A field study was carried out in the Metropolitan Area of Monterrey (MAM), the second most populated city in Mexico, characterized by increasing urbanizati

Atmospheric benzene and carbonyls were studied in San Nicolas de los Garza, Nuevo Leon, during 2011 and 2012. The relative abundance for measured VOCs was the following: formaldehyde (9.06 µg m⁻³) > acetaldehyde (8.06 µg m⁻3) > benzene (0.65 µg m⁻³). All measured VOCs had a clear seasonal trend with higher values of concentration during summer. Benzene and formaldehyde had a marked diurnal trend with the highest levels during morning, whereas acetaldehyde did not show a clear diurnal pattern. Meteorological analysis showed that the dominant winds came from NNE and ENE, suggesting that sources located in these directions contribute to the VOC levels. Principal component analysis (PCA) analysis revealed that photochemical activity influenced benzene and carbonyl levels during summer and that benzene was associated with vehicular traffic emissions during autumn and winter, showing good correlation with CO. Meteorological data showed that measured VOCs were influenced by regional sources. A health risk assessment showed that local exposure to carbonyls and benzene exceeded 1 × 10⁻⁶ for integrated lifetime cancer risk. People living in San Nicolas de los Garza, thus, have a probable risk of suffering cancer in their lifetime. It is, therefore, necessary to improve environmental policies for controlling VOC levels in this area.

Short-term effects of air pollution on the health of residents in the Metropolitan Area of Monterrey, Mexico were assessed from 2012–2015 using a time-series approach. Guadalupe had the highest mean concentrations for SO₂, CO and O₃; whereas Santa Catarina showed the highest NO₂ concentrations. Escobedo and Garcia registered the highest levels for PM₁₀. Only PM₁₀ and O₃ exceeded the maximum permissible values established in the Mexican official standards. Most of pollutants and municipalities showed a great number of associations between an increase of 10% in their current concentrations and mortality, especially for people >60 years. Different scenarios resulting from climatic change were built (increases of 5–25% in daily mean temperature), but only the increase of 25% (5 °C) showed a significant association with air pollutant concentrations and mortality. All pollutants and municipalities showed significant increases in relative risk indexes (RRI) resulting from an increase of 5 °C when people >60 years was considered. Results were comparable to those reported by other authors around the world. The RRI were low but significant, and thus are of public concern. This study demonstrated that the elderly is strongly threatened not only by atmospheric pollution but also by climatic change scenarios in warm and semiarid places.

Levels of BTEX (Benzene, Toluene, Ethylbenzene and p-Xylene) were determined in the ambient air of two urban sites located in the Metropolitan Area of Monterrey (MAM) during two climatic seasons of 2023. The study revealed that BTEX compounds in Santa Catarina and Obispado had the following relative abundance: p-Xylene (20.09 µg m⁻³) > Toluene (19.50 µg m⁻³) > Ethylbenzene (19.34 µg m⁻³) > Benzene (17.39 µg m⁻³). Their concentrations were consistent with global reports, showing diurnal and seasonal variability. Levels were higher during the dry season due to elevated temperatures, low wind speeds, and lack of precipitation, which reduced pollutant dispersion. BTEX concentrations in Santa Catarina (industrial site) and Obispado (urban site) were influenced by local activities like industrial processes, area sources, and vehicular traffic. Wind rose analysis confirmed the influence of local sources, with higher BTEX levels when winds came from the east. This was linked to pollutant transport within MAM and thermal inversions trapping pollutants during the dry season. Benzene/Toluene (B/T) and p-Xylene/Ethylbenzene (X/E) ratios showed that the sampling sites were influenced by vehicular sources and local fresh emissions. Benzene inhalation has an unacceptable lifetime cancer risk, urging MAM authorities to implement stricter regulations to protect public health. While non-cancer risks were within acceptable limits, controlling Benzene and p-Xylene emissions remains critical to improving air quality.

The spatiotemporal distributions of aromatic hydrocarbon levels in the atmosphere were evaluated at ten locations within Monterrey’s Metropolitan Area using passive sampling techniques across three climatic seasons (the rainy season of 2023, the cold front season of 2023, and the dry season of 2024). The observed relative abundance was toluene > p-xylene > benzene > ethylbenzene. The dry season showed the highest concentration values for all measured compounds, and the Santa Catarina site showed the highest average level for toluene (2.79 μg m⁻³). In the rainy season, the highest average concentrations were recorded in Santa Catarina, with toluene at 1.39 μg m⁻³ and p-xylene at 0.99 μg m⁻³. During the cold fronts season, the greatest average concentration of p-xylene (0.98 μg m⁻³) was found in San Bernabe, while Santa Catarina reported the highest average for toluene at 1.55 μg m⁻³. A health risk assessment indicated that cancer risk coefficients exceeded the reference values set by the EPA. These findings suggest that the presence of the alkyl derivatives of benzene (benzene, toluene, ethylbenzene, and p-xylene) in the studied region poses a potential health issue and highlights the need for enhanced control measures regarding their sources.

Benzene, toluene, ethylbenzene, p-xylene, O₃, NO_x, CO, PM_2.5 and meteorological parameters were measured in urban air of one site in Tijuana, Baja California, Mexico during winter 2016-2017. Samples were collected using 1.5 h time intervals at four different sampling periods (B1: 07:30-09:00 h, B2: 12:00-13:30 h, B3: 15:00-16:30 h, B4: 18:00-19:30 h) before being analyzed by gas chromatography with flame ionization detection. The highest concentrations of BTEX occurred during the morning (B1) and afternoon (B4) 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. The toluene/benzene, xylene/ethylbenzene concentration ratios and meteorological analysis indicated that BTEX levels were influenced by local and fresh emissions (vehicular traffic). Bivariate (Pearson correlation) and multivariate analyses (Principal Component Analysis) were performed in order to correlate BTEX concentrations with criteria air pollutants and meteorological parameters to infer their possible sources. These results suggest that changes in the existing environmental policies should therefore be applied to improve air quality.