Manganese

2022-02-04

Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is not found as a free element in nature, it is often found in combination with iron, and in many minerals. [1]

Manganese is a pinkish-grey, chemically active element. It is a hard metal and is very brittle. It is hard to melt, but easily oxidised. Manganese is reactive when pure, and as a powder it will burn in oxygen, it reacts with water (it rusts like iron) and dissolves in dilute acids. [2]

Uses [3]

Manganese is predominantly used to produce ferromanganese, or metallic manganese, which is used in the production of steel to improve hardness, stiffness, and strength. It is used in carbon steel, stainless steel, high-temperature steel, and tool steel, along with cast iron and superalloys. Manganese finds further applications in a number of non-ferrous alloys, especially with aluminium, magnesium, copper and zinc. The following are some of the applications of manganese compounds:

  • Manganese dioxide is commonly used in the production of batteries, matches, fireworks, porcelain, glass-bonding materials and amethyst glass, as the starting material for production of other manganese compounds, and as an oxidising agent.
  • Manganese chloride is used as a precursor for other manganese compounds, as a catalyst in the chlorination of organic compounds, as dietary supplement/food additive, in animal feed to supply essential trace minerals, in paint driers, fertilisers, in dyeing, disinfecting, purifying natural gas, and in dry-cell batteries.
  • Manganese sulfate is used in glazes, varnishes, ceramics, dyeing, fertilisers, fungicides, and ore flotation. It is also used in medicines and as a nutritional supplement.
  • Potassium permanganate is used as an oxidising agent, a disinfectant, as an anti-algal agent, in metal cleaning, in tanning, bleaching, and as a preservative for fresh flowers and fruits.
  • Manganese gluconate is used as a feed additive, food additive, and dietary supplement.
  • Manganese oxide is used in textile printing, ceramics, paints, coloured glass, animal feeds, fertilisers, and in welding. It is used as a catalyst in the manufacture of allyl alcohol, as food additive and a dietary supplement.
  • Manganese nitrate is used as a colour agent in porcelain and ceramic manufacture, as a catalyst, and in the production of manganese dioxide.
  • Manganese acetate is used in textile dyeing, fertilisers, food packaging, feed additives, and in manufacturing paints and varnishes.
  • Manganese carbonate is used as a pigment, drier for varnishes, in medications, and as a plant nutrient. It is used in the manufacturing of manganese salts, pharmaceuticals, animal feeds, and ceramics.

Sources of Emission & Routes of Exposure

Sources of Emission [3]

  • Industry sources: Problems with air pollution can arise during the mining, crushing, and smelting of ores, during steel production, and from battery factories.
  • Diffuse sources: Some agricultural and gardening applications may use products containing manganese. Some hazardous waste sites may leach manganese.
  • Natural sources: Manganese is a naturally occurring element, although it is not naturally found in the metallic form. The earth’s crust contains approximately 0.1 % manganese on average, with low levels present in lakes, streams, and the ocean. Nodules containing manganese oxides have been found on the seabed of the Pacific. More than 100 manganese minerals are known, including sulfides, oxides, carbonates, silicates, phosphates, and borates. The most important manganese mineral is native manganese dioxide (pyrolusite). Manganese ores very often occur together with iron ores.
  • Transport sources: Mobile sources are normally not associated with emissions of manganese.
  • Consumer products: Alkaline and dry cell batteries, some vitamin/mineral dietary supplements, some fertilisers, some disinfectants, some porcelain and ceramic goods. Some drinking water supplies may contain small amounts of manganese.

Routes of Exposure [4,5]

  • The main routes of exposure to manganese are inhalation, ingestion and contact with the skin and eyes.
  • The primary way you can be exposed to manganese is by eating food or manganese-containing nutritional supplements. Vegetarians, who consume foods rich in manganese such as grains, beans and nuts, as well as heavy tea drinkers, may have a higher intake of manganese than the average person.
  • Certain occupations like welding or working in a factory where steel is made may increase your chances of being exposed to high levels of manganese.
  • Manganese is routinely contained in groundwater, drinking water, and soil at low levels. Drinking water containing manganese or swimming or bathing in water containing manganese may expose you to low levels of this chemical.

Health Effects [6]

Acute Effects

  • No reports of effects in humans following acute (short-term) effects of exposure to manganese are available.
  • Effects to the lung have been reported following acute exposure of rats to manganese via inhalation.
  • Manganese is considered to have moderate acute toxicity based on short-term tests in rats. However, other animal tests in which manganese has been given orally have indicated that manganese has low acute oral toxicity.

Chronic Effects

  • Chronic exposure to manganese at low levels is nutritionally essential in humans. The recommended daily intake of manganese is 2 to 5 mg/d for adults and adolescents.
  • No cases of manganese deficiency have been observed in the general population. However, manganese deficiency in animals has been associated with impaired growth, skeletal abnormalities, impaired reproductive function in females, and testicular degeneration in males.
  • Chronic inhalation exposure of humans to manganese results primarily in effects on the nervous system. Slower visual reaction time, poorer hand steadiness, and impaired eye-hand coordination were reported in several studies of workers occupationally exposed to manganese dust in air.
  • Chronic inhalation exposure of humans to high levels may result in a syndrome called manganism and typically begins with feelings of weakness and lethargy and progresses to other symptoms such as gait disturbances, clumsiness, tremors, speech disturbances, a mask-like facial expression, and psychological disturbances.
  • Other chronic effects reported in humans from inhalation exposure to manganese are respiratory effects such as an increased incidence of cough, bronchitis, dyspnea during exercise, and an increased susceptibility to infectious lung disease.
  • The Reference Concentration (RfC) for manganese is 0.00005 mg/m3 based on impairment of neurobehavioral function in humans.
  • EPA has established a Reference Dose (RfD) for manganese of 0.14 milligrams per kilogram body weight per day (mg/kg/d) based on CNS effects in humans.

Reproductive/Developmental Effects

  • Reproductive effects, such as impotence and loss of libido, have been noted in male workers afflicted with manganism attributed to occupational exposure to high levels of manganese by inhalation. No information is available on developmental effects of manganese in humans.
  • Animal studies have reported degenerative changes in the seminiferous tubules leading to sterility from intratracheal instillation of high doses of manganese (experimentally delivering the manganese directly to the trachea). In young animals exposed to manganese orally, decreased testosterone production and retarded growth of the testes were reported.
  • Decreased activity levels and a decrease in average pup weight have been noted in the offspring of mice exposed to manganese by inhalation.

Cancer Risk

  • Oral human and animal studies on manganese are inadequate. Several animal studies reported an increased incidence of thyroid gland follicular cell adenomas and hyperplasia, or increased incidence of pancreatic tumours.
  • EPA has classified manganese as a Group D, not classifiable as to carcinogenicity in humans.

Safety [7]

First Aid Measures

  • Eye Contact: Check for and remove any contact lenses. In case of contact, immediately flush eyes with plenty of water for at least 15 minutes. Get medical attention if irritation occurs.
  • Skin Contact: Wash with soap and water. Cover the irritated skin with an emollient. Get medical attention if irritation develops.
  • Inhalation: If inhaled, remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult, give oxygen. Get medical attention.
  • Ingestion: Do NOT induce vomiting unless directed to do so by medical personnel. Never give anything by mouth to an unconscious person. Loosen tight clothing such as a collar, tie, belt or waistband. Get medical attention if symptoms appear.

Fire & Explosion Information

  • Manganese in non-flammable.
  • Moderate fire potential, in the form of dust or powder, when exposed to flame.
  • If heated in the vapour of phosphorus at a very dull red heat, union occurs with incandescence.
  • Concentrated nitric acid reacts with powdered manganese with incandescence and explosion.
  • Powdered manganese ignites in chlorine.
  • Moderate explosion potential, in the form of dust or powder, when exposed to flame.

Exposure Controls & Personal Protection

Engineering Controls

  • Use process enclosures, local exhaust ventilation, or other engineering controls to keep airborne levels below recommended exposure limits.
  • If user operations generate dust, fume or mist, use ventilation to keep exposure to airborne contaminants below the exposure limit.

Personal Protective Equipment

The following personal protective equipment is recommended when handling manganese:

  • Safety glasses;
  • Lab coat;
  • Dust respirator (be sure to use an approved/certified respirator or equivalent);
  • Gloves.

Personal Protective Equipment in Case of a Large Spill:

  • Splash goggles;
  • Full suit;
  • Dust respirator;
  • Boots;
  • Gloves;
  • A self contained breathing apparatus should be used to avoid inhalation of the product.
  • Suggested protective clothing might not be sufficient; consult a specialist BEFORE handling this product.

Regulation

United States [5,8]

OSHA: The Occupational Safety & Health Administration has set the following Permissible Exposure Limit (PEL)for manganese:

  • General Industry: 29 CFR 1910.1000 Table Z-1 — 5 mg/m3 Ceiling
  • Construction Industry: 29 CFR 1926.55 Appendix A — 5 mg/m3 Ceiling
  • Maritime: 29 CFR 1915.1000 Table Z-Shipyards — 5 mg/m3 Ceiling

ACGIH: The American Conference of Governmental Industrial Hygienists has set a Threshold Limit Value (TLV) for manganese of 0.2 mg/m3 TWA (TLV listed as Manganese and inorganic compounds, as Mn)

NIOSH: The National Institute for Occupational Safety and Health has set a Recommended Exposure Limit (REL) for manganese of 1 mg/m3 TWA; 3 mg/m3 STEL

EPA: The Environmental Protection Agency has determined that exposure to manganese in drinking water at concentrations of 1 mg/L for up to 10 days is not expected to cause any adverse effects in a child. It has also established that lifetime exposure to 0.3 mg/L manganese is not expected to cause any adverse effects.

FDA: The Food & Drug Administration has determined that the manganese concentration in bottled drinking water should not exceed 0.05 mg/L.

Australia [3]

Safe Work Australia: Safe Work Australia has set the exposure standard for manganese dust, fume, and compounds (as manganese) to 1 mg/m3 (TWA). The recommended short-term exposure level (STEL) for manganese fume should not exceed 3 mg/m3.

Australian Drinking Water Guidelines specify the following limits:

  • Health: Maximum of 0.5 mg/L (i.e. 0.0005 g/L)
  • Aesthetic: Maximum of 0.1 mg/L (i.e. 0.0001 g/L)

References

http://en.wikipedia.org/wiki/Manganese

http://www.lenntech.com/periodic/elements/mn.htm

http://www.npi.gov.au/resource/manganese-compounds

http://www.atsdr.cdc.gov/toxguides/toxguide-151.pdf

http://www.atsdr.cdc.gov/toxfaqs/tf.asp?id=101&tid=23

http://www.epa.gov/ttn/atw/hlthef/manganes.html

http://www.sciencelab.com/msds.php?msdsId=9924577

https://www.osha.gov/dts/chemicalsampling/data/CH_250190.html