Pneumonia due to Pasteurella multocida, case report and considerations.

Community acquired pneumonia is frequent in the elderly but a pathogen is identified in less than fifty per cent of the cases. It is rarely produced by Pasteurella multocida, a Gram-negative oral commensal of many dogs and cats. We report the case of an elderly man with chronic obstructive respiratory disease who owned a dog and developed severe pneumonia due to P. multocida.

Relationship between air quality and asthma-related emergency hospital admissions in Mexico City 2017-2019.

BACKGROUND: Previous studies found exposure to air pollution leads to exacerbations of asthma in paediatric and adult patients and increases asthma-related emergency hospital admissions (AREHA). METHODS: AREHAs and levels of air pollutants (PM10, PM2.5 and NO2) were obtained from Mexico City for the period 2017-2019. A time-series approach was used to explore the relationship between air pollutants and AREHA. Relative risks of AREHA were estimated using a negative binomial regression in young children (less than 5 years) and adults (greater than 18 years). RESULTS: There was a positive association between AREHA and PM10, PM2.5 and NO2 in adults, which remained after mutual adjustment for these pollutants. The relative risk (RR) of admission in adults increased by 3% (95% CI 1% to 4%) for a 10 µg/m3 increase in PM10, 1% (0.03% to 3%) for a 5 µg/m3 increase in PM2.5 and by 1% (0.06% to 2%) for a 5 µg/m3 increase in NO2. In contrast, in young children, AREHAs were negatively associated with PM10 after adjustment for NO2 (RR 0.97 (0.95 to 0.99) for a 10 µg/m3 and with NO2 after adjustment for PM10 and PM2.5 (RR 0.98 (0.96 to 0.99) and 0.97 (0.96 to 0.99), respectively, for a 5 µg/m3 increase in NO2). AREHAs in children were not associated with PM2.5 after adjustment for NO2. CONCLUSIONS: Ambient air pollution, within the previous week, was associated with emergency hospital admissions for asthma to public hospitals in adults in Mexico City. The relationship in children was less consistent. Further work is needed to explore why differences between adults and children exist to inform appropriate interventions to benefit public health.

Persistently high incidence rates of childhood acute leukemias from 2010 to 2017 in Mexico City: A population study from the MIGICCL.

Introduction: Over the years, the Hispanic population living in the United States has consistently shown high incidence rates of childhood acute leukemias (AL). Similarly, high AL incidence was previously observed in Mexico City (MC). Here, we estimated the AL incidence rates among children under 15 years of age in MC during the period 2010-2017. Methods: The Mexican Interinstitutional Group for the Identification of the Causes of Childhood Leukemia conducted a study gathering clinical and epidemiological information regarding children newly diagnosed with AL at public health institutions of MC. Crude age incidence rates (cAIR) were obtained. Age-standardized incidence rates worldwide (ASIRw) and by municipalities (ASIRm) were calculated by the direct and indirect methods, respectively. These were reported per million population <15 years of age; stratified by age group, sex, AL subtypes, immunophenotype and gene rearrangements. Results: A total of 903 AL cases were registered. The ASIRw was 63.3 (cases per million) for AL, 53.1 for acute lymphoblastic leukemia (ALL), and 9.4 for acute myeloblastic leukemia. The highest cAIR for AL was observed in the age group between 1 and 4 years (male: 102.34 and female: 82.73). By immunophenotype, the ASIRw was 47.3 for B-cell and 3.7 for T-cell. The incidence did not show any significant trends during the study period. The ASIRm for ALL were 68.6, 66.6 and 62.8 at Iztacalco, Venustiano Carranza and Benito Juárez, respectively, whereas, other municipalities exhibited null values mainly for AML. Conclusion: The ASIRw for childhood AL in MC is among the highest reported worldwide. We observed spatial heterogeneity of rates by municipalities. The elevated AL incidence observed in Mexican children may be explained by a combination of genetic background and exposure to environmental risk factors.

Reduction of atmospheric emissions due to switching from fuel oil to natural gas at a power plant in a critical area in Central Mexico.

A case study was conducted to evaluate the SO2 emission reduction in a power plant in Central Mexico, as a result of the shifting of fuel oil to natural gas. Emissions of criteria pollutants, greenhouse gases, organic and inorganic toxics were estimated based on a 2010 report of hourly fuel oil consumption at the "Francisco Pérez Ríos" power plant in Tula, Mexico. For SO2, the dispersion of these emissions was assessed with the CALPUFF dispersion model. Emissions reductions of > 99% for SO2, PM and Pb, as well as reductions >50% for organic and inorganic toxics were observed when simulating the use of natural gas. Maximum annual (993 µg/m3) and monthly average SO2 concentrations were simulated during the cold-dry period (152-1063 µg/m3), and warm-dry period (239-432 µg/m3). Dispersion model results and those from Mexico City's air quality forecasting system showed that SO2 emissions from the power plant affect the north of Mexico City in the cold-dry period. The evaluation of model estimates with 24 hr SO2 measured concentrations at Tepeji del Rio suggests that the combination of observations and dispersion models are useful in assessing the reduction of SO2 emissions due to shifting in fuels. Being SO2 a major precursor of acid rain, high transported sulfate concentrations are of concern and low pH values have been reported in the south of Mexico City, indicating that secondary SO2 products emitted in the power plant can be transported to Mexico City under specific atmospheric conditions. Implications: Although the surroundings of a power plant located north of Mexico City receives most of the direct SO2 impact from fuel oil emissions, the plume is dispersed and advected to the Mexico City metropolitan area, where its secondary products may cause acid rain. The use of cleaner fuels may assure significant SO2 reductions in the plant emissions and consequent acid rain presence in nearby populated cities and should be compulsory in critical areas to comply with annual emission limits and health standards.

[Identificación de fármacos reguladores de la actividad del promotor Egr-1 en fibroblastos humanos transducidos con AdΔegr-1-Luc7]. / Identification of drugs as regulators on the activity of Egr-1 promoter in human fibroblasts transduced with AdΔegr-1-Luc7.

INTRODUCCIÓN: La proteína de respuesta temprana a crecimiento 1 (EGR-1) es un factor de transcripción involucrado en la diferenciación y la proliferación celulares, cuya expresión es regulada por su promotor en respuesta a diversos factores físicos y químicos, y a fármacos. Aquí se describen algunos de los principales efectos de los fármacos esteroides y del factor de crecimiento epitelial 1 (EGF-1) sobre la actividad del promotor, mediante un sistema reportero transducido por el adenovirus AdΔegr-1-Luc7 en fibroblastos primarios humanos. MÉTODO: Los fibroblastos primarios humanos fueron cultivados en pase 5, transducidos con AdΔegr-1-Luc7 y expuestos a betametasona, hidrocortisona, dexametasona, testosterona, beta-estradiol y EGF-1 durante 1, 3 y 6 horas. La actividad de reportero fue cuantificada por luminometría y ajustada a la concentración de proteínas totales. RESULTADOS: La actividad del promotor en presencia de betametasona, hidrocortisona, dexametasona, testosterona y beta-estradiol fue similar a la actividad basal del promotor a las 1, 3 y 6 horas. El control positivo mostró una actividad 17.8 veces mayor a las 6 horas (p ≤ 0.05). De manera similar, las células expuestas a EGF-1 mostraron una actividad 22.07 veces mayor que las células sin fármaco. CONCLUSIÓN: La actividad del promotor Egr-1 en fibroblastos humanos es regulada negativamente por los fármacos esteroides y positivamente por el EGF-1. INTRODUCTION: The early growth response protein (EGR-1) is a transcription factor involved in cell differentiation and proliferation, whose expression is regulated by its promoter in response to various physical, chemical and drug factors. Hereby, we describe some of the main effects of steroid drugs and EGF-1 on promoter activity, through a reporter system transduced by AdΔegr-1-Luc7 in human primary fibroblasts (HPF). METHODS: Human primary fibroblasts transduced with AdΔegr-1-Luc7 were exposed to betamethasone, hydrocortisone, dexamethasone, testosterone, beta-estradiol, and EGF-1 during 1, 3 and 6 h. Reporter assay was quantified by luminometry. RESULTS: The activity of the promoter in presence of betamethasone, hydrocortisone, dexamethasone, testosterone and beta-estradiol were similar to the basal activity of the promoter at 1, 3 and 6 h. The positive control showed an activity 17.8 folds higher (p ≤ 0.05) at 6 h. EGF-1 showed activity of 22.07 folds greater than cells without drug. CONCLUSION: The activity of the EGR-1 promoter in human fibroblasts is negatively regulated by steroid drugs and positively by the EGF-1.

Clinical efficacy and safety of a new 1000-mg suspension versus twice-daily 500-mg tablets of MPFF in patients with symptomatic chronic venous disorders: a randomized controlled trial.

BACKGROUND: Chronic venous disorders (CVD) is estimated to affect 30% to 50% of women and 10% to 30% of men. The most widely prescribed treatment for CVD worldwide is micronized purified flavonoid fraction 500 mg (MPFF). The aim of this clinical trial was to develop a new once daily 1000-mg oral suspension of MPFF. METHODS: In an international, randomized, double-blind, parallel-group study, symptomatic individuals classified CEAP C0s to C4s were randomized in either treatment arm and treated for 8 weeks. Lower limb symptoms (discomfort, pain and heaviness) were assessed using Visual Analog Scales (VAS), and quality of life (QoL) was measured with the CIVIQ-20 Questionnaire. RESULTS: A total of 1139 patients were included in the study. Both MPFF treatment regimens were well tolerated and associated with a significant reduction in lower limb symptoms. A non-inferiority of MPFF 1000-mg oral suspension once daily compared to MPFF 500-mg tablet twice daily (P<0.0001) was found for lower limb discomfort (-3.33 cm for MPFF 1000 mg and -3.37 cm for MPFF 500 mg), leg pain (-3.27 cm for MPFF 1000 mg and -3.31 cm for MPFF 500 mg) and leg heaviness (-3.41 cm for MPFF 1000 mg and -3.46 cm for MPFF 500 mg). The patients' QoL was improved by about 20 points on the CIVIQ scale in both groups (19.33 points for MPFF 1000 mg and 20.28 points for MPFF 500 mg). CONCLUSIONS: MPFF 1000-mg oral suspension and MPFF 500-mg tablets treatments were associated with similar reductions in lower limb symptoms and QoL improvement. The new once daily MPFF1000-mg oral suspension has a similar safety profile to two tablets of MPFF 500 mg, with the advantage of one daily intake, potentially associated with improved patient adherence and easier CVD management.

TNFα and IL-6 Responses to Particulate Matter in Vitro: Variation According to PM Size, Season, and Polycyclic Aromatic Hydrocarbon and Soil Content.

BACKGROUND: Observed seasonal differences in particulate matter (PM) associations with human health may be due to their composition and to toxicity-related seasonal interactions. OBJECTIVES: We assessed seasonality in PM composition and in vitro PM pro-inflammatory potential using multiple PM samples. METHODS: We collected 90 weekly PM10 and PM2.5 samples during the rainy-warm and dry-cold seasons in five urban areas with different pollution sources. The elements, polycyclic aromatic hydrocarbons (PAHs), and endotoxins identified in the samples were subjected to principal component analysis (PCA). We tested the potential of the PM to induce tumor necrosis factor alpha (TNFα) and interleukin 6 (IL-6) secretion in cultured human monocytes (THP-1), and we modeled pro-inflammatory responses using the component scores. RESULTS: PM composition varied by size and by season. PCA identified two main components that varied by season. Combustion-related constituents (e.g., vanadium, benzo[a]pyrene, benzo[a]anthracene) mainly comprised component 1 (C1). Soil-related constituents (e.g., endotoxins, silicon, aluminum) mainly comprised component 2 (C2). PM from the rainy-warm season was high in C2. PM (particularly PM2.5) from the dry-cold season was rich in C1. Elevated levels of cytokine production were associated with PM10 and C2 (rainy-warm season), whereas reduced levels of cytokine production were associated with PM2.5 and C1 (dry-cold season). TNFα secretion was increased following exposure to PM with high (vs. low) C2 content, but TNFα secretion in response to PM was decreased following exposure to samples containing ≥ 0.1% of C1-related PAHs, regardless of C2 content. The results of the IL-6 assays suggested more complex interactions between PM components and particle size. CONCLUSIONS: Variations in PM soil and PAH content underlie seasonal and PM size-related patterns in TNFα secretion. These results suggest that the mixture of components in PM explains some seasonal differences in associations between health outcomes and PM in epidemiologic studies. CITATION: Manzano-León N, Serrano-Lomelin J, Sánchez BN, Quintana-Belmares R, Vega E, Vázquez-López I, Rojas-Bracho L, López-Villegas MT, Vadillo-Ortega F, De Vizcaya-Ruiz A, Rosas Perez I, O'Neill MS, Osornio-Vargas AR. 2016. TNFα and IL-6 responses to particulate matter in vitro: variation according to PM size, season, and polycyclic aromatic hydrocarbon and soil content. Environ Health Perspect 124:406-412; http://dx.doi.org/10.1289/ehp.1409287.

Induction of c-Jun by air particulate matter (PM10) of Mexico city: Participation of polycyclic aromatic hydrocarbons.

The carcinogenic potential of urban particulate matter (PM) has been partly attributed to polycyclic aromatic hydrocarbons (PAHs) content, which activates the aryl hydrocarbon receptor (AhR). Here we report the effect of PM with an aerodynamic size of 10 µm (PM10) on the induction of AhR pathway in A549 cells, evaluating its downstream targets CYP1B1, IL-6, IL-8 and c-Jun. Significant increases in CYP1B1 protein and enzyme activity; IL-6 and IL-8 secretion and c-Jun protein were found in response to PM10. The formation of PAH-DNA adducts was also detected. The involvement of AhR pathway was confirmed with Resveratrol as AhR antagonist, which reversed CYP1B1 and c-Jun induction. Nevertheless, in IL-6 and IL-8 secretion, the Resveratrol was ineffective, suggesting an effect independent of this pathway. Considering the role of c-Jun in oncogenesis, its induction by PM may be contributing to its carcinogenic potential through induction of AhR pathway by PAHs present in PM10.

Variation in the composition and in vitro proinflammatory effect of urban particulate matter from different sites.

Spatial variation in particulate matter-related health and toxicological outcomes is partly due to its composition. We studied spatial variability in particle composition and induced cellular responses in Mexico City to complement an ongoing epidemiologic study. We measured elements, endotoxins, and polycyclic aromatic hydrocarbons in two particle size fractions collected in five sites. We compared the in vitro proinflammatory response of J774A.1 and THP-1 cells after exposure to particles, measuring subsequent TNFα and IL-6 secretion. Particle composition varied by site and size. Particle constituents were subjected to principal component analysis, identifying three components: C(1) (Si, Sr, Mg, Ca, Al, Fe, Mn, endotoxin), C(2) (polycyclic aromatic hydrocarbons), and C(3) (Zn, S, Sb, Ni, Cu, Pb). Induced TNFα levels were higher and more heterogeneous than IL-6 levels. Cytokines produced by both cell lines only correlated with C(1) , suggesting that constituents associated with soil induced the inflammatory response and explain observed spatial differences.

The oxidative potential and biological effects induced by PM10 obtained in Mexico City and at a receptor site during the MILAGRO Campaign.

As part of a field campaign that studied the impact of Mexico City pollution plume at the local, sub-regional and regional levels, we studied transport-related changes in PM(10) composition, oxidative potential and in vitro toxicological patterns (hemolysis, DNA degradation). We collected PM(10) in Mexico City (T(0)) and at a suburban-receptor site (T(1)), pooled according to two observed ventilation patterns (T(0) → T(1) influence and non-influence). T(0) samples contained more Cu, Zn, and carbon whereas; T(1) samples contained more of Al, Si, P, S, and K (p < 0.05). Only SO(4)(-2) increased in T(1) during the influence periods. Oxidative potential correlated with Cu/Zn content (r = 0.74; p < 0.05) but not with biological effects. T(1) PM(10) induced greater hemolysis and T(0) PM(10) induced greater DNA degradation. Influence/non-influence did not affect oxidative potential nor biological effects. Results indicate that ventilation patterns had little effect on intrinsic PM(10) composition and toxicological potential, which suggests a significant involvement of local sources.

Estrés postraumático en la población pediátrica atendida en el Hospital Infantil del estado de Chihuahua, México / Posttraumatic stress disorder in a pediatric population treated at the Children's Hospital of the State of Chihuahua, Mexico

Introducción. Ante el incremento de acciones violentas de diversa índole en nuestra comunidad surge la preocupación respecto a las consecuencias psicológicas en los niños que viven algún evento traumático. Por lo anterior, el objetivo del presente estudio fue identificar los factores relacionados con el desarrollo de trastorno de estrés postraumático en la población pediátrica atendida en el área de Psicología Infantil del Hospital Infantil del estado de Chihuahua. Métodos. Se realizó un estudio transversal retrospectivo en el que se analizaron los expedientes de de pacientes atendidos en el área de psicología infantil del Hospital Infantil del estado de Chihuahua durante un periodo de 3 meses. Se realizó el estudio de frecuencias y el análisis bivariado. Resultados. Se analizaron 125 expedientes que representaron 51% del total de la consulta del Departamento de Salud Mental. De estos, 41.6% correspondieron al género masculino y 58.4% al femenino. En 52 pacientes el evento desencadenante fue la violencia, mientras que en 73 pacientes éste se debió a accidentes. La edad de los pacientes se encontró dentro del rango de los 5 y los 15 años y la mayor prevalencia entre los 5 y 7 años y medio. No se encontró asociación estadísticamente significativa entre la escolaridad de los padres, la religión de la familia ni el tipo de familia (integrada o desintegrada) con el desarrollo de trastorno de estrés postraumático. Conclusiones. El trastorno de estrés postraumático en la población pediátrica ha aumentado de forma considerable en los últimos años. La identificación adecuada de los pacientes que presentan datos sugestivos del diagnóstico es de suma importancia para poder imple-mentar terapias que permitan evitar las consecuencias psicológicas.

Background. Due to the increase in various types of violent actions in our community, there is a preoccupation regarding the psychological consequences for children who survive a traumatic event. The aim of this study was to identify factors related to the development of posttraumatic stress disorder (PTSD) in pediatric patients treated in the Department of Child Psychology at Children's Hospital of the State of Chihuahua (HIECH). Methods. We conducted a retrospective cross-sectional study examining the clinical files during a 3-month period of patients treated in the Department of Child Psychology of HIECH. The study was conducted with frequencies and bivariate analysis. Results. We analyzed a total of 125 clinical files of which 41.6% corresponded to males and 58.4% to females. In 52 patients the triggering event was a violent action, whereas in 73 patients the event was due to accidents. The age of the patients was between 5 and 15 years and the highest prevalence was found in patients between 5 and 7 years of age. No statistically significant association was found in regard to parental education, religion, or family type (integrated or disintegrated) with the development of PTSD. Conclusions. Posttraumatic stress disorder in the pediatric population has increased considerably in recent years. Proper identification of patients with data suggestive of the diagnosis is important in order to implement therapies that avoid the psychological consequences.

Malaria in paradise: characterization of imported cases in Gran Canaria Island (1993-2006).

BACKGROUND: Spain obtained the official certificate of malaria eradication in 1964. However, imported malaria cases have been increasing during the last few decades in this country. This study aims to describe the clinical and epidemiological features of patients diagnosed with malaria on Gran Canaria Island. METHODS: A retrospective study was conducted based on case review of all patients diagnosed with malaria microbiologically confirmed from 1993 to 2006, at the three referral teaching hospitals on Gran Canaria Island. RESULTS: One hundred eighty-four episodes in 181 patients were diagnosed, 170 of them were analyzed. Most of them (82%) were travelers. Nearly 15% (14.7%) declared having had some chemoprophylaxis, but only half of them completed the treatment. Twenty cases (10.9%) were diagnosed who had just arrived as immigrants, mainly children. Malaria was acquired in Africa by 94.7% of the cases and Plasmodium falciparum was responsible for the majority of the cases (84.1%). Clinical and epidemiological differences were observed among different groups of patients formed by their origin and travel purposes. At least one indicator of severe malaria was established in 22.9% of the cases. However, global mortality was 3.8%. CONCLUSIONS: Malaria in Gran Canaria Island is imported from endemic areas, mainly from African countries, observed mostly among young adult males, but clinical and epidemiological features may change among different groups of patients. The number of immigrants diagnosed with malaria is increasing in this area nowadays.

Consumo y dependencia al tabaco como factor asociado a la tuberculosis pulmonar / Consumption and dependence to the tobacco like factor associated with the pulmonary tuberculosis

Objetivo: determinar la asociación entre el consumo y dependencia al tabaco como factor asociado a la tuberculosis pulmonar. Material y método: estudio analítico, retrospectivo de casos y controles, con pacientes registrados en la Estrategia Sanitaria Nacional de Prevención y Control de la Tuberculosis (ESN-PCT) de dos centros de salud DISA V Lima- Ciudad. La muestra estuvo conformada por 35 pacientes con tuberculosis pulmonar (casos) y 70 sintomáticos respiratorios (controles), fueron incluidos pacientes de ambos sexos que se encontraban dentro de los 6 meses del esquema I y sintomáticos respiratorios que tuvieron baciloscopía negativa. Para la recolección de datos se usó una ficha sociodemográfica, se aplicó la prueba de Fagerstrõm y se solicitó la participación mediante el consentimiento informado. Resultados: se halló que 94,3% (casos) y 90,0% (controles), respondió que alguna vez en su vida habían fumado, de ellos el 65,7% (casos) y el 64,3% (controles) fumó durante los últimos 30 días. A su vez que el mayor porcentaje en casos asociado con la dependencia a la nicotina moderado-severa fue 51,4%. Conclusiones: las personas que consumen cigarro tienen mayor posibilidad de contraer la enfermedad y que la dependencia a este se considera factor asociado a la tuberculosis pulmonar porque el odds ratio es significativo. Con mayor predominancia en el sexo masculino entre los 18 a 40 años.

Objective: Was to determine the association between snuff use and dependence as a factor associated with pulmonary tuberculosis. Material and methods: Analytical, Case-control retrospective, with patients enrolled in the Health Strategy for Prevention and Control of Tuberculosis (ESN-PCT) from two health centers DISA V Lima-City. The sample consisted of 35 patients with pulmonary tuberculosis (cases) and 70 with respiratory symptoms (controls) were included patients of both sexes who were within six months of Schedule I and respiratory symptoms who were smear negative. For data collection will use a demographic sheet, we apply the Fagerstrõm test and asked to participate through informed consent. In terms of results it was found that smoking was answered affirmatively. Results: By 94.3% (cases) and 90.0% (control), once in his life smoked, of whom 65.7% (cases) and 64.3 % (controls) smoked during the past 30 days. At the same time that the greatest percentage of cases associated with nicotine dependence was moderate-severe 51.4%. Conclusion: That people who consume cigarettes are more likely to contract the disease and that this dependence is considered factor associated with pulmonary tuberculosis because the odds ratio is significant. With higher predominance of males between 18-40 years.

Screening for tuberculosis infection in spanish healthcare workers: Comparison of the QuantiFERON-TB gold in-tube test with the tuberculin skin test.

OBJECTIVE: The risk of latent tuberculosis (LTBI) in healthcare workers (HCWs) is high. Until recently, the tuberculin skin test (TST) was the only diagnostic test available for Mycobacterium tuberculosis infection. A new enzyme-linked immunosorbent assay test, the QuantiFERON-TB Gold (QFT-G) test, was recommended by the US Centers for Disease Control and Prevention as an alternative test for the diagnosis of LTBI in HCWs. The purpose of our study was to compare the TST and the QFT-G test in Spanish HCWs in order to improve procedures for the detection of LTBI. METHODS: A cross-sectional study with blinded comparison of TST and QFT-G test results was carried out among 134 HCWs at an 800-bed Spanish university hospital. The level of interferon-gamma production stimulated by the QFT-G test was measured. A concentration of at least 0.35 IU/mL was considered a positive result. An induration of at least 5 mm in non-BCG-vaccinated or at least 15 mm in BCG-vaccinated HCWs for the TST was considered positive. RESULTS: Of the 134 HCWs included (mean age, 33.4 years; 101 [75.4%] women; 47 [35.1%] BCG vaccinated), the LTBI prevalence diagnosed with any test was 11.2% (95% confidence interval, 6.6%-18.1%), with the TST was 8.96%, and with the QFT-G test was 5.97% (nonsignificant differences). The QFT-G test value was higher in subjects with TST induration of at least 15 mm than in subjects with TST induration of less than 15 mm (P < .001). Overall agreement between the results of the two tests was found in 94% of HCWs (kappa = 0.56), but agreement was only 59% in HCWs who had a positive result for both tests. Disagreement was present in the results found for 5% of HCWs. CONCLUSIONS: Few studies have compared both tests in populations with high M. tuberculosis exposure but low BCG vaccination prevalence. Agreement between both tests is high, especially among negative results. Studies are needed to clarify the reasons for disagreement and to establish the best TST and QFT-G test cutoff point.

Fine particle receptor modeling in the atmosphere of Mexico City.

Source apportionment analyses were carried out by means of receptor modeling techniques to determine the contribution of major fine particulate matter (PM2.5) sources found at six sites in Mexico City. Thirty-six source profiles were determined within Mexico City to establish the fingerprints of particulate matter sources. Additionally, the profiles under the same source category were averaged using cluster analysis and the fingerprints of 10 sources were included. Before application of the chemical mass balance (CMB), several tests were carried out to determine the best combination of source profiles and species used for the fitting. CMB results showed significant spatial variations in source contributions among the six sites that are influenced by local soil types and land use. On average, 24-hr PM2.5 concentrations were dominated by mobile source emissions (45%), followed by secondary inorganic aerosols (16%) and geological material (17%). Industrial emissions representing oil combustion and incineration contributed less than 5%, and their contribution was higher at the industrial areas of Tlalnepantla (11%) and Xalostoc (8%). Other sources such as cooking, biomass burning, and oil fuel combustion were identified at lower levels. A second receptor model (principal component analysis, [PCA]) was subsequently applied to three of the monitoring sites for comparison purposes. Although differences were obtained between source contributions, results evidence the advantages of the combined use of different receptor modeling techniques for source apportionment, given the complementary nature of their results. Further research is needed in this direction to reach a better agreement between the estimated source contributions to the particulate matter mass.

Fine and coarse particulate matter chemical characterization in a heavily industrialized city in central Mexico during Winter 2003.

This paper presents the results of the first reported study on fine particulate matter (PM) chemical composition at Salamanca, a highly industrialized urban area of Central Mexico. Samples were collected at six sites within the urban area during February and March 2003. Several trace elements, organic carbon (OC), elemental carbon (EC), and six ions were analyzed to characterize aerosols. Average concentrations of PM with aerodynamic diameter of less than 10 microm (PM10) and fine PM with aerodynamic diameter of less than 2.5 microm (PM2.5) ranged from 32.2 to 76.6 [g m(-3) and 11.1 to 23.7 microg m(-3), respectively. OC (34%), SO4= (25.1%), EC (12.9%), and geological material (12.5%) were the major components of PM2.5. For PM10 geological material (57.9%), OC (17.3%), and SO4= (9.7%) were the major components. Coarse fraction (PM,, -PM2.5), geological material (81.7%), and OC (8.6%) were the dominant species, which amounted to 90.4%. Correlation analysis showed that sulfate in PM2.5 was present as ammonium sulfate. Sulfate showed a significant spatial variation with higher concentrations to the north resulting from predominantly southwesterly winds above the surface layer and by major SO2 sources that include a power plant and refinery. At the urban site of Cruz Roja it was observed that PM2.5 mass concentrations were similar to the submicron fraction concentrations. Furthermore, the correlation between EC in PM2.5 and EC measured from an aethalometer was r(2) = 0.710. Temporal variations of SO2 and nitrogen oxide were observed during a day when the maximum concentration of PM2.5 was measured, which was associated with emissions from the nearby refinery and power plant. From cascade impactor measurements, the three measured modes of airborne particles corresponded with diameters of 0.32, 1.8, and 5.6 microm.

Analysis of PM2.5 and PM10 in the atmosphere of Mexico City during 2000-2002.

During the last 10 years, high atmospheric concentrations of airborne particles recorded in the Mexico City metropolitan area have caused concern because of their potential harmful effects on human health. Four monitoring campaigns have been carried out in the Mexico City metropolitan area during 2000-2002 at three sites: (1) Xalostoc, located in an industrial region; (2) La Merced, located in a commercial area; and (3) Pedregal, located in a residential area. Results of gravimetric and chemical analyses of 330 samples of particulate matter (PM) with an aerodynamic diameter less than 2.5 microm (PM2.5) and PM with an aerodynamic diameter less than 10 microm (PM10) indicate that (1) PM2.5/PM10 average ratios were 0.42, 0.46, and 0.52 for Xalostoc, La Merced, and Pedregal, respectively; (2) the highest PM2.5 and PM10 concentrations were found at the industrial site; (3) PM2.5 and PM10 concentrations were lower at nighttime; (4) PM2.5 and PM10 spatial averages concentrations were 35 and 76 microg/m3, respectively; and (5) when the PM2.5 standard was exceeded, nitrate, sulfate, ammonium, organic carbon, and elemental carbon concentrations were high. Twenty-four hour averaged PM2.5 concentrations in Mexico City and Sao Paulo were similar to those recorded in the 1980s in Los Angeles. PM10 concentrations were comparable in Sao Paulo and Mexico City but 3-fold lower than those found in Santiago.

Spatial differences in outdoor PM10 mass and aerosol composition in Mexico City.

Twenty-five MiniVol samplers were operated throughout the Mexico City metropolitan region from February 22 through March 22, 1997, to evaluate the variability of PM10 concentrations and composition. The highest PM10 concentrations were found in neighborhoods with unpaved or dirty roads, and elements related to crustal material were the main cause of differences from nearby (<200 m) monitors that were not adjacent to the roadbed. SO4(2-) concentrations were homogeneous across the city. SO4(2-) measured at the city boundaries was about two-thirds of the concentrations measured within the urbanized area, indicating that most SO4(2-) is of regional origin. Elemental carbon (EC) and organic carbon (OC) concentrations were highly variable, with higher concentrations in areas that had high diesel traffic and older vehicles. Spatial correlations among PM10 concentrations were high, even though absolute concentrations were variable, indicating a common effect of meteorology on the concentration or dispersion of local emissions.

Chemical composition of PM2.5 and PM10 in Mexico City during winter 1997.

PM2.5 and PM10 were measured over 24-h intervals at six core sites and at 25 satellite sites in and around Mexico City from 23 February to 22 March 1997. In addition, four 6-h samples were taken each day at three of the core sites. Sampling locations were selected to represent regional, central city, commercial, residential, and industrial portions of the city. Mass and light transmission concentrations were determined on all of the samples, while elements, ions and carbon were measured on approximately two-thirds of the samples. PM10 concentrations were highly variable, with almost three-fold differences between the highest and lowest concentrations. Fugitive dust was the major cause of PM10 differences, although carbon concentrations were also highly variable among the sampling sites. Approximately 50% of PM10 was in the PM2.5 fraction. The majority of PM mass was comprised of carbon, sulfate, nitrate, ammonium and crustal components, but in different proportions on different days and at different sites. The largest fine-particle components were carbonaceous aerosols, constituting approximately 50% of PM2.5 mass, followed by approximately 30% secondary inorganic aerosols and approximately 15% geological material. Geological material is the largest component of PM10, constituting approximately 50% of PM10 mass, followed by approximately 32% carbonaceous aerosols and approximately 17% secondary inorganic aerosols. Sulfate concentrations were twice as high as nitrate concentrations. Sulfate and nitrate were present as ammonium sulfate and ammonium nitrate. Approximately two-thirds of the ammonium sulfate measured in urban areas appears to have been transported from regions outside of the study domain, rather than formed from emissions in the urban area. Diurnal variations are apparent, with two-fold increases in concentration from night-time to daytime. Morning samples had the highest PM2.5 and PM10 mass, secondary inorganic aerosols and carbon concentrations, probably due to a shallow surface inversion and rush-hour traffic.