Relationship Between the Concentration of Airborne Benzene Pollutant and the Amount of Urinary Metabolites of Trans, Trans-muconic Acid, and Hippuric Acid in Employees Working in Different Plants of Bou Ali Sina Petrochemical Company

The petrochemical industry as a modern industry, despite the positive outcomes it has brought to mankind, is a source of gaseous and aerosol pollution and industrial effluents on a large scale, which can have direct and indirect destructive effects on the environment and human life. This study investigated the relationship between the amount of airborne benzene with the amount of trans,trans-muconic acid (ttMA) and hippuric acid metabolites in the urine of workers working in petrochemical complexes with different exposure times and methods.

For this purpose, breathing the air of different petrochemical plants of Bou Ali Sina was sampled by the National Institute for Occupational Safety and Health 1501 method, and the urine of workers (n = 24) was also sampled in these units. In addition, the amount of benzene in the air samples and the amount of urinary metabolites of ttMA and hippuric acid were analyzed in urine samples sent to the laboratory using a high-performance gas chromatography-mass spectrometry device and gas-liquid chromatography. Finally, urinary creatinine was measured by an ultraviolet-visible spectrophotometer.

The results showed that the concentration of benzene in the aromatic unit had the highest value, which had a higher level of pollution than both standards. The xylene mixing unit with a concentration of 3.6 μg/m3, the loading unit with a benzene content of 3.4 μg/m3, and a tank unit with 2.8 μg/m3 had a lower amount of benzene pollution compared to the Occupational Safety and Health Administration permissible exposure limit-short-term exposure limit (OSHA PEL-STEL) standard but had higher pollution levels in comparison to the OSHA PEL-TWA (time-weighted average) standard. In the sampling unit of the laboratory with a benzene amount of 0.94 μg/m3 and in the technician unit of the laboratory, the amount of pollution was lower than both OSHA PEL-TWA and OSHA PEL-STEL standards. The aromatic unit demonstrated the highest amount of benzene, while the lowest amount was related to the laboratory section.

The results of the measurement of urinary benzene metabolites revealed that the concentration of urinary phenol and inhaled benzene in evening shift workers was higher than the corresponding amount in the morning shift workers, which may be due to the high level of pollution evenings compared to the morning. On the other hand, the results represented that the average hippuric acid in the exposed people (n = 24) was higher than the control (n = 20) so that it was 0.35 in the exposed and 0.26 in the control subjects. In addition, the average muconic acid in the exposed and control subjects decreased to 1.57 and 0.89, respectively. The minimum and maximum amounts of muconic and hippuric acids in the exposed subjects were 0.97 and 2.62, as well as 0.14 and 0.83, respectively. The maximum and minimum concentrations of muconic and hippuric acids were 2.62 and 0.97, as well as 0.83 and 0.14 in exposed subjects, respectively, which was less than muconic acid.