Scientific basis for an occupational standard for cadmium

Area of Science:

• Environmental Health
• Occupational Medicine
• Toxicology

Background:

• The U.S. Occupational Safety and Health Administration (OSHA) proposed revised 8-hour permissible exposure limits (PELs) for cadmium.
• These proposed limits are 1 or 5 micrograms/m3, aiming to prevent lung cancer and kidney dysfunction.

Purpose of the Study:

• To evaluate the scientific basis for OSHA's proposed cadmium exposure limits.
• To compare OSHA's risk estimates with empirical data from published literature.

Main Methods:

• Review of at least seven epidemiologic studies on renal tubular proteinuria and cumulative cadmium exposure.
• Analysis of qualitative and quantitative evidence for lung cancer carcinogenicity in human occupational cohorts.
• Comparison of risk estimates derived from mathematical modeling versus empirical data.

Main Results:

• Some studies indicate increased proteinuria at cumulative exposures below 500 micrograms/m3-year (equivalent to a PEL of 11.1 micrograms/m3).
• One study showed increased proteinuria between 100 and 299 micrograms/m3 (equivalent to a PEL of 2.2-6.6 micrograms/m3).
• Qualitative evidence suggests cadmium is a human carcinogen; quantitative risk estimates from human data are more plausible than rodent bioassay data.

Conclusions:

• Insufficient data exist to establish a no-effect level for cadmium-induced kidney toxicity.
• The permissible exposure limit (PEL) for cadmium should not exceed 5 micrograms/m3.
• This limit is recommended to protect workers from kidney dysfunction and lung cancer over a working lifetime.