Urinary metabolites as exposure biomarkers of benzene, toluene, ethylbenzene, and xylene in footwear workers and assessment of pulmonary function

Aim: This pilot cross-sectional study focused on biological monitoring of the benzene, toluene, ethylbenzene, and xylene (BTEX) urinary metabolites trans, trans-muconic acid (tt-MA), s-phenyl mercapturic acid (SPMA), hippuric acid (HA), mandelic acid (MA), and methylhippuric acid (MHA) and measured the effects of workplace BTEX exposure on pulmonary function of workers engaged in footwear manufacturing. Materials and Methods: Urinary metabolites tt-MA, SPMA, HA, MA, and MHA concentration in urine samples of study participants (N = 35) were analyzed by reverse-phase high-pressure liquid chromatography. Pulmonary function parameters were measured by spirometer and peak flow meter. Demographic information and work exposure information of study participants were collected by questionnaire interview. Results: In exposed workers, concentration of urinary SPMA, tt-MA, and HA was significantly higher (P < 0.01, in all) than the control group. Reduction in both force expiratory volume in 1 s (Forced expiratory volume in one second) and peak expiratory flow rate (PEFR) were inversely associated (P < 0.01) with growing years of age among all workers. Inverse association was measured between urinary tt-MA and decline in forced vital capacity and PEFR (P < 0.05, for each) in workers. Based on the questionnaire interview, workers were not found to be aware of workplace exposure hazards. Conclusions: Exposure biomarkers of benzene (tt-MA and SPMA) and toluene (HA) were significantly higher in workers than the control group. Study results evident the presence of occupational exposure to benzene and toluene in footwear workers. Deterioration in FEV1 and PEFR were also measured among all workers with growing years of age. The sample size was small in the present study, so further research required to confirm our results.