Equation for Calculating the Concentration of Solvent in Air That Discriminates between Exposure and Non-exposure Based on Biomarker Concentrations in the Urine of Workers

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<p>To develop a new method for evaluating the intensity of workers’ exposures to toluene alone or toluenein mixed solvents, regression equations were calculated between the concentrations of toluene towhich workers were exposed and the concentrations of hippuric acid or toluene in workers’ urinesamples taken at the end of their shifts. Thereafter, the discriminant exposure concentration of thesolvents in air, which was the concentration considered to discriminate exposure from non-exposurewithin a fi xed level of error using fi ducial ranges of individual specimens (DEC-I) or using confi denceranges of regression equation (DEC-R), was measured by a scale. The devised equations were appliedto calculate DEC-I or DEC-R accurately using the formulas expressing a regression line and its fi ducialranges or confi dence ranges. The equations can calculate not only more precise values of DEC-Ior DEC-R than can be measured by a scale, but can also calculate values corresponding to any levelof error. Moreover, DEC-I and DEC-R can be defi ned by the equations. The concentration capableof discriminating TLV (threshold limit value) exposure from non-TLV exposure was estimated usingfi ducial ranges (DTL-I) and then using confi dence ranges of the regression equation (DTL-R).</p>