Atmospheric Levels of BTEX and Criteria Pollutants (CO, NO2, O3 and PM2.5) in an Urban Site Located in North Baja California, Mexico: Source Implications and Health Risk

Atmospheric levels of BTEX (benzene, toluene, ethylbenzene, p-xylene) and criteria air pollutants (O3, NO2, CO, PM2.5) were measured in urban air of one site located in North Baja California, Mexico during winter 2017. Diurnal variation was studied collecting samples at 1.5 h time intervals in different sampling periods: 07:30-09:00 h, 12:00-13:30 h, 15:00-16:30 h, and 18:00-19:30 h and then analyzed by gas chromatography with flame ionization detection. The highest concentrations of BTEX occurred during the morning (07:30-09:00h) and afternoon (18:00-19:30h) sampling periods. Mean concentrations of BTEX were 32.40 μg/m3 for benzene; 13.28 μg/m3 for toluene; 17.16 μg/m3 for p-xylene; and 7.02 μg/m3 for ethylbenzene. BTEX concentration ratios and meteorological analysis indicated that these compounds were influenced by local and fresh emissions. Pearson correlation and Principal Component Analysis were performed in order to correlate BTEX concentrations with criteria air pollutants and meteorological parameters to infer their possible sources. A health risk assessment showed that local exposure to benzene exceeded 1 x 10-6 for integrated lifetime cancer risk. It suggests that people living in Tijuana, Baja California, Mexico may have a probable risk of suffering cancer in their lifetime. These results indicate that changes in the existing environmental policies should therefore be applied to improve air quality in this region.