DETERMINATION OF THE URINARY METABOLITES OF STYRENE - ESTIMATION OF THE METHOD EVALUATION FUNCTION AND EVALUATION OF REFERENCE VALUES IN DANISH SUBJECTS

A European study on styrene exposure was initiated in 1989 to evaluate the health effects of environmental and occupational exposure. A part of this study included the development of an analytical method for us e in a biological monitoring program. The urinary metabolites of styre ne, mandelic acid (MA) and phenylglyoxylic acid (PGA) were quantitated by a direct and convenient high-performance liquid chromatography met hod. Urine samples were diluted with eluent and analysed by HPLC with a C, reversed-phase column and a buffer to acetonitrile (9:1) eluent w ith a counterion added. The detector used was a variable UV dectector and the wavelength was lambda = 210 nm. The method was statistically e valuated by a method evaluation demonstrating no systematic error. The uncertainty was 23.8 mu mol/l and 11.5 mu mol/l for MA and PGA, respe ctively. The limit of detection (LOD) of MA is 71.4 mu mol/l and the L OD of PGA is 34.5 mu mol/l, sufficiently low for the measurement of st yrene exposure at a low exposure level. The present study indicates th at reference values for MA and PGA are low. The fraction of reference values below LOD was 0.80 for MA and 0.66 for PGA; consequently, the r eference values were described by a non-parametric one-sided tolerance interval. The 95% one-sided upper tolerance limits calculated for MA and PGA were 31.0 mu mol/mmol creatinine and 20.1 mu mol/mmol creatini ne, respectively, with the coverage 0.95 +/- 0.045 for both metabolite s. The method has been used for biological monitoring in several studi es of environmentally and occupationally exposed subjects in concentra tions up to 200 mu mol/mmol creatinine for MA and 150 mu mol/mmol crea tinine for PGA.