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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 r2 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.

Item Type:	Refereed Article
Keywords:	biological exposure index; biological monitoring; methylhippuric acid; xylene
Research Division:	Medical and Health Sciences
Research Group:	Pharmacology and Pharmaceutical Sciences
Research Field:	Toxicology (incl. Clinical Toxicology)
Objective Division:	Health
Objective Group:	Public Health (excl. Specific Population Health)
Objective Field:	Environmental Health
Author:	Jacobson, GA (Dr Glenn Jacobson)
Author:	McLean, SR (Professor Stuart McLean)
ID Code:	28441
Year Published:	2003
Web of Science® Times Cited:	14
Deposited By:	Pharmacy
Deposited On:	2003-08-01
Last Modified:	2011-05-25
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