Trends in Elevated Blood and Urine Mercury Levels in Michigan, 2006–2023

Mining and fossil fuel combustion release mercury into the environment, where it enters the food chain and can lead to adverse human health effects. Michigan began requiring clinical laboratories to report all blood and urine mercury results in 2005. For levels that exceeded the action thresholds, the source of exposure was investigated and categorized as work-related and nonwork-related exposures. Between 2006 and 2023, 398 individuals had elevated blood and/or urine mercury levels. Elevated blood levels ranged from 11 µg/L to 94 µg/L and elevated urine levels ranged from 11 µg/L to 4,813 µg/L. Among the 271 individuals with an identified exposure source, 254 (94%) were nonwork-related exposures and 17 (6%) were work-related exposures. Of the nonwork-related exposures, 229 (90%) were from the consumption of fish. Work exposures included recycling fluorescent bulbs, laboratory spills, hazardous waste disposal, and the manufacture of mercury-containing products. Laboratory tracking of elevated mercury provides a mechanism for educating the public about the recommended quantity and species of fish to eat to minimize exposure as well as a way to identify cases that could require a public health response.