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Estudios epidemiológicos han demostrado la relación entre los contaminantes atmosféricos y el incremento en la mortalidad por causas cardiovasculares, en especial en personas con enfermedad cardiopulmonar previa. Sin embargo, los mecanismos fisiopatológicos mediante los cuales estos padecimientos ocurren no son bien conocidos. Se ha sugerido que una de las vías mediante las cuales las partículas suspendidas respirables y otros contaminantes producen su efecto es alterar la regulación del corazón por el sistema nervioso autónomo. El análisis de los cambios en la variabilidad de la frecuencia cardiaca (VFC) es un indicador de efecto sobre este mecanismo. En este trabajo se realiza una revisión de las bases fisiológicas de este método, de sus ventajas y limitaciones y de los resultados que se obtienen al relacionarlo con la exposición a contaminantes atmosféricos. A partir del análisis de la literatura disponible, se sugieren alternativas relacionadas con el diseño de los estudios, la selección de poblaciones en riesgo, los métodos para evaluar la exposición y los métodos de análisis estadístico que pueden servir para utilizar mejor el análisis del registro electrocardiográfico ambulatorio en relación con los riesgos cardiacos por exposición a contaminantes atmosféricos.

La exposición al plomo es una amenaza seria para la salud de los niños, que se encuentra ampliamente distribuida en la Región de América Latina. Los funcionarios de salud pública necesitan identificar fuentes de exposición al plomo, así como sus efectos en la salud, para poder diseñar, implantar y evaluar las actividades preventivas y de control. Para evaluar la magnitud del problema del plomo es necesario definir tres elementos clave: a) las fuentes potenciales de exposición, b) los indicadores que se utilizarán para evaluar los efectos en la salud y la exposición en el medio ambiente, y c) las estrategias de muestreo de la población en riesgo. Se pueden utilizar varias estrategias con el fin de seleccionar la población blanco dependiendo de los objetivos del estudio, el tiempo límite y los recursos disponibles. Si el objetivo es evaluar la magnitud y las fuentes del problema pueden emplearse los siguientes métodos de muestreo: a) el muestreo al azar basado en la población; b) el muestreo al azar basado en las facilidades dentro de los hospitales, las guarderías o las escuelas; c) el muestreo objetivo de los grupos de alto riesgo; d) el muestreo de conveniencia (de voluntarios), y e) el reporte de los casos (éste puede conducir a la identificación de las poblaciones en riesgo, además de las fuentes de exposición). Para todos los diseños de muestreo, la información debe incluir tanto el uso de un cuestionario para el informe general de los participantes y de las fuentes potenciales locales de exposición, como la recolección de las muestras biológicas. En la interpretación de los datos se debe considerar el tipo de muestreo utilizado, el porcentaje de falta de respuesta y los factores que pueden influir en las mediciones del plomo en sangre, como la edad y la variación de la temporada. Las mediciones del plomo en la sangre se deben integrar dentro de una estrategia general para la prevención de toxicidad.

OBJECTIVE: Lead poisoning can, in some cases, be traced to a specific route or source of exposure on the basis of the individual's blood lead isotope ratio. To assess the major source of lead exposure among women residing in Mexico City, we compared blood, ceramic, and gasoline lead isotope ratios. MATERIAL AND METHODS: The study population, randomly selected from participants of a large trial, (1/1996-12/1996) comprised of 16 women whose lead levels exceeded 10 µg/dl and who reported using lead-glazed ceramics. Lead isotope ratios were performed on a Perkin Elmer 5000 Inductively Coupled Plasma Mass Spectrometer (ICP-MS) interfaced with a Perkin Elmer HGA-600MS Electrothermal Vaporization System (ETV). RESULTS: The isotope ratios (206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb) of both the blood specimens and their corresponding ceramic specimens were highly correlated, with r=0.9979, r²=0.9958, r=0.9957, r²=0.9915 and r=0.9945, r²=0.9890 values for the three isotope ratios, respectively, suggesting that the lead exposure most likely resulted from the use of these ceramic. Measurements of lead isotope ratios from leaded gasoline in use at the time of blood sampling, differed from those in blood and ceramics. CONCLUSIONS: Determining lead isotope ratios can be an efficient tool to identify a major source of lead exposure and to support the implementation of public health prevention and control measures.

OBJETIVO: Evaluar la asociación entre los niveles séricos maternos de DDT/DDE y el riesgo de hipospadias. MATERIAL Y MÉTODOS: Estudio de casos y controles, efectuado en la Ciudad de México durante el periodo 1997-1999, con 41 casos de hipospadias y 28 controles. La informacion obtenida por cuestionario y las muestras sanguíneas fueron evaluadas mediante modelos multivariados de regresión logística. RESULTADOS: Las concentraciones materna de DDT y DDE no mostraron asociación con el riesgo de hipospadias (RM 1.13; IC 95% 0.24-5.29 y RM 0.48; IC 95% 0.15-1.60, respectivamente). Los predictores encontrados fueron hijos de madres con mayor edad (RM 8.69; IC 95% 1.69-44.9), y la actividad laboral durante el embarazo (RM, 4.68; IC 95% 1.15-18.9). CONCLUSIONES: Dado que se cuenta con escasa información sobre los efectos endocrinos a diferentes concentraciones de DDT/DDE en humanos, la dosis pudiera ser un factor determinante sobre el tipo de efecto.

Objetivo. Determinar la prevalencia y severidad del asma, de la rinitis y del eczema en escolares. Material y métodos. Estudio transversal efectuado entre abril de 1998 y mayo de 1999 en Ciudad Juárez, Chihuahua, México, a una muestra aleatoria de 6 174 niños de 53 escuelas. Se aplicó la metodología propuesta por el International Study of Asthma and Allergies in Childhood (ISAAC) (etapas 1 y 2) para determinar la prevalencia y severidad del asma, rinitis y eczema. La información de prevalencia, tanto actual como acumulada para dichos padecimientos, se obtuvo mediante un cuestionario ya estandarizado y contestado por los padres de los niños. El diseño de la muestra se hizo por un muestreo mixto, en el cual se estratificó por nivel de contaminación ambiental. Se estimaron prevalencias actual y acumulada estratificando por grupo de edad, sexo, área e historia familiar de asma. Resultados. La prevalencia acumulada de asma por diagnóstico médico y sibilancia (silbidos) fue de 6.8% (IC95% 6.2-7.4) y 20.% (IC95% 19.7-21.8), respectivamente; la prevalencia de sibilancia en los últimos 12 meses fue mayor en el grupo de 6-8 años que en el de 11-14 años(9.7%) contra 5.8% (phttp://www.insp.mx/salud/index.html

OBJETIVO: Analizar la relación entre las concentraciones ambientales de partículas de diámetro

En este trabajo se discute la problemática de la contaminación del aire en tres megaciudades de América Latina (Ciudad de México, São Paulo y Santiago); en particular se revisan los programas de control de la contaminación atmosférica que han puesto en marcha los gobiernos de esas ciudades y la evolución de los niveles de contaminantes durante el periodo 1988-1995 en Santiago de Chile y São Paulo, y hasta 1997 en la Ciudad de México, con el objeto de evaluar el impacto de esos programas. En las tres megaciudades se observó un descenso en las concentraciones de PTS, PM10, SO2, NO2, CO y O3 durante el periodo mencionado, aunque la mayoría de los contaminantes siguen rebasando la norma de calidad del aire. Cabe destacar que el mayor impacto de los programas ha sido sobre los niveles de SO2. Se recomienda el desarrollo de políticas de transporte sostenible; en ese sentido, en la Conferencia Europea de Ministros del Transporte la Organización para la Cooperación y el Desarrollo Económico (OCDE) propuso distintas estrategias. Por otra parte, la participación ciudadana es importante al tomar decisiones relacionadas con las políticas de transporte.

Objective. To assess the reproducibility and validity of a 116 item semi-quantitative food frequency questionnaire (FFQ), designed to assess the relation between dietary intake and chronic diseases. Material and methods. To test the reproducibility of the FFQ questionnaire, the FFQ was administered twice to 134 women residing in Mexico City at an interval of approximately one year; to assess the validity we compared results obtained by the FFQs with those obtained by four 4-day 24-hour recalls at three month intervals. Validity and reproducibility were evaluated using regression analysis and Pearson and intraclass correlation coefficients of log-e and calorie-adjusted nutrient scores. Results. Mean values for intake of most nutrients assessed by the two food frequency questionnaires were similar. However, means for the 24-hr recall were significantly lower. Intraclass correlation coefficients for nutrient intakes, assessed by questionnaires, administered one year apart, ranged from 0.38 for cholesterol to 0.54 for crude fiber. Correlation coefficients between energy-adjusted nutrient intakes, measured by diet recalls, and the first FFQ ranged from 0.12 for polyunsaturated fatty acids to 0.67 for saturated fatty acids. Regression coefficients between 24-hr recall and FFQ,s were all significant were significant for all nutrients, except for polyunsaturated fat, folic acid, vitamin E and Zinc. Conclusions. These data indicate that this semi-quantitative FFQ is reproducible and provides a useful estimate by which to categorize individuals by level of past nutrient intake. However, its application outside Mexico City or in different age and gender populations will require additional modifications and validation efforts.

Los efectos nocivos del plomo han sido conocidos desde tiempos antiguos por su amplia gama; este metal afecta prácticamente todos los órganos y sistemas del cuerpo humano. Recientemente se han documentado efectos tóxicos crónicos en los sistemas cardiovascular y nervioso, con niveles que antes se consideraban seguros. El sitio primario de almacenamiento de plomo en el organismo es el hueso, pero sólo hasta fechas recientes se ha clarificado la significancia toxicológica de este hecho. En este artículo se analiza el papel del plomo en hueso como fuente de exposición endógena, como biomarcador de exposición crónica y como tejido blanco. Se presentan además los avances recientes para la medición de plomo en hueso mediante los rayos X-fluorescentes (XRF). Finalmente se revisa la importancia, para la salud pública, de estudiar y medir el plomo en hueso en lugares con una historia de exposición crónica como la Ciudad de México y en los ambientes ocupacionales, especialmente como fuente remanente de exposición. Se analiza especialmente el caso de mujeres en edad reproductiva, quienes pueden convertirse en fuentes de exposición para el feto y para el niño amamantado.

Objetivo. Modelar la variabilidad en el número de consultas infantiles diarias por motivos respiratorios como consecuencia de los cambios diarios en los niveles de contaminación ambiental, observada en los servicios de urgencias y medicina familiar de un hospital de especialidades del Instituto Mexicano del Seguro Social ubicado en la zona suroeste de la Ciudad de México durante 1993. Material y métodos. Se estudió la correlación entre la presencia de infecciones respiratorias altas y bajas con la exposición a ozono y bióxido de nitrógeno. Para modelar esta asociación se utilizó la técnica de regresión Poisson aplicada sobre modelos de riesgo lineal y no lineal con periodos de latencia entre las mediciones ambientales y la consulta de uno, dos y tres días, así como el promedio de las mediciones de los tres, cinco y siete días previos a la consulta. Resultados. El modelo utilizado estima que un incremento de 50 ppb en el promedio horario de ozono de un día ocasionaría, al día siguiente, un incremento del 9.9% en las consultas de urgencias por infecciones respiratorias altas en el periodo invernal, pudiendo incrementarse hasta en un 30% si el incremento se diera en cinco días consecutivos como promedio. Conclusiones. Los resultados sugieren que la exposición de los menores de 15 años al ozono y bióxido de nitrógeno inciden significativamente sobre el número de consultas ocasionadas por motivos respiratorios en esta zona de la Ciudad de México.

Objetivo. La medición del asma, la rinitis y el eczema ha sido motivo de controversia metodológica por la falta de uniformidad en los diagnósticos operacionales. Con el fin de probar la aplicabilidad de una metodología estandarizada para comparaciones en tiempo y espacio se determinó la prevalencia del asma y de otras enfermedades alérgicas en una muestra aleatoria de escolares (n= 6 238) de 6 a 8 años y de 11 a 14 años residentes de Cuernavaca, Morelos, México. Material y métodos. Se aplicó la metodología propuesta por el International Study of Asthma and Allergies in Childhood (ISAAC) para determinar la prevalencia y severidad del asma, la rinitis y el eczema. La información de prevalencia tanto actual como acumulada para dichos padecimientos se obtuvo a través de un cuestionario estandarizado contestado por los padres de los niños. Resultados. La prevalencia acumulada de asma por diagnóstico médico y sibilancia fue de 5.8% (5.2-6.4) y 21.8% (20.7-22.9) respectivamente; la prevalencia de sibilancia en los últimos 12 meses fue de 8.9% en el grupo de 6 a 8 años contra 6.6% en el de 11 a 14 años, p< 0.001. La prevalencia de diagnóstico médico de rinitis fue de 4.9% (4.3-5.5). Con relación a los síntomas típicos de rinitis, en los últimos 12 meses la prevalencia fue de 9.6% (6 a 8 años) y de 10.1% (11 a 14 años). La prevalencia de eczema por diagnóstico médico fue de 4.1% (3.6-4.6). La prevalencia de síntomas de eczema en los últimos 12 meses fue de 10.1% (6 a 8 años) y de 10.6% (11 a 14 años). Los síntomas severos de asma fueron significativamente más prevalentes en el grupo de 6 a 8 años y en los meses de otoño. Conclusiones. La prevalencia de asma tanto por diagnóstico médico como por síntomas resulta relativamente baja en relación con otros estudios realizados con la misma metodología. Se analizan las bondades del uso de una metodología estandarizada.

Objective. Recently, 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. Material and methods. We reviewed the process of generalization of these results to Latin American countries addressing possible differences in air pollution mixtures, exposure profiles, and population susceptibility. Results. A 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. Conclusions. Despite 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.

Objetivo. Identificar los factores de exposición asociados a las concentraciones de plomo en niños de escuelas primarias públicas y privadas de la ciudad de México. Material y métodos. Se realizó un estudio transversal en 340 niños que asistían a la escuela primaria. Las escuelas se seleccionaron por conveniencia y los niños en forma aleatoria. Se aplicó un cuestionario y se tomaron muestras de sangre venosa. Los niveles de plomo se determinaron por espectrofotometría de absorción atómica. Se compararon medias mediante la prueba t de Student-Fisher y ANDEVA; y para el análisis multivariado, regresión lineal múltiple. Debido a que los niveles de plomo no seguían una distribución normal, se transformó con logaritmo neperiano, con la que se trabajó en todo el análisis estadístico. Resultados. Las medias geométricas para escuelas privadas y públicas fueron: MG=8.76 µg/dl, IC95%=9.1-10.5; MG=11.5 µg/dl, IC95%=9.4-13.5, respectivamente. Los niveles de plomo son más elevados en los niños que asisten a la escuela pública y que presentan las siguientes características: ser varones, tener entre seis y ocho años de edad y cursar el primer o segundo grado de primaria; las madres de estos niños son profesionistas; en sus hogares se utiliza la cerámica vidriada y cerca de sus domicilios existen diferentes tipos de talleres contaminantes con plomo. Conclusiones. Los factores de exposición que predicen las concentraciones de plomo en sangre son: tener entre seis y ocho años de edad, la ocupación de la madre, la utilización de cerámica vidriada, la cercanía de diferentes tipos de talleres contaminantes con plomo a los domicilios y cursar el segundo año de primaria.

Objective: To evaluate the test-retest reliability and validity of the long-form International Physical Activity Questionnaire (IPAQ-long form)., Materials and Methods: A subsample of 86 teachers underwent telephone interviews and clinic visits in Mexico City. Through 22 months, physical activity (PA) levels were obtained from accelerometers (months 6 and 22) and IPAQ long-form (months 1, 3, 6, 9 and 12). Minutes per week of moderate (MPA), walking (WPA), vigorous (VPA) and moderate-to-vigorous physical activity (MVPA) were calculated for each intensity and domain. Variables were loga-rithmically transformed. Intra-class and Pearson correlations were used to determine the relationship between instru-ments., Results: Test-retest reliability of the average IPAQs long-form varied across intensities and domains (ranged from r= 0.24 to r= 0.65). Minutes per week of VPA and MVPA ac-celerometer 1 (AC1) were fairly associated to International Physical Activity Questionnaire-long form 3 (IPAQ3) (r= 0.60 and r= 0.31, respectively) one week apart., Conclusions: IPAQ long-form is fairly reliable for MVPA and valid for as-sessing MVPA and VPA in a subsample of Mexican teachers.

Objective: To describe the rationale and the methodology of a multicenter project to study the etiology of breast cancer in young Latin American women., Materials and Methods: The International Agency for Research on Cancer has established an international collaborative population-based case-control study in four countries in Latin America: Chile, Colombia, Costa Rica, and Mexico (the PRECAMA study). Standardized methodologies were developed to collect information on reproductive variables, lifestyle, anthropometry, diet, clinical and pathological data, and biological specimens. The study will be extended to other countries in the region., Conclusions: PRECAMA is unique in its multidisciplinary approach that combines genetics, genomics, and metabolomics with lifestyle factors. Then data generated through this project will be instrumental to identify major risk factors for molecular subtypes of breast cancer in young women, which will be important for pre- vention and targeted screening programs in Latin America., Competing Interests: Declaration of conflict of interests. The authors declare that they have no conflict of interests.

Objective:: To compare direct and self-reported anthropometry in Mexican women., Materials and Methods:: Women aged 30-72 years, participating in the Mexican Teachers' Cohort, completed a questionnaire with their anthropometric data in 2006-2008. After eleven months (median time), technicians performed anthropometry in 3756 participants. We calculated correlations and multivariable-adjusted mean differences between direct and self-reported anthropometric measures., Results:: Correlations between direct and self-reported anthropometric measures ranged from 0.78 (waist circumference) to 0.93 (weight). On average, women over-reported their height by 2.2 cm and underreported their weight, body mass index (BMI) and waist and hip circumferences by 1.3 kg, 1.3 kg/m2, 1.8 cm and 1.9 cm, respectively. Errors in self-reported anthropometry increased with rising measured BMI and were also independently associated with age, education and socioeconomic status., Conclusion:: Self-reported anthropometry is sufficiently valid for epidemiological purposes in adult Mexican women. Errors in self-reported anthropometry might result in underestimation of the prevalence of overweight and obesity.

Diet is an important modifiable risk factor for cancer. Adequate diet modification may play a key role in reducing the incidence of some cancers. A growing body of epidemiological evidence suggested links of some nutritional exposures with individual cancers. This review updates and summarises the existing data on diet related factors for cancer prevention, evaluated in 2007 by World Cancer Research Fund/American Institute for Cancer Research and identifies the areas where more research is needed. Mechanisms of action of nutrients are discussed. For cancer prevention, more apparent association pertains to the role of foods from plant origin, processed meat products and alcohol. There is a lack of evidence to clarify the relationship of dairy and cereal products, different types of carbohydrates, micronutrients naturally found in foods vs supplements, industrial trans-fats, food preparation and handling techniques and dietary patterns and cancer, in order to implement safe cancer prevention strategies.

Objective: To conduct a health impact assessment (HIA) to quantify health benefits for several PM and O3 air pollution reduction scenarios in the Mexico City Metropolitan Area (MCMA). Results from this HIA will contribute to the scientific support of the MCMA air quality management plan (PROAIRE) for the period 2011-2020., Materials and Methods: The HIA methodology consisted of four steps: 1) selection of the air pollution reduction scenarios, 2) identification of the at-risk population and health outcomes for the 2005 baseline scenario, 3) selection of concentration-response functions and 4) estimation of health impacts., Results: Reductions of PM10 levels to 20 μg/m³ and O3 levels to 0.050ppm (98 µg/m³) would prevent 2300 and 400 annual deaths respectively. The greatest health impact was seen in the over-65 age group and in mortality due to cardiopulmonary and cardiovascular disease., Conclusion: Improved air quality in the MCMA could provide significant health benefits through focusing interventions by exposure zones.

Breast cancer is a major public health problem in Latin America (LA) and the most common form of cancer among women. An important variability according to ethnicity/race with respect to incidence/mortality, clinical characteristics, and prognosis is observed throughout LA. In addition, women are more likely to develop breast cancer (BC) at younger age and to be diagnosed at an advanced stage compared to western women. While little is known about specific risk factors, changes in reproductive pattern (parity, breastfeeding) and lifestyle factors including sedentary behaviours, unhealthy diet, and alcohol intake may contribute to the increase of BC incidence. In this paper we give an overview of the burden and patterns of BC, review the leading causes of BC and discuss the possible ways to improve BC prevention and control in LA.

Objective: To evaluate the modification effect of socioeconomic status (SES) on the association between acute exposure to particulate matter less than 10 microns in aerodynamic diameter (PM10) and mortality in Bogota, Colombia., Materials and Methods: A time-series ecological study was conducted (1998-2006). The localities of the cities were stratified using principal components analysis, creating three levels of aggregation that allowed for the evaluation of the impact of SES on the relationship between mortality and air pollution., Results: For all ages, the change in the mortality risk for all causes was 0.76% (95%CI 0.27-1.26) for SES I (low), 0.58% (95%CI 0.16-1.00) for SES II (mid) and -0.29% (95%CI -1.16-0.57) for SES III (high) per 10µg/m³ increment in the daily average of PM10 on day of death., Conclusions: The results suggest that SES significantly modifies the effect of environmental exposure to PM10 on mortality from all causes and respiratory causes.

Objective: To analyze the association between daily mortality from different causes and acute exposure to particulate matter less than 10 microns in aerodynamic diameter (PM10), in Bogota, Colombia., Materials and Methods: A time-series ecological study was conducted from 1998 to 2006. The association between mortality (due to different causes) and exposure was analyzed using single and distributed lag models and adjusting for potential confounders., Results: For all ages, the cumulative effect of acute mortality from all causes and respiratory causes increased 0.71% (95%CI 0.46-0.96) and 1.43% (95%CI 0.85-2.00), respectively, per 10µg/m³ increment in daily average PM10 with a lag of three days before death. Cumulative effect of mortality from cardiovascular causes was -0.03% (95%CI -0.49-0.44%) with the same lag., Conclusions: The results suggest an association between an increase in PM10 concentrations and acute mortality from all causes and respiratory causes.

Objective: To study the relationship between light absorption measurements of PM2.5 at various distances from heavy traffic roads and diesel vehicle counts in Mexico City., Materials and Methods: PM2.5 samples were obtained from June 2003-June 2005 in three MCMA regions. Light absorption (b abs) in a subset of PM2.5 samples was determined. We evaluated the effect of distance and diesel vehicle counts to heavy traffic roads on PM2.5 b abs using generalized estimating equation models., Results: Median PM2.5 b abs measurements significantly decrease as distance from heavy traffic roads increases (p<0.002); levels decreased by 7% (CI95% 0.9-14) for each 100 additional meters from heavy traffic roads. Our model predicts that PM2.5 b abs measurements would increase by 20% (CI95% 3-38) as the hourly heavy diesel vehicle count increases by 150 per hour., Conclusion: PM2.5 b abs measurements are significantly associated with distance from motorways and traffic density and therefore can be used to assess human exposure to traffic-related emissions.

Both diet and nutrition have been studied in relationship with breast cancer risk, as the great variation among different countries in breast cancer incidence could possibly be explained through the inflammatory and immune response, as well as antioxidant intake, among others. To date, no clear association with diet beyond overweight and weight gain has been found, except for alcohol consumption. Nonetheless, the small number of studies done in middle to low income countries where variability of food intake is wider, is beginning to show interesting results.

Objective: To evaluate the relation between diet and the development of asthma and allergic rhinitis in schoolchildren from Cuernavaca, Morelos, Mexico., Material and Methods: We apply the ISAAC's questionnaire in 5460 schoolchildren from 6 to 8 and 11-14-year-old of elementary level selected in random form. Six groups of food were formed using a hierarchic clusters analysis and the association was evaluated using logistic regression models., Results: The consumption of fast food had an adverse effect for current wheezing (OR=1.82; CI95%=1.16-2.87) and the consumption of tidbits for more than three episodes of wheezing (OR=2.26; CI95%=1.04-4.95) and nasal symptoms without cold, OR=1.35 (IC95%;1.06-1.71)., Conclusions: This study provides evidence that the diet plays a very important role since the high consumption of fast food and tidbits increased the risk of asthma and rhinitis symptoms.

We provide an overview of the role of adiposity, physical activity and diet in the risk for breast cancer in Mexican women. Lack of physical activity, diets high in carbohydrates and in glycemic load and low intake of folate and vitamin B12 have been shown to increase the risk of breast cancer in Mexican women, in particular postmenopausal breast cancer. Other dietary factors that may begin to play a more relevant role in breast cancer incidence in Mexico are alcohol intake and vitamin D status. Recommendations to maintain a healthy weight, practice moderate physical activity, decrease intake of rapidly absorbed carbohydrates and increase consumption of fruits and vegetables could have an important impact on the epidemic of breast cancer in Mexico.

Objective: To evaluate the effect of moderate physical activity (hours per week and METs hours per week) on the risk of breast cancer (BC) in Mexican women., Material and Methods: This is the initial stage of a case control multicentric study based in the Federal District, Monterrey and Veracruz, Mexico, during 2004. Fifty eight cases paired to 58 control cases on quinquennium of age, and belonging to the health system were analyzed: three hospitals from the IMSS, three from ISSSTE and three from SS participated., Results: In postmenopausal women, there was a reduction of the risk in BC by every additional hour per week of moderate physical activity (RM= 0.91; IC95% 0.85-0.97); in premenopausal women, the reduction of the risk was not statistically significant (RM= 0.99; IC95% 0.94-1.05) (p= 0.048, effect modification)., Conclusions: Moderate physical activity reduces the risk of BC in postmenopausal Mexican women.

Objective: A study was conducted to evaluate personal ozone exposure (O3p) among asthmatic children residing in Mexico City., Material and Methods: A total of 158 children were recruited from December 1998 to April 2000. On average, three O3p measurements were obtained per child using passive badges. Time-activity patterns were recorded in a diary. Daily ambient ozone measurements (O3a) were obtained from the fixed station, according to children's residence. Levels of O3a and ozone, weighted by time spent in different micro-environments (O3w), were used as independent variables in order to model O3p concentrations using a mixed-effects model., Results: Mean O3p was 7.8 ppb. The main variables in the model were: time spent indoors, distance between residence and fixed station, follow-up group, and two interaction terms (overall R(2)=0.50, p<0.05)., Conclusions: The O3w concentrations can be used as a proxy for O3p, taking into account time-activity patterns and the place of residence of asthmatic Mexican children.

Objective: To determine the concordance between maximum peak expiratory flow records (PEFr) reported by the parents of asthmatic children and the electronic values stored by the AirWatch device (PEFe)., Material and Methods: Records of PEF measurements between October 1998 and 1999 were obtained from 42 asthmatic children 5 to 15 years of age recruited at the Hospital Infantil de Mexico Federico Gomez, in Mexico City. Parents recorded the maximum value in the health diary. Spearman correlation was calculated between PEFe and PEFr and a mixed-effects logistic model was used., Results: The correlation between PEFe and PEFr was r=0.96 (p<0.05) among children with a diagnosis of moderate or severe asthma and r=0.40 (p<0.05) among children diagnosed with mild asthma. Follow-up time, asthma severity, gender and age of the child and their interactions were predictors of the differences between PEFe and PEFr., Conclusions: Parents of children with moderate or severe asthma from 6 to 8 years of age report PEF values with greater accuracy during follow-up than others.

Objective: To assess the impact of atmospheric pollutants on the respiratory health of children of different age groups in Juarez City, Chihuahua, Mexico., Material and Methods: Data on emergency room visits between 1997 and 2001 for respiratory diseases in children less than 17 years old were obtained from hospitals in the Juarez City belonging to the Mexican Social Security Institute (IMSS). Diseases were classified into three groups according to ICD 9th and 10th codes: a) upper respiratory diseases, b) lower respiratory diseases, and c) asthma attacks. This information was stratified by age group (< = 5 years and > 5 years). Daily air pollution data (ozone and PM10) and weather conditions were obtained from the Monitoring Network System in Juarez City. Statistical analysis was carried out using a Generalized Additive Model assuming a Poisson distribution., Results: Ozone concentrations, but not PM 10, were statistically associated with emergency room visits for respiratory diseases, mainly among children 5 years old or younger. In this group, an increase of 20 ppb 1-hr maximum for ozone was associated with an increase of 8.3% in the number of emergency room visits for upper respiratory diseases, with a 3-day exposure lag; and an increase of 12.7% in the number of emergency room visits for lower respiratory diseases when considering a 4-day exposure lag in a maximum 8-hr mobile average. The largest effect for the complete sample and for the group 6 to 16 years of age was observed for 3-day lag (5.1% for an increase of 20 ppb 1-hr maximum for ozone). For the 6 to 16 year old group we did not find a significant effect., Conclusion: The wide range of risk is quite important and might represent a substantial cost for the health system as well as for the society. Our results emphasize the need to implement preventive and control measures for air pollution and avoid the worsening of the present situation.

Epidemiological studies have shown the association between atmospheric pollutants and increase in mortality due to cardiovascular causes, especially in patients with previous cardio-respiratory diseases. However, the pathophysiological mechanisms by which these events take place have not been elucidated. One of the proposed mechanisms by which suspended respirable particles and other pollutants produce their effect is that they modify autonomic heart control. The analysis of changes in heart rate variability (HRV) is an indicator of pollutant effect on this mechanism. The article reviews the physiologic basis of this non-invasive method, its advantages and disadvantages, and the results obtained to date through HRV analysis associated with air pollution. After reviewing the available literature, we suggest alternatives for study design, selection of risk population, exposure assessment methods, and statistical analysis methods that may be used to improve the analysis of the ambulatory ECG record to assess the cardiac risk related to exposure to air pollution.

Objective: To assess PM2.5 levels at different distances from a heavy traffic road., Material and Methods: Daily measurements of PM2.5 were taken between August 26 and 30, 2002, at different distances from Tecnológico Avenue in Ciudad Juarez, Chihuahua, Mexico. Data analysis consisted of descriptive statistics for each distance and KruskalWallis and cross trend for ranks., Results: We found a significantly decreasing trend of PM2.5 median levels with increasing distance from Tecnológico Avenue (p<0.001). At 100 m distance from the avenue, PM2.5 levels decreased by 9.5 microg/m3 (40.6%) when compared to median levels registered on the avenue. The results showed a highly significant negative correlation between PM2.5 measurements and the distance from the avenue (r=-0.70, n=20 and p=0.0005)., Conclusions: PM2.5 median levels decreased significantly after 100 meters from heavy traffic roads. These results are of great relevance when assessing exposure to PM2.5 in epidemiological studies.

Objective: To identify the relationship between emergency visits for acute respiratory illnesses, acute bronchial asthma crisis (ABAC) and acute respiratory infections (ARI), in children less than 14 years of age, and the daily changes of air pollutant levels, in two central hospitals of Havana City, between October 1st 1996 and March 16 1998., Material and Methods: An ecological time series study was conducted. We assessed the relationship between the presence of acute respiratory illnesses, ABAC, and IRA, and exposure to levels of particles less than 10 microg/m3 (PM10), smoke, and sulfur dioxide (SO2); negative binomial regression models were used to assess latency periods of one to five days as well as the cumulative effect of seven days before the emergency visit., Results: The levels of atmospheric pollutants were low, in general. The 24-hour mean values for PM10 levels, smoke, and SO2, were 59.2 microg/m3 (SD=29.2), 27.7 microg/m3 (SD=21.2), and 21.1 microg/m3 (SD=20.1), respectively. An increase of 20 microg/m3 in the daily average of black smoke was associated with a 2.2% increase (95% CI 0.9-3.6) in the number of emergency visits for ABAC. A 20 microg/m3 increase in the daily average of black smoke and SO was associated with an increase in ARI of 2.4% (95% CI 1.2-3.6), and 5% (95% CI 1.3-5.3), respectively, with a 5-day lag. We also observed a cumulative effect for all the contaminants studied., Conclusions: These results suggest that air pollution levels in Havana City affect children's respiratory health; therefore implementation of control measures is necessary, especially those aimed at decreasing motor vehicle exhaust fumes. The English version of this paper is available at: http://www.insp.mx/salud/index.html.

Objective: To assess the extent of exposure for Volatile Organic Compounds (VOCs) among nonoccupationally exposed commuters in Mexico City., Material and Methods: Blood concentrations of benzene, toluene, ethylbenzene, m-/p-xylene, o-xylene and methyl tert-butyl ether were determined on samples collected from participants after the morning commute., Results: Median blood concentrations of benzene (0.11 microg/l), ethylbenzene (0.081 microg/l), m-/p-xylene (0.32 microg/l) and toluene (0.56 microg/l) in the Mexico City participants were all approximately two times higher than in a nonsmoking subset of the Third National Health and Nutrition Examination Survey population of the United States. On the other hand, median VOC blood levels were similar to medians observed in other studies involving commuters in specific U.S. cities, despite the fact that only half the Mexico City study participants commuted by personal vehicles compared with all U.S. commuters., Conclusions: These results reflect the extent of the air pollution problem in Mexico City. The surrounding topography exacerbates the problems caused by heavy vehicular traffic, poor emission-control devices on older vehicles, and poor maintenance practices. Elevated levels of gasoline components in the blood of nonoccupationally exposed commuters emphasize the need for regulatory initiatives and mass-transit options to reduce hydrocarbon emissions and thus reduce the risk for nonoccupational exposure for the residents of Mexico City.

Objective: To evaluate the association between maternal serum DDT/DDE levels and risk of hypospadias., Material and Methods: A case-control study in Mexico City was conducted during 1997-1999 among 41 subjects with hypospadias and 28 controls. Blood samples were obtained from study subjects. Information was obtained using a standardized questionnaire. Data were analyzed using multivariate logistic regression models., Results: Maternal DDT and DDE levels showed no association with hypospadias (OR 1.13; 95% CI 0.24-5.29 and OR = 0.48; 95% CI 0.15-1.60, respectively). Associated factors were older age of mothers (OR 8.69; 95% CI 1.69-44.9), and working during pregnancy (OR 4.68; 95% CI 1.15-18.9)., Conclusions: Information about the endocrine effects of different levels of DDT/DDE in human subjects is scarce; dosage may be a determinant factor of the type of effect. The English version of this paper is available at:http://www.insp.mx/salud/index.html.

Exposure to lead is a widespread and serious threat to the health of children in Latin America. Health officials should monitor sources of exposure and health outcomes to design, implement, and evaluate prevention and control activities. To evaluate the magnitude of lead as a public health problem, three key elements must be defined: I) the potential sources of exposure, 2) the indicators to evaluate health effects and environmental exposure, and 3) the sampling methods for the population at risk. Several strategies can be used to select the study population depending on the study objectives, the time limitations, and the available resources. If the objective is to evaluate the magnitude and sources of the problem, the following sampling methods can be used: I) population-based random sampling; 2) facility-based random sampling within hospitals, daycare centers, or schools; 3) target sampling of high risk groups; 4) convenience sampling of volunteers; and 5) case reporting (which can lead to the identification of populations at risk and sources of exposures). For all sampling methods, information gathering should include the use of a questionnaire to collect general information on the participants and on potential local sources of exposure, as well as the collection of biological samples. In interpreting data, one should consider the type of sampling used and the non-response rates, as well as factors that might influence blood lead measurements, such as age and seasonal variability. Blood lead measurements should be integrated in an overall strategy to prevent lead toxicity in children. The English version of this paper is available at: http://www.insp.mx/salud/index.html.

Objective: To assess the prevalence and severity of asthma and allergic diseases in schoolchildren residing in Ciudad Juarez, Chihuahua., Material and Methods: A cross-sectional study was conducted from April 1998 to May 1999, among 6,174 children from 53 schools in Ciudad Juarez, Chihuahua. The method used was the one recommended by the International Study of Asthma and Allergies in Childhood (ISAAC) to determine the prevalence and severity of asthma, rhinitis, and eczema. Parents were asked to answer a standardized questionnaire on current and cumulative prevalence of asthma, rhinitis, and eczema. A sample stratified by level of pollution was selected., Results: The cumulative prevalence of medically diagnosed asthma and wheezing was 6.8% (95% CI 6.2, 7.4) and 20% (95% CI 19.7, 21.8), respectively. The prevalence of wheezing in the last 12 months was higher in the group aged 6-8 years than in those aged 11-14 years (9.7% vs. 5.8%, p < 0.01). The prevalence of medically diagnosed rhinitis was 5.0% (95% CI 4.5, 5.6). The prevalence of medically diagnosed eczema was 4.9% (4.3, 5.4). The prevalence of eczema symptoms in the last 12 months was 12.7% in the 6-8 years group and 13.3% in the 11-14 year group, respectively. Severe symptoms of asthma were significantly higher in the 6-8 years group and during the autumn months., Conclusions: The prevalence of medically diagnosed and symptomatic asthma was relatively low in comparison with findings from others studies that use similar methods, but the prevalence rates of rhinitis and eczema were higher.

Objective: To assess the relationship of < or = 10 microns particles (PM10) and atmospheric ozone concentrations, with the daily number of emergency visits due to asthma and acute respiratory diseases, among children aged under 15, living in Ciudad Juarez, Chihuahua, Mexico., Material and Methods: Between 1998 and 1999, an ecologic study was conducted. Atmospheric data were obtained from the Environmental Protection Agency (EPA), from eight monitoring stations located in Ciudad Juarez, Chihuahua, and EI Paso, Texas. From July 1997 to December 1998, data from emergency room visits for respiratory illness were abstracted from existing medical records of two Mexican Institute of Social Security (IMSS) hospitals in Ciudad Juarez. Diagnoses were classified into two groups: a) asthma, and b) upper respiratory infections (URI), according to the International Classification of Diseases (ICD-9 and/or IDC-10). Statistical analysis was carried out using the Poisson regression time series method., Results: During the study period, the mean 24-hour PM10 level was 34.46 micrograms/m3 (SD = 17.99) and the mean ozone level was 51.60 ppb (SD = 20.70). The model shows that an increase of 20 micrograms/m3 in the mean 24-hour exposure to PM10 was related to an increase of 4.97% (95% CI 0.97-9.13) in emergency visits for asthma, with a 5-day lag, as well as to an increase of 9% (95% CI 1.8-16.8) when a cumulative 5-day exposure was considered. URI increased 2.95% as a cause of emergency room visits, for each 20 micrograms/m3 increase in the mean 24-hour exposure to PM10. The impact of PM10 on emergency visits for asthma was greater on days with ozone ambient levels exceeded 49 ppb (median value)., Conclusions: A positive association was found between environmental PM10 and ozone concentrations and the daily number of emergency room visits due to asthma and acute respiratory diseases, even with levels lower than the Mexican standard levels. Also, a synergic effect between PM10 and O3 was found.

The present work discusses the problems of atmospheric pollution of three Megacities of Latin America (Mexico City, Sao Paulo and Santiago). The environmental pollution control programs implemented by the Government are revised and the evolution of pollution levels during the period of 1988-1995 at Santiago de Chile and Sao Paulo, but until 1997 at Mexico City, in order to evaluate the impact of these programs. During this period, a decreasing trend is observed in the three cities in the levels of PTS, PM10, SO2, NO2, CO and O3, although most of these contaminants still exceed the air quality standards. It must be emphasized that the largest impact has been on the levels of SO2. We recommend the development of sustainable transport policies; in this context, various strategies were proposed by the Organization for Economic Cooperation and Development (OECD) in the European Conference of Ministers of Transport. Additionally, public participation is important when decisions are taken on transport policies.

Objective: To identify exposure factors contributing to lead poisoning in school children from Mexico City., Material and Methods: Cross-sectional study of 340 children. A convenience sample of schools and a random sample of children were selected. A questionnaire was filled out and venous blood samples were taken. Lead levels were measured by atomic absorption spectrophotometry. Statistical analysis consisted of comparison of means using Student's t test and ANOVA. Multiple linear regression was used for multivariate analysis. Logarithmic transformation of lead blood levels were used to account for their non-normal distribution., Results: Geometric means for private and public schools were: GM = 8.76 micrograms/dl, 95% CI = 9.1-10.5; GM = 11.5 micrograms/dl, 95% CI = 9.4-13.5. Lead levels were higher among children from public schools who are male, between 6 and 8 years of age, in first and second grade, whose mothers have a profession, who use glazed earthenware utensils, and who live near glazed earthenware shops or factories., Conclusions: Exposure predictors of lead blood levels are: being between 6 and 8 years of age, having a professional mother, using glazed earthenware utensils, living near glazed earthenware shops or factories, and studying the second grade of elementary school.

The adverse effects of lead have been known for long since the metal affects practically all organs and systems of the human body. Recently, toxic effects have been reported in the cardiovascular and nervous systems at lead levels previously considered to be secure. The main lead storage site in the body is bone. The toxicologic significance of this fact has been clarified only recently. The present study analyzes the role of lead as an endogenous source of exposure, as a chronic exposure biomarker and as a target organ. Recent advances to measure bone lead through fluorescent X-Rays are discussed. Additionally, the importance of bone lead from a public health perspective in places with a chronic history of exposure such as Mexico City, and in some occupational environments is reviewed with particular attention placed on reproductive age women, who are potential lead sources for the fetus and lactating infant.

Objective: To model the variability of medical visits by children for respiratory reasons as a consequence of the daily changes in environmental pollution observed in the emergency and family medicine departments of a hospital of the Instituto Mexicano del Seguro Social located in the southwest of Mexico City during 1993., Materials and Methods: The correlation between the presence of upper and lower respiratory tract infections and exposure to ozone and nitrogen dioxide was studied. To model this association, the authors used multivariate Poisson regression models with linear and non-linear risk, with lag periods between the environmental measurements and the medical visits of one, two and three days, as well as the average of the measurements of three, five and seven days previous to the visit., Results: The model estimates that an increment of 50 ppb in the daily average of ozone would cause an increase of 9.9% in emergency visits due to high respiratory tract infections during the winter, which could rise to 30% if the increment would last five consecutive days in average., Conclusions: Results suggest that exposure of children younger than 15 years of age to ozone and nitrogen dioxide significantly affect the number of medical visits for respiratory causes in this part of Mexico City.

Objective: The measurement of asthma, rhinitis and eczema have been subject of controversy due to lack of a standardized methodology. To test the applicability of a standardized methodology for comparisons of time and space we determined the prevalence of asthma and other allergic diseases in a random sample of schoolchildren (n = 6,238) from 6 to 8 and 11 to 14 years of age living in Cuernavaca, Morelos, Mexico., Material and Methods: The methodology proposed by the International Study of Asthma and Allergies in Childhood (ISAAC) to determine prevalence and severity of asthma, rhinitis and eczema was applied. Current and accumulated information on prevalence was obtained by means of a standardized questionnaire answered by the children's parents., Results: The accumulated prevalence of asthma by medical diagnosis and wheezing was 5.8% (5.2-6.4) and 21.8% (20.7-22.9) respectively; prevalence of wheezing in the last 12 months was 8.9% in the group of 6 to 8 years against 6.6% in the 11 to 14 year old group p < 0.001. Prevalence of the medical diagnosis of rhinitis was 4.9% (4.3-5.5). Regarding the typical symptoms of rhinitis, in the last 12 months prevalence was 9.6% (6-8 years) and 10.1% (11-14 years). Prevalence of eczema by medical diagnosis was 4.1% (3.6-4.6). Prevalence of eczema symptoms in the last 12 months was 10.1% (6-8 years) and 10.6% (11-14 years). Prevalence of severe asthma symptoms was significantly higher in the 6 to 8 year olds and in the autumn., Conclusions: Prevalence of asthma by medical diagnosis and by symptoms is relatively low with respect to other studies performed with the same methodology. The benefits of using a standardized methodology were analyzed.

This essay describes the different theoretical constructions of breast cancer models, such as the biological, hygienist-preventive and epidemiological. An anecdotal account of the Hippocratic model is also presented. This disease will be one of the major challenges posed by noncommunicable diseases in coming years, due to a significant increase of life expectancy and to a decrease of the overall annual growth rate-resulting in the ageing of the population-, as well as to lifestyle changes-particularly the considerable decrease of fertility rates and breastfeeding practices-, and to the poor efficiency and effectiveness of breast cancer screening programs. In this context, one of the main challenges for breast cancer control is to secure the multidisciplinary approach offered by public health. After analyzing the different models, we favor the sociomedical model as the one that incorporates several areas of knowledge to formulate an effective response to breast cancer.

The aim of this study was to evaluate the validity and reproducibility between ozone measurements obtained with passive ozone monitors and those registered with a continuous ozone monitor, to determine the applicability of passive monitors in epidemiological research. The study was carried out during November and December 1992. Indoor and outdoor classroom air ozone concentrations were analyzed using 28 passive monitors and using a continuous monitor. The correlation between both measurements was highly significant (r = 0.089, p < 0.001), indicating a very good validity. Also, the correlation between the measurements obtained with two different passive monitors exposed concurrently was very high (r = 0.97, p < 0.001), indicating a good reproducibility in the measurements of the passive monitors. The relative error between the concentrations measured by the passive monitors and those from the continuous monitor tended to decrease with increasing ozone concentrations. The results suggest that passive monitors should be used to determine cumulative exposure of ozone exceeding 100 ppb, corresponding to an exposure period greater than five days, if used to analyze indoor air.

Risk factors that contribute to high blood lead concentrations were determined in 113 infants, aged 3 to 7 years old, that attended pediatric consultation at the American British Cowdray Hospital (ABC) from May 1991 to October 1992. The range of blood lead concentrations was 4 to 45 micrograms/dl, with an average value of 15.6 micrograms/dl (DE = 7.0), and a geometric mean of 14.2 micrograms/dl (IC 95% = 11.9-16.5). Seventy six percent of the children presented blood lead concentrations of over 10 micrograms/dl. The main predictors of blood lead levels were the use of glazed pottery for cooking rice (ANOVA, p = 0.0000) and the storage of food in glazed pottery (t-test, p = 0.005). There was a significant association between the use of glazed pottery for cooking rice and blood lead concentrations (tendency p = 0.000). The attributable risk of this population due to the use of glazed pottery was 81 per cent. This study sustains the need to develop and enforce public health policies for programs of lead poisoning prevention.