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]

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

Hepatotoxin, Secondary

ACGIH Carcinogen

Confirmed Animal

Links to Other NLM Databases
Health Studies

Human Health Effects from Hazardous Substances Data Bank:

Toxicity Information


Chemical Information

Search ChemIDplus

Biomedical References

Search PubMed

Related Information in HazMap

Industrial Processes with risk of exposure: