Incidents poisoning, mercury

The cardinal neurological marker of mercury vapor intoxication is tremor. Workers in the hat industry frequently suffered from mercury poisoning. Mercury compounds helped convert the stiff, straight animal fur into a limp, flexible mat that could be shaped into a hat. Vapor escaped during the process, and, inhaled day after day by the workers, sometimes evoked tremor so severe that some found it difficult even to walk without support. A survey of hat factories conducted by the US Public Health Service in 1940 found a clear relationship between workplace mercury levels and the severity and incidence of tremor. Eventually, the mercury compounds were replaced. 

One of the worst incidents of mercury poisoning occurred in Minamata and Niigata, Japan, in 1950. At that time, the ocean was polluted with high levels of mercury from industrial wastes. Because fish were a major food in the diet, more than 2000 people were affected with mercury poisoning and many died or developed neural damage. In the United States, between 1988 and 1997, the use... 

Another major incident concerning methyl mercury was the severe pollution of Minamata bay in Japan (see Box 8.1). Here fish, fish-eating and scavenging birds, and humans feeding upon fish all died from organomercury poisoning. There may have been localized declines of marine species in this area due to methyl mercury, but there is no clear evidence of this. 

Fungicides have caused a number of human health disasters. In the late 1950s, approximately 4000 people in Turkey were poisoned by hexachlorobenzene that had been applied to seed grain to protect against soil fungus. Adults and particularly children developed diseases of the skin and bone. In Iraq, a similar incident occurred when people consumed grain coated with a mercury compound. 

When used in therapeutic doses, dimercaprol is associated with a high incidence of adverse effects, including hypertension, tachycardia, nausea, vomiting, lacrimation, salivation, fever (particularly in children), and pain at the injection site. Its use has also been associated with thrombocytopenia and increased prothrombin time—factors that may limit intramuscular injection because of the risk of hematoma formation at the injection site. Despite its protective effects in acutely intoxicated animals, dimercaprol may redistribute arsenic and mercury to the central nervous system, and it is not advocated for treatment of chronic poisoning. Water-soluble analogs of dimercaprol—unithiol and succimer—have higher therapeutic indices and have replaced dimercaprol in many settings. 

The most notorious incident of widespread mercury poisoning in modem times occurred in the Minimata Bay region of Japan during the period of 1953 to 1960. Mercury waste from a chemical plant draining into the bay contaminated seafood consumed regularly by people in the area. Overall, 111 cases of poisoning with 43 deaths and 19 congenital birth defects were documented. The seafood was found to contain 5 to 20 ppm of mercury. 

There are several incidents of heavy metal intoxication and contamination of livestock feedstuffs. The source of the heavy metals was from smelters being deposited on forage or heavy metals as contaminants being incorporated into feedstuffs (Curley et al, 1971 Rice et al, 1987 Coppock et al, 1988 Galey et al, 1990 Swarup et al, 2005). The risk for translocation of lead to milk appears to increase with blood lead levels above 0.20 pg/ml. Human poisoning has occurred when meat from pigs fed methyl mercury was consumed. 

In one tragic incident, an entire community on Minamata Bay in Japan was poisoned, with extremely serious birth defects, very painful reactions, mental disorders, and many deaths. Only after lengthy research was the cause determined to be mercury compounds discarded into a river by a plastics factory. Whether it was inorganic salts or methylmercury compounds seems uncertain, but the contamination was immense and methylmercury compounds were found in the silt and in animals and humans. The methylmercury was readily taken up by the organisms living in the bay and, because the people of the community depended on fish and other seafood from the bay for much of their diet, the entire community was poisoned. 

The nervous system is very sensitive to mercury. In poisoning incidents that occurred in other countries, some people who ate fish contaminated with large amounts of methylmercury or seed... 

The literature describes several mercury poisoning epidemics. Outbreaks occurred in Iraq, Pakistan, and Guatemala from bread made with mercury-contaminated grain. Three separate incidents of mass poisonings occurred in Iraq in 1956,1960, and 1972 (Bakir et al. 1973). In the 1972 epidemic, 6,530 people were hospitalized, and 450 died (Maghazaji 1974). In 1969, a New Mexico family became ill after they consumed organic mercury-contaminated pork (Roueche 1970). 

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