A comparative analysis of regional infection risk due to wastewater recontamination in the Mezquital Valley, Mexico.

Urban wastewater reuse for agriculture provides reliable nutrient-rich water, reduces water stress, and strengthens food systems. However, wastewater reuse also presents health risks and characterizing the spatial dynamics of wastewater can help optimize risk mitigation. We conducted comparative risk analysis of exposure to wastewater in irrigation canals, where we compared those exposed to a) treated vs. untreated wastewater, and b) wastewater upstream vs. downstream from communities in the Mezquital Valley. The canal system with treated wastewater was sampled prior to being treated, directly after treatment, as well as before and after it flowed through a community. Along the canal system that carried untreated wastewater, we sampled before and after a community. We quantified the concentrations of bacterial, protozoal, and viral pathogens in the wastewater. Pathogen concentration data were used to calculate measures of relative risk between sampling points. Wastewater treatment reduced predicted bacterial pathogen infection risk in post-treatment locations (RR = 0.73, 95 % CI 0.61, 0.87), with no evidence of similar reductions in Giardia or viral pathogens (RR = 1.02, 95 % CI 0.56, 1.86 and RR = 1.18, 95 % CI 0.70, 2.02 respectively). Although infection risk decreased further down the canals, infection risk increased for bacterial pathogens after our sentinel community (RR = 1.94, 95 % 1.34, 2.86). For Giardia and viral pathogens infection risk was elevated but not significantly. We found similar evidence for increases in risk when comparing the treated section of the canal system with a canal section whose wastewater was not treated, i.e., the risk benefits of wastewater treatment were lost after our sentinel community for bacteria (RR = 5.27 vs. 2.08 for sampling points before and after our sentinel community respectively) and for Giardia (RR = 6.98 vs. 3.35 respectively). The increase in risk after transit through communities could have resulted from local community recontamination of the treated wastewater stream.

Short-term exposure to PM2.5 and 1.5 million deaths: a time-stratified case-crossover analysis in the Mexico City Metropolitan Area.

BACKGROUND: Satellite-based PM2.5 predictions are being used to advance exposure science and air-pollution epidemiology in developed countries; including emerging evidence about the impacts of PM2.5 on acute health outcomes beyond the cardiovascular and respiratory systems, and the potential modifying effects from individual-level factors in these associations. Research on these topics is lacking in low and middle income countries. We aimed to explore the association between short-term exposure to PM2.5 with broad-category and cause-specific mortality outcomes in the Mexico City Metropolitan Area (MCMA), and potential effect modification by age, sex, and SES characteristics in such associations. METHODS: We used a time-stratified case-crossover study design with 1,479,950 non-accidental deaths from the MCMA for the period of 2004-2019. Daily 1 × 1 km PM2.5 (median = 23.4 µg/m3; IQR = 13.6 µg/m3) estimates from our satellite-based regional model were employed for exposure assessment at the sub-municipality level. Associations between PM2.5 with broad-category (organ-system) and cause-specific mortality outcomes were estimated with distributed lag conditional logistic models. We also fit models stratifying by potential individual-level effect modifiers including; age, sex, and individual SES-related characteristics namely: education, health insurance coverage, and job categories. Odds ratios were converted into percent increase for ease of interpretation. RESULTS: PM2.5 exposure was associated with broad-category mortality outcomes, including all non-accidental, cardiovascular, cerebrovascular, respiratory, and digestive mortality. A 10-µg/m3 PM2.5 higher cumulative exposure over one week (lag06) was associated with higher cause-specific mortality outcomes including hypertensive disease [2.28% (95%CI: 0.26%-4.33%)], acute ischemic heart disease [1.61% (95%CI: 0.59%-2.64%)], other forms of heart disease [2.39% (95%CI: -0.35%-5.20%)], hemorrhagic stroke [3.63% (95%CI: 0.79%-6.55%)], influenza and pneumonia [4.91% (95%CI: 2.84%-7.02%)], chronic respiratory disease [2.49% (95%CI: 0.71%-4.31%)], diseases of the liver [1.85% (95%CI: 0.31%-3.41%)], and renal failure [3.48% (95%CI: 0.79%-6.24%)]. No differences in effect size of associations were observed between age, sex and SES strata. CONCLUSIONS: Exposure to PM2.5 was associated with non-accidental, broad-category and cause-specific mortality outcomes beyond the cardiovascular and respiratory systems, including specific death-causes from the digestive and genitourinary systems, with no indication of effect modification by individual-level characteristics.

Long-term exposure to ambient fine particulate matter and carotid intima media thickness at bilateral, left and right in adults from Mexico City: Results from GEA study.

BACKGROUND: PM2.5 exposure has been associated with intima-media thickness (cIMT) increase. However, very few studies distinguished between left and right cIMT in relation to PM2.5 exposure. AIM: To evaluate associations between chronic exposure to PM2.5 and cIMT at bilateral, left, and right in adults from Mexico City. METHODS: This study comprised 913 participants from the control group, participants without personal or family history of cardiovascular disease, of the Genetics of Atherosclerosis Disease Mexican study (GEA acronym in Spanish), recruited at the Instituto Nacional de Cardiología Ignacio Chávez from June 2008 to January 2013. To assess the associations between chronic exposure to PM2.5 (per 5 µg/m3 increase) at different lag years (1-4 years) and cIMT (bilateral, left, and right) we applied distributed lag non-linear models (DLNMs). RESULTS: The median and interquartile range for cIMT at bilateral, left, and right, were 630 (555, 735), 640 (550, 750), and 620 (530, 720) µm, respectively. Annual average PM2.5 exposure was 26.64 µg/m3, with median and IQR, of 24.46 (23.5-25.46) µg/m3. Results from DLNMs adjusted for age, sex, body mass index, low-density lipoproteins, and glucose, showed that PM2.5 exposure for year 1 and 2, were positively and significantly associated with right-cIMT [6.99% (95% CI: 3.67; 10.42) and 2.98% (0.03; 6.01), respectively]. Negative associations were observed for PM2.5 at year 3 and 4 and right-cIMT; however only year 3 was statistically significant [-2.83% (95% CI: 5.12; -0.50)]. Left-cIMT was not associated with PM2.5 exposure at any lag year. The increase in bilateral cIMT followed a similar pattern as that observed for right-cIMT, but with lower estimates. CONCLUSIONS: Our results suggest different susceptibility between left and right cIMT associated with PM2.5 exposure highlighting the need of measuring both, left and right cIMT, regarding ambient air pollution in epidemiological studies.

Lead Exposure Can Affect Early Childhood Development and Could Be Aggravated by Stunted Growth: Perspectives from Mexico.

BACKGROUND: Lead can affect early childhood development (ECD) differentially due to nutritional deficiencies that lead to stunted growth, defined as being at least two standard deviations below the average height-for-age. These deficiencies are more frequent among children living in rural locations or with lower socioeconomic status (SES); however, studies at a population level are scarce worldwide. Early childhood development plays a crucial role in influencing a child's health and wellbeing throughout life. Therefore, the aim of this study was to analyze how stunted growth can modify the association between lead exposure and ECD in children from disadvantaged communities. METHODS: Data were analyzed from the 2018 National Health and Nutrition Survey in localities with fewer than 100,000 inhabitants in Mexico (ENSANUT-100K). Capillary blood lead (BPb) levels were measured using a LeadCare II device and dichotomized as detectable (cutoff point ≥ 3.3 µg/dL) and non-detectable. As a measure of ECD, language development was assessed in n = 1394 children, representing 2,415,000 children aged 12-59 months. To assess the association between lead exposure and language z-scores, a linear model was generated adjusted by age, sex, stunted growth, maternal education, socioeconomic status, area, region (north, center, south), and family care characteristics; afterwards, the model was stratified by stunted growth. RESULTS: Fifty percent of children had detectable BPb and 15.3% had stunted growth. BPb showed a marginal inverse association with language z-scores (ß: -0.08, 95% CI: -0.53, 0.36). Children with detectable BPb and stunted growth had significantly lower language z-scores (ß: -0.40, 95% CI: -0.71, -0.10) than those without stunted growth (ß: -0.15, 95% CI: -0.36, 0.06). CONCLUSIONS: Children with stunted growth are more vulnerable to the adverse effects of lead exposure. These results add to previous research calling for action to reduce lead exposure, particularly in children with chronic undernutrition.

Daily exposure to PM2.5 and 1.5 million deaths: A time-stratified case-crossover analysis in the Mexico City Metropolitan Area.

Background: Satellite-based PM2.5 predictions are being used to advance exposure science and air-pollution epidemiology in developed countries; including emerging evidence about the impacts of PM2.5 on acute health outcomes beyond the cardiovascular and respiratory systems, and the potential modifying effects from individual-level factors in these associations. Research on these topics is lacking in Latin America. Methods: We used a time-stratified case-crossover study design with 1,479,950 non-accidental deaths from Mexico City Metropolitan Area for the period of 2004-2019. Daily 1×1 km PM2.5 (median=23.4 µg/m3; IQR=13.6 µg/m3) estimates from our satellite-based regional model were employed for exposure assessment at the sub-municipality level. Associations between PM2.5 with broad-category (organ-system) and cause-specific mortality outcomes were estimated with distributed lag conditional logistic models. We also fit models stratifying by potential individual-level effect modifiers including; age, sex, and individual SES-related characteristics namely: education, health insurance coverage, and job categories. Results: PM2.5 exposure was associated with higher total non-accidental, cardiovascular, cerebrovascular, respiratory, and digestive mortality. A 10-µg/m3 PM2.5 higher cumulative exposure over one week (lag06) was associated with higher cause-specific mortality outcomes including hypertensive disease [2.28% (95%CI: 0.26%-4.33%)], acute ischemic heart disease [1.61% (95%CI: 0.59%-2.64%)], other forms of heart disease [2.39% (95%CI: -0.35%-5.20%)], hemorrhagic stroke [3.63% (95%CI: 0.79%-6.55%)], influenza and pneumonia [4.91% (95%CI: 2.84%-7.02%)], chronic respiratory disease [2.49% (95%CI: 0.71%-4.31%)], diseases of the liver [1.85% (95%CI: 0.31%-3.41%)], and renal failure [3.48% (95%CI: 0.79%-6.24%)]. No differences in effect size of associations were observed between SES strata. Conclusions: Exposure to PM2.5 was associated with mortality outcomes beyond the cardiovascular and respiratory systems, including specific death-causes from the digestive and genitourinary systems, with no indications of effect modification by individual SES-related characteristics.

Prenatal Co-Exposure to Manganese, Mercury, and Lead, and Neurodevelopment in Children during the First Year of Life.

Lead (Pb), mercury (Hg), and manganese (Mn) are neurotoxic, but little is known about the neurodevelopmental effects associated with simultaneous prenatal exposure to these metals. We aimed to study the associations of Pb, Hg, and Mn prenatal levels (jointly and separately) with neurodevelopment in the first year of life. Methods: Pb, Hg, and Mn blood lead levels were measured in 253 pregnant women. Their offspring's neurodevelopment was assessed through the Bayley Scale of Infant Development III® at one, three, six, and twelve months. The metals' mean blood levels (µg/L) were Pb = 11.2, Hg = 2.1, and Mn = 10.2. Mean language, cognitive, and motor development scores of the infants at each age were between low-average and average. Multilevel models' results showed that language development coefficients of the offspring decreased by 1.5 points per 1 µg/dL increase in maternal blood lead levels (p = 0.002); the magnitude of the aforementioned association increased in children with maternal blood Mn < 9.6 µg/L (ß = -1.9, p = 0.003) or Hg > 1.9 µg/L (ß = -1.6, p = 0.013). Cognitive and motor development had negative associations with maternal blood Pb levels; the latter was statistically significant when the interaction term between Pb, Mn, and Hg was included (ß = -0.037, p = 0.03). Prenatal exposure to low Pb levels may impair infants' neurodevelopment in the first year of life, even more so if they are exposed to Hg or deficient in Mn.

A Call for Biomonitoring Systems in Latin America and the Caribbean: Considerations for Potentially Toxic Metals/Metalloids.

The Latin America and the Caribbean (LAC) region makes up 8.4% of the world's population. Human biomonitoring (HBM) programs, which can shed light on population-level exposure to environmental contaminants such as toxic metals and thus, improve the health of the populations are inexistent in LAC countries. We call for the creation of HBM programs in the region and identify three viable design options for HBM at the individual level, through national surveys, newborn blood collection, and biobanks. We highlight some of challenges to the implementation of HBM programs, including financial and human resources, technical constrains (laboratory), sample, and data logistics. Finally, we provide the case studies of Brazil, Chile, Mexico, and Uruguay, to illustrate a range of responses to toxic metal exposure in non-occupational populations. Although different in many respects, the individual country responses share two commonalities: 1) academic centers drive the research to raise awareness of governmental entities; 2) reference levels are adapted from international norms rather than arising from the studied populations. Well-designed and sufficiently funded biomonitoring systems need to be established in each country of the LAC region. HBM programs are key to promoting human health by informing the public and contributing to policy processes that establish sustainable environmental controls and health prevention programs.

Prediction of daily mean and one-hour maximum PM2.5 concentrations and applications in Central Mexico using satellite-based machine-learning models.

BACKGROUND: Machine-learning algorithms are becoming popular techniques to predict ambient air PM2.5 concentrations at high spatial resolutions (1 × 1 km) using satellite-based aerosol optical depth (AOD). Most machine-learning models have aimed to predict 24 h-averaged PM2.5 concentrations (mean PM2.5) in high-income regions. Over Mexico, none have been developed to predict subdaily peak levels, such as the maximum daily 1-h concentration (max PM2.5). OBJECTIVE: Our goal was to develop a machine-learning model to predict mean PM2.5 and max PM2.5 concentrations in the Mexico City Metropolitan Area from 2004 through 2019. METHODS: We present a new modeling approach based on extreme gradient boosting (XGBoost) and inverse-distance weighting that uses AOD, meteorology, and land-use variables. We also investigated applications of our mean PM2.5 predictions that can aid local authorities in air-quality management and public-health surveillance, such as the co-occurrence of high PM2.5 and heat, compliance with local air-quality standards, and the relationship of PM2.5 exposure with social marginalization. RESULTS: Our models for mean and max PM2.5 exhibited good performance, with overall cross-validated mean absolute errors (MAE) of 3.68 and 9.20 µg/m3, respectively, compared to mean absolute deviations from the median (MAD) of 8.55 and 15.64 µg/m3. In 2010, everybody in the study region was exposed to unhealthy levels of PM2.5. Hotter days had greater PM2.5 concentrations. Finally, we found similar exposure to PM2.5 across levels of social marginalization. SIGNIFICANCE: Machine learning algorithms can be used to predict highly spatiotemporally resolved PM2.5 concentrations even in regions with sparse monitoring. IMPACT: Our PM2.5 predictions can aid local authorities in air-quality management and public-health surveillance, and they can advance epidemiological research in Central Mexico with state-of-the-art exposure assessment methods.

Short term exposure to ambient air pollutants and cardiovascular emergency department visits in Mexico city.

Available data on the acute cardiovascular effect of ambient air pollution (AAP) in Latin America is limited considering that over 80% of its 1 billion inhabitants live in urban settlements with poor air quality. The study aim was to evaluate the association between Cardiovascular Emergency Department Visits (CEDVs) and AAP in Mexico City from 2016 to 2019 using generalized additive models with distributed lags to examine the percentage change of CEDVs and a backward approach of time-series model to calculate attributable fractions. A total of 48,891 CEDVs were recorded in a period of 1019 days. We estimated a significant percentage increase for each 10 µg/m3 of PM10 at Lag0-5 (2.8%, 95%CI 0.6-5.0), PM2.5 at Lag0-6 (3.7%, 95%CI 0.1-7.6), O3 at Lag0-5 (1.1%, 95%CI 0.2-2.0), NO2 at Lag0-4 (2.5%, 95%CI 0.3-4.7) and for each 1 mg/m3 of CO at Lag0 (6.6%, 95%CI 0.3-13.2). Overall, 10.3% of CEDVs in Mexico City may be related to PM10 exposure, 9.5% to PM2.5, 10.3% to O3, 11% to NO2 and 5.7% to CO. AAP significantly increase cardiovascular morbidity impacting on emergency medical services.

Environmental and occupational exposure to metals (manganese, mercury, iron) and Parkinson's disease in low and middle-income countries: a narrative review.

OBJECTIVES: We designed and conducted a narrative review consistent with the PRISMA guidelines (PROSPERO registration number: CRD42018099498) to evaluate the association between environmental metals (manganese, mercury, iron) and Parkinson's Disease (PD) in low and middle-income countries (LMIC). METHODS: Data sources: A total of 19 databases were screened, and 2,048 references were gathered. Study selection: Randomized controlled trials, cluster trials, cohort studies, case-control studies, nested case-control studies, ecological studies, cross-sectional studies, case series, and case reports carried out in human adults of LMIC, in which the association between at least one of these three metals and the primary outcome were reported. Data extraction: We extracted qualitative and quantitative data. The primary outcome was PD cases, defined by clinical criteria. A qualitative analysis was conducted. RESULTS: Fourteen observational studies fulfilled the selection criteria. Considerable variation was observed between these studies' methodologies for the measurement of metal exposure and outcome assessment. A fraction of studies suggested an association between the exposure and primary outcome; nevertheless, these findings should be weighted and appraised on the studies' design and its implementation limitations, flaws, and implications. CONCLUSIONS: Further research is required to confirm a potential risk of metal exposure and its relationship to PD. To our awareness, this is the first attempt to evaluate the association between environmental and occupational exposure to metals and PD in LMIC settings using the social determinants of health as a framework.

Air pollution exposure and incidence of type 2 diabetes in women: A prospective analysis from the Mexican Teachers' Cohort.

BACKGROUND: Air pollution is a risk factor for type 2 diabetes (T2D). However, scarse longitudinal studies have evaluated this association in low- and middle-income countries, where 80% of the worldwide cases of T2D occur. OBJECTIVE: Our aim was to estimate the association between PM2.5 and NO2 exposure and incident T2D, in the Mexican Teachers' Cohort (MTC). METHODS: We selected a subsample of female teachers from the MTC from Mexico City metropolitan area (MCMA), recruited in 2008 and with active follow-up every three years. We assigned the monthly time-weighted exposures (PM2.5 and NO2) using home and work addresses, until failure, censoring or death. We developed two high resolution (1 × 1-km) spatiotemporal predictive generalized additive models of PM2.5 and NO2. Incident diabetes was identified through self-report and two administrative databases of registered diabetes patients. We fitted time-varying Cox models to estimate hazard ratios of the relation between PM2.5 and NO2 and incident T2D, adjusting for confounding variables that were identified using a causal model. RESULTS: A total of 13,669 teachers were followed-up for a maximum of 11.5 years, over which 996 incident T2D cases (88 cases per 100,000 person-months) occurred. Incident T2D increased by 72% (HR = 1.72 [1.47-2.01]) for each 10 µg/m3 increase of PM2.5, and 52% for each 10 ppb of NO2 (HR = 1.52 [1.37-1.68]). DISCUSSION: Mid-term exposure to PM2.5 and NO2 was associated with a higher risk of T2D after adjusting for indoor wood smoke, socioeconomic status, and physical activity. These associations were attenuated in two-pollutant models but remained positive when evaluated long-term exposure. This is the first prospective study to evaluate T2D risk by exposure to both pollutants, PM2.5 and NO2 in a population from an upper middle-income country in the Americas.

Health and Economic Impacts Assessment of O3 Exposure in Mexico.

Health effects related to exposure to air pollution such as ozone (O3) have been documented. The World Health Organization has recommended the use of the Sum of O3 Means Over 35 ppb (SOMO35) to perform Health Impact Assessments (HIA) for long-term exposure to O3. We estimated the avoidable mortality associated with long-term exposure to tropospheric O3 in 14 cities in Mexico using information for 2015. The economic valuation of avoidable deaths related to SOMO35 exposure was performed using the willingness to pay (WTP) and human capital (HC) approaches. We estimated that 627 deaths (95% uncertainty interval (UI): 227-1051) from respiratory diseases associated with the exposure to O3 would have been avoided in people over 30 years in the study area, which confirms the public health impacts of ambient air pollution. The avoidable deaths account for almost 1400 million USD under the WTP approach, whilst the HC method yielded a lost productivity estimate of 29.7 million USD due to premature deaths. Our findings represent the first evidence of the health impacts of O3 exposure in Mexico, using SOMO35 metrics.

Climate Trends and Consumption of Foods and Beverages by Processing Level in Mexican Cities.

Background: Little is known about the potential impact of climate change on food systems and diet. We aimed to estimate the association of changes in rainfall and temperatures with consumption of unprocessed and processed foods among residents of Mexican cities by climate region. Methods: We analyzed 3,312 participants of the 2012 Mexican National Health and Nutrition Survey with dietary intake and sociodemographic information linked to historical rainfall and temperature data collected by the Mexican National Weather Service. We classified foods as unprocessed, processed, or ultra-processed. We performed multilevel linear regression to estimate the association of annual change in rainfalls (for each 0.5 mm decrease) and temperatures (for each 0.1°C increase) at municipality level over the past 5 years with consumption of processed and unprocessed foods measured as the contribution to total energy intake. We investigated whether associations differed by climate region (tropical, temperate, and arid). Results: Each 0.5 mm annual decrease in precipitation was associated with lower consumption of unprocessed foods and higher consumption of ultra-processed foods [mean differences in percent contribution to total energy intake -0.009% (95% CI: -0.019, < -0.001) and 0.011% (95% CI: 0.001, 0.021), respectively]. Each 0.1 degree Celsius annual increase in temperature was also associated with lower consumption of unprocessed and higher consumption of ultra-processed foods [mean differences in percent contribution to total energy intake was -0.03 (95% CI: -0.05, -0.01) and 0.03% (95% CI: <0.01, 0.05)]. When stratified by climate region these associations were only observed in tropical regions. Conclusions: Decreases in rainfalls and increases in temperature were associated with lower consumption of unprocessed foods but higher consumption of ultra-processed foods, especially in tropical regions. Previous studies have established how food production affects the climate, our study suggests that climate change could, in turn, reinforce modern food production, closing a vicious circle with clear negative implications for planetary health.

Asociación entre mortalidad por Covid-19 y contaminación atmosférica en ciudades mexicanas / Association between Covid-19 mortality and atmospheric pollution in Mexican cities

Resumen: Objetivo: Analizar la asociación entre la exposición crónica a contaminantes atmosféricos y la tasa de mortalidad por Covid-19 en ciudades mexicanas. Material y métodos: Estudio ecológico en 25 ciudades mexicanas utilizando el reporte de casos diarios de muertes por Covid-19 (febrero a junio 2020) y datos validados de contaminantes atmosféricos, considerando concentraciones promedio en cada ciudad en el último año. Se utilizaron modelos de regresión Poisson, con modelos aditivos generalizados y variables de ajuste. Resultados: Se encontró un incremento significativo de 3.5% (IC95% 2.3-4.7) en la tasa de mortalidad por Covid-19 por incremento de 1µg/m3 de NO2. La asociación con PM2.5 fue no significativa, con un incremento de 1.8% por cada µg/m3. Conclusiones: Los resultados sugieren una asociación entre la mortalidad por Covid-19 y la exposición a NO2. Esta primera aproximación del riesgo asociado con la contaminación del aire requiere de análisis más precisos, pero es consistente con estudios de otras regiones.

Abstract Objective: To analyze the relationship between chronic exposures to air pollution with Covid-19 death rate in Mexican cities. Materials and methods: Ecological study in 25 Mexican cities using the report of daily Covid-19 deaths (from February to June 2020) and validated data of air pollutants, considering average concentrations in each city for the last year. Poisson regression models using generalized additive models with adjustment variables (GAM) were used. Results: A significant increase of 3.5% (95% CI 2.3-4.7) was found in Covid-19 death rate for each 1µg/m3 in annual concentration of NO2. The association with PM2.5 was not significant, with an increase of 1.8% for each 1µg/m3. Conclusions: Results suggest an association between Covid-19 mortality and chronic exposure to NO2. This first approximation of the risk associated with air pollution requires a more precise analysis, but is consistent with what was observed in other studies.

Asociación entre mortalidad por Covid-19 y contaminación atmosférica en ciudades mexicanas.

Objetivo. Analizar la asociación entre la exposición crónica a contaminantes atmosféricos y la tasa de mortalidad por Covid-19 en ciudades mexicanas. Material y métodos. Estudio ecológico en 25 ciudades mexicanas utilizando el reporte de casos diarios de muertes por Covid-19 (febrero a junio 2020) y datos validados de contaminantes atmosféricos, considerando concentraciones promedio en cada ciudad en el último año. Se utilizaron modelos de regresión Poisson, con modelos aditivos generalizados y variables de ajuste. Resultados. Se encontró un incremento significativo de 3.5% (IC95% 2.3-4.7) en la tasa de mortalidad por Covid-19 por incremento de 1µg/m3 de NO2. La asociación con PM2.5 fue no significativa, con un incremento de 1.8% por cada µg/ m3. Conclusiones. Los resultados sugieren una asociación entre la mortalidad por Covid-19 y la exposición a NO2. Esta primera aproximación del riesgo asociado con la contami-nación del aire requiere de análisis más precisos, pero es consistente con estudios de otras regiones.

Exposure to PM2.5 and Obesity Prevalence in the Greater Mexico City Area.

Exposure to PM2.5 has been associated with the prevalence of obesity. In the Greater Mexico City Area (GMCA), both are ranked among the highest in the world. Our aim was to analyze this association in children, adolescents, and adults in the GMCA. We used data from the 2006 and 2012 Mexican National Surveys of Health and Nutrition (ENSANUT). Participants' past-year exposure to ambient PM2.5 was assessed using land use terms and satellite-derived aerosol optical depth estimates; weight and height were measured. We used survey-adjusted logistic regression models to estimate the odds ratios (ORs) of obesity (vs. normal-overweight) for every 10 µg/m3 increase in annual PM2.5 exposure for children, adolescents, and adults. Using a meta-analysis approach, we estimated the overall odds of obesity. We analyzed data representing 19.3 million and 20.9 million GMCA individuals from ENSANUT 2006 and 2012, respectively. The overall pooled estimate between PM2.5 exposure and obesity was OR = 1.96 (95% CI: 1.21, 3.18). For adolescents, a 10 µg/m3 increase in PM2.5 was associated with an OR of 3.53 (95% CI: 1.45, 8.58) and 3.79 (95% CI: 1.40, 10.24) in 2006 and 2012, respectively. More studies such as this are recommended in Latin American cities with similar air pollution and obesity conditions.

Prenatal PM2.5 exposure and neurodevelopment at 2 years of age in a birth cohort from Mexico city.

BACKGROUND: Recent studies have reported that air pollution exposure may have neurotoxic properties. OBJECTIVE: To examine longitudinal associations between prenatal particles less than 2.5 µm in diameter (PM2.5) exposure and neurodevelopment during the first two years of children's life. METHODS: Analysis was conducted in PROGRESS, a longitudinal birth cohort between 2007 and 2013 in Mexico City. We used satellite data to predict daily PM2.5 concentrations at high spatial resolution. Multivariate mixed-effect regression models were adjusted to examine cognitive, language and motor scores in children up to 24 months of age (n = 740) and each trimester-specific and whole pregnancy exposure to PM2.5. RESULTS: Models adjusted by child sex, gestational age, birth weight, smoking and mother's IQ, showed that each increase of 1 µg/m3 of PM2.5 was associated with a decreased language function of -0.38 points (95% CI: -0.77, -0.01). PM2.5 exposure at third trimester of pregnancy contributed most to the observed association. CONCLUSION: Our findings suggest that language development up to 24 months of age may be particularly sensitive to PM2.5 exposure during pregnancy.

Revisión rápida de los efectos de la variación de la temperatura y la humedad en la morbilidad y mortalidad por Covid-19 / Rapid review of the effects of temperature and humidity variation on the Covid-19 morbidity and mortality

Resumen: Objetivo: Resumir y analizar la evidencia de la asociación entre Covid-19 y factores climáticos. Material y métodos: Se utilizó la metodología de revisiones rápidas de Cochrane. Se buscaron artículos publicados del 1 de enero al 27 de abril de 2020 en una base de datos académica y preprints. Los títulos y resúmenes fueron revisados por dos investigadores y los textos completos por cinco investigadores. Resultados: De 354 artículos identificados, 26 cumplieron los criterios de elegibilidad establecidos. De éstos, 20 observaron una asociación inversa. Al evaluar su calidad, nueve calificaron con validez moderada, porque si bien ajustaron por covariables en el análisis, son estudios ecológicos. Conclusiones: A pesar de la homogeneidad de resultados, los factores climáticos explican un porcentaje pequeño de la variación de Covid-19. Son necesarios estudios con periodo de análisis más largo que capten tendencia y estacionalidad e incluyan factores de riesgo individuales.

Abstract: Objective: To summarize and analyze the evidence of the association between Covid-19 and climatic factors Materials and methods: We used the Cochrane rapid review methodology. An academic database and preprints were examined with the searches restricted from January 1 to April 27. Titles and abstracts were reviewed by two researchers and full texts were reviewed by the five authors. Results: We identified 354 articles, 26 met the established eligibility criteria. Of these, 20 reported an inverse association. When evaluating their quality, nine were qualified with moderate validity, this is because they adjusted for covariates in the analysis, but they are ecological studies. Conclusions: Despite homogeneity of results, climatic factors explained a small percentage of Covid-19 incidence variability. Future studies need to include individual risk factors and longer period of data to capture trend or seasonality.

[Association between Covid-19 mortality and atmospheric pollution in Mexican cities]. / Asociación entre mortalidad por Covid-19 y contaminación atmosférica en ciudades mexicanas.

Objective. To analyze the relationship between chronic exposures to air pollution with Covid-19 death rate in Mexican cities. Materials and methods. Ecological study in 25 Mexican cities using the report of daily Covid-19 deaths (from February to June 2020) and validated data of air pollutants, considering average concentrations in each city for the last year. Poisson regression models using generalized additive models with adjustment variables (GAM) were used. Results. A significant increase of 3.5% (95% CI 2.3-4.7) was found in Covid-19 death rate for each 1µg/m3 in annual concentration of NO2. The association with PM2.5 was not significant, with an increase of 1.8% for each 1µg/m3. Conclusions. Results suggest an association between Covid-19 mortality and chronic exposure to NO2. This first approximation of the risk associated with air pollution requires a more precise analysis, but is consistent with what was observed in other studies.

Household water quality in areas irrigated with wastewater in the Mezquital Valley, Mexico.

Wastewater for irrigation in low- and middle-income countries can recharge aquifers and potentially contaminate supply sources. The infiltration rate has increased 13-fold in Mexico's Mezquital Valley, the largest agricultural area wastewater-irrigated worldwide, thus we assume that wastewater had contaminated supply sources. Fecal indicator bacteria (FIB) counts were enumerated in household water of two wastewater-irrigated areas, Tula and Tlahuelilpan, and a groundwater irrigated area, Tecozautla. During 2016-2017, household water, wastewater, and groundwater were sampled, analyzing fecal coliforms, fecal enterococci, and Escherichia coli, following membrane filtration procedures, and confirming the presence of E. coli by polymerase chain reaction. Nearly 50% of household water contained fecal contamination of up to 4.62 × 104 CFU/100 mL. Significant differences between FIB counts in household water from Tula and Tecozautla were observed by Kruskal-Wallis and Dunnett tests. Household water samples from Tula contained highest FIB counts. Wastewater from Tula and Tlahuelilpan contained counts of six orders-of-magnitude of FIB. Counts were high when residual chlorine was <0.2 mg L-1 and underwater storage. This research serves as a baseline to observe improvement with a newly installed wastewater treatment plant. Safe irrigation wastewater reuse should be performed under strict surveillance, considering human safety a priority.