Comparison of Trans, Trans-Muconic Acid Level between Roadside Occupations and Office Group in Maptaphut Area, Rayong Province, Thailand

Abstract

The purpose of this study was to compare the urine level of trans, trans-muconic acid (t,t-MA), a biomarker of occupational or environmental exposure to benzene, among roadside occupations and office group in Map Ta Phut area, Rayong province. The study subjects were 80 roadside-working individuals (gas-station employees, traffic police, motorcycle taxi drivers and grilled-meat vendors) assigned as the study groups, and 20 office workers as the control group. Data were collected using questionnaire; and urine samples were collected before and the end of work, and subsequently transported for laboratory investigation for t,t-MA level using high pressure liquid chromatography. Descriptive statistics, Wilcoxon signed ranks test and Mann-Whitney U-test were used for data analysis. It was found that urine geometric mean (GM) ± geometric standard deviation (GSD) of t,t-MA level among the gas-station employees, the traffic police, the motorcycle taxi drivers and the grilled-meat vendors before work was 1.392±66.681, 0.158±22.275, 0.560±48.852, 0.035±1.000 µg/g Cr respectively; and the level for the control group was 0.035±1.000 µg/g. At the end of work, the level for each of the study groups was 2.631±86.141, 0.402±46.887, 1.564±50.349, 0.330±34.834 µg/g Cr respectively; and that for the control group was 0.056±6.769 µg/g Cr. There was a significant increase of the concentrations of t,t-MA between before-and-after work for grilled-meat vendors (p<0.05). The gas-station employees and motorcycle taxi drivers had significantly higher levels of t,t-MA than the control group. It is recommendations that people with roadside occupations should have regular risk assessment. These informal workers, not entitled for occupational compensation, should undergo annual screening t,t-MA and be advised to occasionally refrain from roadside work.