title: Validation of urine density correction in cases of hippuric acid and un-metabolized toluene in urine of workers exposed to toluene.
abstract: To investigate if it is appropriate to apply urine density correction when a urine sample is dense or dilute. Data on hippuric acid (HA-U), toluene (Tol-U), creatinine (CR) and specific gravity (SG) in end-of-shift urine samples and exposure to air-borne toluene were cited from previous publications. In practice, 837 cases were available, and they were classified into dense, intermediate and dilute groups taking 0.3 and 3.0 g/l of CR and 1.010 and 1.030 of SG as cut-off points. Lines of regression of HA-U and Tol-U (as observed, CR-corrected or SG-corrected) with air-borne toluene were calculated for each density groups, and correlation coefficients (CCs) were compared. The dense groups gave CCs similar to those of the intermediate groups. Dilute versus intermediate group comparison also gave promising results. These conclusions were however based primarily on the findings with observed values, because the numbers of cases in the dilute or dense group were limited when CR- or SG-correction was applied. Literature survey showed that urine density correction does not always improve the correlation between solvents in air and exposure makers in urine. It was concluded that no correction for urine density may be necessary in evaluating HA-U and Tol-U in dense (and probably also dilute) urine samples as markers of occupational toluene exposure. Just in case when correction for urine density is desired for any reason, SG-correction may be recommended.
authors.affiliation: Osaka Occupational Health Service Center, Japan Industrial Safety and Health Association, Nishi-ku, Osaka, Japan.
authors.forename: Toshio
authors.initials: T
authors.lastname: Kawai
authors.forename: Yoko
authors.initials: Y
authors.lastname: Eitaki
authors.forename: Hirohiko
authors.initials: H
authors.lastname: Ukai
authors.forename: Osamu
authors.initials: O
authors.lastname: Inoue
authors.forename: Yuki
authors.initials: Y
authors.lastname: Maeshima
authors.forename: Naohiro
authors.initials: N
authors.lastname: Ueda
authors.forename: Fumiko
authors.initials: F
authors.lastname: Ohashi
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Sakurai
authors.forename: Masayuki
authors.initials: M
authors.lastname: Ikeda
mesh_terms: D000395:Air Pollutants, Occupational / Q000032:analysis*; D003404:Creatinine / Q000652:urine; D006626:Hippurates / Q000652:urine*; D006801:Humans; D016273:Occupational Exposure / Q000032:analysis*; D015203:Reproducibility of Results; D013046:Specific Gravity; D014050:Toluene / Q000652:urine*; D016482:Urinalysis / Q000379:methods
chemical_list: D000395:Air Pollutants, Occupational; D006626:Hippurates; D014050:Toluene; D003404:Creatinine; C030514:hippuric acid