title: Biological monitoring of low level occupational xylene exposure and the role of recent exposure.
abstract: The correlation between low level time-weighted average (TWA) atmospheric xylene exposure (p.p.m.) and urinary methylhippuric acid (MHA) expressed per gram of creatinine was examined. Subjects were recruited from workplaces that utilized xylene. Ambient monitoring of o-, m- and p-xylene isomers was carried out using passive diffusion vapour monitors. Adjusted (post-shift minus pre-shift) and post-shift urinary levels of xylene metabolites (2-, 3- and 4-MHA) were determined by GC-MS. Twenty subjects were recruited into the study. Total xylene TWA exposures were 3.36 +/- 3.63 p.p.m. (mean +/- SD) with a range of 0.03-14.44 p.p.m. The r(2) values for the regression equations between xylene exposure and individual and total adjusted MHA isomers were 0.390, 0.709, 0.677 and 0.631 for o-, m-, p- and total xylenes, respectively, which was greater than the respective correlations between non-adjusted samples. In conclusion, biological monitoring of occupational xylene exposure at levels <15 p.p.m. using urinary MHA showed a good correlation with atmospheric levels and is a valid complement to ambient monitoring. Even though occupational xylene exposure in the workplaces studied was generally low, MHA was found in the pre-shift urine of all workers and the use of adjusted values showed modest improvements in correlations. Recent exposure prior to sampling, either from occupational or non-occupational sources, should be considered when biological monitoring of xylene is undertaken. Extrapolation of data from this study predicted a MHA concentration in post-shift urine of 1.3 g/g creatinine after exposure to a TWA of 100 p.p.m. xylene.
authors.affiliation: School of Pharmacy, University of Tasmania, GPO Box 252-26, Hobart, Tasmania 7001, Australia. glenn.jacobson@utas.edu.au
authors.forename: G A
authors.initials: GA
authors.lastname: Jacobson
authors.forename: S
authors.initials: S
authors.lastname: McLean
mesh_terms: D000328:Adult; D000395:Air Pollutants, Occupational / Q000009:adverse effects / Q000652:urine*; D003404:Creatinine / Q000032:analysis*; D004784:Environmental Monitoring / Q000379:methods*; D005260:Female; D006626:Hippurates / Q000652:urine*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016273:Occupational Exposure / Q000009:adverse effects* / Q000032:analysis; D012997:Solvents / Q000032:analysis; D014992:Xylenes / Q000378:metabolism / Q000652:urine*
chemical_list: D000395:Air Pollutants, Occupational; D006626:Hippurates; D012997:Solvents; D014992:Xylenes; D003404:Creatinine; C030514:hippuric acid