Toxicity Profiles

RAGs A Format for Manganese - CAS Number 7439965

Manganese is a silver-colored, naturally occurring metal that is found in many types of rocks and makes up about 0.10% of the earth's crust. Manganese is not found alone but combines with other substances such as oxygen, sulfur, or chlorine. Manganese can also be combined with carbon to make organic manganese compounds, including pesticides (e.g., maneb or mancozeb) and methylcyclopentadienyl manganese tricarbonyl (MMT), a fuel additive in some gasolines. Manganese is an essential trace element and is necessary for good health. Normal nutritional requirements of manganese are satisfied through the diet, which is the normal source of the element, with minor contributions from water and air. The National Research Council recommends a dietary allowance of 2-5 mg/day for a safe and adequate intake of manganese for an adult human. Manganese can be found in several food items, including grains, cereals, and tea.

Manganese can elicit a variety of serious toxic responses upon prolonged exposure to elevated concentrations, either orally or by inhalation. The central nervous system is the primary target. Initial symptoms are headache, insomnia, disorientation, anxiety, lethargy, and memory loss. These symptoms progress with continued exposure and eventually include motor disturbances, tremors, and difficulty in walking, symptoms similar to those seen with Parkinsonism. These motor difficulties are often irreversible. Some individuals exposed to very high levels of manganese for long periods of time at work developed mental and emotional disturbances and slow and clumsy body movements. This combination of symptoms is a disease called "manganism."

There are no human cancer data available for manganese. Some conflicting data exist on possible carcinogenesis following injections of manganese chloride and manganese sulfate in mice. However, the EPA weight-of-evidence classification is D, not classifiable as to human carcinogenicity, based on no evidence in humans and inadequate evidence in animals.

The following is a presentation of the toxicity information associated with Manganese.

Noncarcinogenic Health Effects
  • The Oral Chronic Reference Dose for Manganese in the diet is 1.40E-01 (mg/kg-day).
  • The Oral Chronic Reference Dose for Manganese in water is 4.60E-02 (mg/kg-day).
  • The Oral Chronic Reference Dose has a modifying factor of 1.
  • The Oral Chronic Reference Dose has an uncertainty factor of 1.
  • The Oral Chronic Reference Dose is based on the NRC study from 1989.
  • The Oral Chronic Reference Dose study critical effect is CNS effects.
  • The overall confidence in the Oral Chronic Reference Dose is medium.

  • The Inhalation Chronic Reference Concentration is 5.00E-05 (mg/m3).
  • The Inhalation Chronic Reference Concentration has a modifying factor of 1.
  • The Inhalation Chronic Reference Concentration has an uncertainty factor of 1000.
  • The Inhalation Chronic Reference Concentration is based on the Roels et al. study from 1992.
  • The Inhalation Chronic Reference Concentration study critical effect is impairment of neuro-behavioral function.
  • The overall confidence in the Inhalation Chronic Reference Concentration is medium.

  • The Dermal Chronic Reference Dose for Manganese in the diet is 5.60E-03 (mg/kg-day).
  • The Dermal Chronic Reference Dose for Manganese in water is 1.84E-03 (mg/kg-day).
  • The Dermal Chronic Reference Dose is based on a gastrointestinal absorption factor of 0.0400.