What is the most hazardous form of mercury ingestion?

• A. Vapor
• B. Methylmercury
• C. Ethylmercury
• D. Inorganic mercury

Answer: (A)

The most hazardous form when mercury is ingested is the organic form that includes methylmercury. This compound is absorbed very efficiently from the gastrointestinal tract and travels in the bloodstream to critical organs, including the brain, where it can cause serious neurodevelopmental and neurological effects. It also bioaccumulates in the food chain, so dietary exposure through fish and seafood is a common route. Ethylmercury behaves similarly but is cleared from the body more quickly, so its long-term hazard via ingestion is typically lower than that of methylmercury. Inorganic mercury salts are less readily absorbed from the gut than methylmercury, making ingestion-related toxicity less severe in comparison. Mercury vapor, by contrast, is a major hazard through inhalation, not ingestion, since elemental mercury vapor is poorly absorbed when swallowed but readily absorbed via the lungs.