Study On The Biological Exposure Limit Of Occupational Exposure To Xylene

Background Prevention of occupational exposure to xylene was essentially to be solved for occupational health. Many countries proposed the occupational exposure limit values of xylene to protect workers’health, and correspondently established biological xylene limit values for occupational exposure to xylene and relevant determination method for regularly environmental surveillance and biomonitoring to evaluate the exposure extent of xylene. In China the time-weighted average of xylene(TWA) in workplace air is50mg/m3,and the the permissible concentration-short-term exposure limit (PC-STEL) is100mg/m3. The biological exposure limit values for MHA was formulated respectively in Germany and America, Germany recommended BAT of MHA in the urine for2.0g/L after long-term exposure at the end of the shift or after exposure in2008, and for the United States, BEI of MHA in the urine at the end of the shift was1.5g/g Cr in2006, but China had not established relevant standardized testing methods and biological exposure limit values for MHA in urine. Medical College in Wuhan University of Science and Technology and Wuhan Municipal Occupational Disease Prevention Hospital jointly apply to the Professional Committee of occupational health standards belong to Ministry of Health in China for the subject of the biological exposure limit values for MHA and its detection method, what’s more item number was20110206. So it was important to recommend the biological exposure limit values for MHA in China.Object To recommend the biological exposure limit values for MHA in China.Methods Choosing the workers of no occupational exposure to xylene for research object of urine sample and using appropriate pretreatment method,the MHA in samples was qualitatively analysised at the chromatogram condition of ODS C18chromatogram column,35℃column temperature,25℃temperature indoor,230nmUV detection wavelengh and methyl alcohol:glacial acetic acid(33:67,V/V). Confecting different MHA concentration standard and facturing standard curve,the concentration linearity range of MHA was tested.The correlation of urinary Methyl hippuric acid (MHA) levels and the concentrations of toluene in workplace air was found out, and it was recommended of biological exposure limit values for MHA through out hygiene survey and site-detected concentration of xylene on the three companies using the xylene, the determination of urinary Methyl hippuric acid (MHA)in workers exposed to different doses of xylene, combined with occupational epidemiological investigation.Results The MHA concentration in urine for occupational xylene-exposed was tested by high performance liquid chromatography.The linearity range of calibration curve was significantly correlated at the MHA concentration of0.025～1.0mg/ml.The detection limits of the method wereo-MHA:4.59μg/ml; m-MHA:4.33μg/ml; p-MHA:4.54μg/ml.The precisions(RSD) for the analysis were2.0～9.7%.The average recovery rate range was from91.4～101.4%.The research shows that there was a good correlation of urinary Methyl hippuric acid (MHA) levels and the concentrations of toluene in workplace air. The regression analysis of the equation was Y=0.0052X+0.0112(r=0.731,n=57,p<0.001), compared to six of the linear regression equation abroad, according to China’s current environmental air exposure limit values to xulene of50mg/m3(PC-TWA), the biological exposure limit values for urinary MHA was respectively0.271g/g、Cr0.203g/L、0.181g/L、0.209g/L、0.229g/L、0.230g/g Cr、0.161g/g Cr.They were between to0.161～0.271g/gCr (g/L)Conclusions According to China’s current environmental air exposure limit values to xylene of50mg/m3(PC-TWA) and in combination with the other studies at home and abroad,the biological exposure limit values for urinary MHA in China was proposed as0.3g/g Cr.