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Molybdenum (as Mo), insoluble compounds (total dust)

General Description

Synonyms: Metallic molybdenum

OSHA IMIS code: 1790

CAS number: 7439-98-7

Exposure Limits and Health Effects (Updated September 6, 2012)

Standard Set By Exposure Limit Health Effect Codes -- Health Effects and Target Organs
OSHA PEL - General Industry
See 29 CFR 1910.1000 Table Z-1
15 mg/m3
HE16 -- mild eye, nose, throat, and skin irritation
OSHA PEL - Construction Industry
See 29 CFR 1926.55 Appendix A
15 mg/m3
HE16 -- mild eye, nose, throat, and skin irritation
OSHA PEL - Shipyard Employment
See 29 CFR 1915.1000 Table Z - Shipyards
15 mg/m3
HE16 -- mild eye, nose, throat, and skin irritation
NIOSH REL Not established  
ACGIH TLV® (1999) 10 mg/m3 (inhalable particulate matter) TWA
3 mg/m3 (respirable particulate matter) TWA
HE16 -- mild eye, nose, throat, and skin irritation
CAL/OSHA PELs 10 mg/m3 TWA (total dust)
3 mg/m3 TWA (respirable)
HE16 -- mild eye, nose, throat, and skin irritation

Carcinogenic classification:

  • NTP: Not listed
  • IARC: Not listed
  • EPA: Not listed

EPA Inhalation Reference Concentration (RfC): Not established

ATSDR Inhalation Minimal Risk Levels (MRLs): Not established

NIOSH IDLH concentration: 5000 mg/m3 (as Mo)

Notes on other potential health effects and hazards:

  1. While molybdenum can be combustible, it is so only during specific conditions (NIOSH/IPCS 2006).
  2. In general, molybdenum toxicity is low, given that it is an essential element necessary for human health (ACGIH 2003).
  3. Certain forms of molybdenum appear to be more toxic than others. For instance, in some studies, molybdenum trioxide and ammonium molybdate have been shown to be more toxic than molybdenum disulfide, molybdenum dioxide, or metallic molybdenum (ACGIH 2003).
  4. A 1984 study of mining and metallurgy workers found exposures to 60 to 600 mg/m3 of molybdenum were associated with nonspecific symptoms such as weakness, fatigue, headache, and joint/muscle pain (ACGIH 2003).
  5. Other studies have linked molybdenum exposure to incidences of gout and bone disease, but the U.S. National Research Council (NRC) concluded that those associations were speculative at best (ACGIH 2003).
  6. The first human data on molybdenum and cancer was published in 1999, examining the link between molybdenum exposure and lung cancer. The findings raised the possibility that molybdenum could be a human carcinogen (ACGIH 2003).

Partial reference list:

  • ACGIH: Documentation of the Threshold Limit Values (TLVs) and Biological Exposure Indices (BEIs) - Molybdenum and Compounds. 2016.
  • NIOSH: Occupational Health Guideline for Molybdenum and Insoluble Molybdenum. September 1978.
  • NIOSH/CEC/IPCS: International Chemical Safety Cards - Molybdenum. October 10, 2006.

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