Comparison of Filter and Wall Deposits From Samplers Used to Collect Airborne Lead-Containing Dusts at Field Sites

Abstract

and 37 mm closed face cassette samplers (CFC) were deployed where occupational exposures to lead-containing dusts were known to occur. Discrete particle analyses of wall and filter deposits were performed by Scanning Electron Microscopy-Energy Dispersive Xray Spectrometry (SEM-EDX). From the elemental composition and projected area diameter of each particle a density, volume, and mass were calculated, and a mass-weighted size distribution for each filter and corresponding wall deposit determined. Comparison of pairs of wall and filter mass-weighted size distributions by Mann-Whitney statistical analysis shows that in only 3 of 72 examples from either sampler were the distributions significantly different that suggests that the mechanisms of particle deposition on the sampler walls for particles in this size range (0.5 µm through 20 µm) do not differ for the different samplers. Furthermore, in only 4 of 33 sampler pairs did the IOM and CFC results differ. Although these results originate from several distinct processes characterized by different chemical and physical dust generation mechanisms, they suggest that in these environments the measurement of "total dust" by the CFC and inhalable dust by the IOM will be very similar when both samplers are processed the same way with respect to the including or excluding wall deposits with the filter catch. However, these results may not be applicable to environments where larger particles exist.

Preliminary Studies on the Use of Acid-Soluble Cellulose Acetate Internal Capsules for Workplace Metals Sampling and Analysis

“…(2) This underestimation results from a significant accumulation of sampled particles on internal sampler walls that is not included in many analytical procedures. (2,3) A significant mass of material, up to or even exceeding that found on the filter, can be deposited on the internal surfaces of the air sampling device during sampling and subsequent handling. (2)(3)(4)(5)(6)(7)(8) Sampling for airborne metal dusts in occupational environments requires the evaluation of all particles entering the sampler, whether or not they are found on the filter.…”

“…(2,3) A significant mass of material, up to or even exceeding that found on the filter, can be deposited on the internal surfaces of the air sampling device during sampling and subsequent handling. (2)(3)(4)(5)(6)(7)(8) Sampling for airborne metal dusts in occupational environments requires the evaluation of all particles entering the sampler, whether or not they are found on the filter. (2)(3)(4)(5) Procedures to incorporate this material, such as wiping (4) or rinsing, (9) with the filter for subsequent analysis, are labor intensive.…”

Comparison of a Wipe Method With and Without a Rinse to Recover Wall Losses in Closed Face 37-mm Cassettes used for Sampling Lead Dust Particulates

“…However, there is a risk of underestimating actual exposures if only the filter is analyzed. Particles containing lead have shown no qualitative difference in the size distribution when aerosols deposit on the filter or on the internal surfaces of the cassette in controlled laboratory (Lee et al 2009) and field (Chisholm et al 2012) experiments.…”

Recent Advances in Occupational Exposure Assessment of Aerosols

“…However, the issue has also been studied for airborne organic materials, including bacterial endotoxin [ 34 ], wood [ 35 ], and pharmaceutical dusts [ 22 ]; another relevant study reported results from investigations in thermosetting plastics, wood, paper, and animal breeding [ 36 ]. Except in the case of very large wood dust particles, there is no evidence to suggest that wall deposited particles are sufficiently different from those found on the collection substrate to warrant their exclusion [ 37 , 38 ]. Wall deposits are not limited to aerosol samplers for larger airborne particles but may also be found in samplers for finer particles [ 39 , 40 ].…”