Southwest Mexico City Research Articles

Elemental analysis of PM10 in southwest Mexico City and source apportionment using positive matrix factorization

Elemental analysis of PM10 in southwest Mexico City and source apportionment using positive matrix factorization

CORRELACIÓN PAN-O3 EN EL SUROESTE DE LA CIUDAD DE MÉXICO

Peroxyacetyl nitrate (PAN) and NO 2 (true) were measured during two short campaigns in June and October, 2017 with a gas chromatography-luminol detection method in southwest Mexico City. The maximum and total hourly mixing ratio measured averages of PAN were 5.2 and 1.3 ppb v in June and 3.3 and 0.6 ppb v in October, respectively, being these values slightly lower than those reported in 2003 suggesting that PAN precursor levels have only partially decreased during the last 15 years. PAN hourly averages of the two campaigns were correlated with O 3 , NO 2 (by chemiluminescence), solar radiation, temperature, and wind speed measured in the same monitoring site in order to obtain a combined empirical model (CEM) for the diagnosis of PAN concentrations for other periods of the year. The resulting CEM was integrated with several multiple linear correlations which are applied depending on the period of the day and the ambient temperature. The correlation between both, the simulated and measured PAN resulted in a coefficient R 2 = 0.87. The CEM was applied to records of the above mentioned variables measured at the Centro de Ciencias de la Atmosfera monitoring station at Ciudad Universitaria for the 2017 ozone season. A positive temperature dependent correlation was obtained between PAN and ozone, but the correlation was weaker as ambient temperature exceeded the 20 oC.

Opposing seasonal trends for polycyclic aromatic hydrocarbons and PM10: Health risk and sources in southwest Mexico City

This study reports the measurement of polycyclic aromatic hydrocarbons (PAHs) in airborne particles ≤10μm (PM10) during four years. Seasonal variation was observed for PM10 and PAH in southwest Mexico City, with major mass concentrations during the dry season (November–April). A non linear decreasing trend of PM10 was observed during this period, while a linear increase (in the four years) was obtained for benzo[a]pyrene (88pgm−3), phenanthrene (29pgm−3), fluoranthene (88pgm−3), and benzo[ghi]perylene (438pgm−3). Coronene also showed an increasing trend but it was nonlinear. This suggests that air control strategies implemented by the government contributed to maintaining PM10 under the 24h maximum limit and resulted in a decreasing trend during this period. However, these strategies did not result in controlling some organic constituents with mutagenic and/or carcinogenic properties as it is the case of benzo[a]pyrene. The annual average of this PAH exceeded the UK recommendation. It was estimated a median (10th–90th) lifetime health risk of 7.6 (3.4–17.2) additional cases of cancer per 10million people in this zone exists and the health risk of PAH is almost three times greater in dry seasons than it is in rainy seasons. Specific humidity, temperature and wind speed acted as cleaners for PM10 and PAH from the atmosphere. PAH diagnostic ratios and correlation and principal component analyses suggest incomplete combustion from gasoline and diesel engines as the main contributor to PAH found in southwest Mexico City, where factor 1 grouped all PAH emitted from gasoline engines during first three years. During last year, factor 1 only grouped PAH markers of diesel engines. This suggests a change of emission amounts between gasoline and diesel combustion sources or a contribution of other source(s) which changed the PAH profiles. During four years retene was always separated from factors which grouped the rest of PAH, due to its wood combustion origin.

Intra-city Differences in Cardiac Expression of Inflammatory Genes and Inflammasomes in Young Urbanites: A Pilot Study

Southwest Mexico City (SWMC) air pollution is characterized by high concentrations of ozone and particulate matter < 10 μm (PM10) containing lipopolysaccharides while in the North PM2.5 is high. These intra-city differences are likely accounting for higher CD14 and IL-1β in SWMC v NMC mice myocardial expression. This pilot study was designed to investigate whether similar intra-city differences exist in the levels of myocardial inflammatory genes in young people. Inflammatory mediator genes and inflammasome arrays were measured in right and left autopsy ventricles of 6 southwest/15 north (18.5 ± 2.6 years) MC residents after fatal sudden accidental deaths. There was a significant S v N right ventricle up-regulation of IL-1β (p=0.008), TNF-α (p=0.001), IL-10 (p=0.001), and CD14 (p=0.002), and a left ventricle difference in TNF-α (p=0.007), and IL-10 (p=0.02). SW right ventricles had significant up-regulation of NLRC1, NLRP3 and of 29/84 inflammasome genes, including NOD factors and caspases. There was significant degranulation of mast cells both in myocardium and epicardial nerve fibers. Differential expression of key inflammatory myocardial genes and inflammasomes are influenced by the location of residence. Myocardial inflammation and inflammasome activation in young hearts is a plausible pathway of heart injury in urbanites and adverse effects on the cardiovascular system are expected.

Immunotoxicity and Environment: Immunodysregulation and Systemic Inflammation in Children

Environmental pollutants, chemicals, and drugs have an impact on children's immune system development. Mexico City (MC) children exposed to significant concentrations of air pollutants exhibit chronic respiratory inflammation, systemic inflammation, neuroinflammation, and cognitive deficits. We tested the hypothesis that exposure to severe air pollution plays a role in the immune responses of asymptomatic, apparently healthy children. Blood measurements for markers of immune function, inflammatory mediators, and molecules interacting with the lipopolysaccharide recognition complex were obtained from two cohorts of matched children (aged 9.7 +/- 1.2 years) from southwest Mexico City (SWMC) (n = 66) and from a control city (n = 93) with criteria pollutant levels below current standards. MC children exhibited significant decreases in the numbers of natural killer cells (p = .003) and increased numbers of mCD14+ monocytes (p < .001) and CD8+ cells (p = .02). Lower concentrations of interferon gamma (p = .009) and granulocyte-macrophage colony-stimulating factor (p < .001), an endotoxin tolerance-like state, systemic inflammation, and an anti-inflammatory response were also present in the highly exposed children. C-reactive protein and the prostaglandin E metabolite levels were positively correlated with twenty-four- and forty-eight-hour cumulative concentrations of PM(2.5). Exposure to urban air pollution is associated with immunodysregulation and systemic inflammation in children and is a major health threat.

Biodirected mutagenic chemical assay of PM 10 extractable organic matter in Southwest Mexico City

The concentration of breathable particles (PM 10) in urban areas has been associated with increases in morbidity and mortality of the exposed populations, therein the importance of this study. Organic compounds adsorbed to PM 10 are related to the increased risk to human health. Although some studies have shown the lack of correlation between specific mutagenic compounds in an organic complex mixture (OCM) and the mutagenic response in several bioassays, the same organic compounds selectively separated in less complex groups can show higher or lower mutagenic responses than in the OCM. In this study, we fractionated the OCM, from the PM 10 in four organic fractions of increasing polarity (F1–F4). The Salmonella bioassay with plate incorporation was applied for each one using TA98, with and without S9 (mammalian metabolic activation), and YG1021 (without S9) strains. The most polar fraction (F4) contained the greatest mass followed by F1 (non-polar), F2 and F3 (moderately polar). The concentrations of the OCM as well as the F4 were the only variables correlated with PM 10, atmospheric thermal inversions, fire-prone area, NO 2, SO 2, CO, rain and relative humidity. This indicated that polar organic compounds were originated in gas precursors formed during the atmospheric thermal inversions as well as the product of the incomplete combustion of vehicular exhausts and of burned vegetation. The percentages of the total PAH, and the individual PAH with molecular weight ≥ 228 g mol −1 (except retene) correlated with the percentages of indirect-acting mutagenicity in TA98 + S9. The percentages of the total nitro-PAH and most of the analyzed individual nitro-PAH correlated with percentages of the direct-acting mutagenicity in both TA98 − S9 and YG1021, the latter being more sensitive. In general, the highest mutagenic activity (indirect and direct) was found in F3 (moderately polar) and in F4 (polar). The non-polar fraction (F1) did not exhibit any kind of mutagenicity. In 77% of the cases, mutagenic activity was higher in the sum fractions with respect to their OCM. The combinations between F1, F2 and F4, with F3 under different or equal proportions suggested that mutagenicity reduction, in the combined matter of January (with TA98 + S9 and YG1021) and of May (with YG1021), was due to concentrations of mutagens and non-mutagens in each fraction, and not to an antimutagenic effect. The organic compounds present in the non-polar fractions showed no antagonism, inhibition or reduction in the most mutagenic fractions in both indirect- and direct-acting mutagenicity, and the less polar organic compounds in F3 reduced mutagenicity in F4, in both months.

Mutagenicity and polycyclic aromatic hydrocarbons associated with extractable organic matter from airborne particles ⩽10 μm in southwest Mexico City

A year-long sampling and analysis of 24 h airborne particles equal to or less than 10 μm (PM 10) was conducted in Southwest (SW) Mexico City in 1998. The amount of airborne PM 10 and its extractable organic matter (EOM) were highly correlated. The year 1998 was particularly dry with many fires, and higher values of PM 10 and EOM were obtained in the fire period (February–May) compared to the without fire period (January, June–December). The indirect-acting mutagenicity ( Salmonella typhimurium strain TA98 with mammalian metabolic activation, S9) did not correlate with the monthly concentrations of PM 10 and EOM, while the direct-acting mutagenicity (strains TA98 and YG1021, without mammalian metabolic activation) did correlate. The highest monthly mutagenic potency of TA98+S9 and of TA98−S9 were registered in May which correspond to the fire period, while for YG1021 the highest was in December, a without fire month. The highest TA98+S9/TA98−S9 ratios appeared from April to September (with the exception of June), indicating that emission of the direct mutagens occurred in the rest of the year (the coldest months), and December showed the highest mutagenicity of YG1021. The correlation of this mutagenicity with the number of ground-based inversions indicated a greater emissions of nitroarenes in the coldest months emitted mainly by vehicular traffic as shown by the correlation between YG1021 with CO and with NO 2. We did not find a correlation in the EOM of the complex mixtures between TA98+S9 and the total concentration of polycyclic aromatic hydrocarbons (PAH) nor between TA98+S9 and specific PAH. The analysis by gas chromatography/mass spectrometry indicated the presence of retene, a PAH found in the fire period and considered a softwood burning marker. The concentrations of fluoranthene and benz[ a]anthracene correlated with that of retene and with the burned area; they were the only PAH that presented significant differences between the periods with fire and without fire, showing that these compounds could have a similar origin. Benzo[ ghi]perylene, coronene and indeno[1,2,3 -cd]pyrene were the most abundant PAH of the 17 analyzed in SW Mexico City, indicating that the main emission source for PAH in the airborne particle phase in this zone were vehicles with the combustion of gasoline and diesel rather than wood burning. The mean concentrations for most PAH were higher during the fire period, except for perylene and coronene, suggesting that the fires were not the emission source for these two last PAH.

Lung Radiology and Pulmonary Function of Children Chronically Exposed to Air Pollution

We analyzed the chest radiographs (CXRs) of 249 clinically healthy children, 230 from southwest Mexico City and 19 from Tlaxcala. In contrast to children from Tlaxcala, children from southwest Mexico City were chronically exposed to ozone levels exceeding the U.S. National Ambient Air Quality Standards for an average of 4.7 hr/day and to concentrations of particulate matter (PM) with aerodynamic diameters ≤2.5 μm (PM2.5) above the annual standard. CXRs of Mexico City children demonstrated bilateral hyperinflation (151 of 230) and increased linear markings (121 of 230). Hyperinflation and interstitial markings were significantly more common in Mexico City children (p < 0.0002 and 0.00006 respectively). Mexico City boys had a higher probability of developing interstitial markings with age (p = 0.004). Computed tomography (CT) scans were obtained in 25 selected Mexico City children with abnormal CXRs. Mild bronchial wall thickening was seen in 10 of 25, prominent central airways in 4 of 25, air trapping in 8 of 21, and pulmonary nodules in 2 of 21. Only 7.8% of Mexico City children had abnormal lung function tests based on predicted values. These findings are consistent with bronchiolar, peribronchiolar, and/or alveolar duct inflammation, possibly caused by ozone, PM, and lipopolysaccharide exposure. The epidemiologic implications of these findings are important for children residing in polluted environments, because bronchiolar disease could lead to chronic pulmonary disease later in life.

Do associations between airborne particles and daily mortality in Mexico City differ by measurement method, region, or modeling strategy?

We evaluated whether associations between PM10 and daily mortality in Mexico City differ by the PM10 measurement device or by regional differences in particle composition. Additionally, we reanalyzed previously collected data in light of recent insights about flaws in commonly used time series analysis techniques. We examined daily associations between mortality and four indicators of ambient PM10 using Poisson regression, controlling for temperature and time trends with cubic natural splines. Associations were calculated for five subregions corresponding to five monitoring sites and pooled for the entire metropolitan area. PM10 was measured with three methods: Tapered Element Oscillating Microbalance (TEOM), Sierra-Anderson High Volume (Hi-Vol) and Harvard Impactor (HI), the latter only at one site. In addition, predicted values of daily PM10 were developed using the Hi-Vol measurements, which were taken every sixth day, and weather, visibility and other pollutant data. We assigned deaths to the exposure from the monitor nearest to their residence. We also re-evaluated the HI PM2.5 and mortality association in southwest Mexico City, which was estimated previously using nonparametric statistical models. Slight decreases in effect estimates were observed (a 1.45% increase (95% CI: 0.09%, 2.83%) in total mortality per 10 microg/m(3) increment of PM2.5 at lag 0) compared to a 1.68% change (95% CI: 0.45%, 2.93%) using the previously employed nonparametric approach. Using data pooled over all the regions, PM10 measured by the TEOM and the predicted PM10 values showed little association with mortality at any of the lags examined. The pooled estimates for Hi-Vol PM10 (using one sixth of the data) were positive across all lags examined and significant for lags 3 and 5. No consistent patterns of differing associations were seen across regions that would correspond with particle toxicity or composition. Particulate air pollution, measured with gravimetric methods, is associated with daily mortality and presents a risk to health in Mexico City. The reanalysis suggests that previous research is robust to statistical method and likely to yield the same overall conclusions about the short-term effects of airborne particles on mortality.

Particulate and Ozone Pollutant Effects on the Respiratory Function of Children in Southwest Mexico City

We assessed the contributions of particulate matter with aerodynamic diameters < or =10 and < or =2.5 microm (PM2.5 and PM10) and ozone (O3) to peak expiratory flow (PEF) and respiratory symptoms in 40 schoolchildren 8-11 years of age for 59 days during three periods in 1991 at a school in southwest Mexico City. We measured peak expiratory flow in the morning on the children's arrival at school and in the afternoon before their departure from school. Separately for morning and afternoon, we normalized each child's daily measurement of peak flow by subtracting his or her mean peak flow from the daily measurement. Child-specific deviations were averaged to obtain a morning and afternoon mean deviation (APEF) for each day. Mean 24-hour O3 level was 52 parts per billion (ppb; maximum 103 ppb); mean 24-hour PM2.5 and PM10 were 30 microg/m3 (maximum 69 microg/m3) and 49 microg/m3 (maximum 87 microg/m3), respectively. We adjusted moving average and polynomial distributed lag multiple regression analyses of APEF vs pollution for minimum daily temperature, trend, and season. We examined effects of PM2.5, PM10, and O3, on deltaPEF separately and in joint models. The models indicated a role for both particles and O3 in the reduction of peak expiratory flow, with shorter lags between exposure and reduction in peak expiratory flow for O3 than for particle exposure (0-4 vs 4-7 days). The joint effect of 7 days of exposure to the interquartile range of PM2.5 (17 microg/m3) and O3 (25 ppb) predicted a 7.1% (95% confidence interval = 11.0-3.9) reduction in morning peak expiratory flow. Pollutant exposure also predicted higher rates of phlegm; colinearity between pollutants limited the potential to distinguish the relative contribution of individual pollutants. In an area with chronically high ambient O3 levels, school children responded with reduced lung function to both O3 and particulate exposures within the previous 1 to 2 weeks.

Mortality and Ambient Fine Particles in Southwest Mexico City, 1993-1995

Children are highly susceptible to deleterious effects of environmental toxins. Those who live in underserved communities may be particularly at risk because environmental pollution has been found to be disproportionately distributed among communities. Mounting evidence suggests that asthma rates are rising and that this disease can be caused or aggravated by air pollution. Although ambient air quality has generally improved, these improvements have not reached minority communities in equal proportions. This and other data has fueled the concept of environmental justice or environmental equity, which has led to community activism and government actions. One possible example of environmental inequity and its consequences is the Hunt's Point community, in the South Bronx, New York. This community experiences a high pollution burden with the siting of facilities that emit hazardous wastes into the air. Our approach to this problem has been the formation of mechanisms for bidirectional communication between community residents, government entities, and academic institutions such as Mount Sinai Medical Center. As a result of this experience, we believe that the key to achieving environmental health, especially in communities of color where many children are at risk, is to empower residents to take charge of their environment by providing relevant educational opportunities. Strategies for environmental health education include multitiered training approaches that include community residents, parent education, direct children education, and community education through professional counselors and train-the-trainer approaches. We propose that academic researchers must use community residents not just as subjects of our studies, but to increase our mutual understanding of environmental health, resulting in active participation of community members in research design, data collection, analysis, and dissemination of results in order to make intervention strategies more effective.

Mortality and ambient fine particles in southwest Mexico City, 1993-1995.

++Epidemiologic studies have focused attention on the health effects of fine particulate air pollutants <2.5 microm in diameter (PM2.5). To further characterize the potential effects of fine particles, we investigated the relationship of air pollution to mortality in Mexico City during 1993-1995. The concentration of PM2.5 was measured on a 24-hr integrated basis; concentrations of NO2 and ozone were measured hourly and reduced to 24-hr means. Daily mortality was determined from death registration records, and Poisson regression was used to model daily death counts as a function of air pollutant levels on the same and previous days, while controlling for temperature and periodic cycles. Without taking other air pollutants into account, a 10 microg/m3 increase in the level of PM2.5 was associated with a 1.4% increase in total mortality, both on the current day and 4 days after exposure [95% confidence interval (CI), 0.2-2.5]. An equivalent increase in PM2.5 was also associated with somewhat larger excesses of deaths among people over 65 years of age and from cardiovascular and respiratory causes, which occurred after a lag of 4 days. The mean concentration of ozone over a 2-day period was associated with a 1.8% increase in mortality from cardiovascular diseases. NO2 was not consistently related to mortality. Fine particles had an independent effect on mortality when modeled simultaneously with other pollutants, and the association of ozone with cardiovascular mortality was strengthened after adjusting for NO2 and PM2.5. These results support previous findings that urban air pollution at current levels leads to excess mortality and suggest that fine particles may play a causal role in producing that excess.

Mortality and ambient fine particles in southwest Mexico City, 1993-1995.

Mortality and ambient fine particles in southwest Mexico City, 1993-1995.