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- Published on: 9 September 2019
- Published on: 9 September 2019Thinking outside the box is important, but carries some risk
We read with interest the article by Bhandare and Ruchi (1). They diagnosed severe organic mercury (Hg) poisoning in a 69 year old man with known hypertension and diabetes who presented with a transient altered mental status. The diagnosis was based on a history of increased fish consumption and a blood Hg level of 35 ng/mL. Methylmercury (MeHg) is the form present in seafood, but there are multiple chemical forms of Hg and each has different health consequences. Everyone who consumes seafood is exposed to MeHg, but it is the dosage that is critical. The US EPA determined the MeHg reference dose (defined as “…a daily oral exposure …that is likely to be without an appreciable risk of deleterious effects during a lifetime”) to be 5.8 ng/mL in blood. That value was based on dividing the lowest observed adverse effect level of 58 ng/mL (a value reported from a large, controversial epidemiological study) by a safety factor of 10. Blood MeHg exposures of 35 ng/mL and higher are common, with no evidence of clinical symptoms. For example, residents of the Seychelles islands consume large amounts of marine fish, have documented blood MeHg exposures at or above 35 ng/mL, and are asymptomatic. A recent Seychelles study of 1,266 mothers reported that they ate fish with meals 8.5 ± 4.5 times per week while pregnant and had a mean blood Hg level of 18.2 ng/mL (2). The maximum blood Hg level in that study was 84.2 ng/mL and no mother reported clinical manifestations. The mean...
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None declared.