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Abstract: A field study was carried out in the Metropolitan Area of Monterrey (MAM), the second most populated city in Mexico, characterized by increasing urbanization, high traffic density, and intense industrial activity. These characteristics commonly present high concentrations of air pollutants leading to the degradation of air quality. PM2.5 was analyzed for heavy metals at two urban sites located within the MAM (Juarez and San Bernabe) in order to determine sources, health risk, morphology, and elemental content during the COVID-19 pandemic (autumn 2020 and spring 2021). Twenty-four-hour samples of PM2.5 were collected at each site during 30-day periods using high-volume equipment. Gravimetric concentrations and 11 metals were measured (Ca, Cd, Co, Cu, Fe, K, Mg, Mn, Ni, Cr, and Pb) by different analytical techniques (flame atomic absorption spectroscopy, graphite furnace atomic absorption spectroscopy, and inductively coupled plasma optical emission spectroscopy). Selected samples were analyzed by scanning electron microscopy-energy-disperse spectroscopy in order to characterize their morphology and elemental content. PM2.5 concentrations exceeded the Mexican standard and WHO guidelines in Juarez during spring 2021. Cu, Cd, and Co were highly enriched by anthropogenic sources, and Ni, K, Cr, and Pb had a moderate enrichment. Mg, Mn, and Ca were of crustal origin. Bivariate statistics and PCA confirmed that alkaline metals originated from crustal sources and that the main sources of trace metals included traffic emissions, resuspension from soil/road dust, steel industry, smelting, and non-exhaust emissions at both sites. Lifetime cancer risk coefficients did not exceed the permissible levels established by EPA and WHO, implying that local residents are not at risk of developing cancer. Non-carcinogenic risk coefficients revealed that there is a possible risk of suffering cardiovascular and respiratory diseases due to inhalation of cobalt at the study sites. Supplementary Information: The online version contains supplementary material available at 10.1007/s11869-023-01372-7.

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Emissions of gaseous elemental mercury (GEM or Hg0) from different sources in urban areas are important subjects for environmental investigations. In this study, atmospheric Hg measurements were conducted to investigate air pollution in the urban environment by carrying out several mobile surveys in Mexico City. This work presents atmospheric concentrations of GEM in terms of diurnal variation trends and comparisons with criteria for pollutant concentrations such as CO, SO2, NO2, PM2.5, and PM10. The concentration of GEM was measured during the pre-rainy period by using a high-resolution active air sampler, the Lumex RA 915 M mercury analyzer. In comparison with those for other cities worldwide, the GEM concentrations were similar or slightly elevated, and they ranged from 0.20 to 30.23 ng m-3. However, the GEM concentration was significantly lower than those in contaminated areas, such as fluorescent lamp factory locations and gold mining zones. The GEM concentrations recorded in Mexico City did not exceed the WHO atmospheric limit of 200 ng m-3. We performed statistical correlation analysis which suggests equivalent sources between Hg and other atmospheric pollutants, mainly NO2 and SO2, emitted from urban combustion and industrial plants. The atmospheric Hg emissions are basically controlled by sunlight radiation, as well as having a direct relationship with meteorological parameters. The area of the city studied herein is characterized by high traffic density, cement production, and municipal solid waste (MSW) treatment, which constantly release GEM into the atmosphere. In this study, we included the simulation with the HYSPLIT dispersion model from three potential areas of GEM release. Emissions from industrial corridors and volcanic plumes localized outside the urban area contribute to the pollution of Mexico City and mainly affect the northern area during specific periods and climate conditions. Using the USEPA model, we assessed the human health risk resulting from exposure to inhaled GEM among residents of Mexico City. The results of the health risk assessment indicated no significant noncarcinogenic risk (hazard quotient (HQ) < 1) or consequent adverse effects for children and adults living in the sampling area over the study period. GEM emissions inventory data is necessary to improve our knowledge about the Hg contribution and effect in urban megacity areas with the objective to develop public safe policy and implementing the Minamata Convention.

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Human remains and corpses' cremation is an increasing practice worldwide alternative to burials, which have increased their cost and reduced spaces in cemeteries. Alike to other combustion processes, cremation produces pollutant emissions that contribute to worsen air quality in modern cities. A 6-month sampling campaign was performed in order to characterize emissions from corpse cremation in three different crematorium ovens and develop emission factors which were used to determine the population exposure to those pollutants during cremation activities applying a dispersion model. The main difference among crematoria was the inclusion or non-inclusion of controlled air supply devices. Using isokinetic samplings in the chimneys crematoria, emissions were measured and characterized with different chemical analyses. No significant differences were found in arsenic and metal concentrations among different crematories, although carbon monoxide, particles, elemental carbon, organic carbon, and polycyclic aromatic hydrocarbon concentrations in facilities without controlled air supply were up to seven times higher than those with controlled air supply. Nevertheless, these pollutants exceeded standards in all crematoria. Except for elemental and organic carbon concentration that correlated with corpse weight, other recorded cadaver characteristics bear no relation with pollutant emissions. Emission factors among different ovens did not present significant differences; then, they were used for dispersion modeling of particles and mercury emissions over Mexico City when 35 crematoria operate simultaneously through an hour showing that PM2.5 and Hg increase 0.01-1 µg m-3 and 0.01-0.1 ng m-3, respectively, in that scenario.

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Mercury exposure has been shown to affect the reproductive system in many organisms, although the molecular mechanisms are still elusive. In the present study, we exposed Drosophila melanogaster Canton-S adult females to concentrations of 0 mM, 0.1 mM, 0.3 mM, 3 mM, and 30 mM of mercury chloride (HgCl2) for 24 h, 48 h, or 72 h to determine how mercury could affect fertility. Alkaline assays performed on dissected ovaries showed that mercury induced DNA damage that is not only dose-dependent but also time-dependent. All ovaries treated for 72 h have incorporated mercury and exhibit size reduction. Females treated with 30 mM HgCl2, the highest dose, had atrophied ovaries and exhibited a drastic 7-fold reduction in egg laying. Confocal microscopy analysis revealed that exposure to HgCl2 disrupts germinal and somatic cell organization in the germarium and leads to the aberrant expression of a germline-specific gene in somatic follicle cells in developing egg chambers. Together, these results highlight the potential long-term impact of mercury on germline and ovarian cells that might involve gene deregulation.

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The present study was designed to detect the effect of heavy metals in two zones of the Metropolitan Area of Mexico City (MAMC), the Centro de Ciencias de la Atmósfera (CCA), and the Altzomoni station in the Iztaccíhuatl-Popocatépetl National Park. Taraxacum officinale was selected as the indicator organism of responses to atmospheric contamination by heavy metals. Determinations of heavy metals were performed, and total mRNA was extracted to quantify the expression of microRNA398 (miR398), superoxide dismutase 2 (CSD2), and the amounts of free radicals using the bromide of 3-(4,5-dimethylthiazole-2-ilo)-2,5-diphenyltetrazole (MTT) salts reduction assay. Results from the Altzomoni station showed high concentrations of five heavy metals, especially Aluminum, while three heavy metals were identified in the CCA-UNAM zone, most importantly, Vanadium, both in the dry season; miR398 expression presented subtle changes but was greater in the leaves from the stations with higher concentrations of heavy metals. Observations included a significant expression of CSD2, mainly in the dry season in both study zones, where levels were significant with respect to controls (p < 0.05). Reduced MTT was also higher in the dry season than in the rainy season (p < 0.05). In conclusion, the increase in heavy metals on the leaves of Taraxacum officinale induces increased expression of the CSD2 gene and reduced MTT; thus, they can be used as indicators for biomonitoring heavy metal concentrations.

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RNA processing is an essential pathway in the regulation of genetic expression in the cell. In this work, Bacillus subtilis was used to understand the effects of mercury on the mechanism of tRNA metabolism. The CVAAS (cold vapor atomic absorption spectroscopy) method revealed that from the addition of HgCl2 (0.75 µg ml(-1)) during the bacterial exponential phase, ca. 48% of the added mercury was taken up by the cells. This led to an immediate reduction in the rate of cell division. During this response, we observed accumulation of species shorter than mature tRNA(Cys) over a 10 h period. We did not observe this accumulation for another five tRNAs analyzed. tRNA processing is largely dependent on RNase R and PNPase in B. subtilis. Thus, when the exonuclease PNPase was absent, we found that the shorter tRNA(Cys) species increased and mature tRNA(Cys) decreased after mercury addition, but this proportion changed during the time analyzed. However, in the absence of RNase R and PNPase the accumulation of the shorter tRNA(Cys) was more pronounced and the mature form was not recovered. In the single rnr mutant strain the shorter tRNA(Cys) was not observed. All together, we provide in vivo evidence that PNPase and RNase R are indispensable in controlling tRNA(Cys) quality in the presence of mercury.

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Calypso (thiacloprid), Poncho (clothianidin), Gaucho (imidacloprid), and Jade (imidacloprid) are commercial neonicotinoid insecticides, a new class of agrochemicals in México. However, genotoxic and cytotoxic studies have not been performed. In the present study, human peripheral blood lymphocytes (PBL) were exposed in vitro to different concentrations of the four insecticides. The genotoxic and cytotoxic effects were evaluated using the alkaline comet and trypan blue dye exclusion assays. DNA damage was evaluated using two genotoxicity parameters: tail length and comet frequency. Exposure to 9.5 × 10(-6) to 5.7 × 10(-5) M Jade; 2.8 × 10(-4) to 1.7 × 10(-3) M Gaucho; 0.6 × 10(-1) to 1.4 × 10(-1) M Calypso; 1.2 × 10(-1) to 9.5 × 10(-1) M Poncho for 2 h induced a significant increase DNA damage with a concentration-dependent relationship. Jade was the most genotoxic of the four insecticides studied. Cytotoxicity was observed in cells exposed to 18 × 10(-3) M Jade, 2.0 × 10(-3) M Gaucho, 2.0 × 10(-1) M Calypso, 1.07 M Poncho, and cell death occurred at 30 × 10(-3) M Jade, 3.3 × 10(-3) M Gaucho, 2.8 × 10(-1) M Calypso, and 1.42 M Poncho. This study provides the first report of genotoxic and cytotoxic effects in PBL following in vitro exposure to commercial neonicotinoid insecticides.