Development and Evaluation of a Method to Estimate Potential Formaldehyde Dose from Inhalable Dust/Fibers

Abstract

A method for the estimation of formaldehyde dose from inhalable dust/fibers using a commercially available inhalable sampler was developed. Filters containing sampled dust/fibers were placed in 10 ml of distilled water and incubated at 37°C for 4 hours to liberate the formaldehyde from the dust/fibers. After incubation, the filter extracts were passed with a 0.45 μm filter to remove particles left in the extracts. Two analytical procedures were used for the analysis of the filter extracts. Either a 4-ml aliquot was analyzed using the chromotropic acid procedure, as outlined in NIOSH Method 3500, or a 1-ml aliquot was treated with 2,4-dinitrophenylhydrazine and a catalytic amount of perchloric acid and analyzed by high-performance liquid chromatography for the resulting 2,4-dinitrophenylhydrazone. The limits of detection for the chromotropic acid procedure and the 2,4-dinitrophenylhydrazine procedure were 0.44 and 0.08 μg per filter sample, respectively. Relative standard deviations of replicate determinations of formaldehyde content by the chromotropic acid procedure were 3.4 percent for textile samples (ca. 180 μg and 8.2-6.6 percent for wood dust samples (7-11 μg).

Two comparisons of the inhalable samplers with closed-face cassette samplers were conducted at a garment manufacturing plant and a waterbed accessory production plant. The inhalable samplers on average collected more dust/fibers than the closed-face cassette samplers in both studies. In the garment manufacturing plant study, the formaldehyde levels in the dust/fibers were greater for the inhalable samplers than the closed-face cassettes. In the waterbed accessory plant, the formaldehyde levels were comparable for both sampler types. Although the hydrolysis procedure used in this method to liberate formaldehyde from the dust/fibers may not be fully representative of the hydrolysis occurring in the nasal and oropharyngeal passages, the formaldehyde in dust/fibers may be considered an approximation of the localized dose at the point of particle retention in the breathing passages. These results should be reported separately from vapor phase levels of formaldehyde until sufficient data has been collected to allow appropriate epidemiological interpretation of formaldehyde-containing particulate exposures.