Evaluation of a prototype inhalable sampler: metal aerosols

Occupational exposure limits are generally decreasing and traditional samplers used for quantifying occupational exposures have numerous limitations: cost, disposability, detection of low concentrations, and some even fail to match international inhalable sampling conventions. A low cost, high-flow (10 L min-1) inhalable prototype sampler was developed from the 37-mm cassette and tested in previous studies. These studies called for additional field testing as an area and personal sampler. The sampler was paired with the IOM (2 L min-1), a traditional inhalable air sampler, and deployed in metal working facilities. The samplers were compared to determine whether the prototype matched the IOM and whether the new sampler could improve the sensitivity for detecting lower concentrations of metals. The following processes were sampled: welding, grinding, soldering, pouring, sawing, tending and shooting guns. A total of 21 out of 28 paired samples had detectable metals out of 15 possible metals. There were seven out of eight personal samples and 14 out of 20 area samples with detectable metal concentrations. The average sample time was seven hours, but ranged from 4.2 – 8.3 hours. The most common metals that were detected on 10 or more samples were iron, manganese, zinc, copper, and lead. Metal concentrations collected by the two samplers were not statistically different for the aggregate metal concentrations collected (p = 0.67), metals collected by sample type, personal or area (p = 0.52) or by particle “sizes,” small or large (p = 0.40), collected from the processes. While the samplers were not statistically different, linear regression equations to assess the sampler relationships showed that there were significant differences between the two samplers. Over the total metal concentrations collected, the prototype collected about 71% of what the IOM collected. By sample type, the prototype performed better during area sampling as opposed to personal sampling and by particle size, the prototype performed better in the collection of smaller, heat generated particles, as opposed to larger, mechanically generated particles. Though minor differences were found between concentrations detected on the prototype and IOM, it was determined that in general, these differences were negligible in their interpretation and comparison to occupational exposure limits. Plots also indicated that the prototype sampler performs well at sampling low concentrations of metals, however, only a small amount of metals were detected on the prototype that were not found on the IOM, therefore, the improvement of sensitivity was not assessed. High-flow sampling was hindered by the ability of air sampling pumps to maintain the required operation flow rate of 10 L min-1 for the duration of a work shift. Additional field studies are needed to determine whether the sensitivity for detecting lower concentrations of metals can be improved.