Formaldehyde risk assessment for occupationally exposed workers.

Formaldehyde has been shown to be carcinogenic in animals and should be considered potentially carcinogenic in humans. The mechanism of action is unknown but formaldehyde is weakly genotoxic and also may act as a late stage carcinogen or promoter. An estimated 1.3 million workers are potentially exposed to formaldehyde through their occupation. Of those exposed workers, about 3.5% were found to be exposed to formaldehyde air concentrations greater than the 3 ppm set by OSHA as a permissible exposure level. Fewer than 12% were exposed to concentrations greater than 1 ppm, but over 88% were exposed to concentrations of 0.5 ppm or more. A quantitative risk assessment, using the multistage low-dose extrapolation model, found the (maximum likelihood) estimate of lifetime risk for excess cancers to be 620 per 100,000 at the OSHA permissible exposure level. The estimated risk is 23 per 100,000 at 1 ppm and 2.8 per 100,000 at 0.5 ppm. Reduction of the OSHA permissible exposure level to 1 ppm would significantly decrease risk with minor economic disruption for most industries involved. However, reduction of risk to levels which have been generally regarded by other regulatory agencies as acceptable, i.e., 10(-5) to 10(-6), would require increased control by all the industries reviewed.