An outbreak of methylmercury poisoning due to consumption of contaminated grain.

An outbreak of methylmercury poisoning took place in the fall and winter of 1971-72 in Iraq. Six thousand five hundred and thirty cases were admitted to hospitals throughout the country and 459 died in hospital. The outbreak was the result of eating homemade bread prepared from wheat treated with a methylmercury fungicide. The wheat was intended for planting purposes only. Signs and symptoms of poisonings in adults indicate that the major site of action of this form of mercury is the central nervous system. Severe brain damage also resulted from prenatal exposure when the mother ingested large amounts of the contaminated bread. The frequency of signs and symptoms in an exposed population was found to be related to the estimated maximum blood levels, i.e., the concentration in blood at the end of exposure. A small percentage of the population exhibited a significant increase in complaints of paresthesia at maximum blood levels in the range of 240 to 480 ng Hg/ml. At higher blood levels a greater proportion of the population complained of paresthesia and other signs and symptoms became apparent.