Human biological monitoring of mercury for exposure assessment

Mercury (Hg) is a naturally occurring element that has metallic, inorganic and organic forms, each with their own implications for human health. Exposure to mercury primarily occurs by inhalation of metallic mercury vapors and by dietary intake of organic mercury. Early health effects are often not well detected. Therefore, determination of the internal dose is a valuable approach in primary prevention. With this review, we aim to give an overview of the different human biological monitoring (HBM) approaches for shortand long-term exposure to different chemical forms of mercury. We performed a literature search in PubMed using Medical Subject Headings (MeSH) terms as well as free text words. From 417 reviews found, we selected 8 reviews. In addition, online information from national and international health authorities was used. The format of the biological application datasheets from the BIOMONECS project was used to provide an overview of the different biological media for HBM of mercury and methyl mercury. Recent exposure to metallic mercury can be assessed by blood sampling within 24 h after exposure. If children are involved, breath sampling can be considered as a less invasive alternative. Urinary mercury levels mainly reflect long-term inhalation exposure to elemental mercury vapors and divalent mercury. Mercury in blood and hair reflects midand long-term exposure to methyl mercury, whereas analysis of a hair segment close to the scalp indicates recent exposure. A flow chart was developed to support the selection of the most suitable HBM approach. For each of the different biological matrices, we provided an overview of advantages and limitations. Depending on the source and duration of exposure, blood, exhaled air, urine or hair can be used for mercury exposure assessment.