The application of diffusive sampling combined with thermal desorption in occupational exposure monitoring--field evaluation.

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Diffusive sampling combined with thermal desorption (DSTD) is considered useful in monitoring workers' exposures to organic vapors, not only due to its simplicity of operation in the field but, also, its simplifying the sample treatment, eliminating the use of extracting solvent, and increasing analytical sensitivity. Herein, the feasibility of applying DSTD in field conditions was assessed through a comparison of the results with those from the well-accepted active/charcoal method. Side-by-side active and diffusive (tube-type, Tenax TA as the adsorbent) samples, both personal and area, were collected and analyzed for xylenes, ethyl acetate, styrene, and n-butyl acetate in four different industrial settings. Statistically significant correlations were found between the two methods in personal samples with the correlation coefficients of 0.92, 0.90, 0.83, 0.88, and 0.97 for m&p-xylenes, o-xylene, n-butyl acetate, styrene, and ethyl acetate, respectively. A paired t-test revealed significant difference between the two methods for n-butyl acetate and styrene. For area sampling, statistical differences (p < 0.05) were found between the two methods, except for xylenes. The DSTD method had, mostly, a lower concentration than the active method, with the bias ranging from 10.2 to -54.4 percent. The possible causes for the discrepancies are discussed. These results suggest that though DSTD protocols can be considered as a simple approach for screening workers' exposures to volatile organics, they should be applied with caution since diffusive sampling is potentially affected by various environmental conditions and adsorptive characteristics.