Mercury in Food

Since mercury is ubiquitous, everyone consumes trace amounts. It can be found in all food and water, with higher concentrations in foods grown in areas having higher concentrations of mercury in soil. The short‐chain alkyl mercury compounds, methyl, dimethyl and ethyl mercury, are more toxic than elemental mercury, inorganic salts of mercury and the aryl mercury compounds. Since mercury is excreted in feces, sweat and exhaled breath as well as in urine, a daily intake of 1.0 mg per day of elemental mercury or inorganic mercury salts appears safe. The USDL established an allowable level of 0.1 mg elemental mercury vapor or inorganic salts of mercury and 0.01 mg alkyl mercury per cubic meter of air for industrial exposures. The average U.S. diet contains less than 1/50 this amount. Epidemiological studies in several locations of elevated mercury content show no cases of methyl mercury poisoning resulting from fish consumption in the U.S. F&DA does not allow the sale of fish containing more than 0.5 ppm (0.5 mg/kg) of mercury, and the canned tuna industry now includes mercury content as one of their quality specifications. The naturally occurring element, mercury, does not appear to pose a toxic hazard in the food supply of the U.S. and there is no evidence that alkyl mercury formed by microorganisms in nature has led to methyl mercury poisoning; however, this does not imply there is no reason to control the release of elemental mercury and inorganic salts of mercury into the environment from industrial operations. It does indicate the problem has been recognized. Steps have been taken to reduce discharges of elemental mercury and inorganic salts of mercury and to reduce or eliminate use of mercurials in agriculture providing an increasing margin of safety against the possibility of an excessive amount of mercury in any form finding its way into any portion of the U.S. food supply.