Agent Name
Alternative Name
Molybdenum and compounds
CAS Number
7439-98-7; varies
Mo, varies
Major Category
Molybdenum metal, Molybdenum compounds; [NIOSH] Molybdenum and compounds
Elements, Metallic
Dark gray or black powder with a metallic luster; [NIOSH]
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]
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

Exposure Assessment

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

Adverse Effects

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

Diseases, Processes, and Activities Linked to This Agent


Industrial Processes with risk of exposure: