Is There Such a Thing as a Safe Level of Mercury?

While mercury and compounds including mercury are toxic, scientists still debate just how toxic they are. Toxic effects may be occurring at lower concentrations than previously thought. However, this can be difficult to prove because the suspected toxic effects are subtle, and their mechanisms are complex. Methylmercury is of particular concern because it can accumulate along the food chain to reach high concentrations.

Methylmercury

This is also true about methylmercury because large numbers of people are exposed to it, and scientists understand its toxicity more clearly. Methylmercury in food is a particular health hazard because it is easily taken up into the body through the stomach and intestines. It is poisonous to the nervous system and may affect the heart and circulatory systems. Exposure during pregnancy must be avoided because it may harm the development of the unborn baby’s brain.

In addition, evidence is accumulating that suggests methylmercury can cause cancer in humans, but it is not conclusive. The International Agency for Research on Cancer (IARC) has classified methylmercury as “possibly carcinogenic to humans.”

Elemental mercury

Elemental mercury is also poisonous to the nervous system. Exposure occurs by inhalation, and the mercury enters the body through the lungs. It is spread into the bloodstream and brain. However, when elemental mercury is ingested, little is absorbed into the body.

Inhaling elemental mercury can cause neurological and behavioral disorders, such as tremors, emotional instability, insomnia, memory loss, neuromuscular changes and headaches. It may also harm the kidneys and thyroid. High exposure can cause death. Currently, no evidence exists that elemental mercury causes cancer.