Animal studies have reported reproductive effects such as sterility and developmental effects such as decreased activity levels in the offspring of animals exposed to manganese. No information is available regarding the carcinogenic effects of manganese in humans, and animal studies have reported mixed results. EPA has classified manganese as a Group D, not classifiable as to carcinogenicity in humans. Exceedance of the RfC does not imply that an adverse health effect would necessarily occur. As the amount and frequency of exposures exceeding the RfC increase, the probability of adverse health effects also increases.
Several tests are available for measuring manganese in blood, urine, hair, or feces.
However, because manganese is a normal part of the body, some manganese is always found in these materials. In addition, excess manganese is usually removed from the body within a few days, making it difficult to measure past exposure to manganese. However, other animal tests in which manganese has been given orally have indicated that manganese has low acute oral toxicity. No cases of manganese deficiency have been observed in humans. However, manganese deficiency in animals has been associated with impaired growth, skeletal abnormalities, impaired reproductive function in females, testicular degeneration in males, and ataxia.