercury is a naturally occurring toxin that bioaccumulates and biomagnifies within its host. In the context of toxicity to humans, we are looking at organic mercury, specifically methyl mercury which is formed by the transformation of inorganic mercury by aquatic life. It can be initially found in the air, soil, and water before ending up in the host. Elevated mercury levels are on the rise in Canada, and even more so in remote areas where higher ingestion of fish occurs.
Acute and urgent exposure to organic mercury (methyl mercury) can cause impaired vision, psychosis, kidney damage, numbness, and balance issues. Now this may not occur to the everyday consumer of fish, but what is more insidious, is the “chronic low-dose poisoning” that can occur. Chronic low-dose poisoning can cause kidney damage, liver damage, cognitive issues, and central nervous system damage (such as neuropathy-numbness and tingling). There is also a risk to a developing fetus whose mothers are exposed to high levels of mercury, putting that fetus at risk of developmental delays, growth and coordination impairment, and potentially cerebral palsy. Now all these things may sound scary, but we do have guidelines available.
Health Canada and the Minnesota Department of Health have consumption guidelines for exposure assessment and acceptable fish intake. However, mercury levels differ from lake to lake, and from fish to fish, so we cannot assume one species of fish holds the same amount of mercury in every lake. There are helpful resources such as those mentioned, however, some lakes and rivers do not have data available, which may be attributed to the vast amount of lakes within the Lake Superior region, the financial cost associated with surveying every lake, the geographical distance to travel to each lake, and available scientists to do so.
In the study I conducted in the summer/fall of 2023, it was found that most healthcare providers (midwives, doctors, and nurse practitioners) did not ask their patients about fish consumption. It was also found that the majority of the healthcare providers were not familiar with fish guides. Although these guides to eating fish are amazing tools, it may be unrealistic for some remote regions (who may not have internet access) to access such a guide or for our healthcare providers to be versed in such a guideline.
So, what can we do? We do not have to stop eating fish. Still, perhaps we as individual consumers of fish should be more aware of such risks, eat fish that are less predatory (less bioaccumulation), be aware of what lakes may have more organic mercury found within them, and advocate for ourselves when we see our healthcare providers. We can also look at supporting our healthcare providers in screening for high fish consumption, perhaps even look at pathways to help them navigate when to screen.
Consuming fish is not only beneficial to our health regarding nutrients, but it’s also a way of life for many anglers. We just need to be collectively more aware and share our insight with those who may not have access to such awareness. Check out these resources for more information:
- health.state.mn.us/fish
- bit.ly/mn-eat-fish-often-pdf
- ontario.ca/fishing
- bit.ly/canada-mercury-health