Caracterización de la exposición a benceno, tolueno y xileno (BTX's) en trabajadores de tres refinerías sudamericanas

Resum

The major purpose of this study raises the characterization of occupational daily exposure to benzene, toluene and xylene of different workplaces, in three refineries in the petrochemical industry in South America, with a total population of 1,225 workers distributed in 168 jobs. To achieve this objective, we made first a measurement program of screening aimed at the identification of contaminants in the atmosphere of the workplace, to know the order of magnitude of the concentrations of these pollutants and to locate emission sources (fugitive emissions). Subsequently, we proceeded to design an appropriate monitoring strategy, to represent the daily exposure of workers to benzene, toluene and xylene (BTX's). To represent the daily exposure of workers to these three pollutants, we used a methodology proposed by the UNE-EN-689, "Workplace atmospheres. Guidance for the assessment of exposure by inhalation to chemical agents for comparison with limit values and measurement strategy", which is based on the selection of homogeneous groups with respect to the exposure, taking as unit of study and analysis the homogeneous group instead of the workplace. During the field phase, an environmental monitoring was conducted using active samplers (suction pumps) to determine the daily exposure (DE) to benzene, toluene and xylene, for workplaces and homogeneous exposure groups. Moreover, the biological exposure indexes (BEI's) were determined by biological controls for benzene, toluene and xylene, taking a sample of workers biological fluid (urine) of the population sample (n = 403) at the end of shift. One of the objective was to establish whether there was a correlation between environmental measurements and biological controls. Among the results, it must be underlined that in one of the three refineries, the limit values of environmental exposure to benzene are exceeded for 5 of the workplaces; likewise, the biological limit value (VLB) set for benzene in urine samples of exposed workers is exceeded. However the daily exposure to toluene and xylene found in the three refineries had levels of low or very low concentration, which was confirmed by the biological indicators of exposure for these two pollutants. The short-term exposures to toluene and xylene exceeds the limit value (VLA-EC = 100 ppm) in some Exposure Homogeneous Groups (EHG), in the three refineries in study. In some of the workplaces in the administrative area that are not located within the areas or benzene exposure groups, were found positive results for biomarkers in the analyzed urine (biological indexes of benzene exposure), still these cases always matched with active smoking workers. The environmental concentration values for benzene exposure found in our study (n = 403) are in the range of 0.020 to 3.85 ppm, with an average of 0.43 ppm and an SD = 0.41; they are somewhat higher, although similar to those found in other studies. This study confirms the correlation found by other authors, between environmental measurements of occupational exposure to benzene and biological measurements obtained from biological exposure indexes obtained from urine samples taken at the end of shift. We agree with other researchers, in that the environmental monitoring seems to be the best method of assessing personal exposure in conditions of low concentration levels of benzene; although the biological monitoring remains a useful addition, as a measure of exposure assessment.