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.

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.

Short-term effects of air pollution on the number of hospital admissions in eight municipalities of the Metropolitan Area of Monterrey, Mexico, were assessed from 2016 to 2019 using a time-series approach. Air quality data were obtained from the Atmospheric Monitoring System of Nuevo Leon State (SIMA) which belongs to SINAICA (National System of Air Quality Information), providing validated data for this study. Epidemiological data were provided by SINAIS (National System of Health Information), considering admission by all causes and specific causes, gender and different age groups. 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 permissible maximum values established in Mexican official standards. A basal Poisson model was constructed to assess the association between daily morbidity and air pollutants, from this, a second scenario in which daily mean concentrations of air pollutant criteria increase by 10% was considered. Most of pollutants and municipalities studied showed a great number of associations between an increase of 10% in their current concentrations and morbidity, especially for the age group between 5 and 59 years during cold months, excepting ozone which showed a strongest correlation during summer. Results were comparable to those reported by other authors around the world, however, in spite of relative risk index (RRI) values being low, they are of public concern. This study demonstrated that considering the nature of their activities, economically active population and students, they could be more vulnerable to air pollution effects. Results found in this study can be used by decision makers to develop public policies focused on protecting this specific group of the population in metropolitan areas in Mexico.

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.

This study reports the trace metal concentrations in PM₁₀ collected in two urban sites of Campeche, Mexico (the INAH site, located in the downtown, and the TNL site, located in the Tecnologico Nacional de Mexico campus Lerma). Trace metals (Cd, Co, Cu, Fe, Mn, and Zn) were determined by flame atomic absorption spectroscopy, with Fe and Mn being the most dominant species. Cd and Co showed high values of enrichment factors, indicating that they were highly enriched by anthropogenic sources. A health risk assessment was carried out according to the IRIS-EPA methodology considering both carcinogenic and non-carcinogenic effects and different age and gender population groups. The TNL site showed cancer risk coefficients that exceed the maximum limits established by the EPA and the WHO (1 × 10⁻⁶ and 1 × 10⁻⁵, respectively), being higher for Cd and Co. The non-carcinogenic risk exceeded the limits recommended by the EPA, being higher in the INAH site for cobalt (HQ = 28.92). There is a latent risk that the exposed population may develop cardiovascular and respiratory diseases due to inhalation of the metals measured in PM₁₀. It is necessary to carry out more continuous monitoring campaigns of trace metals linked to PM₁₀ in this area to enable a better understanding of the effects of these contaminants on the health of the exposed population. The results of the present work constitute the first efforts to evaluate the trace metals concentrations in PM₁₀ in urban areas of the city of Campeche, Campeche and can be used to develop programs focused on improving air quality.