Agent Name

Molybdenum

Alternative Name

Molybdenum and compounds

CAS Number

7439-98-7; varies

Formula

Mo, varies

Major Category

Metals

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]

Exposure Assessment
Skin Designation (ACGIH)

Insufficient data

TLV (ACGIH)

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)

PEL (OSHA)

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

IDLH (NIOSH)

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

Hepatotoxin, Secondary

ACGIH Carcinogen

Confirmed Animal

Links to Other NLM Databases
Health Studies

Human Health Effects from Hazardous Substances Data Bank:

Toxicity Information

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Chemical Information

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Biomedical References

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Related Information in HazMap
Processes

Industrial Processes with risk of exposure: