Environmental and Biological Assessment of Exposure to Benzene in Petroleum Workers

Occupational exposure to benzene was measured in two gasoline marketing terminals and five major refineries in Singapore. A total of 280 workers were monitored over two years. This assessment was carried out with two primary objectives: (1) To find out the extent of occupational exposure to benzene in the petroleum industry in Singapore, (2) To identify suitable biomarkers for monitoring of low levels of benzene exposure. The exposure was measured in five different categories of petroleum and petrochemical workers, i.e., truck drivers, despatch assistant, process operators, oil movements operators and laboratory technicians. The results revealed wide variations in exposure, from 0.01 to 13.6 ppm for personal time weighted average (TWA) exposure over the whole workshift. The exposure of truck drivers appeared to be the highest, with geometric mean (GM) of 1.98 ppm (ranged from 0.25 to 13.6 ppm). The average benzene exposure for process operators was relative low with a GM of 0.04 ppm. Lowest benzene exposure was found in the laboratory technicians, with a GM of 0.02 ppm. As cigarette smoking is known to affect metabolism of benzene, data analyses on the relationships with environmental exposure were conducted only on the 190 nonsmokers. The results showed that urinary trans, trans-muconic acid (ttMA), unmetabolized benzene in urine (UBZ) and benzene in blood (BBZ) were better biomarkers for low level benzene exposure as compared to urinary phenolic metabolites in urine, such as hydroquinone, phenol and catechol.     

Study of solubility of isoproturon by its complexation with beta-cyclodextrin

The inclusion complexes of beta-cyclodextrin-isoproturon were prepared using techniques such as kneading, co-evaporation, and co-precipitation. These complexes were characterised for physical properties and spectral studies such as UV, FTIR, and 1HNMR spectroscopy. To investigate the stoichiometry of the complexes Phase solubility method was adopted. Most of the complexes showed an increase in the dissolution rate of the herbicide. The best results were obtained when inclusion complexes were prepared by co-precipitation and co-evaporation method. Findings of this paper will allow the rational use of isoproturon with increase in its efficacy.