Atmospheric levels of BTEX in urban regions of southeastern Mexico: health risk and associated sources.

Benzene, toluene, ethylbenzene, and xylene (BTEX) concentrations were measured using active sampling during discrete, multiday campaigns conducted in 2022 and 2024 across three cities in southeastern Mexico. Sampling was performed at five sites during three daily periods (morning, midday, and evening) to represent typical human activity conditions. The BTEX compounds exhibited clear spatial differences among the three studied cities. Ciudad del Carmen presented the highest concentrations, with the following order: benzene (4.20 ± 1.32 µg m⁻3) > toluene (3.89 ± 1.18 µg m⁻3) > xylenes (3.69 ± 0.33 µg m⁻3) > ethylbenzene (3.64 ± 0.12 µg m⁻3). In Minatitlan, concentrations were lower but showed a different pattern, with ethylbenzene (3.65 ± 0.06 µg m⁻3) as the dominant compound, followed by p-xylene (3.58 ± 0.12 µg m⁻3), benzene (3.50 ± 0.42 µg m⁻3), and toluene (3.23 ± 0.42 µg m⁻3). In contrast, Campeche exhibited substantially lower BTEX levels, with benzene (0.36 ± 0.29 µg m⁻3) remaining the most abundant, followed by xylenes (0.30 ± 0.09 µg m⁻3), ethylbenzene (0.26 ± 0.27 µg m⁻3), and toluene (0.22 ± 0.33 µg m⁻3). These spatial variations reflect differences in emission intensity, with petroleum-related and urban sources dominating in Ciudad del Carmen and Minatitlan, while Campeche represents a lower-intensity urban background environment influenced by dispersion and atmospheric processing. Noncarcinogenic risk (HQ < 1) remained within acceptable limits, while lifetime cancer risk (LCR) associated with benzene indicated potential carcinogenic concern. BTEX also contributed to secondary pollutant formation, with p-xylene dominating ozone formation potential (contributing over 40% at all sites) and ethylbenzene dominating the secondary organic aerosol formation potential. BTEX variability is primarily driven by petroleum-related and urban emissions, highlighting the need for sustained monitoring and targeted air quality management in southeastern Mexico.