Which form of mercury is primarily considered an environmental pollutant?

• A. Organic mercury
• B. Elemental mercury
• C. Inorganic mercury
• D. All forms equally

Answer: (A)

Mercury exists in several forms, but the form that is most concerning as an environmental pollutant is the organic form, particularly methylmercury. This compound is created in the environment when bacteria methylate inorganic mercury in waterways. It is highly persistent and lipophilic, which means it easily moves into and through biological membranes. Once in aquatic ecosystems, methylmercury readily bioaccumulates in organisms and biomagnifies up the food chain, so top predators like large fish end up with high concentrations. Humans are mainly exposed through consumption of contaminated fish and shellfish, which can lead to neurodevelopmental effects, especially in fetuses and young children. While elemental mercury and inorganic mercury compounds are toxic as well, they do not accumulate in organisms to the same extent as methylmercury, making the organic form the primary environmental pollutant.