Experimental Evaluation of Oil Mists Using a Semivolatile Aerosol Dichotomous Sampler
Division of Environmental Health Sciences, School of Public Health, University of Minnesota, Minneapolis, Minnesota, USA.Journal of Occupational and Environmental Hygiene (Impact Factor: 1.17). 04/2010; 7(4):203-15. DOI: 10.1080/15459620903582244
The sampling performance of the semivolatile aerosol dichotomous sampler (SADS) was tested and compared with existing vapor and particle sampling methods: filtration, electrostatic precipitation, and vapor adsorption. Seven different test fluids were used to generate test droplets, and their concentrations and composition in each phase were evaluated using gas chromatography. The amount of wall loss inside the SADS was also evaluated. Combined vapor and particle concentrations for each test aerosol were not statistically different from one another as a function of test method. However, the particle concentrations estimated using the SADS were statistically higher than those from the other methods. In experiments with hexadecane, the particle concentrations estimated using the SADS, an electrostatic precipitator, and a glass fiber filter were 2.50 mg/m3, 0.05 mg/m3, and 0.01 mg/m3, respectively. For commercial metalworking fluid (MWF) droplets, compounds having low molecular weight were more prevalent in the vapor phase than those compounds with high molecular weight. The compositions of the particle phase were similar to those of the original fluids. The wall losses of hexadecane and bis(2-ethylhexyl) sebacate (BEHS) were 0.25% and 26.5% of combined vapor and particle concentrations in the SADS sampling, respectively. Because it can avoid evaporative losses, SADS will sample semivolatile aerosols more accurately than common filtration methods and may often yield higher particle concentrations than can be measured using the other methods.
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ABSTRACT: Abstract Phase distribution of airborne chemicals is important because intake and uptake mechanisms of each phase are different. The phase distribution and concentrations are needed to determine strategies of exposure assessment, hazard control, and worker protection. However, procedures for establishing phase distribution and concentration have not been standardized. The objective of this study was to compare measurements of an airborne semivolatile pesticide (chlorpyrifos) by phase using two different procedures. Six pesticide applications in two facilities were studied and at each site, samples were collected for three time slots: T1, the first 1 or 2 hours after the commencement of application; T2, a six-hour period immediately following T1; and T3, a six-hour period after the required reentry interval (24 hours for chlorpyrifos).Two phase-separating devices were collocated at the center of each greenhouse: Semivolatile Aerosol Dichotomous Sampler (SADS) using flow-rates of 1.8 l.min(-1) and 0.2 l.min(-1), corresponding to a total inlet flow rate of 2.0 l.min(-1) with a vapor phase flow fraction of 0.1, and electrostatic precipitator (ESP), along with a standard OVS XAD-2 tube. Chlorpyrifos in vapor and particulate form in SADS sampling train and that in vapor form in ESP sampling train were collected in OVS tubes. Chlorpyrifos in particulate form in ESP setting would have been collected on aluminum substrate. However, no chlorpyrifos in particulate form was recovered from the ESP. Overall (vapor plus particle) concentrations measured by OVS ranged 11.7-186.6 μg/m(3) at T1 and decreased on average 77.1% and 98.9% at T2 and T3, respectively. Overall concentrations measured by SADS were 66.6%, 72.7%, and 102% of those measured by OVS on average at T1, T2, and T3, respectively. Particle fractions from the overall concentrations measured by SADS were 60.0%, 49.2%, and 13.8%, respectively, for T1, T2, and T3. SADS gives better guidance on the distribution of chlorpyrifos than does the ESP, although the accuracy of the concentration distribution cannot be verified in the absence of a standardized procedure for determining phase division.
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