Molybdenum

Synonyms

Molybdenum metal, Molybdenum compounds; [NIOSH] Molybdenum and compounds

Category

Elements, Metallic

Description

Dark gray or black powder with a metallic luster; [NIOSH]

Sources/Uses

Used in heat-resistant alloys and tools (metal); in glazes, enamels, pigments, and corrosion inhibitors (molybdenum trioxide); and in lubricants and catalysts (molybdenum disulfide); [ACGIH] Used in sheep feed to reduce copper toxicity; [Nordberg, p. 1078]

Comments

An essential trace element in the body, molybdenum appears to have, "low animal and human toxicity." [ACGIH] Causes changes in the liver, kidneys, and spleen in animal experiments; Cows grazing in pastures with high molybdenum had evidence of copper deficiency; Elevated uric acid levels and symptoms of gout have been reported in heavily exposed workers and in populations living in areas with high molybdenum and low copper concentrations in soil and plants. [Nordberg, p. 1077] Abnormal liver function tests reported in Mo-Cu workers in Russia; Fatty liver degeneration in animal experiments; [HSDB] Soluble molybdenum compounds include nitrates, acetates, chlorides, bromides, iodides, sulfates, and salts of sodium, potassium and ammonium. [Nordberg, p. 15]

Biomedical References

Insufficient data

10 mg/m3, as Mo, inhal. fraction, 3 mg/m3, as Mo, respir. fraction (metal and insol. compds), 0.5 mg/m3, as Mo, respir. fraction (sol. compds)

5 mg/m3, as Mo (sol. compds), 15 mg/m3, as Mo, total dust (metal and insol. compds.)

5000 mg/m3(metal), 1000 mg/m3, as Mo (sol. compds)

Excerpts from Documentation for IDLHs

Animal data: No fatalities were reported among animals that ingested amounts of molybdenum disulfide in doses as great as 6,000 mg Mo/kg [Fairhall et al. 1945]. No changes were observed in rats over a 4­week period following inhalation exposures to metallic molybdenum at 25,000 to 30,000 mg/m3 or to molybdenum dioxide at 10,000 to 12,000 mg/m3 for 1 hour [FDA 1975]. \ Human data: Mining and metallurgy workers chronically exposed to 60 to 600 mg Mo/m3 reported an increased incidence of nonspecific symptoms that included weakness, fatigue, headache, anorexia, and joint and muscle pain [Lener and Bibr 1984].

Plasma clearance in humans: 4-70 minutes (fast component) and 3-30 hours (slow component); [Nordberg, p. 734]

Hepatoxic (a) from occupational exposure (secondary effect) or (b) in animal studies or in humans after ingestion

Confirmed Animal

Processes

Industrial Processes with risk of exposure:

• Metal Thermal Spraying
• Steel Producing
• Welding