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.
Sources:
Brodkin E, et al. Lead and mercury exposures: interpretation and action. CMAJ. Jan 2 2007;176(1):59-63. PMID: 17200393.
Kales SN, et al. Mercury exposure: current concepts, controversies, and a clinic’s experience. J Occup Environ Med. 2002 Feb;44(2):143-54. PMID: 11851215.
Lambrinos A. Testing for Blood Mercury Levels in the General Population: a rapid review [Internet]. Toronto (ON): Health Quality Ontario; 2014 Aug [cited 2014 September 19].
Myers GJ, et al. Twenty-seven years studying the human neurotoxicity of methylmercury exposure. Environ Res. 2000 Jul;83(3):275-85. PMID: 10944071.
Wong SL, et al. Lead, mercury and cadmium levels in Canadians. Health Rep. 2008 Dec;19(4):31-6. PMID: 19226925.