Health Effects of Manganese and Nickel
Both Manganese and Nickel are substances identified as Toxic Air Contaminants by the California Air Resources Board.
According to section 39655 of the California Health and Safety Code, a toxic air contaminant is "an air pollutant which may cause or contribute to an increase in mortality or an increase in serious illness, or which may pose a present or potential hazard to human health."
Health Effects of Manganese
Manganese is essential to iron and steel production by virtue of its sulfur-fixing, deoxidizing, and alloying properties.
Manganese has long been known to be a health hazard to workers at high doses. Its effects at low doses are poorly understood. There appear to be three major targets for toxicity: the brain, the lungs, and the testes. At high doses, such as those found in some workplaces, manganese causes a severe, degenerative neurological condition almost indistinguishable from Parkinson's disease. This disease, known as manganism, begins as a loss of appetite, apathy, fatigue, psychotic behavior, and clumsiness. The final stages include an expressionless, mask-like face, difficulty initiating movements, a shuffling gait, and tremors. At lower levels of exposure, delayed reaction time, poor hand-eye coordination, memory loss and tremors have been reported.
Several studies suggest a subtle effect of manganese on behavioral characteristics and learning ability in children. Infants fed formula enriched with manganese have significantly higher hair manganese levels and more trouble with hyperactivity and learning disabilities.
Although infants are unquestionably a susceptible population, the elderly may also be at risk of accelerated neurological decline from low-level manganese exposure. Victims of Parkinson's disease may be particularly susceptible.
Inhalation of manganese is toxic to the lungs, and produces an inflammatory reaction that increases susceptibility to pneumonia and bronchitis. Low-level air exposures have been reported to increase the prevalence of respiratory symptoms (phlegm, wheezing, sore throat) in school children.
Animal studies have shown that exposure to manganese during fetal development at doses below those, which cause other toxic effects retards growth of the testes and reduces testosterone concentrations. The research in male rats is supported by similar findings in human workers. In one study, workers exposed at levels averaging one fifth of the allowable workplace exposure limit had significantly fewer children during the period of exposure to the metal compared to similar unexposed workers. This finding suggests an adverse effect of manganese on male fertility.
Health Effects of Nickel
Based on findings of carcinogenicity and the results of risk and exposure assessment, the California Air Resources Board has determined that nickel and nickel compounds are toxic air contaminants.
Nickel is a silvery white, soft metal that is highly resistant to atmospheric corrosion and retains a high polish. Nickel is used for the production of various metal alloys, cast irons, and electroplated goods.
The International Agency for Research on Cancer (IARC) has found sufficient evidence of carcinogenicity in humans to classify nickel compounds in Group 1, which includes the chemicals and group of chemicals, which are "causally associated with cancer in humans. The IARC classifies metallic nickel in Group 2B or "possibly carcinogenic to humans."
The Environmental Protection Agency (EPA) concludes that there is sufficient evidence of carcinogenicity in humans to place nickel refinery dust and nickel subsulfide in Group A (known human carcinogens). EPA has also concluded that there is sufficient evidence of carcinogenicity in animals to classify nickel carbonyl, the most toxic form of nickel, in Group B2 (probable human carcinogens).
The State of California has determined that all nickel compounds should be considered potentially carcinogenic to humans by inhalation. Several studies of nickel refinery workers have demonstrated that there is an association between respiratory cancer mortality and nickel exposure. California’s Department of Health staff found this association to be consistent, replicable, of substantial magnitude, and having a clear
dose-response relationship with high statistical significance.
Greater Boston Physicians for Social Responsibility
California Air Resources Board 1991 staff report recommending nickel compounds be listed as toxic air contaminants.