An evaluation of the “GGP” personal samplers under semi-volatile aerosols: sampling losses and their implication on occupational risk assessment

Abstract

Semi-volatile (SV) aerosols still represent an important challenge to occupational hygienists due to toxicological and sampling issues. Particularly problematic is the sampling of hazardous SV that are present in both particulate and vapour phases at a workplace. In this study we investigate the potential evaporation losses of SV aerosols when using off-line filter-adsorber personal samplers. Furthermore, we provide experimental data showing the extent of the evaporation loss that can bias the workplace risk assessment. An experimental apparatus consisting of an aerosol generator, a flow tube and an aerosol monitoring and sampling system was set up inside a temperature controlled chamber. Aerosols from three n-alkanes were generated, diluted with nitrogen and sampled using on-line and off-line filter-adsorber methods. Parallel measurements using the on-line and off-line methods were conducted to quantify the bias induced by filter sampling. Additionally, two mineral oils of different volatility were spiked on filters and monitored for evaporation depending on the samplers flow rate. No significant differences between the on-line and off-line methods were detected for the sum of particles and vapour. The filter-adsorber method however tended to underestimate up to 100% of the particle mass, especially for the more volatile compounds and lower concentrations. The off-line sampling method systematically returned lower particle and higher vapour values, an indication for particle evaporation losses. We conclude that using only filter sampling for the assessment of semi-volatiles may considerably underestimate the presence of the particulate phase due to evaporation. Thus, this underestimation can have a negative impact on the occupational risk assessment if the evaporated particle mass is no longer quantified.

Development and field testing of a miniaturized sampling system for simultaneous sampling of vapours and droplets

“…As previously mentioned, the compound partitioning between lters and adsorbers is depending on concentration, on the substances' vapour pressure, on sampling temperature, on the volume of air passed through the lters and on RH. While the rst three parameters were discussed in the previous sections, the effect of ow rates on phase fractionation was previously reported by Dragan et al 8 The effect of RH on evaporation losses from lters was tested on DEG and TEGME as polar compounds and on C16 as non-polar compound. The lter-adsorber fractionation was studied on three concentrations for each compound and two levels of RH: 40% and 80%.…”

“…The measurement method employed in Germany for metalworking uids for example is based upon collection of the aerosols by means of the GSP sampling head and a downstream XAD-2 adsorber resin layer. 8 Depending on the adsorption tube type, vapour sampling is usually performed at ow rates of between 66 and 333 ml min À1 . Particle sampling however is generally performed at substantially higher ow rates than vapour sampling.…”

“…A Topas SLG 270 aerosol generator (Topas GmbH, Germany) was chosen to produce monodisperse droplets of adjustable PSD. The generator's operation principle was described in detail by Altmann and Peters 29,30 and was found to be suitable for oil mist generation by Dragan et al 8,14 For this study monodisperse droplets in the size range of 1 to 4 mm were generated at a ow rate of 5 l min À1 .…”

“…On-line analysis. The apparatus used for the on-line analysis of the aerosols is described in more detail by Dragan et al 8,14 For the on-line analysis the apparatus consisting of an FID (JUM 109A, JUM Engineering GmbH, Germany) and an Optical Particle Counter (OPC, Welas digital 3000, Palas GmbH, Germany) was set up to quantify the total analyte mass concentration (TM) and particle mass concentration (PM) respectively. The vapour mass concentration (VM) was calculated as the difference between FID and OPC measurements (VM ¼ TM À PM).…”

“…6 Sampling of aerosols containing SV compounds using methods like lter sampling can prove to be challenging. [7][8][9] The particles trapped on lters can readily evaporate [10][11][12] or vapours can adsorb 13 on ltration substrates, thus leading to measurement errors as a consequence.…”