For adults, Health Canada’s guidance value for total blood mercury concentrations is 8 µg/L (40 nmol/L) for childbearing women and 20 µg/L (100 nmol/L) for females ≥ 50 years and males > 18 years. Although clinically significant exposures may still occur in Canada, less than 1% of Canadian adults have total blood mercury concentrations above Health Canada’s guidance value. As such, the large majority of individuals who present with concerns of metal toxicity do not actually have toxicity, and testing results in false positives (values above the reference range but not in the range of toxicity). Occupationally exposed workers and childbearing women are susceptible subgroups therefore testing in these populations is warranted in cases where a careful occupational and/or environmental history suggests a significant exposure. In the absence of clinical presentation and history indicating toxicity risk, testing should be avoided because it may lead to misinterpretation and unnecessary concern or interventions (dietary restriction, chelation) that may cause harm.

Conditions: Mercury Toxicity, Mercury Poisioning

Diagnostic Tests: Blood Mercury Level