Mexico City Metropolitan Area Research Articles

How healthy are horticultural plants cultivated in urban gardens in polluted cities? The case of Mexico City

Soil-to-plant metal(loid) accumulation has been highly evaluated recently due to its significant impact on human health. This study reports the concentrations of 15 metal(oid)s in four vegetables (tomato, onion, chili, and lettuce) cultivated in a greenhouse and three shade houses (two roofs of buildings and one in the UNAM Botanical Garden) in four locations in the metropolitan area of Mexico City. In this experiment, the contribution of metals and metalloids due to atmospheric deposition and irrigation may be negligible. Hence, the concentration of metals depends only on transfer from the soil. Soil analysis indicates that only vanadium in one location (a rooftop garden in the municipality of Venustiano Carranza) exceeds the permissible limits according to Mexican regulations. Lettuce shows the highest concentrations and transfer factors for most metals compared to the other vegetables studied. Transfer factors were exceptionally high for Cd (lettuce) and Hg (tomato), presenting values above 1. Concentrations of As, Cd, Hg, and Pb were compared with limit values recommended by different international agencies for vegetables. It was observed that, except for As, these values are exceeded in various vegetables harvested in this study. This information must be corroborated with more detailed studies evaluating the chemical species in which those metal(oid)s are present and identify the physical and chemical parameters of the soil that may have interfered with the soil-plant transfer factor.

Urban XCO2 Gradients From a Dense Network of Solar Absorption Spectrometers and OCO‐3 Over Mexico City

AbstractSatellite measurements of urban CO2 plumes offer a global approach to track CO2 emissions for large cities. To examine and to quantify the feasibility of space‐based monitoring, an intensive measurement campaign (MERCI‐CO2) using seven solar‐tracking Fourier transform infrared (FTIR) spectrometers has been conducted over the Mexico City Metropolitan Area (MCMA) to monitor urban emissions and to evaluate Snapshot Area Map (SAM) observations from the NASA's Orbiting Carbon Observatory‐3 (OCO‐3) mission. Once adjusted for their respective averaging kernels, we diagnosed a positive difference between OCO‐3 and FTIR column measurements (1.06 ppm). Thanks to this unprecedented amount of column observations over a large city, we demonstrate that XCO2 gradients within OCO‐3 SAMs align with the inter‐calibrated FTIR measurements (mean bias of 0.3 ppm), confirming the potential to track CO2 emissions from space over large metropolitan areas. XCO2 urban‐rural differences across the FTIR network, show a strong correlation with observed gradients, with Pearson's correlation coefficients (R) around 0.92. The correlation is significantly lower when considering intra‐urban gradients, where R drop to around 0.24. Simulated XCO2 enhancements (ΔXCO2) based on X‐STILT for both FTIR and OCO‐3 show relatively high correlations (R is around 0.6) using high‐resolution footprints and two gridded inventories. Spatial correlations with OCO‐3 improve when aggregating satellite retrievals at coarser resolutions (10 km). Our study demonstrates the capabilities of detecting urban gradients by FTIR network and OCO‐3 SAM observations over MCMA, a promising result to evaluate the evolution of MCMA's emissions over the coming decade.

Impacts of projected urban growth on simulated near-surface temperature in Mexico City Metropolitan Area: Implications for urban vulnerability

Urbanization impacts the surface temperature fields increasing the vulnerability of urban residents to heat exposure. Identifying vulnerable urban populations to extreme heat exposure is crucial to develop mitigation and adaptation strategies towards sustainability. We used an urban growth model (SLEUTH) to simulate emerging urban areas in Mexico City Metropolitan Area (MCMA) under a hypothetical land-use policy scenario projected to 2060 in which no restrictions were posed to urban growth. SLEUTH outputs were used in the numerical model Weather Research and Forecasting (WRF) to quantify expected changes in near-surface temperature within the MCMA. We calculated and mapped heat exposure as differences in average (Tmean), maximum (Tmax) and minimum (Tmin) temperatures over the diurnal cycle between future and current land cover conditions. Population vulnerability to projected increases in heat exposure was determined using a set of socioeconomic indicators. SLEUTH simulations showed an urban area expansion of nearly 4,790 km2 by 2060. Overall, changes in Tmin were greater than changes observed for Tmax and Tmean. Tmean, Tmax and Tmin increases up to 0.6°C, 1.3°C and 2.6°C, respectively, were recorded for the MCMA with greatest temperature changes observed in the State of Mexico. Results suggested the presence of socioeconomic disparities in the projected spatial exposure of urban-induced heat in MCMA. We argue that our results could be used to inform and guide locally tailored actions aimed at reducing exposure and increasing population´s capacities to cope and adapt to future threats.

HIV-Related Stigma and Treatment Adherence Among Gay, Bisexual, and Other Men Who Have Sex with Men Who Use Crystal Meth in the Metropolitan Area of Mexico City.

Internationally, HIV-related stigma and crystal methamphetamine (meth) use have been described as barriers to treatment adherence among gay, bisexual, and other men who have sex with men (gbMSM). Crystal meth use has been increasing among gbMSM in the Metropolitan Area of Mexico City (MAMC). Therefore, this study aimed to determine the association between HIV-related stigma and HIV treatment adherence among gbMSM who use crystal meth in the MAMC. This study was undertaken as part of an exploratory study of crystal meth use in the MAMC. The data were collected from September to December 2021 through an encrypted online survey. Participants (n = 89) were gbMSM adults living with HIV who reported crystal meth use in the past month that were recruited through an online snowball sampling. The online survey included questions about HIV treatment adherence, sexual behaviors, the Alcohol, Smoking, and Substance Involved Screening Test, and the HIV-Related Stigma Mechanisms Scale. Logistic regression analyses assessed the association between HIV-related stigma and HIV treatment adherence. The multivariate logistic regression model showed that, controlling for health insurance [adjusted odds ratio (AOR) = 0.13; 95% confidence intervals (CI) =0.02-0.59] and educational level (AOR = 0.16; 95% CI =0.02-0.88), non-adherence to HIV treatment was independently associated with higher HIV-related stigma (AOR = 1.06; 95% CI=1.01-1.12). Public health policies must include HIV-related stigma and substance use in treating gbMSM with HIV.

Limnological dynamics of methane (CH4) and carbon dioxide (CO2) emissions from a tropical hypertrophic reservoir lake

Abstract Methane (CH4) and carbon dioxide (CO2) emissions from tropical freshwater ecosystems have been understudied, particularly in terms of their interaction with limnological dynamics, their cycling, and the emission mechanisms of CH4. To help reduce that knowledge gap, this study addressed these processes in Valle de Bravo (VB), a tropical (19° 11. 65′ N) reservoir lake, that provides water supply to Mexico City metropolitan area. CH4 and CO2 concentrations and emissions from VB were measured during four field campaigns distributed along the annual limnological cycle of the reservoir. Dissolved CH4 concentration varied over four orders of magnitude (0.015–176.808 μmol L−1), and dissolved CO2 varied from below atmospheric saturation (15.062 μmol L−1) to 10 times that concentration (219.505 μmol L−1). CH4 fluxes ranged from 23.25 to 1220.80 μmol m−2 day−1, while CO2 fluxes ranged from −60.11 to 254.99 mmol m−2 day−1. Seasonal monitoring also allowed the assessment of the annual emissions as well as the greenhouse gas (GHG) storage during thermal stratification, which accounted for >58% of the total GHG annual emissions from VB. Overall, VB is a source of GHG, and its major contribution is the CH4 released during the autumn overturn.

Wild Edible Mushroom Lore in A Suburban Mestizo Community

Objective: To record the mycological lore related to wild edible mushrooms (WEM) in Santa Ana Jilotzingo, a mestizo rural community greatly influenced by the urban area of Mexico City. Design/Methodology/Approach: Unstructured and semi-structured interviews were conducted over the course of three years. Results: Sixty-six WEM species were recorded. Ninety-one traditional names were documented: 65 Spanish names, 3 Nahuatl names, 4 mixed names, and 19 indeterminate names. Local gatherers have a precise knowledge of the biology, ecology, and distribution of the used species; the knowledge preserved by older people is more diverse and accurate. Nowadays, gathering WEM in the rainy season has lost its relevance as an economic activity. However, WEM foraging as a livelihood food supplement remains important for the community. Study Limitations/Implications: The 2020 pandemic hindered the field work. Findings/Conclusions: In the study area, relevant mycological lore still survives despite complex adverse conditions, such as acculturation, migration, and deforestation.

Innovative methodology for estimating Mountain-Front Recharge in data-scarce regions: A case study in Mexico City

Despite the critical role mountainous regions play in the hydrological cycle, the scarcity of subsurface hydrogeological data hampers accurate estimations of mountain-front recharge (MFR) and its components. This research proposes a cost-effective and replicable methodology for the preliminary estimation of MFR components in conditions of data scarcity. The proposed methodology, encompassing three phases, involves developing a hydrological conceptual model, creating a rainfall-runoff model, and estimating MFR values and their components (surface mountain-front recharge and mountain-block recharge); it enhances understanding of hydrologic processes in mountain zones by interpreting relationships among precipitation, altitude, and geology, influencing variations in recharge and water table position. A key contribution is the methodology's replicability in any mountainous area, even in the absence of detailed information, such as in protected natural areas. A case study is presented by estimating MFR in the Conservation Area of Mexico City (officially known as Suelo de Conservación), composed by the mountain ranges of Sierra de las Cruces and Chichinautzin Volcanic Field. The results emphasize the distinct distribution of MFR components and water table position in the two mountain regions, suggesting a need for a tailored approach to water management in the basin. The proposed methodology is cost-effective to understand the water dynamics in data-scarce regions, contributing to mountain-front recharge management.

Construction of wetlands in La Piedad Lagoon: a strategy to mitigate climate change in Mexico

ABSTRACT The freshwater systems located within the Metropolitan Area of Mexico City (Mexico City and the State of Mexico) are depleted. La Piedad Lagoon is recognized as a critical water resource as it serves as a run-off reservoir during the rainy season. However, the Lagoon is highly contaminated by untreated wastewater discharge due to disorderly and unplanned urban development. Inadequate sanitation has caused significant biodiversity loss and negatively impacted the population's health. Climate change models estimate that surface water availability could be reduced by over 30% in the short term, increasing the risk of a regional water crisis. This complex situation is urgent and demands the ecological restoration of La Piedad Lagoon as it provides an alternative source of water for Mexico City. Here, the intervention and efforts currently performed to rescue La Piedad Lagoon are described, involving its transformation and analysis of the environmental conditions of the area, land uses and ownership, as well as available infrastructure. Finally, it examines key environmental parameters for the construction of wetlands in the Lagoon. The removal contamination capacities of Eichhornia crassipes and Lemna minor, two aquatic plants in the area, were assessed. The lessons learned from this intervention can provide valuable lessons.

Mobile mini-DOAS measurements of the outflow of nitrogen dioxide from the Toluca Valley Metropolitan Area, Mexico

NO2 outflow fluxes were calculated from the City of Toluca, Mexico during January-February 2017 using a mobile zenith viewing mini-DOAS instrument. Measurements were performed in a cross-section of the outflow plume from the Toluca Valley Metropolitan Area with an instrument operating in the visible wavelength region (356 to 510 nm). NO2 retrievals were conducted in the 405 to 465 nm wavelength range. From these measurements, differential vertical columns of NO2 along the measurement route were derived. Using mass-averaged wind speed and wind direction from the Weather Research & Forecasting model, with a 1 km resolution, outflow fluxes of NO2 were calculated from each of the transect measurements. The average NO2 outflow flux for the entire campaign was 1.81 kg/s (156.24 ton/day). To our knowledge, this is the first time that mobile mini-DOAS measurements have been conducted around the City of Toluca and therefore the first time that NO2 outflow fluxes have been reported for this metropolitan area. Comparing our results with emissions inventories we found large variabilities of NOx emissions reported in emissions inventories and between emissions inventories and our measurements. From these discrepancies we infer that emissions inventories underestimate NOx emissions from the TVMA. This study contributes to our understanding of outflow fluxes from metropolitan areas and their possible exchange, being the Toluca Valley Metropolitan Area a few kilometers away from the Mexico City Metropolitan Area, one of the largest megacities of the world.

Hydrogeochemical and isotopic assessment of the origin of NO3− and N–NH3 contents in the aquifer located in a closed lacustrine volcano-sedimentary basin in the metropolitan area of Mexico City

AbstractTo explain the presence and spatial distribution of NO3− and N–NH3 in the Aquifer of the Metropolitan Area of Mexico City (AMAMC), a hydrogeochemical and isotopic analysis using 13CDIC (as well as the stable isotopes 18O and 2H) in groundwater was conducted. This aquifer is located in an old closed lacustrine volcano-sedimentary basin; some wells hosted in the semi-confined zone contain high N–NH3 concentrations, while others present NO3− contents in the recharge zones (hosted in an oxidizing environment). In this study, a change in the isotopic signature (primarily in 18O and 2H) was observed from the recharge zones to the basin center in some of the wells with high NO3− concentrations, this behavior can be attributed to evaporation during the incorporation of recently infiltrated water. In addition, the results for 13C (along with 2H) in wells with the highest N–NH3 concentrations exhibited an atypically broad range of values. Results indicated the occurrence of hydrogeochemical and/or biochemical processes in the aquifer (in an oxidizing or reducing environment), such as organic degradation, bacterial decomposition (primarily in the ancient Lake Texcoco and which acts as a natural sink for carbon, nitrogen, sulfur, and phosphorus), besides rock weathering and dissolution, which may be responsible for a very marked isotopic modification of the 13C (and, to a lesser extent, 2H). Methanotrophic bacterial activity and methanogenic activity may be related to N–NH3 removal processes by oxidation and residual water incorporation respectively, whereas the increase in the NO3− content in some wells is due to the recent contribution of poor-quality water due to contamination.

Air Pollution and Climate Change Risk Perception among Residents in Three Cities of the Mexico Megalopolis

Recent reports of the criteria pollutants in the Megalopolis, located in the central part of Mexico, consistently show air quality standard exceedances in most of the cities that make it up, since it is a large concentration where approximately 17% of the national population resides and because it has significant commercial and industrial development. To investigate the similarities and disparities in risk perception concerning air pollution and climate change among residents living in Central Mexico, a cross-sectional survey study was carried out within three metropolitan areas encompassed by the Megalopolis. A total of 1750 questionnaire surveys were conducted across 21 municipalities within the Mexico City Metropolitan Area (MCMA), 16 municipalities within the Toluca Valley Metropolitan Area (TVMA), and 8 municipalities within the Cuernavaca Metropolitan Area. The three metropolitan areas showed significant differences in terms of air quality perception, risk perception, attitudes, and causal attribution perception, but health-related perception did not have significant differences among the areas. The MCMA exhibited higher knowledge about air pollution, although it associated the causes with urban activities such as car usage, while the Toluca and Cuernavaca areas linked this issue to the burning of garbage, coal, wood, and agricultural activities. Although residents expressed concern about air pollution, climate change, and their effects, they do not know how to act to contribute to the solution.

Knowledge, experience, and perception of molar incisor hypomineralisation among dentists in the metropolitan area of Mexico City: a cross-sectional study

BackgroundMolar-incisor hypomineralisation (MIH) is the most common developmental abnormality observed in teeth. Being a relatively new condition, its treatment can present a challenge for the dentist. There is currently no study available that has evaluated the knowledge of Mexican dental personnel. This study aimed to evaluate the knowledge, experience, and perceptions of dental surgeons regarding the detection, assessment, and treatment of MIH in the metropolitan area of Mexico City.MethodsA cross-sectional study was designed. Dentists from Mexico City and its metropolitan area were invited through social networks to answer a questionnaire of 30 questions related to MIH. Participants were classified into general practice dentists, paediatric dentists, and other speciality dentists. Pearson’s chi-square test was used for data analysis.ResultsThe questionnaire was answered by 391 dentists. A total of 86% (338 out of 391) of them identified MIH lesions, while 84% of them reported having observed MIH lesions in their practice. The most frequently observed lesions were yellow-brown opacities which accounted for 47% of the lesions, 46% were white opacities, while only 7% were observed as post-eruptive fractures in the enamel as part of the manifestations of MIH. The most frequently reported problem in the management of teeth with MIH was insufficient training for treating children with MIH. A total of 84% of dentists stated that they would like more information on the treatment of MIH lesions.ConclusionsMost of the surveyed dentists recognised MIH and reported having observed MIH lesions in their practice. Most of the dentists indicated that the main problem for the management of the MIH is the lack of training.

Geographical approach analysis of the impact of air pollution on newborn intrauterine growth and cord blood DNA damage in Mexico City

Abstract Background Few epidemiologic studies have focused on the specific source of ambient air pollution and adverse health effects in early life. Here, we investigated whether air pollutants from different emission sources were associated with decreased birth anthropometry parameters and increased DNA adduct formation in mother-child pairs residing in the Mexico City Metropolitan Area (MCMA). Methods This cross-sectional study included 190 pregnant women recruited during their last trimester of pregnancy from two hospitals at MCMA, and a Modeling Emissions Inventory (MEI) to calculate exposure to ambient air pollutants from different emissions sources (area, point, mobile, and natural) for two geographical buffers 250 and 750 m radii around the participants households. Results Contaminants were positively correlated with umbilical cord blood (UCB) adducts, but not with maternal blood (MB) adducts. PM10 emissions (area and point sources, overall emissions), PM2.5 (point sources), volatile organic compounds (VOC), total organic compounds (TOC) from point sources were positively correlated with UCB adducts. Air pollutants emitted from natural sources were correlated with a decrease in MB and UCB adducts. PM10 and PM2.5 were correlated (p < 0.05) with a decrease in birth weight (BW), birth length (BL) and gestational age at term (GA). In multivariate analyses adjusted for potential confounders, PM10 was associated with an increase in UCB adducts. PM10 and PM2.5 from overall emissions were associated with a decrease in BW, BL and GA at term. Impact Results suggested higher susceptibility of newborns compared to mothers to damage related to ambient air pollution. PMs are associated with birth anthropometry parameters and DNA damage in adjusted models, highlighting the need for more strict regulation of PM emissions.

Ozone responses to reduced precursor emissions: A modeling analysis on how attainable goals can improve air quality in the Mexico City Metropolitan Area

High tropospheric ozone (O3) concentrations prevent the improvement of the air quality in the Mexico City Metropolitan Area (MCMA). Although the problem has improved considerably since the 1990s, a rebound in O3 levels in recent years has raised concerns about the deteriorating air quality. The nonlinear relationship between O3 formation and the emissions of its main precursors, i.e., volatile organic compounds (VOCs) and nitrogen oxides (NOx), is a challenge when measures are enacted for effective mitigation of the O3 problem. This study evaluated the reduction in precursors, VOCs and NOx, using an up-to-date regional air quality model (HERMES-Mex-WRF-CMAQ). For evaluating realizable scenarios, the decline in VOC achieved in Japan after policy implementation was the targeted VOC reduction (40 % from area sources), and the NOx reduction observed in the MCMA during the COVID-19 pandemic was the targeted NOx reduction (40 % from mobile sources). The analysis evaluated the O3 responses to changes in a single precursor and a combination of both during a period of high O3 concentrations (April 2019). The results showed that 40 % reduction in VOC emissions would decrease the O3 8-h maximum concentrations by 16 %. However, 40 % reduction in NOx emissions would increase O3 by >15 %. The simultaneous reduction of both precursors did not significantly affect O3 levels. The diagnosis of ozone sensitivity using the H2O2/HNO3 ratios reinforced the simulation findings, indicating that VOC emissions limited ozone formation in most MCMA areas. As the simulated scenarios were based on factual case studies, our research offers insights into the realistic aims of MCMA policies to reduce O3 levels.

Urbanization in the Mexico City Metropolitan Area 1900–2020: Urban Dynamics and Driving Factors

The variability of urban growth in the Mexico City conurbation reflects the complexity of changes and uncertainty experienced in many urban areas. The goal of this project is to identify how the urban expansion of the Mexico City conurbation reflects the changes in socioeconomic variables of the region over recent decades. The authors first spatially quantified the rate of urban growth from 1990 to 2020 using Landsat data and then identified the socioeconomic variables associated with this urban expansion. Results showed a progressive loss in vegetated land and an increase in urban land. The population’s access to roads and the marginalization index had the highest positive correlation with the observed urban growth. Although these variables were highly correlated with each other, access to roads was not found to be a variable of importance for projecting urban growth. Finally, two distinct zones of urban growth were determined using cluster statistics; the first showed no growth, which corresponded with more established, older municipalities closer to the city centre, and the second zone had significant growth, which corresponded to municipalities away from the centre, coinciding with urban decentralization and new lifestyle patterns. The identification of urban growth zones and socioeconomic variables associated with that growth will assist with effective planning, infrastructure development, and resource management.

La banqueta (acera): entre circulación y otros usos, los retos de un orden urbano híbrido

Through a case study of the sidewalk in the Mexico City metropolitan area, we use the notion of hybrid order to understand the variable place that mobility and public space occupy in the ongoing logics of the material, social and cultural production of different sidewalks. This proposal contributes to a critique of European-centric conceptions of public spaces and underlying dichotomies. The production and governance of sidewalks are inscribed within a culture of informality common in Latin American, but the concept of hybrid order can be extended to other objects and other contexts. We conclude that the interest in walking and the sidewalk can lead to a disruption of the conventional hierarchy that places at the bottom end of governance the management of uses, by integrating it upstream in the decision-making, planning and design processes.

Decreased DNA repair capacity caused by exposure to metal mixtures is modulated by the PARP1 rs1136410 variant in newborns from a polluted metropolitan area

BackgroundDNA damage caused by exposure to metal mixtures and the potential modulating role of genes involved in DNA repair and the antioxidant response have not been evaluated in newborns. AimThe aim was to evaluate the association between prenatal exposure to metal mixtures and DNA repair capacity (DRC) in newborns from the Metropolitan Area of Mexico City (MAMC), a heavily polluted area, and the impact of variants in genes involved in DNA repair and the antioxidant response on this association. MethodsWe analyzed cord blood samples obtained at delivery from 125 healthy newborns from the MAMC. Twenty-four elements were determined by inductively coupled plasma mass spectrometry (ICP‒MS), but only 12 (Cu, I, Se, Zn, As, Ba, Cs, Mn, Sb, Sr, Pb, and Ti) were quantified in most samples. DRC was assessed by the challenge-comet assay, and OGG1, PARP1, and NFE2L2 genotyping was performed with TaqMan probes. Metal mixtures were identified and analyzed using principal component analysis (PCA) and weighted quantile sum (WQS) regression. Independent adjusted linear regression models were used to evaluate the associations. ResultsA null DRC was observed in 46% of newborns. The metals with the highest concentrations were Mn, Sr, Ti, and Pb. Essential elements showed normal levels. Only the mixture characterized by increased As, Cs, Cu, Se, and Zn levels was inversely associated with DRC. As was the principal contributor (37.8%) in the negative direction in the DRC followed by Ba and Sb, according to the WQS regression. Newborns carrying of the derived (G) allele of the PARP1 rs1136410 variant showed decreased DRC by exposure to some potentially toxic metals (PTMs) (As, Cs, and Ba). ConclusionPrenatal exposure to metal mixtures negatively affected DRC in newborns, and the PARP1 rs1136410 variant had a modulating role in this association.

Generalizability and Out-of-Sample Predictive Ability of Associations Between Neuromelanin-Sensitive Magnetic Resonance Imaging and Psychosis in Antipsychotic-Free Individuals

The link between psychosis and dopaminergic dysfunction is established, but no generalizable biomarkers with clear potential for clinical adoption exist. To replicate previous findings relating neuromelanin-sensitive magnetic resonance imaging (NM-MRI), a proxy measure of dopamine function, to psychosis severity in antipsychotic-free individuals in the psychosis spectrum and to evaluate the out-of-sample predictive ability of NM-MRI for psychosis severity. This cross-sectional study recruited participants from 2019 to 2023 in the New York City area (main samples) and Mexico City area (external validation sample). The main samples consisted of 42 antipsychotic-free patients with schizophrenia, 53 antipsychotic-free individuals at clinical high risk for psychosis (CHR), and 52 matched healthy controls. An external validation sample consisted of 16 antipsychotic-naive patients with schizophrenia. NM-MRI contrast within a subregion of the substantia nigra previously linked to psychosis severity (a priori psychosis region of interest [ROI]) and psychosis severity measured using the Positive and Negative Syndrome Scale (PANSS) in schizophrenia and the Structured Interview for Psychosis-Risk Syndromes (SIPS) in CHR. The cross-validated performance of linear support vector regression to predict psychosis severity across schizophrenia and CHR was assessed, and a final trained model was tested on the external validation sample. Of the 163 included participants, 76 (46.6%) were female, and the mean (SD) age was 29.2 (10.4) years. In the schizophrenia sample, higher PANSS positive total scores correlated with higher mean NM-MRI contrast in the psychosis ROI (t37 = 2.24, P = .03; partial r = 0.35; 95% CI, 0.05 to 0.55). In the CHR sample, no significant association was found between higher SIPS positive total score and NM-MRI contrast in the psychosis ROI (t48 = -0.55, P = .68; partial r = -0.08; 95% CI, -0.36 to 0.23). The 10-fold cross-validated prediction accuracy of psychosis severity was above chance in held-out test data (mean r = 0.305, P = .01; mean root-mean-square error [RMSE] = 1.001, P = .005). External validation prediction accuracy was also above chance (r = 0.422, P = .046; RMSE = 0.882, P = .047). This study provided a direct ROI-based replication of the in-sample association between NM-MRI contrast and psychosis severity in antipsychotic-free patients with schizophrenia. In turn, it failed to replicate such association in CHR individuals. Most critically, cross-validated machine-learning analyses provided a proof-of-concept demonstration that NM-MRI patterns can be used to predict psychosis severity in new data, suggesting potential for developing clinically useful tools.

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

BackgroundSatellite-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.MethodsWe 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.ResultsPM2.5 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.ConclusionsExposure 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.

CHANGES IN FOSSIL CO2 EMISSIONS IN MEXICO CITY DURING THE COVID-19 LOCKDOWN DEDUCED FROM ATMOSPHERIC RADIOCARBON CONCENTRATIONS

ABSTRACT We present atmospheric radiocarbon concentrations in CO2 integrated samples taken between January 2019 and December 2021 in the Mexico City Metropolitan Area (MCMA) and explain the variations in terms of changes in emission sources associated with the COVID-19 lockdown restrictions imposed from March 2020. Δ14C values for samples collected during 2019 range between –44.15‰ and –13.17‰, with lower values during months with higher fossil fuels consumption and air stagnation, whereas higher values were found for periods with high number of fires around MCMA or wet months with higher contribution of heterotrophic respiration. For samples collected during 2020, Δ14C values range between –17.7‰ and 2.25‰, with an increasing trend immediately after the initial lockdown and higher values obtained for samples collected during lockdown phases 2 and 3 and the period of extremely high epidemic risk. This agrees with the 38% and 52% decrease in gasoline and diesel sales. Once essential activities gradually opened from July 2020, Δ14C follow a decreasing trend as vehicle traffic started to increase again. Δ14C values for samples collected during 2021 range from –32.89‰ to –10.27‰, with the higher value obtained during a period of extremely high epidemic risk with a 30% reduction in gasoline and diesel consumption. Despite the complexity of emission sources in MCMA, from Δ14C variations it was possible to identify changes in fossil CO2 emissions resulting from the significant reduction in vehicle traffic due to the COVID-19 lockdown and the restrictions imposed to control transmission of the disease.