Thiomersal is very toxic by inhalation, ingestion, and in contact with skin (EC hazard symbol T+), with a danger of cumulative effects. It is also very toxic to aquatic organisms and may cause long-term adverse effects in aquatic environments (EC hazard symbol N). In the body, it is metabolized or degraded to ethylmercury (C2H5Hg+) and thiosalicylate.
Cases have been reported of severe poisoning by accidental exposure or attempted suicide, with some fatalities. Thiomersal rapidly dissociates to release ethylmercury after injection; that the disposition patterns of mercury are similar to those after exposure to equivalent doses of ethylmercury chloride; and that the central nervous system and the kidneys are targets, with lack of motor coordination being a common sign.
Fecal excretion accounts for most of the elimination from the body. Ethylmercury clears from blood with a half-life of about 18 days in adults. Ethylmercury clears from the brain in about 14 days in infant monkeys. Inorganic mercury metabolized from ethylmercury has a much longer clearance, at least 120 days; it appears to be much less toxic than the inorganic mercury produced from mercury vapor, for reasons not yet understood.
Risk assessment for effects on the nervous system have been made by extrapolating from dose-response relationships for methylmercury. Methylmercury and ethylmercury distributes to all body tissues, crossing the blood-brain barrierand the placental barrier, and ethylmercury also moves freely throughout the body.
FACT: All forms of mercury are toxic.