Queimadas de cana-de-a����car no Brasil: efeitos �� sa��de respirat��ria

O artigo objetivou atualizar as informa����es sobre a produ����o cient��fica referente aos efeitos da queima da cana-de-a����car �� sa��de respirat��ria, em vista da expans��o das planta����es de cana no Brasil e no estado de S��o Paulo. S��o comentados estudos publicados no per��odo de 1996-2006 que tratam de efeitos �� sa��de da queima da cana e/ou de poluentes atmosf��ricos produzidos pela queima. Os estudos sugerem que uma parcela da popula����o - sobretudo de idosos, crian��as e asm��ticos - tem sua sa��de agravada pela queima da cana-de-a����car, demandando atendimento dos servi��os de sa��de e assim onerando os servi��os de sa��de e suas fam��lias

Mecanismos de inflama����o br��nquica resultantes da exposi����o a factores ambientais

RESUMO Tratando-se a asma de uma doen��a respirat��ria, desde h�� v��rias d��cadas que tem sido abordada a hip��tese de que factores ambientais, nomeadamente os relacionados com a qualidade do ar inalado, possam contribuir para o seu agravamento. Para al��m dos aeroalergenos, outros factores ambientais como a polui����o atmosf��rica estar��o associados ��s doen��as respirat��rias. O ar respirado cont��m uma variedade de poluentes atmosf��ricos, provenientes quer de fontes naturais quer de origem antropog��nica, nomeadamente de actividades industriais, dom��sticas ou das emiss��es de ve��culos. Estes poluentes, tradicionalmente considerados como um problema de foro ambiental, t��m sido cada vez mais encarados como um problema de sa��de p��blica. Tamb��m a qualidade do ar interior, tem sido associada a queixas respirat��rias, n��o s�� em termos ocupacionais mas tamb��m em exposi����es dom��sticas. Dentro dos principais poluentes, encontramos a mat��ria particulada (como as PM10), o O3, NO2, e os compostos org��nicos vol��teis (COVs). Se �� verdade que os tr��s primeiros t��m como principais fontes de exposi����o a combust��o f��ssil associada aos ve��culos autom��veis, j�� os COVs (como o benzeno, tolueno, xileno, etilbenzeno e formalde��do) s��o poluentes mais caracter��sticos do ar interior. Os mecanismos fisiopatol��gicos subjacentes �� agress��o dos poluentes do ar n��o se encontram convenientemente esclarecidos. Pensa-se que ap��s a sua inala����o, induzam um grau crescente de stress oxidativo que ser�� respons��vel pelo desenvolvimento da inflama����o das vias a��reas. A progress��o do stress oxidativo e da inflama����o, associarse- ��o posteriormente a les��o local (pulmonar) e sist��mica. Neste trabalho pretendeu-se avaliar os efeitos da exposi����o individual a diversos poluentes, do ar exterior e interior, sobre as vias a��reas, recorrendo a par��metros funcionais, inflamat��rios e do estudo do stress oxidativo. Neste sentido, desenvolveu-se um estudo de painel na cidade de Viseu, em que foram acompanhadas durante 18 meses, 51 crian��as com hist��ria de sibil��ncia, identificadas pelo question��rio do estudo ISAAC. As crian��as foram avaliadas em quatro Visitas (quatro medidas repetidas), atrav��s de diversos exames, que inclu��ram execu����o de espirometria com broncodilata����o, medi����o ambulat��ria do PEF, medi����o de FENO e estudo do pH no condensado br��nquico do ar exalado. O estudo dos 8-isoprostanos no condensado br��nquico foi efectuado somente em duas Visitas, e o do doseamento de malonalde��do urin��rio somente na ��ltima Visita. Para al��m da avalia����o do grau de infesta����o de ��caros do p�� do colch��o, para cada crian��a foi calculado o valor de exposi����o individual a PM10, O3, NO2, benzeno, tolueno, xileno, etilbenzeno e formalde��do, atrav��s de uma complexa metodologia que envolveu t��cnicas de modela����o associadas a medi����es directas do ar interior (na casa e escola da crian��a) e do ar exterior. Para a an��lise de dados foram utilizadas equa����es de estima����o generalizadas com uma matriz de correla����o de trabalho uniforme, com excep����o do estudo das associa����es entre poluentes, 8-isoprostanos e malonalde��do. Verificou-se na an��lise multivari��vel a exist��ncia de uma associa����o entre o agravamento dos par��metros espirom��tricos e a exposi����o aumentada a PM10, NO2, benzeno, tolueno e etilbenzeno. Foram tamb��m encontradas associa����es entre diminui����o do pH do EBC e exposi����o crescente a PM10, NO2, benzeno e etilbenzeno e associa����es entre valores aumentados de FENO e exposi����o a etilbenzeno e tolueno. O benzeno, o tolueno e o etilbenzeno foram associados com maior recurso a broncodilatador nos 6 meses anteriores �� Visita e o tolueno com desloca����es ao servi��o de urg��ncia. Os resultados dos modelos de regress��o que inclu��ram o efeito do poluente ajustado para o grau de infesta����o de ��caros do p�� foram, de uma forma geral, id��nticos ao da an��lise multivari��vel anterior, com excep����o das associa����es para com o FENO. Nos modelos de exposi����o com dois poluentes, com o FEV1 como vari��vel resposta, somente o benzeno persistiu com significado estat��stico. No modelo com dois poluentes tendo o pH do EBC como vari��vel resposta, somente persistiram as PM10. Os 8-isoprostanos correlacionaram-se com alguns COVs, designadamente etilbenzeno, xileno, tolueno e benzeno. Os valores de malonalde��do urin��rio n��o se correlacionaram com os valores de poluentes. Verificou-se no entanto que de uma forma geral, e em particular mais uma vez para os COVs, as crian��as mais expostas a poluentes, apresentaram valores superiores de malonalde��do na urina. Verificou-se que os poluentes do ar em geral, e os COVs em particular, se associaram com uma deteriora����o das vias a��reas. A exposi����o crescente a poluentes associou-se n��o s�� com obstru����o br��nquica, mas tamb��m com FENO aumentado e maior acidez das vias a��reas. A exposi����o crescente a COVs correlacionou-se com um maior stress oxidativo das vias a��reas (medido pelos 8-isoprostanos). As crian��as com exposi����o superior a COVs apresentaram maiores valores de malonalde��do urin��rio. Este trabalho sugere uma associa����o entre exposi����o a poluentes, inflama����o das vias a��reas e stress oxidativo. Vem refor��ar o interesse dos poluentes do ar, nomeadamente os associados a ambientes interiores, frequentemente esquecidos e que poder��o ser explicativos do agravamento duma crian��a com sibil��ncia.-----------ABSTRACT: Asthma is a chronic respiratory disease that could be influenced by environmental factors, as allergens and air pollutants. The air breathed contains a diversity of air pollutants, both from natural or anthropogenic sources. Atmospheric pollution, traditionally considered an environmental problem, is nowadays looked as an important public health problem. Indoor air pollutants are also related with respiratory diseases, not only in terms of occupational exposures but also in domestic activities. Particulate matter (such as PM10), O3, NO2 and volatile organic compounds (VOCs) are the main air pollutants. The main source for PM10, O3, NO2 exposure is traffic exhaust while for VOCs (such as benzene, toluene, xylene, ethylbenzene and phormaldehyde) the main sources for exposure are located in indoor environments. The pathophysiologic mechanisms underlying the aggression of air pollutants are not properly understood. It is thought that after inhalation, air pollutants could induce oxidative stress, which would be responsible for airways inflammation. The progression of oxidative stress and airways inflammation, would contribute for the local and systemic effects of the air pollutants. The present study aimed to evaluate the effects of individual exposure to various pollutants over the airways, through lung function tests, inflammatory and oxidative stress biomarkers. In this sense, we developed a panel study in the city of Viseu, that included 51 children with a history of wheezing. Those children that were identified by the ISAAC questionnaire, were followed for 18 months. Children were assessed four times (four repeated measures) through the following tests: spirometry with bronchodilation test, PEF study, FENO evaluation and exhaled breath condensate pH measurement. 8-isoprostane in the exhaled breath condensate were also measured but only in two visits. Urinary malonaldehyde measurement was performed only in the last visit. Besides the assessment of the house dust mite infestation, we calculated for each child the value of individual exposure to a wide range of pollutants: PM10, O3, NO2, benzene, toluene, xylene, ethyl benzene and formaldehyde. This strategy used a complex methodology that included air pollution modelling techniques and direct measurements indoors (homes and schools) and outdoors. Generalized estimating equations with an exchangeable working correlation matrix were used for the analysis of the data. Exceptions were for the study of associations between air pollutants, malonaldehyde and 8-isoprostanes. In the multivariate analysis we found an association between worsening of spirometric outcomes and increased exposure to PM10, NO2, benzene, toluene and ethylbenzene. In the multivariate analysis we found also negative associations between EBC pH and exposure to PM10, NO2, benzene, ethylbenzene and positive associations between FENO and exposure to ethylbenzene and toluene. Benzene, toluene and ethylbenzene were associated with increased use of bronchodilator in the 6 months prior to the visit and toluene with emergency department visits. Results of the regression models that included also the effect of the pollutant adjusted for the degree of infestation to house dust mites, were identical to the previous models. Exceptions were for FENO associations. In the two-pollutant models, with the FEV1 as dependent variable, only benzene persisted with statistical significance. In the two pollutant model with pH of EBC as dependent variable, only PM10 persisted. 8-isoprostanes were well correlated with some VOCs, namely with ethylbenzene, xylene, toluene and benzene. Urinary malonaldehyde did not present any correlation with air pollutants exposure. However, those children more exposed to air pollutants (namely to VOCs), presented higher values of malonaldehyde. It was found that air pollutants in general, and namely VOCs, were associated with deterioration of the airways. The increased exposure to air pollutants was associated not only with airways obstruction, but also with increased FENO and higher acidity of the airways. The increased exposure to VOCs was correlated with increased airways oxidative stress (measured by 8-isoprostane). Children with higher levels of exposure to VOCs had higher values of urinary malonaldehyde. This study suggests a relation between air pollution, airways inflammation and oxidative stress. It suggests also that attention should be dedicated to air quality as air pollutants could cause airways deterioration.

Tr��fego veicular e mortalidade por doen��as do aparelho circulat��rio em homens adultos

OBJETIVO: Analisar a associa����o entre indicadores de exposi����o �� polui����o por tr��fego veicular e mortalidade por doen��as do aparelho circulat��rio em homens adultos. M��TODOS: Foram analisadas informa����es sobre vias e volume de tr��fego no ano de 2007 fornecidas pela companhia de engenharia de tr��fego local. Mortalidade por doen��as do aparelho circulat��rio no ano de 2005 entre homens ��� 40 anos foram obtidas do registro de mortalidade do Programa de Aprimoramento de Informa����es de Mortalidade do Munic��pio de S��o Paulo, SP. Dados socioecon��micos do Censo 2000 e informa����es sobre a localiza����o dos servi��os de sa��de tamb��m foram coletados. A exposi����o foi avaliada pela densidade de vias e volume de tr��fego para cada distrito administrativo. Foi calculada regress��o (�� = 5%) entre esses indicadores de exposi����o e as taxas de mortalidade padronizadas, ajustando os modelos para vari��veis socioecon��micas, n��mero de servi��os de sa��de nos distritos e autocorrela����o espacial. RESULTADOS: A correla����o entre densidade de vias e volume de tr��fego foi modesta (r�� = 0,28). Os distritos do centro apresentaram os maiores valores de densidade de vias. O modelo de regress��o espacial de densidade de vias indicou associa����o com mortalidade por doen��as do aparelho circulat��rio (p = 0,017). N��o se observou associa����o no modelo de volume de tr��fego. Em ambos os modelos ��� vias e volume de tr��fego (ve��culos leves/pesados) ��� a vari��vel socioecon��mica foi estatisticamente signi��� cante. CONCLUS��ES: A associa����o entre mortalidade por doen��as do aparelho circulat��rio e densidade de vias converge com a literatura e encoraja a realiza����o de mais estudos epidemiol��gicos em n��vel individual e com m��todos mais acurados de avalia����o da exposi����o.

A combined analysis of the short-term effects of photochemical air pollutants on mortality within the EMECAM project.

In recent years, some epidemiologic studies have attributed adverse effects of air pollutants on health not only to particles and sulfur dioxide but also to photochemical air pollutants (nitrogen dioxide and ozone). The effects are usually small, leading to some inconsistencies in the results of the studies. Furthermore, the different methodologic approaches of the studies used has made it difficult to derive generic conclusions. We provide here a quantitative summary of the short-term effects of photochemical air pollutants on mortality in seven Spanish cities involved in the EMECAM project, using generalized additive models from analyses of single and multiple pollutants. Nitrogen dioxide and ozone data were provided by seven EMECAM cities (Barcelona, Gij��n, Huelva, Madrid, Oviedo, Seville, and Valencia). Mortality indicators included daily total mortality from all causes excluding external causes, daily cardiovascular mortality, and daily respiratory mortality. Individual estimates, obtained from city-specific generalized additive Poisson autoregressive models, were combined by means of fixed effects models and, if significant heterogeneity among local estimates was found, also by random effects models. Significant positive associations were found between daily mortality (all causes and cardiovascular) and NO(2), once the rest of air pollutants were taken into account. A 10 microg/m(3) increase in the 24-hr average 1-day NO(2)level was associated with an increase in the daily number of deaths of 0.43% [95% confidence interval (CI), -0.003-0.86%] for all causes excluding external. In the case of significant relationships, relative risks for cause-specific mortality were nearly twice as much as that for total mortality for all the photochemical pollutants. Ozone was independently related only to cardiovascular daily mortality. No independent statistically significant relationship between photochemical air pollutants and respiratory mortality was found. The results in this study suggest that, given the present levels of photochemical pollutants, people living in Spanish cities are exposed to health risks derived from air pollution.

Combined Analysis of the Short-Term Effects of Photochemical Air Pollutants on Mortality within the EMECAM Project

In recent years, some epidemiologic studies have attributed adverse effects of air pollutants on health not only to particles and sulfur dioxide but also to photochemical air pollutants (nitrogen dioxide and ozone). The effects are usually small, leading to some inconsistencies in the results of the studies. Furthermore, the different methodologic approaches of the studies used has made it difficult to derive generic conclusions. We provide here a quantitative summary of the short-term effects of photochemical air pollutants on mortality in seven Spanish cities involved in the EMECAM project, using generalized additive models from analyses of single and multiple pollutants. Nitrogen dioxide and ozone data were provided by seven EMECAM cities (Barcelona, Gij��n, Huelva, Madrid, Oviedo, Seville, and Valencia). Mortality indicators included daily total mortality from all causes excluding external causes, daily cardiovascular mortality, and daily respiratory mortality. Individual estimates, obtained from city-specific generalized additive Poisson autoregressive models, were combined by means of fixed effects models and, if significant heterogeneity among local estimates was found, also by random effects models. Significant positive associations were found between daily mortality (all causes and cardiovascular) and NO2, once the rest of air pollutants were taken into account. A 10 ��g/m3 increase in the 24-hr average 1-day NO2 level was associated with an increase in the daily number of deaths of 0.43% [95% confidence interval(CI), ���0.003���0.86%] for all causes excluding external. In the case of significant relationships, relative risks for cause-specific mortality were nearly twice as much as that for total mortality for all the photochemical pollutants. Ozone was independently related only to cardiovascular daily mortality. No independent statistically significant relationship between photochemical air pollutants and respiratory mortality was found. The results in this study suggest that, given the present levels of photochemical pollutants, people living in Spanish cities are exposed to health risks derived from air pollution

The effects of chronic exposure to traffic derived air pollution on the ocular surface

Objectives: The purpose of this study was to explore the clinical relevance of chronic exposure to ambient levels of traffic derived air pollution on the ocular surface. Methods: A panel study involving 55 volunteers was carried out in Sao Paulo, Brazil. We measured the mean individual levels of nitrogen dioxide (NO(2)) exposure for 7 days. All subjects answered the Ocular Symptom Disease Index (OSDI) and a symptoms inventory. Subsequently, subjects underwent Schirmer I test, biomicroscopy, vital staining and tear breakup time (TOUT) assessment. Subject`s mean daily exposure to NO(2) was categorized in quartiles. Statistical analysis was performed using one-way ANOVA, Tukey HSD and Chi-Square tests. Results: A dose-response pattern was detected between OSDI scores and NO(2) quartiles (p < 0.05). There was a significant association between NO(2) quartiles and reported ocular irritation (X(2) = 9.2, p < 0.05) and a significant negative association between TBUT and NO(2) exposure (p < 0.05, R = -0.316. Spearman`s correlation). There was a significant increase in the frequency of meibomitis in subjects exposed to higher levels of NO(2) (p < 0.05). Conclusions: Subjects exposed to higher levels of traffic derived air pollution reported more ocular discomfort symptoms and presented greater tear film instability, suggesting that the ocular discomfort symptoms and tear breakup time could be used as convenient bioindicators of the adverse health effects of traffic derived air pollution exposure. (C) 2010 Elsevier Inc. All rights reserved.

Air pollution effects on myocardial infarction

OBJECTIVE: Myocardial infarction is an acute and severe cardiovascular disease that generally leads to patient admissions to intensive care units and few cases are initially admitted to infirmaries. The objective of the study was to assess whether estimates of air pollution effects on myocardial infarction morbidity are modified by the source of health information. METHODS: The study was carried out in hospitals of the Brazilian Health System in the city of S��o Paulo, Southern Brazil. A time series study (1998-1999) was performed using two outcomes: infarction admissions to infirmaries and to intensive care units, both for people older than 64 years of age. Generalized linear models controlling for seasonality (long and short-term trends) and weather were used. The eight-day cumulative effects of air pollutants were assessed using third degree polynomial distributed lag models. RESULTS: Almost 70% of daily hospital admissions due to myocardial infarction were to infirmaries. Despite that, the effects of air pollutants on infarction were higher for intensive care units admissions. All pollutants were positively associated with the study outcomes but SO2 presented the strongest statistically significant association. An interquartile range increase on SO2 concentration was associated with increases of 13% (95% CI: 6-19) and 8% (95% CI: 2-13) of intensive care units and infirmary infarction admissions, respectively. CONCLUSIONS: It may be assumed there is a misclassification of myocardial infarction admissions to infirmaries leading to overestimation. Also, despite the absolute number of events, admissions to intensive care units data provides a more adequate estimate of the magnitude of air pollution effects on infarction admissions.

The effects of air pollution on cardiovascular diseases: lag structures

OBJECTIVE: To assess the lag structure between air pollution exposure and elderly cardiovascular diseases hospital admissions, by gender. METHODS: Health data of people aged 64 years or older was stratified by gender in S��o Paulo city, Southeastern Brazil, from 1996 to 2001. Daily levels of air pollutants (CO, PM10, O3, NO2, and SO2) , minimum temperature, and relative humidity were also analyzed. It were fitted generalized additive Poisson regressions and used constrained distributed lag models adjusted for long time trend, weekdays, weather and holidays to assess the lagged effects of air pollutants on hospital admissions up to 20 days after exposure. RESULTS: Interquartile range increases in PM10 (26.21 mug/m��) and SO2 (10.73 mug/m��) were associated with 3.17% (95% CI: 2.09-4.25) increase in congestive heart failure and 0.89% (95% CI: 0.18-1.61) increase in total cardiovascular diseases at lag 0, respectively. Effects were higher among female group for most of the analyzed outcomes. Effects of air pollutants for different outcomes and gender groups were predominately acute and some "harvesting" were found. CONLUSIONS: The results show that cardiovascular diseases in S��o Paulo are strongly affected by air pollution.

Long-term effects of air pollutants: in canine species /

Mode of access: Internet.

Principal components and generalized linear modeling in the correlation between hospital admissions and air pollution

OBJECTIVE To analyze the association between concentrations of air pollutants and admissions for respiratory causes in children. METHODS Ecological time series study. Daily figures for hospital admissions of children aged < 6, and daily concentrations of air pollutants (PM10, SO2, NO2, O3 and CO) were analyzed in the Regi&#227;o da Grande Vit&#243;ria, ES, Southeastern Brazil, from January 2005 to December 2010. For statistical analysis, two techniques were combined: Poisson regression with generalized additive models and principal model component analysis. Those analysis techniques complemented each other and provided more significant estimates in the estimation of relative risk. The models were adjusted for temporal trend, seasonality, day of the week, meteorological factors and autocorrelation. In the final adjustment of the model, it was necessary to include models of the Autoregressive Moving Average Models (p, q) type in the residuals in order to eliminate the autocorrelation structures present in the components. RESULTS For every 10:49 &#956;g/m3 increase (interquartile range) in levels of the pollutant PM10 there was a 3.0% increase in the relative risk estimated using the generalized additive model analysis of main components-seasonal autoregressive &#8211; while in the usual generalized additive model, the estimate was 2.0%. CONCLUSIONS Compared to the usual generalized additive model, in general, the proposed aspect of generalized additive model &#8722; principal component analysis, showed better results in estimating relative risk and quality of fit.

Air pollution and its impacts on health in Vitoria, Espirito Santo, Brazil

ABSTRACT OBJECTIVE To analyze the impact of air pollution on respiratory and cardiovascular morbidity of children and adults in the city of Vitoria, state of Espirito Santo. METHODS A study was carried out using time-series models via Poisson regression from hospitalization and pollutant data in Vitoria, ES, Southeastern Brazil, from 2001 to 2006. Fine particulate matter (PM10), sulfur dioxide (SO2), and ozone (O3) were tested as independent variables in simple and cumulative lags of up to five days. Temperature, humidity and variables indicating weekdays and city holidays were added as control variables in the models. RESULTS For each increment of 10 ��g/m3 of the pollutants PM10, SO2, and O3, the percentage of relative risk (%RR) for hospitalizations due to total respiratory diseases increased 9.67 (95%CI 11.84-7.54), 6.98 (95%CI 9.98-4.17) and 1.93 (95%CI 2.95-0.93), respectively. We found %RR = 6.60 (95%CI 9.53-3.75), %RR = 5.19 (95%CI 9.01-1.5), and %RR = 3.68 (95%CI 5.07-2.31) for respiratory diseases in children under the age of five years for PM10, SO2, and O3, respectively. Cardiovascular diseases showed a significant relationship with O3, with %RR = 2.11 (95%CI 3.18-1.06). CONCLUSIONS Respiratory diseases presented a stronger and more consistent relationship with the pollutants researched in Vitoria. A better dose-response relationship was observed when using cumulative lags in polynomial distributed lag models.

Case-Crossover Analysis of Air Pollution Health Effects: A Systematic Review of Methodology and Application

Case-crossover is one of the most used designs for analyzing the health-related effects of air pollution. Nevertheless, no one has reviewed its application and methodology in this context. Objective: We conducted a systematic review of case-crossover (CCO) designs used to study the relationship between air pollution and morbidity and mortality, from the standpoint of methodology and application.Data sources and extraction: A search was made of the MEDLINE and EMBASE databases.Reports were classified as methodologic or applied. From the latter, the following information was extracted: author, study location, year, type of population (general or patients), dependent variable(s), independent variable(s), type of CCO design, and whether effect modification was analyzed for variables at the individual level. Data synthesis: The review covered 105 reports that fulfilled the inclusion criteria. Of these, 24 addressed methodological aspects, and the remainder involved the design���s application. In the methodological reports, the designs that yielded the best results in simulation were symmetric bidirectional CCO and time-stratified CCO. Furthermore, we observed an increase across time in the use of certain CCO designs, mainly symmetric bidirectional and time-stratified CCO. The dependent variables most frequently analyzed were those relating to hospital morbidity; the pollutants most often studied were those linked to particulate matter. Among the CCO-application reports, 13.6% studied effect modification for variables at the individual level.Conclusions: The use of CCO designs has undergone considerable growth; the most widely used designs were those that yielded better results in simulation studies: symmetric bidirectional and time-stratified CCO. However, the advantages of CCO as a method of analysis of variables at the individual level are put to little use

Leaf contents of nitrogen and phenolic compounds and their bearing with the herbivore damage to Tibouchina pulchra Cogn. (Melastomataceae), under the influence of air pollutants from industries of Cubat��o, S��o Paulo

The Atlantic Forest on the slopes of Serra do Mar around Cubat��o (S��o Paulo, Brazil) has been affected by massive emissions of pollutants from the local growing industrial complex. The effects of air pollution on the amounts of leaf nitrogen, total soluble phenols and total tannins of Tibouchina pulchra Cogn., a common species in the area of Cubat��o, were investigated, as well as the possible influence of the altered parameters on the leaf area damaged by herbivores. Fully expanded leaves were collected at two sites: the valley of Pil��es river (VP), characterized by a vegetation virtually not affected by air pollution and taken as a reference; and valley of Mogi river (VM), close to the core region of the industrial complex, and severely affected by air pollution. No differences were observed for any parameters between samples collected in the summer and winter in both sites. On the other hand, compared to VP, individuals growing in VM presented higher amounts of nitrogen and lower amounts of total soluble phenols and total tannins, as well as higher percentages of galls per leaf and higher leaf area lost to herbivores. Regression analysis revealed that the increase in leaf area lost to herbivores can be explained by the increase of the content of nitrogen and decrease in the contents of total soluble phenols and total tannins. Although significant, the coefficients of explanation found were low for all analyses, suggesting that other biotic or abiotic factors are likely to influence leaf attack by herbivores.

Case-Crossover Analysis of Air Pollution Health Effects: A Systematic Review of Methodology and Application

Case-crossover is one of the most used designs for analyzing the health-related effects of air pollution. Nevertheless, no one has reviewed its application and methodology in this context. Objective: We conducted a systematic review of case-crossover (CCO) designs used to study the relationship between air pollution and morbidity and mortality, from the standpoint of methodology and application.Data sources and extraction: A search was made of the MEDLINE and EMBASE databases.Reports were classified as methodologic or applied. From the latter, the following information was extracted: author, study location, year, type of population (general or patients), dependent variable(s), independent variable(s), type of CCO design, and whether effect modification was analyzed for variables at the individual level. Data synthesis: The review covered 105 reports that fulfilled the inclusion criteria. Of these, 24 addressed methodological aspects, and the remainder involved the design���s application. In the methodological reports, the designs that yielded the best results in simulation were symmetric bidirectional CCO and time-stratified CCO. Furthermore, we observed an increase across time in the use of certain CCO designs, mainly symmetric bidirectional and time-stratified CCO. The dependent variables most frequently analyzed were those relating to hospital morbidity; the pollutants most often studied were those linked to particulate matter. Among the CCO-application reports, 13.6% studied effect modification for variables at the individual level.Conclusions: The use of CCO designs has undergone considerable growth; the most widely used designs were those that yielded better results in simulation studies: symmetric bidirectional and time-stratified CCO. However, the advantages of CCO as a method of analysis of variables at the individual level are put to little use

Determining associations and assessing methodological issues in a case-control study of hazardous air pollutants and neural tube defects

Recent studies have reported positive associations between maternal exposures to air pollutants and several adverse birth outcomes. However, there have been no assessments of the association between environmental hazardous air pollutants (HAPs) such as benzene, toluene, ethylbenzene, and xylene (BTEX) and neural tube defects (NTDs) a common and serious group of congenital malformations. Before examining this association, two important methodological questions must be addressed: (1) is maternal residential movement likely to result in exposure misclassification and (2) is it appropriate to lump defects of the neural tube, such as anencephaly and spina bifida, into a composite disease endpoint (i.e., NTDs). ^ Data from the National Birth Defects Prevention Study and Texas Birth Defects Registry were used to: (1) assess the extent to which change of residence may result in exposure misclassification when exposure is based on the address at delivery; (2) formally assess heterogeneity of the associations between known risk factors for NTDs, using polytomous logistic regression; and (3) conduct a case-control study assessing the association between ambient air levels of BTEX and the risk of NTDs among offspring. ^ Regarding maternal residential mobility, this study suggests address at delivery was not significantly different from using address at conception when assigning quartile of benzene exposure (OR 1.0, 95% CI 0.9, 1.3). On the question of effect heterogeneity among NTDs, the effect estimates for infant sex P = 0.017), maternal body mass index P = 0.016), and folate supplementation P = 0.050) were significantly different for anencephaly and spina bifida, suggesting it is often more appropriate to assess potential risk factors among subgroups of NTDs. For the main study question on the association between environmental HAPs and NTDs, mothers who have offspring with isolated spina bifida are 2.4 times likely to live in areas with the highest benzene levels (95% CI 1.1, 5.0). However, no other significant associations were observed.^ This project is the first to include not only an assessment of the relationship between environmental levels of BTEX and NTDs, but also two separate studies addressing important methodological issues associated with this question. Our results contribute to the growing body of evidence regarding air pollutant exposure and adverse birth outcomes. ^