In nature, toxic metals generally are bound with other elements rather than being present in their pure form. However, with the advent of large-scale industrial processes to extract metals from naturally occurring compounds, humans let the genie out of the bottle, contributing significantly to the distribution of mercury, aluminum and other heavy metals in the environment. When released from nature’s semi-protective hold, these “invariably toxic” metals wreak havoc on living systems, including humans, animals and plants alike.

Modern-day scientists have been amassing evidence of mercury’s toxicity for decades, with a growing focus in recent years on the metal’s association with neurodevelopmental disorders, including autism spectrum disorder (ASD). A new review article in the multidisciplinary journal Environmental Research pulls together a wide body of literature with the aim of summing up current research and emerging trends in mercury toxicology. Geir Bjørklund, the study’s lead author, is the founder of Norway’s non-profit Council for Nutritional and Environmental Medicine and has published prolifically on topics related to heavy metals, autoimmune disorders and ASD.

Multiple avenues of exposure

Exposure to mercurial compounds remains widespread, despite feeble attempts to ban some uses. Bjørklund et al.’s review covers all three categories of mercury: elemental, organic and inorganic. Exposure to volatile elemental mercury can come about as a result of occupational contact or vapor from dental amalgam fillings. Organic mercury—the most frequent form of exposure, according to Bjørklund and colleagues—exists as methylmercury (in fish) and ethylmercury (in the vaccine preservative thimerosal). Coal-fired power plants send inorganic mercury into the environment, where the toxic metal works its way up the marine food chain.