Ortho-cresol as indicator for toluene exposure among workers

Abstract

Toluene is a volatile organic solvent used by most industries and household items such as lacquers, paints, glue and nail polish. Recently, the negative health effects on exposure to toluene have attracted various studies. To combat the negative effects, American Conference of Governmental Industrial Hygienists (ACGIH) had lowered the occupational exposure limit from 100 ppm to 50 ppm of toluene vapour. Therefore, this could be translated into the need for a new, simple and more specific indicator test to monitor the degree of toluene exposure among workers. Reports showed that toluene is transformed into its metabolites once consumed or exposed to it. The qualitative detection of these metabolites therefore can be used as an indicator for toluene exposure. Presently in Malaysia, hippuric acid detected in urine is used as the indicator for the degree of toluene exposure. However, hippuric acid is also influenced by one’s dietary intake like black tea, acidic food and sodium benzoate as in food preservatives. In addition, at low levels of toluene exposure, hippuric acid showed poor correlation and linearity in analysis. Thus, in this study, another metabolite of toluene, ortho-cresol was introduced. It was found that urinary ortho-cresol was more specific and sensitive in monitoring toluene exposure. In this study, the degree of toluene exposure of six workers (real samples) was analyzed using urinary ortho-cresol. The samples, along with standards, were characterized using UV-Vis spectrophotometer. Three samples out of six samples were found to have ortho-cresol concentrations between 3.00 ppm - 3.05 ppm. These concentrations are all above the permitted value of 3.00 ppm. A detector kit which establishes the presence of ortho-cresol in urine was also developed in this study. The kit, which exploits a simple colour test with 0.2 ppm as its lowest limit of detection is indispensible especially to monitor the health of workers that are exposed almost daily to toluene.