Study of the dynamic behaviour of hazardous semi-volatile multi-component aerosols and impact on workplace sampling (SEVOMEGA)

Status:

completed 05/2018

Aims:

Aerosols originating from Semi-Volatile Organic Compounds (SVOC) represent a big challenge to industrial hygienists due to toxicological and sampling issues. Hazardous semi-volatiles can be found in both particulate and vapor phases in the workplace, which makes the sampling especially problematic. Likewise, more attention has to be drawn to these dynamic aerosol systems as the particle-vapor distribution is considerably depending on the sampling conditions. This study was carried out to address the issue of semi-volatile aerosol particle evaporation both theoretically and experimentally as well as to test new approaches / personal samplers towards measurements of SVOC aerosols in workplaces.

Activities/Methods:

SVOC Aerosols of several polar and non-polar substances and particle diameters were generated, diluted with particle free nitrogen and monitored for particle evaporation losses. The aerosols were quantified using on-line and off-line methods. The on-line approach for analyzing SVOC aerosols comprised the detection of the total mass (TM) using a Flame Ionization Detector (FID) coupled with a heated transfer line. The particle mass (PM) was calculated from the particle diameter measured via an optical particle sizer, while the vapor mass (VM) was calculated as the difference between the measured total and particulate mass (VM=TM-PM). The on-line method provided the reference towards the partitioning of SVOC aerosols between vapor and particle phase. One important aspect of the project was to test the possibility of measuring the real particle-vapor partitioning of SVOC aerosols with off-line samplers that can also be used for workplace measurements. The aerosols’ vapor and particulate phases were collected using three substrates (denuder-filter-adsorber).

Results:

Measurements have shown that SVOC particles can evaporate completely within a very short time or remain unchanged, depending on substance volatility, vapor saturation, particle diameter and sampling temperature. Prototypes of new personal samplers were found to be appropriate for workplace measurements, with over 96% collection efficiency of the vapor phase and particle losses below 5%.

The sampler which suited best for workplace measurements was used to quantify the particle-vapor distribution of SVOC aerosols in an underground mine. Field measurements in the platinum mine revealed a predominance of alkanes in the air. PAHs were also present in a substantial amount, in both the particle and the vapor phase.

Conclusions: Our results show that aerosol particle evaporation can be predicted with good accuracy and that new sampling methods can add new information towards measuring the particle-vapor partitioning of workplace aerosols. The use of new samplers can provide reliable data approaching the composition of the particulate and vapor phases. This in turn allows for a better interpretation of the exposure data and a more accurate risk assessment.

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