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This work have like purpose quantitative estimates of the short-term effects of air pollution on the health of residents of five municipalities of the Metropolitan Area of Guadalajara, Mexico from 2012 to 2015 using time-series approach. Air Quality was assessed for CO, NO2, SO2, O3 and PM10. Tlaquepaque had the highest mean concentrations for CO (0.88 ppm), NO2 (24.55 ppb), SO2 (0.0036 ppm) and PM10 (53.81 µg m–3), whereas, Zapopan registered the highest mean value for O3 (25.06 ppb). Only PM10 and Ozone exceeded the maximum permissible values established in the Mexican official standards. SO2 presented the highest RRI values in MAG, especially for Zapopan and Tonala, for the majority of the population: 0–59 years and > 60 years. Regarding to CO, excepting Guadalajara and Tlaquepaque, associations were not significant in the most of studied municipalities. The increase of risk as percentage for NO2 was 1.77% for 0–59 years in Guadalajara and Tlaquepaque, 1.87% by respiratory causes in Tlaquepaque, 1.73% > 60 years in Tonala, and 1.25% for 0–59 years in Zapopan. The association between daily mortality and increased O3 levels were significant, however, values were low for all studied municipalities. Finally, regarding to PM10, only Zapopan and Tonala showed statistical significance. This study cannot predict if reductions in criteria pollutants levels would have an important effect on a reduction in daily mortality, however, considering the large size of population exposed, even when observed associations were small but significant, RRI values found are of public concern. Keywords: Relative risk index; Mortality; Megacities; Criteria air pollutants; Mexico.

Atmospheric deposition of sulfur and nitrogen was measured in the Metropolitan Area of Merida, Yucatan in Mexico during the dry season of 2016. Passive samplers type "throughfall" based on ion exchange resins were used to measure the hydrological flows in a total of 9 sampling sites distributed throughout the city. The ions retained in the resin were analyzed by turbidimetry and colorimetry to determine Ammonium, Nitrate and Sulfate. Deposition fluxes of S and N obtained were 6.25 and 5.19 Kg ha-1 yr-1. Both, sulfur and nitrogen atmospheric deposition fluxes were higher in urban sites, exceeding almost 2 times, the reference values proposed internationally for sensitive ecosystems. From the analysis of wind roses and air masses trajectories, it was possible to establish that during this climatic season, in addition to the local vehicular emissions, regional emissions generated upwind (from E-SE) contributed to atmospheric deposition of these ions. Finally, N and S deposition fluxes and their relationship with criteria pollutants were assessed, and maps for atmospheric deposition fluxes of Ammonium, Sulfate and Nitrate were generated using geo-statistical tools in order to identify critical deposition zones in this Metropolitan zone.

Benzene,toluene,ethylbenzene,p-xylene,O3,NOx,CO,PM2.5 andmeteorologicalparameters were measured in urban air of two sites in Merida, Yucatan, Mexico during 2016–2017. Samples were collected using 1.5 h time intervals at three different sampling periods before being analyzed by gas chromatographywithflameionizationdetection. ThehighestconcentrationsofBTEXoccurredduring midday and afternoon in spring and summer seasons. Mean concentrations of, BTEX for the Cholul and SEDUMA sites, respectively, were 40.91 µg/m3 and 32.86 µg/m3 for benzene; 6.87 µg/m3 and 3.29 µg/m3 for toluene; 13.87 µg/m3 and 8.29 µg/m3 for p-xylene; and 6.23 µg/m3 and 4.48 µg/m3 for ethylbenzene. The toluene/benzene and xylene/ethylbenzene concentration ratios indicated that BTEX levels at both sites were influenced by local and fresh emissions (vehicular traffic). Bivariate and multivariate analyses were performed in order to correlate BTEX concentrations with criteria air pollutants to infer their possible sources. Health risk assessment revealed that exposure to benzene exceeded the recommended value for the integrated lifetime cancer risk. These results suggest that Merida’s population is exposed to cancer risk, and changes in the existing environmental policies should therefore be applied to improve air quality. Keywords: volatile organic compounds; BTEX; tropospheric ozone; Merida; air pollution