Víctor Hugo Borja-Aburto

Air pollution and infant mortality in Mexico City.

Historic air pollution episodes of the 1950s led to acute increases in infant mortality, and some recent epidemiologic studies suggest that infant or child mortality may still result from air pollution at current levels. To investigate the evidence for such an association, we conducted a time-series study of infant mortality in the southwestern part of Mexico City in the years 1993 to 1995 using mortality data from death registrations and air pollution measurements from a monitoring station we operated. Excess infant mortality was associated with the level of fine particles in the days before death, with the strongest association observed for the average concentration of fine particles during the period 3 to 5 days previously: a 10-microg m(-3) increase in the mean level of fine particles during these 3 days was associated with a 6.9% excess of infant deaths (95% confidence interval 2.5-11.3%). Infant mortality was also associated with the levels of nitrogen dioxide and ozone 3 to 5 days before death, but not as consistently as with particles.

Urinary Trivalent Methylated Arsenic Species in a Population Chronically Exposed to Inorganic Arsenic

Chronic exposure to inorganic arsenic (iAs) has been associated with increased risk of various forms of cancer and of noncancerous diseases. Metabolic conversions of iAs that yield highly toxic and genotoxic methylarsonite (MAsIII) and dimethylarsinite (DMAsIII) may play a significant role in determining the extent and character of toxic and cancer-promoting effects of iAs exposure. In this study we examined the relationship between urinary profiles of MAsIII and DMAsIII and skin lesion markers of iAs toxicity in individuals exposed to iAs in drinking water. The study subjects were recruited among the residents of an endemic region of central Mexico. Drinking-water reservoirs in this region are heavily contaminated with iAs. Previous studies carried out in the local populations have found an increased incidence of pathologies, primarily skin lesions, that are characteristic of arseniasis. The goal of this study was to investigate the urinary profiles for the trivalent and pentavalent As metabolites in both high- and low-iAs–exposed subjects. Notably, methylated trivalent arsenicals were detected in 98% of analyzed urine samples. On average, the major metabolite, DMAsIII, represented 49% of total urinary As, followed by DMAsV (23.7%), iAsV (8.6%), iAsIII (8.5%), MAsIII (7.4%), and MAsV (2.8%). More important, the average MAsIII concentration was significantly higher in the urine of exposed individuals with skin lesions compared with those who drank iAs-contaminated water but had no skin lesions. These data suggest that urinary levels of MAsIII, the most toxic species among identified metabolites of iAs, may serve as an indicator to identify individuals with increased susceptibility to toxic and cancer-promoting effects of arseniasis.

Airborne Coarse Particles and Mortality

Some recent epidemiologic studies suggest a stronger effect of fine particles (PM2.5) than of coarser particulate matter. To examine the support for such a differential effect, the authors conducted a daily time-series analysis of mortality in relation to measurements of PM2.5, PM10, and PM10-2.5 in southwestern Mexico City in the years 1992–1995. A generalized linear model based on Poisson regression was used to control for weather and periodic cycles, and the average concentration of the previous five days was the index of particle exposure. The mean concentrations of PM 2.5 and PM10 were 27.4 μg m−3 and 44.6 μg m-3, respectively, and the mean concentration of PM10-2.5 was 17.2 μg m-PM10 was highly correlated with both the fine and coarse fractions, but PM 2.5 and PM 10–2.5 were rather weakly correlated with each other (correlation coefficient 0.52). All three particle size fractions were associated individually with mortality: a 10-μg m3 increase in PM10 Supported by cooperative agreements CR-820076 and CR-821762 between the U.S. Environmental Protection Agency and the University of North Carolina and Harvard University Schools of Public Health and a grant from the Mexico-U.S. Commission for Educational and Cultural Exchange. We thank Bill McDonnell, Armando Retama, Daniel Varela, and Silvia Bierswinski for contributions to the research and comments on the manuscript. Address correspondence to Dr. Dana Loomis, Department of Epidemiology, CB-7400, School of Public Health, University of North Carolina, Chapel Hill, NC 27599–7400, USA. E-mail: dana.loomis@unc.edu was associated with a 1.83% increase in total mortality (95% CI −0.01-2.96), and an equal increment in PM2.5 was associated with a 1.48% increase in deaths (95% CI 0.98-2.68%). The largest effect was observed for a 10 μg m−3 increment in PM 10-2.5; mean daily mortality increased 4.07% for each 10 μg m−3 (95% CI 2.49-5.66%). The effect of coarse particles was stronger for respiratory diseases than for total mortality, cardiovascular diseases, or other noninjury causes of death. These patterns persisted after adjustment (or O3 and NO2. When both PM2.5 and PM 10-2.5 were included simultaneously in the regression model, the effect of PMW-2.5 remained about 4% per 10 μg m−3 (95% CI 1.96-6.02%), while the effect of PM2.5 was virtually eliminated (0.18% change). These associations may be attributable to specific combustion or biogenic materials within the coarse particle mass. Understanding these relationships will require analyses of the composition of coarse particles. The findings also suggest a need to that the relative effects of coarse and fine particles on mortality should be examined in more cities with a wider variety of climates, population characteristics, and air pollutants.

Pesticide exposure alters follicle-stimulating hormone levels in Mexican agricultural workers

Organophosphorous pesticides (OPs) are suspected of altering reproductive function by reducing brain acetylcholinesterase activity and monoamine levels, thus impairing hypothalamic and/or pituitary endocrine functions and gonadal processes. Our objective was to evaluate in a longitudinal study the association between OP exposure and serum levels of pituitary and sex hormones. Urinary OP metabolite levels were measured by gas–liquid chromatography, and serum pituitary and sex hormone levels by enzymatic immunoassay and radioimmunoassay in 64 men. A total of 147 urine and blood samples were analyzed for each parameter. More than 80% of the participants had at least one OP metabolite in their urine samples. The most frequent metabolite found was diethylthiophosphate (DETP; 55%), followed by diethylphosphate (DEP; 46%), dimethylthiophosphate (DMTP; 32%), and dimethyldithiophosphate (DMDTP; 31%). However, the metabolites detected at higher concentrations were DMTP, DEP, DMDTP, and dimethylphosphate. There was a high proportion of individuals with follicle-stimulating hormone (FSH) concentrations outside the range of normality (48%). The average FSH serum levels were higher during the heavy pesticide spraying season. However, a multivariate analysis of data collected in all periods showed that serum FSH levels were negatively associated with urinary concentrations of both DMTP and DMDTP, whereas luteinizing hormone (LH) was negatively associated with DMTP. We observed no significant associations between estradiol or testosterone serum levels with OP metabolites. The hormonal disruption in agricultural workers presented here, together with results from experimental animal studies, suggests that OP exposure disrupts the hypothalamic–pituitary endocrine function and also indicates that FSH and LH are the hormones most affected.

Particulate air pollution and daily mortality: Can results be generalized to Latin American countries?

OBJECTIVEnRecently, a series of reports, based on ecological analyses of routinely collected data, have shown positive associations between measures of particle concentration and daily mortality counts in various cities of the US and Europe.nnnMATERIAL AND METHODSnWe reviewed the process of generalization of these results to Latin American countries addressing possible differences in air pollution mixtures, exposure profiles, and population susceptibility.nnnRESULTSnA limitation to the process of generalization is the lack of a well-established biological mechanism by which particles may act on daily mortality. Also, sources and levels of ambient air pollution as well as population characteristics and habits vary widely between Northern communities of Europe and the US, and Latin American countries, which impairs the process of generalization. However, results of studies conducted in Latin American countries suggest a similar effect to that observed in Northern countries of Europe and the US.nnnCONCLUSIONSnDespite uncertainty about the mechanism, there is sufficient evidence that particles are harmful for health. Control measures of particle emission are urgently needed in Latin American countries. Given the potential of misclassification of exposure, the dose-response relationship observed in Northern Europe and the US may not be adequate for Latin American populations. There is a need for a new generation of epidemiological studies including a specific assessment of exposure to fine particles and of events surrounding death.

Surveillance of acute health effects of air pollution in Mexico City.

Background: A unique, active, timely, low-cost surveillance system for the metropolitan area of Mexico City was established in the mid-1990s. Methods: The system obtained upper and lower respiratory tract symptoms and eye symptoms from daily interviews for a systematic sample of the general nonhospitalized population living within a 2-km radius of air pollution monitors during 1996-1997. Results: Ozone increments (10 ppb) were associated with upper respiratory symptoms (odds ratio [OR] = 1.003; 95% confidence interval [CI] = 1.002-1.004) and ocular symptoms indicators (OR = 1.005; CI = 1.004-1.007), and with a higher risk of lower respiratory symptoms indicator among nonsmokers (OR = 1.003; CI = 1.002-1.005). Increases in relative humidity reduced the risk of increments of sulfur dioxide on the 3 acute health indicators. Association of PM10 with health indicators varied among the 5 regions. During emergency episodes, symptoms increased sharply when ozone reached 281 ppb, a finding that resulted in a change in the ozone criteria for emergency declaration from 294 to 281 ppb. Conclusions: This system has been low cost, timely, and useful for local decision making.

Dificultades en los métodos de estudio de exposiciones ambientales y defectos del tubo neural

Objetivo. Discutir las actitudes en la evaluacion de las exposiciones ambientales como factores de riesgo para defectos de riesgo del tubo neural, al tiempo que se presentan los principales factores estudiados hasta la fecha. Resultados. Las exposiciones ambientales se citan muy a menudo como causa de malformaciones congenitas; sin embargo, ha sido dificil establecer esta asociacion en los estudios de poblaciones humanas, debido a problemas en su diseno y conduccion. Lo anterior es particularmente marcado en el caso del estudio de los defectos del cierre del tubo neural (DTN), que es una de las principales malformaciones y que incluye anencefalia, espina bifida y encefalocele, y su asociacion con exposiciones ambientales. Las dificultades en los metodos surgen de: a) la medida de frecuencia para realizar comparaciones espacio-temporales; b) la clasificacion y heterogeneidad de las malformaciones; c) la consideracion de los factores relacionados con la madre, el padre y el producto, de manera conjunta, y d) la evaluacion de las exposiciones ambientales. Conclusiones. Hipoteticamente las exposiciones ambientales tanto del padre como de la madre pueden producir dano genetico antes y/o despues de la concepcion por la accion directa sobre el embrion o sobre el complejo fetoplacentario, de tal manera que en la evaluacion de exposiciones ambientales: a) deben tomarse en cuenta las exposiciones maternas y paternas; b) debe considerarse el periodo critico de exposicion, esto es, tres meses anteriores a la concepcion para el padre y un mes alrededor de la concepcion para la madre; c) en la medida de lo posible, la evaluacion de la exposicion debera ser cuantitativa, evitando clasificar a los grupos unicamente como expuestos y no expuestos, y d) es recomendable emplear marcadores biologicos de exposicion siempre que sea posible, asi como utilizar marcadores biologicos que permitan clasificar a la poblacion en grupos con distinta susceptibilidad genetica.

Efectos de la aplicación del indicador de años de vida productivos perdidos (modelo inversión producción consumo) en el ordenamiento de las causas de muerte en México, 1990

In the search for methods to support the decision making process and to maximize the benefit resulting from the health priorities, this paper discusses the investment-production-consumption model (IPC). This method attempts to quantify the socio-economic impact of mortality. This type of evaluation takes into account age at death and the potential for future productivity and thus assesses the generation of losses or gains to society, depending on the stage of life in which death occurs. The impact of different causes of death estimated by this method is illustrated from the cause of Mexico. These results are compared with the relative importance attributed by the use of mortality rates and years of potential life lost. The ordering by rates shows heart diseases, accidents and tumors as first causes of deaths. On the other hand, the indicator of years of potential life lost shows causes of death at younger ages to occupy the first place. The YPLLipc, however, gives greater importance to infections, accidents and homicides.En busca de metodos que apoyen la toma de decisiones y maximizar el beneficio al priorizar necesidades, el presente trabajo discute el modelo de inversion-produccion-consumo (IPC) que intenta cuantificar el impacto socio-economico de la mortalidad. Este tipo de evaluacion toma en cuenta la edad al morir y la potencial productividad futura generando asi perdidas o ganancias a la sociedad, dependiendo de la etapa de la vida en que ocurrio la muerte. Se ilustra para el caso de Mexico el impacto de las diferentes causas de muerte y se compara con la importancia relativa a partir de el ordenamiento con tasas de mortalidad y el indicador de anos de vida perdidos. El ordenamiento por tasas muestra a las enfermedades del corazon, accidentes y tumores como las primeras causas. Por otro lado el indicador de anos de vida potencial perdidos tradicional muestra en primer lugar a las causas de muerte en edades menores. El indicador de anos de vida produtivos perdidos, sin embargo, concede mayor importancia las infecciones, los accidentes y los homicidios desde el punto de vista de la produccion y consumo.In the search for methods to support the decision making process and to maximize the benefit resulting from the health priorities, this paper discusses the investment-production-consumption model (IPC). This method attempts to quantify the socio-economic imapct of mortality. This type of evaluation takes into account age at death and the potential for future productivity and thus assesses the generation of losses or gains to society, depending on the stage of life in wich death occurs. The impact of different causes of death estimated by this method is illustrated from the cause of Mexico. These results are compared with the relative importance attributed by the use of mortality rates and years of potential life lost. The ordering by rates shows heart diseases, accidents and tumors as first causes of deaths. On the other hand, the indicator of years of potential life lost shows causes of death at younger ages to occupy the first place. The YPLLipc, however, gives greater importance to infections, accidents and homicides.