Prenatal and childhood lead exposure is prospectively associated with biological markers of aging in adolescence.

Few studies have related early life lead exposure to adolescent biological aging, a period characterized by marked increases in maturational tempo. We examined associations between prenatal and childhood lead exposure and adolescent biological age (mean 14.5 years) utilizing multiple epigenetic clocks including: intrinsic (IEAA), extrinsic (EEAA), Horvath, Hannum, PhenoAge, GrimAge, Skin-Blood, Wu, PedBE, as well as DNA methylation derived telomere length (DNAmTL). Epigenetic clocks and DNAmTL were calculated via adolescent blood DNA methylation measured by Infinium MethylationEPIC BeadChips. We constructed general linear models (GLMs) with individual lead measures predicting biological age. We additionally examined sex-stratified models and lead by sex interactions, adjusting for adolescent age and lead levels, maternal smoking and education, and proportion of cell types. We also estimated effects of lead exposure on biological age using generalized estimating equations (GEE). First trimester blood lead was positively associated with a 0.14 increase in EEAA age in the GLMs though not the GEE models (95%CI 0.03, 0.25). First and 2nd trimester blood lead levels were associated with a 0.02 year increase in PedBE age in GLM and GEE models (1st trimester, 95%CI 0.004, 0.03; 2nd trimester, 95%CI 0.01, 0.03). Third trimester and 24 month blood lead levels were associated with a -0.06 and -0.05 decrease in Skin-Blood age, respectively, in GLM models. Additionally, 3rd trimester blood lead levels were associated with a 0.08 year decrease in Hannum age in GLM and GEE models (95%CI -0.15, -0.01). There were multiple significant results in sex-stratified models and significant lead by sex interactions, where males experienced accelerated biological age, compared to females who saw a decelerated biological age, with respect to IEAA, EEAA, Horvath, Hannum, and PedBE clocks. Further research is needed to understand sex-specific relationships between lead exposure and measures of biological aging in adolescence and the trajectory of biological aging into young adulthood.

Associations of prenatal and childhood Pb exposure with allostatic load in adolescence: Findings from the ELEMENT cohort study.

The biological pathways which link lead (Pb) and long-term outcomes are unclear, though rodent models and a few human studies suggest Pb may alter the body's stress response systems, which over time, can elicit dysregulated stress responses with cumulative impacts. This study examined associations between prenatal and early childhood Pb exposure and adolescent allostatic load, an index of an individual's body burden of stress in multiple biological systems, and further examined sex-based associations. Among 391 (51% male) participants in the ELEMENT birth cohort, we related trimester-specific maternal blood Pb, 1-month postpartum maternal tibia and patella Pb, and child blood Pb at 12-24 months to an allostatic load index in adolescence comprised of biomarkers of cardiovascular, metabolic, neuroendocrine, and immune function. The results were overall mixed, with prenatal exposure, particularly maternal bone Pb, being positively associated with allostatic load, and early childhood Pb showing mixed results for males and females. In adjusted Poisson regression models, 1 mcg/g increase in tibia Pb was associated with a 1% change in expected allostatic load (IRR = 1.01; 95%CI 0.99, 1.02). We found a significant Pb × sex interaction (IRR = 1.05; 95%CI 1.01, 1.10); where males saw an increasing percent change in allostatic load as 12 month Pb levels increased compared to females who saw a decreasing allostatic load. Further examination of allostatic load will facilitate the determination of potential mechanistic pathways between developmental toxicant exposures and later-in-life cardiometabolic outcomes.

Prenatal Pb exposure is associated with reduced abundance of beneficial gut microbial cliques in late childhood: an investigation using Microbial Co-occurrence Analysis (MiCA).

Background: Many analytical methods used in gut microbiome research focus on either single bacterial taxa or the whole microbiome, ignoring multi-bacteria relationships (microbial cliques). We present a novel analytical approach to identify multiple bacterial taxa within the gut microbiome of children at 9-11 years associated with prenatal Pb exposure. Methods: Data came from a subset of participants (n=123) in the Programming Research in Obesity, Growth, Environment and Social Stressors (PROGRESS) cohort. Pb concentrations were measured in maternal whole blood from the second and third trimesters of pregnancy. Stool samples collected at 9-11 years old underwent metagenomic sequencing to assess the gut microbiome. Using a novel analytical approach, Microbial Co-occurrence Analysis (MiCA), we paired a machine-learning algorithm with randomization-based inference to first identify microbial cliques that were predictive of prenatal Pb exposure and then estimate the association between prenatal Pb exposure and microbial clique abundance. Results: With second-trimester Pb exposure, we identified a 2-taxa microbial clique that included Bifidobacterium adolescentis and Ruminococcus callidus, and a 3-taxa clique that added Prevotella clara. Increasing second-trimester Pb exposure was associated with significantly increased odds of having the 2-taxa microbial clique below the 50th percentile relative abundance (OR=1.03,95%CI[1.01-1.05]). In an analysis of Pb concentration at or above vs. below the United States and Mexico guidelines for child Pb exposure, odds of the 2-taxa clique in low abundance were 3.36(95%CI[1.32-8.51]) and 6.11(95%CI[1.87-19.93]), respectively. Trends were similar with the 3-taxa clique but not statistically significant. Discussion: Using a novel combination of machine-learning and causal-inference, MiCA identified a significant association between second-trimester Pb exposure and reduced abundance of a probiotic microbial clique within the gut microbiome in late childhood. Pb exposure levels at the guidelines for child Pb poisoning in the United States, and Mexico are not sufficient to protect against the potential loss of probiotic benefits.

Overweight and obesity status from the prenatal period to adolescence and its association with non-alcoholic fatty liver disease in young adults: cohort study.

OBJECTIVE: To examine the associations of maternal and child overweight status across multiple time-points with liver fat content in the offspring during young adulthood. DESIGN: Cohort study. SETTING: ELEMENT Cohort in Mexico City. POPULATION: Pregnant women with singleton births (n = 97). METHODS: We quantified hepatic triglyceride content (liver fat content) by proton magnetic resonance spectroscopy (1H MRS) and conventional T2-weighted MRIs (3T scanner) in 97 young adults from the ELEMENT birth cohort in Mexico City. Historical records of the cohort were used as a source of pregnancy, and childhood and adolescence anthropometric information, overweight and obesity (OWOB) were defined. Adjusted structural equation models were run to identify the association between OWOB in different life stages with liver fat content (log-transformed) in young adulthood. MAIN OUTCOME: Maternal OWOB at the time of delivery was directly and indirectly associated with the liver fat content in the offspring at young adulthood. RESULTS: Seventeen percent of the participants were classified as having NAFLD. We found a strong association of OWOB between all periods assessed. Maternal OWOB at time of delivery (ß = 1.97, 95% CI 1.28-3.05), and OWOB status in the offspring at young adulthood (ß = 3.17, 95% CI 2.10-4.77) were directly associated with the liver fat content in the offspring. Also, maternal OWOB was indirectly associated with liver fat content through offspring OWOB status. CONCLUSION: We found that maternal OWOB status is related to fatty liver content in the offspring as young adults, even after taking into account OWOB status and lifestyle factors in the offspring. TWEETABLE ABSTRACT: There was an association between pre-pregnancy overweight and the development of NAFLD in adult offspring.

Prenatal lead exposure in relation to age at menarche: results from a longitudinal study in Mexico City.

Animal and cross-sectional epidemiological studies suggest that prenatal lead exposure is related to delayed menarche, but this has not been confirmed in longitudinal studies. We analyzed this association among 200 girls from Mexico City who were followed since the first trimester of gestation. Maternal blood lead levels were analyzed once during each trimester of pregnancy, and daughters were asked about their first menstrual cycle at a visit between the ages of 9.8 and 18.1 years. We estimated hazard ratios (HRs) and 95% confidence intervals (CI) for probability of menarche over the follow-up period using interval-censored Cox models, comparing those with prenatal blood lead level ⩾5 µg/dl to those with prenatal blood lead <5 µg/dl. We also estimated HRs and 95% CI with conventional Cox regression models, which utilized the self-reported age at menarche. In adjusted analyses, we accounted for maternal age, maternal parity, maternal education, and prenatal calcium treatment status. Across trimesters, 36-47% of mothers had blood lead levels ⩾5 µg/dl. Using interval-censored models, we found that during the second trimester only, girls with ⩾5 µg/dl prenatal blood lead had a later age at menarche compared with girls with prenatal blood lead levels <5 µg/dl (confounder-adjusted HR=0.59, 95% CI 0.28-0.90; P=0.05). Associations were in a similar direction, although not statistically significant, in the conventional Cox regression models, potentially indicating measurement error in the self-recalled age at menarche. In summary, higher prenatal lead exposure during the second trimester could be related to later onset of sexual maturation.

Maternal intake of omega-3 and omega-6 polyunsaturated fatty acids during mid-pregnancy is inversely associated with linear growth.

This study investigates relations of maternal N-3 and N-6 polyunsaturated fatty acids (PUFA) intake during pregnancy with offspring body mass index (BMI), height z-score and metabolic risk (fasting glucose, C-peptide, leptin, lipid profile) during peripuberty (8-14 years) among 236 mother-child pairs in Mexico. We used food frequency questionnaire data to quantify trimester-specific intake of N-3 alpha-linolenic acid, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA); N-6 linoleic acid and arachidonic acid (AA); and N-6:N-3 (AA:EPA+DHA), which accounts for the fact that the two PUFA families have opposing effects on physiology. Next, we used multivariable linear regression models that accounted for maternal education and parity, and child's age, sex and pubertal status, to examine associations of PUFA intake with the offspring outcomes. In models where BMI z-score was the outcome, we also adjusted for height z-score. We found that higher second trimester intake of EPA, DHA and AA were associated with lower offspring BMI and height z-score. For example, each 1-s.d. increment in second trimester EPA intake corresponded with 0.25 (95% CI: 0.03, 0.47) z-scores lower BMI and 0.20 (0.05, 0.36) z-scores lower height. Accounting for height z-score in models where BMI z-score was the outcome attenuated estimates [e.g., EPA: -0.16 (-0.37, 0.05)], suggesting that this relationship was driven by slower linear growth rather than excess adiposity. Maternal PUFA intake was not associated with the offspring metabolic biomarkers. Our findings suggest that higher PUFA intake during mid-pregnancy is associated with lower attained height in offspring during peripuberty. Additional research is needed to elucidate mechanisms and to confirm findings in other populations.

Exposure to Bisphenol A and phthalates metabolites in the third trimester of pregnancy and BMI trajectories.

BACKGROUND: Bisphenol A (BPA) and phthalates metabolites are linked to a variety of adverse health consequences but studies have not explored their association with growth trajectories. OBJECTIVE: Explore body mass index (BMI) trajectories for tertile exposures to BPA and phthalates metabolites in the third trimester of pregnancy. METHODS: We constructed BMI (kg/m2 ) trajectories from birth to 14 years in a birth cohort of 249 children from Mexico City using tertiles of third trimester maternal urinary concentrations of BPA and phthalates metabolites. Fractional age polynomials and mixed effects models were fit separately by sex. Predicted models were plotted for each metabolite tertile with the covariates mother's education and BMI centered at average values. RESULTS: Highest predicted BMI trajectories for female children were observed for third tertile exposure to the phthalate metabolite mono(2-ethyl-5-carboxypentyl) phthalate. In male children, first tertile exposure to mono-isobutyl phthalate and monobenzyl phthalate and second tertile exposure to mono(2-ethylhexyl) phthalate and mono(2-ethyl-5-hydroxyhexyl) phthalate predicted the highest BMI trajectory by adolescence. There was no relationshsip between BPA and child growth trajectory. CONCLUSIONS: These results suggest sex-specific differences in BMI trajectories by levels of metabolite exposure. Additional studies are needed to consider growth through adolescence in assessing the association of pregnancy exposures on child's BMI.

Early introduction and cumulative consumption of sugar-sweetened beverages during the pre-school period and risk of obesity at 8-14 years of age.

BACKGROUND: Consumption of sugar-sweetened beverages (SSB) has been associated with risk of obesity, but little evidence exists to evaluate if age of introduction and cumulative SSB consumption increases risk in children. OBJECTIVES: The objective of the study was to estimate the relationship between age of introduction and cumulative SSB consumption with risk of obesity in 227 Mexican children. METHODS: SSB intake was measured every 6 months; age of introduction and cumulative consumption during the pre-school period were calculated. Height, weight, waist circumference, SSB intake and other relevant variables were measured at age 8-14 years and obesity defined using standard criteria. RESULTS: All participants were introduced to SSB before age 24 months and most (73%) before 12 months. Early SSB introduction (≤12 months) was not significantly associated with increased odds of obesity (odds ratio [OR] = 2.00, 95% confidence interval [CI]: 0.87, 4.59). However, children in the highest tertile of cumulative SSB consumption, compared with the lowest, had almost three times the odds of general (OR = 2.99, 95% CI: 1.27, 7.00) and abdominal (OR = 2.70, 95% CI: 1.03, 7.03) obesity at age 8-14 years. CONCLUSIONS: High SSB consumption increased the likelihood of obesity in 8-14-year-old children. Our results suggest that SSB intake should be delayed and excessive SSB consumption in pre-school period should be avoided.

Indirect lead exposure among children of radiator repair workers.

BACKGROUND: Secondary exposure to lead has been identified as a public health problem since the late 1940s; we investigate the risk of lead exposure among families of radiator repair workers. METHODS: A sample of the wives and children, aged 6 months to 6 years (exposed children) (n = 19), of radiator repair workers and a sample of children whose parents were not occupationally exposed to lead (non-exposed children) (n = 29) were matched for age and residence; their geometric mean blood lead levels are compared. Blood samples were obtained by the finger stick method and environmental dust samples by the wipe method; both were analyzed using a portable anodic stripping voltameter. RESULTS: Dust lead levels were significantly higher in the houses of exposed children (143.8 vs. 3.9 microg/g; P < 0.01). In crude analyses, the highest lead levels were observed among children whose fathers worked in home-based workshops (22.4 microg/dl)(n = 6). Children whose fathers worked in an external workshop (n = 13) also had high levels (14.2 microg/dl) (P < 0.01), while blood lead levels in non-exposed children were significantly lower (5.6 microg/dl)(P < 0.01). The observed differences remained significant after adjustment for age and gender. CONCLUSIONS: This study confirms that children of radiator repair workers are at increased risk of lead exposure and public health interventions are needed to protect them.

Multiple micronutrient supplementation increases the growth of Mexican infants.

BACKGROUND: The role of single micronutrient deficiencies in the etiology of growth retardation has recently gained attention. However, because multiple micronutrient deficiencies are common in children in developing countries, it is possible that more than one micronutrient may limit growth and, hence, the correction of a single deficiency may not be enough to improve growth substantially. OBJECTIVE: The objective was to evaluate the effect of multiple micronutrient supplementation on the growth of children aged 8-14 mo whose diets were poor in several micronutrients. DESIGN: Children were randomly assigned to 1 of 2 groups. One group received a multiple micronutrient supplement containing the recommended dietary allowance (RDA) or 1.5 times the RDA of vitamins A, D, E, K, C, B-1, B-6, B-12, riboflavin, niacin, biotin, folic acid, and pantothenic acid, and iron, zinc, iodine, copper, manganese, and selenium. The other group received a placebo. Supplements were administered 6 d/wk for an average of 12.2 mo. Body length was measured at baseline and monthly thereafter until the end of supplementation. RESULTS: Supplemented infants initially aged <12 mo had significantly greater length gains than did the placebo group, with a difference of 8.2 mm (length-for-age z score: 0.3) at the end of supplementation. In contrast, differences in length gains between the supplemented and placebo groups initially aged > or =12 mo were not significant. CONCLUSIONS: Micronutrient deficiencies limited the growth of the Mexican infants studied. Improving micronutrient intakes should be a component of interventions to promote growth in infants living in settings where micronutrient intakes are inadequate.

[Prevalence of asthma and other allergic diseases in school children from Juarez City, Chihuahua]. / Prevalencia de asma y otras enfermedades alérgicas en niños escolares de Ciudad Juárez, Chihuahua.

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.

Daily respiratory mortality and PM10 pollution in Mexico City: importance of considering place of death.

Significant associations have been reported between particles with a 50% cut-off aerodynamic diameter of 10 mm (PM10) and ozone ambient concentrations, and daily number of deaths from respiratory causes. The aim of the present study was to assess such associations among elderly (> or =65 yrs) residents of Mexico City. Ambient air pollution data were provided by the Metropolitan Monitoring Network. During the study period, the average daily PM10 ranged 23.4-175.3 microg x m(-3), and ozone 1 h daily maximums ranged 39.4-216.7 ppb. Information was compiled on the primary and underlying causes of death. The analyses were conducted separately according to place of death (within or out of a hospital unit) using time-series methodology. The total number of deaths from all respiratory causes and mortality for chronic obstructive pulmonary diseases (COPD) were significantly related to PM10 over different lags: an increase of 10 microg x m(-3) was related to a 2.9% (95% (CI): 0.9-4.9%) increase and to a 4.1% (95% CI: 1.3%-6.9%) increase with a 3-day lag when death occurred out of medical units, respectively. For deaths occurring in medical units, a longer lag and smaller risk estimate was observed. An interactive effect between PM10 and ozone was detected. This study confirms that there is an important impact of PM10 on respiratory morbidity among elderly subjects. It also indicates that accounting for primary and underlying causes of death, and considering place of death may reduce misclassification and provide more accurate estimates of the adverse impact of PM10 on mortality.

Risk factors for Giardia intestinalis infection in agricultural villages practicing wastewater irrigation in Mexico.

This study assessed the risk factors for Giardia intestinalis infection in an agricultural population in Mexico. Exposure groups included 2,257 individuals from households exposed to untreated wastewater, 2,147 from a group using the effluent from a series of reservoirs, and 2,344 from rain-fed agricultural villages. Stool samples were collected from 6,748 individuals. Wastewater samples were tested for fecal coliforms/100 ml and Giardia sp. cysts/L. Untreated wastewater samples contained 10(8) fecal coliforms/100 ml and up to 300 Giardia sp. cysts/L. Hydraulic retention (3-7 months) in the reservoirs, however, provided an improved effluent quality (10(1)-10(4) fecal coloforms/100 ml and < or = 5 Giardia sp. cysts/L). Children 1-14 years of age had the highest prevalence of infection (20%). Data showed marginal associations between storing drinking water in unprotected containers and lack of facilities for feces disposal and the risk of infection (odds ratios [ORs] = 1.76 and 1.19, 95% confidence intervals [CIs] = 0.95-3.23, and 0.97-1.45, respectively). Individuals purchasing vegetables at the city market had higher rates of infection than those buying at the village shop (OR = 2.49, 95% CI = 1.00-6.17). No excess risk was found in individuals exposed to untreated wastewater compared with controls (OR = 1.07, 95% CI = 0.84-1.36); the group using reservoir water was not different from the controls (OR = 1.22, 95% CI = 0.94-1.58). No risk from agricultural activities was detected (OR = 0.83). This pattern of infection may be addressed by primary health care and wastewater treatment.

[Relationship between emergency consultations for respiratory diseases and air pollution in Juarez City, Chihuahua]. / Relación entre consultas a urgencias por enfermedad respiratoria y contaminación atmosférica en Ciudad Juárez, Chihuahua.

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.

Call and recall for cervical cancer screening in a developing country: a randomised field trial.

A randomised field trial was used to assess Mexican women's response to a mailed invitation for a Papanicolaou test. A sample of 4,802 women, 20 to 64 years old, chosen at random from the Mexican Social Security Institute Register were randomly assigned to an intervention and to a control group. A letter of invitation and a reminder were sent to the intervention group. A letter was also sent to the control group at the end of the follow-up period (8.5 weeks) in order to compare the response among women who received a letter in both groups. Cumulative incidence and incidence rates were used to determine the response and the speed of response, respectively. The response among women who had received the letter was 33.5% (efficacy) in the intervention group, while 5.9% (p<0.001) in the control group attended a Papanicolaou test. For the total of women invited, the response was 20.1% (effectiveness) and 3.3% (p<0.001), respectively. The response was greater in rural areas (rural vs. urban/suburban; p = 0.002) and eldest women (50-64 vs. 20-49; p = 0. 02). The response rate was 7 times grater in the intervention than in the control group (RR = 7.1; 95% CI 5.4-9.4; p < 0.001). A mailed invitation to have a Papanicolaou test substantially increases attendance by women who receive it. A mailed reminder improves results. This strategy could be implemented in addition to the ones already in use, mainly among rural and elderly women.

Association between levels of fine particulate and emergency visits for pneumonia and other respiratory illnesses among children in Santiago, Chile.

Recent evidence has implicated the fine fraction of particulate as the major contributor to the increase in mortality and morbidity related to particulate ambient levels. We therefore evaluated the impact of daily variation of ambient PM2.5 and other pollutants on the number of daily respiratory-related emergency visits (REVs) to a large pediatric hospital of Santiago, Chile. The study was conducted from February 1995 to August 1996. Four monitoring stations from the network of Santiago provided air pollution data. The PM2.5 24-hr average ranged from 10 to 111 micrograms/m3 during September to April (warm months) and from 10 to 156 micrograms/m3 during May to August (cold months). Other contaminants (ozone (O3), nitrogen dioxide (NO2), and sulfur dioxide (SO2)) were, in general, low during the study period. The increase in REVs was significantly related to PM10 and PM2.5 ambient levels, with the relationship between PM2.5 levels and the number of REVs the stronger. During the cold months, an increase of 45 micrograms/m3 in the PM2.5 24-hr average was related to a 2.7% increase in the number of REVs (95% CI, 1.1-4.4%) with a two-day lag, and to an increase of 6.7% (95% CI, 1.7-12.0%) in the number of visits for pneumonia with a three-day lag. SO2 and NO2 were also related to REVs. We conclude that urban air pollutant mixture, particularly fine particulates, adversely affect the respiratory health of children residing in Santiago.

[Effect of environmental pollution on medical visits for respiratory infections in children in Mexico City]. / Efecto de la contaminación ambiental sobre las consultas por infecciones respiratorias en niños de la Ciudad de México.

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.