Effects of temperature and air pollutants on cardiovascular and respiratory diseases for males and females older than 65 years of age in Tokyo, July and August 1980-1995

We studied exposures to higher daily maximum temperatures and concentrations of air pollutants in Tokyo during the summer months of July and August from 1980 to 1995 and their effects on hospital emergency transports for cardiovascular and respiratory diseases for males and females > 65 years of age. Cardiovascular diseases were angina, cardiac insufficiency, hypertension, and myocardial infarction. Respiratory diseases were asthma, acute and chronic bronchitis, and pneumonia. Except for pneumonia, daily maximum temperatures were not associated with hospital emergency transports. Increasing daily maximum temperatures, however, were associated with decreased hospital emergency transports for hypertension. Concentrations of nitrogen dioxide or particulate matter < or = 10 microm, however, were associated with daily hospital emergency transports for angina, cardiac insufficiency, myocardial infarction, asthma, acute and chronic bronchitis, and pneumonia. For cardiac insufficiency, hypertension, myocardial infarction, asthma, chronic bronchitis, and pneumonia, the expected daily number of emergency transports per million were greater for males than for females. For angina and acute bronchitis, there were no differences for the expected daily numbers of emergency transports per million between males and females.     

Association of cardiovascular risk factors with the different presentations of acute coronary syndrome

OBJECTIVE:

to identify the relationship between different presentations of acute coronary syndrome and cardiovascular risk factors among hospitalized individuals.

METHOD:

cross-sectional study performed in a teaching hospital in São Paulo, in the State of São Paulo (SP). Socio-demographic, clinical and anthropometric data of 150 individuals hospitalized due to acute coronary syndrome were collected through interviews and review of clinical charts. Association between these data and the presentation of the syndrome were investigated.

RESULTS:

there was a predominance of ST segment elevation acute myocardial infarction. There was significant association of systemic hypertension with unstable angina and high values of low density lipoprotein with infarction, without influence from socio-demographic characteristics.

CONCLUSION:

arterial hypertension and high levels of low-density lipoprotein were associated with different presentations of coronary syndrome. The results can provide support for health professionals for secondary prevention programs aimed at behavioural changing.     

Association between air pollution and intrauterine mortality in São Paulo, Brazil.

The associations among daily counts of intrauterine mortality and pollutant concentrations (NO2, SO2, CO, O3, and particulate matter (3/4)10 microm) were investigated for the period ranging from January 1991 to December 1992 in the city of São Paulo, Brazil. We used Poisson regression techniques, adjusted for season and weather. The association between intrauterine mortality and air pollution was strong for NO2 (coefficient = 0.0013/ microg/m3; p<0.01) but lesser for SO2 (coefficient = 0.0005/ microg/m3; p<0.10) and CO (coefficient = 0.0223/ppm; p<0.10). A significant association was observed when an index that combined these three pollutants was considered in the models instead of considering each pollutant individually (p<0.01). These associations exhibited a short time lag, not over 5 days. In addition, some evidence of fetal exposure to air pollution was obtained by disclosing a significant association between the levels of carboxyhemoglobin of blood sampled from the umbilical cord and ambient CO levels in children delivered by nonsmoking pregnant women in the period from May to July 1995. Our results suggest that air pollution in São Paulo may promote adverse health effects on fetuses.     

Air pollution and respiratory illness of children in São Paulo, Brazil

This investigation reports the association between air pollution and paediatric respiratory emergency visits in São Paulo, Brazil, the largest city in South America. Daily records of emergency visits were obtained from the Children's Institute of the University of São Paulo for the period from May 1991 to April 1993. Visits were classified as respiratory and non-respiratory causes. Respiratory visits were further divided into three categories: upper respiratory illness, lower respiratory illness and wheezing. Daily records of SO₂, CO, particulate matter (PM₁₀), O₃ and NO₂ concentrations were obtained from the State Air Pollution Controlling Agency of São Paulo. Associations between respiratory emergency visits and air pollution were assessed by simple comparative statistics, simple correlation analysis and by estimating a variety of regression models. Significant associations between the increase of respiratory emergency visits and air pollution were observed. The most robust associations were observed with PM₁₀, and to a lesser extent with O₃. These associations were stable across different model specifications and several controlling variables. A significant increase in the counts of respiratory emergency visits – more than 20%– was observed on the most polluted days, indicating that air pollution is a substantial paediatric health concern in São Paulo.     

Sediment-contact fish embryo toxicity assay with Danio rerio to assess particle-bound pollutants in the Tietê River Basin (São Paulo, Brazil)

The Tietê River and its tributary Pinheiros River receive a highly complex organic and inorganic pollutants load from sanitary sewage and industrial sources, as well as agricultural and agroindustrial activities. The aim of the present study was to evaluate the embryotoxic and teratogenic effects of sediments from selected locations in the Tietê River Basin by means of the sediment contact embryo toxicity assay with Danio rerio, in order to provide a comprehensive and realistic insight into the bioavailable hazard potential of these sediment samples. Lethal and sub-lethal effects were recorded, and high embryo toxicity could be found in the samples not only in the vicinity of the megacity São Paulo (Billings reservoir and Pinheiros River samples), but also downstream (in the reservoirs Barra Bonita, Promissão and Três Irmãos). Results confirm that most toxicity is due to the discharges of the metropolitan area of São Paulo. However, they also indicate additional sources of pollutants along the river course, probably from industrial, agricultural and agroindustrial residues, which contribute to the degradation of each area. The sediment contact fish embryo test showed to be powerful tool to detect embryo toxicity in sediments, not only by being a sensitive method, but also for taking into account bioavailability. This test provides an ecological highly realistic and relevant exposure scenario, and should therefore be added in ecotoxicological sediment quality assessments.     

Air pollution and ED visits for asthma in Australian children: a case-crossover analysis

OBJECTIVE: We aimed to determine the effects of ambient air pollutants on emergency department (ED) visits for asthma in children. METHODS: We obtained routinely collected ED visit data for asthma (ICD9 493) and air pollution (PM(10), PM(2.5), O(3), NO(2), CO and SO(2)) and meteorological data for metropolitan Sydney for 1997-2001. We used the time stratified case-crossover design and conditional logistic regression to model the association between air pollutants and ED visits for four age-groups (1-4, 5-9, 10-14 and 1-14 years). Estimated relative risks for asthma ED visits were calculated for an exposure corresponding to the inter-quartile range in pollutant level. We included same day average temperature, same day relative humidity, daily temperature range, school holidays and public holidays in all models. RESULTS: Associations between ambient air pollutants and ED visits for asthma in children were most consistent for all six air pollutants in the 1-4 years age-group, for particulates and CO in the 5-9 years age-group and for CO in the 10-14 years age-group. The greatest effects were most consistently observed for lag 0 and effects were greater in the warm months for particulates, O(3) and NO(2). In two pollutant models, effect sizes were generally smaller compared to those derived from single pollutant models. CONCLUSION: We observed the effects of ambient air pollutants on ED attendances for asthma in a city where the ambient concentrations of air pollutants are relatively low.     

Air pollution and emergency room visits due to chronic lower respiratory diseases in the elderly: an ecological time-series study in São Paulo,Brazil

The objective of this study was to investigate the effect of daily air pollution levels (carbon monoxide, nitrogen dioxide, ozone, sulfur dioxide, and particulate matter with an aerodynamic profile < or = 10 microns) on morbidity by using the daily number of emergency room visits due to chronic lower respiratory disease (CLRD) in people older than 64 years of age in the city of S?o Paulo, Brazil, from 1996 to 1998. Generalized additive Poisson regression models adjusted for long-time trend and weather (nonparametric functions), weekdays (dummy variable), and daily number of nonrespiratory admissions were adopted. Ozone and sulfur dioxide were the pollutants statistically associated with CLRD visits. Interquartile range increases in the 6-day moving average of sulfur dioxide (11.82 micrograms/m3) and in the 4-day moving average of ozone(35.87 micrograms/m3) increased CLRD emergency room visits in 18% and 14%, respectively. These results reinforce the idea that air pollution may promote adverse health effects in the elderly.     

Daily time series for cardiovascular hospital admissions and previous day's air pollution in London, UK.

OBJECTIVE: To test for a significant association between air pollution and emergency hospital admissions for circulatory diseases (international classification of diseases-9 390-459) in London, England, that would be consistent with a causal effect of pollution on the previous day. METHODS: Long term concurrent trends, temperature, humidity, day of the week, influenza epidemic of 1989, and cyclical covariations with periodicity > 20 days in daily measures of pollution and admissions for 1987-94 were allowed for. RESULTS: There were 373556 admissions. No association was found between O3 and circulatory diseases. Four other pollutants were associated with acute myocardial infarction and circulatory diseases combined. P values and attributable cases (95% confidence intervals) for acute myocardial infarction were: black smoke P = 0.003, 2.5% (0.8% to 4.3%); NO2 P = 0.002, 2.7% (0.8% to 4.6%); CO P = 0.001, 2.1% (0.7% to 3.5%); and SO2 P = 0.0006, 1.7% (0.7% to 2.6%). There were also associations between black smoke and angina (P = 0.02), NO2 and arrhythmia (P = 0.04), and CO and other circulatory diseases (P = 0.004), but none with heart failure. Acute myocardial infarction was the only diagnosis for which there were significant associations with and without adjustment for cyclical terms. The associations with acute myocardial infarction were significant only in the cool season. CONCLUSION: Population data were consistent with 1 in 50 heart attacks currently presenting at London hospitals being triggered by outdoor air pollution. Further research is now needed to investigate whether background concentrations of black smoke, NO2, CO, and SO2 are a preventable cause of myocardial infarction. These results, if applied to all myocardial infarctions in the United Kingdom, indicate a potential saving of 6000 heart attacks a year.     

Measles,killer of millions in developing countries: strategy for rapid elimination and continuing control

Measles, which is still killing about two million children a year in poor countries, was mostly eliminated within two to three months after the conclusion of a special, national mass vaccination campaign in which all children of a selected age group received measles vaccine subcutaneously during a period of days to months, regardless of a history of previous vaccination or measles. This strategy was tested in the Dominican Republic in 1985, in Cuba in 1986–87, and in the State of São Paulo, Brazil May 11 – June 10, 1987. Subsequent control was maintained by different procedures in the three states.A simple, rapid indirect immunoflueorescent test for IgM measles antibody, used in Greater São Paulo, was more efficient in confirming concurrent infection with measles virus than the hemagglutination inhibition test for IgG antibody, and only one blood specimen taken during the course of the rash was needed to confirm the etiologic diagnosis in 97.5% of 240 cases confirmed by IgM. In Greater São Paulo and Cuba, it was found that over 90% of the small number of suspect measles cases reported during the first year after the mass campaign, were not caused by measles virus.The cost of disposable syringes and needles in the State of São Paulo, where 8,565,230 children were vaccinated in 10,527 centers in 30 days, was U.S. $2,057,753 or 63% of the total. Immunization by aerosol could have vaccinated this number of children more easily and effectively in one day if each of the vaccination centers had been supplied with one plastic foot or hand pressure pump and nebulizer at a cost of only about U.S. $300,000.The work reported here was begun in 1984 at the Fogarty International Center for Advanced Study in the Health Sciences, National Institutes of Health, Bethesda, Maryland, and, after retirement at age 80 in 1986, was continued at home and in the Dominican Republic, Cuba, and São Paulo, Brazil.     

The effects of air pollution on hospitalizations for cardiovascular disease in elderly people in Australian and New Zealand cities

OBJECTIVE: The goal of this study was to estimate the associations between outdoor air pollution and cardiovascular hospital admissions for the elderly. DESIGN: Associations were assessed using the case-crossover method for seven cities: Auckland and Christchurch, New Zealand; and Brisbane, Canberra, Melbourne, Perth, and Sydney Australia. Results were combined across cities using a random-effects meta-analysis and stratified for two adult age groups: 15-64 years and >/= 65 years of age (elderly). Pollutants considered were nitrogen dioxide, carbon monoxide, daily measures of particulate matter (PM) and ozone. Where multiple pollutant associations were found, a matched case-control analysis was used to identify the most consistent association. RESULTS: In the elderly, all pollutants except O3 were significantly associated with five categories of cardiovascular disease admissions. No associations were found for arrhythmia and stroke. For a 0.9-ppm increase in CO, there were significant increases in elderly hospital admissions for total cardiovascular disease (2.2%) , all cardiac disease (2.8%), cardiac failure (6.0%), ischemic heart disease (2.3%), and myocardial infarction (2.9%). There was some heterogeneity between cities, possibly due to differences in humidity and the percentage of elderly people. In matched analyses, CO had the most consistent association. CONCLUSIONS: The results suggest that air pollution arising from common emission sources for CO, NO2, and PM (e.g., motor vehicle exhausts) has significant associations with adult cardiovascular hospital admissions, especially in the elderly, at air pollution concentrations below normal health guidelines. Relevance to clinical and professional practice: Elderly populations in Australia need to be protected from air pollution arising from outdoor sources to reduce cardiovascular disease.     

Multipollutant modeling issues in a study of ambient air quality and emergency department visits in Atlanta

Multipollutant models are frequently used to differentiate roles of multiple pollutants in epidemiologic studies of ambient air pollution. In the presence of differing levels of measurement error across pollutants under consideration, however, they can be biased and as misleading as single-pollutant models. Their appropriate interpretation depends on the relationships among the pollutant measurements and the outcomes in question. In situations where two or more pollutant variables may be acting as surrogates for the etiologic agent(s), multipollutant models can help identify the best surrogate, but the risk estimates may be influenced by inclusion of a second variable that is not itself an independent risk factor for the outcome in question. In this paper, these issues will be illustrated in the context of an ongoing study of emergency visits in Atlanta. Emergency department visits from 41 of 42 hospitals serving the 20-county Atlanta metropolitan area for the period 1993-2004 (n=10,206,389 visits) were studied in relation to ambient pollutant levels, including speciated particle measurements from an intensive monitoring campaign at a downtown station starting in 1998. Relative to our earlier publications, reporting results through 2000, the period for which the speciated data are available is now tripled (6 years in length). Poisson generalized linear models were used to examine outcome counts in relation to 3-day moving average concentrations of pollutants of a priori interest (ozone, nitrogen dioxide, carbon monoxide, sulfur dioxide, oxygenated hydrocarbons, PM10, coarse PM, PM2.5, and the following components of PM2.5: elemental carbon, organic carbon, sulfate, and water-soluble transition metals). In the present analysis, we report results for two outcome groups: a respiratory outcomes group and a cardiovascular outcomes group. For cardiovascular visits, associations were observed with CO, NO2, and PM2.5 elemental carbon and organic carbon. In multipollutant models, CO was the strongest predictor. For respiratory visits, associations were observed with ozone, PM10, CO, and NO2 in single-pollutant models. In multipollutant models, PM10 and ozone persisted as predictors, with ozone the stronger predictor. Caveats and considerations in interpreting the multipollutant model results are discussed.     

空气污染物与绿化环境暴露水平对心肌梗塞死亡交互作用的病例交叉研究

目的 探索空气污染物与绿化暴露水平对心梗死亡的发生所产生的交互作用。方法 主要收集天津市2017—2019年因心梗死亡的个案病例,估计每名病例环境因素的暴露水平,采用条件logistic回归模型,分析空气污染物与绿化暴露水平对心梗死亡的发生所产生的交互作用。结果 在不同的季节,空气污染物浓度、气象因素和绿化环境暴露水平存在着差异（P＜0.001）。在单污染物模型中,每升高10 μg/m3的NO2（lag2期）,可使心梗死亡发生的风险升高0.4%（OR = 1.004,95%CI:1.000～1.008）。在多污染物模型中,每升高10 μg/m3的NO2（lag2期）、PM2.5（lag2期）和PM10（lag6期）,可使心梗死亡发生的风险升高1.1%（OR = 1.011,95%CI:1.005～1.018）、0.4%（OR = 1.004,95%CI:1～1.008）和0.3%（OR = 1.003,95%CI: 1.000～1.006）。对于滞后期lag1、lag2、lag6和lag7的暴露水平来说,颗粒污染物［可入肺颗粒物（PM1）、PM2.5 和PM10］与绿化环境暴露水平对心梗死亡的发生具有拮抗作用。结论 绿化环境可以起到降低颗粒污染物升高心梗死亡风险的作用,为指导人们有效的防护空气污染的危害,减轻颗粒污染物对心梗以及其他心血管疾病的发生和死亡提供依据。     

Ambient air pollution and cardiovascular emergency department visits

BACKGROUND: Despite evidence supporting an association between ambient air pollutants and cardiovascular disease (CVD), the roles of the physicochemical components of particulate matter (PM) and copollutants are not fully understood. This time-series study examined the relation between ambient air pollution and cardiovascular conditions using ambient air quality data and emergency department visit data in Atlanta, Georgia, from January 1, 1993, to August 31, 2000. METHODS: Outcome data on 4,407,535 emergency department visits were compiled from 31 hospitals in Atlanta. The air quality data included measurements of criteria pollutants for the entire study period, as well as detailed measurements of mass concentrations for the fine and coarse fractions of PM and several physical and chemical characteristics of PM for the final 25 months of the study. Emergency department visits for CVD and for cardiovascular subgroups were assessed in relation to daily measures of air pollutants using Poisson generalized linear models controlling for long-term temporal trends and meteorologic conditions with cubic splines. RESULTS: Using an a priori 3-day moving average in single-pollutant models, CVD visits were associated with NO2, CO, PM2.5, organic carbon, elemental carbon, and oxygenated hydrocarbons. Secondary analyses suggested that these associations tended to be strongest with same-day pollution levels. CONCLUSIONS: These findings provide evidence for an association between CVD visits and several correlated pollutants, including gases, PM2.5, and PM2.5 components.     

Air pollution and hospitalization due to angina pectoris in Tehran, Iran: a time-series study

BACKGROUND: Health effects of air pollution have been studied in many different parts of the world. Although a fairly large number of studies have explored the cardiovascular impacts of air pollution, because of its unique location we studied the association between air pollutants and hospital admissions due to angina pectoris in Tehran for the first time. METHODS: This is a retrospective time-series study. The variables of the study include the levels of five air pollutants-nitrogen dioxide (NO(2)), carbon monoxide (CO), ozone (O(3)), sulfur dioxide (SO(2)), and particulate matter <10 microm in aerodynamic diameter (PM(10))-as independent variables; daily hospitalizations due to angina pectoris in 25 academic hospitals in Tehran as the dependent variable; and mean daily temperature and humidity, seasonality, time trend, and day of the week as potential confounders. All variables were measured during a 5-year period from 21 March 1996 to 20 March 2001. The data of mean daily levels of NO(2), CO, O(3), SO(2), and PM(10) were collected from one of the stations of Tehran's Air Quality Control Corp. Data were analyzed using Poisson regression models. Relative risks of angina pectoris admissions were calculated for an increase in 1mg/m(3) for CO and 10 microg/m(3) for the other pollutants. RESULTS: Daily admissions due to angina pectoris were significantly related to the CO level, after controlling for confounder effects. Each unit increase in the CO level caused a 1.00934 increase in the number of admissions (95% CI, 1.00359--1.01512). This association was verified with a lag of 1 day. There was no significant association between the other air pollutants and the number of daily admission due to angina pectoris. CONCLUSIONS: We found that with increasing levels of the pollutant CO, the number of admissions due to cardiac angina rose. Ischemic heart disease is the leading cause of death in Iran. Air pollution control will reduce the number of this preventable disease and resulting deaths.     

银川市空气污染物与心脑血管疾病院前急救的关联性分析

目的 探讨银川市空气污染物与心脑血管疾病院前急救之间的关联。方法 收集2018年1月1日—2020年12月31日银川市人群心脑血管疾病院前急救资料、大气污染物(PM_2.5、PM₁₀、CO、SO₂、NO_x、O₃)和气象数据(平均温度、相对湿度),并作相关性分析。采用广义相加模型(GAM),在控制了星期几效应、气象因素后,研究大气污染物对心脑血管疾病发病的效应。结果 单污染物滞后模型结果显示PM₁₀在升高一个浓度单位后,在其滞后第五天心脑血管疾病的院前急救量增加,ER为0.056 6(95%CI:0.159 0～0.973 0);而O₃浓度在升高一个单位后,在其滞后的第三天和第六天使心脑血管疾病的院前急救量有所减少,其ER值分别为-0.101 0(95%CI:-0.195 2～-0.006 7),-0.114 1(95%CI:-0.207 9～-0.020 2)。在单污染物累积滞后模型中,O₃的累积效应呈负趋势,而N...     

北京市延庆区大气污染物对呼吸系统疾病门急诊量的影响

  目的  探讨北京市延庆区大气污染对人群呼吸系统疾病门急诊量影响。  方法  收集2014-2017年北京市延庆区二级医疗机构的呼吸系统疾病每日门急诊量数据和同期气象数据资料以及大气污染数据资料,运用时间序列的广义相加模型,在控制混杂因素的基础上,分析大气污染物浓度与呼吸系统门急诊量的关系以及滞后效应。  结果  研究表明,大气中空气动力学直径当量直径≤ 2.5 μm的颗粒物（particulate matter 2.5,PM_2.5）每增加10 μg/m3,呼吸系统门急诊量增加0.11%（RR=0.11,95%CI:0.09~0.14,P=0.001）;大气中空气动力学直径当量直径≤ 10 μm的颗粒物（particulate matter 10,PM₁₀）每增加10 μg/m3,呼吸系统门急诊量增加0.17%（RR=0.17,95%CI:0.15~0.19,P=0.001;二氧化氮（nitrogen dioxide,NO₂）每增加10 μg/m3,呼吸系统门急诊量增加0.44%（RR=0.44,95%CI:0.37~0.50,P=0.001）;一氧化碳（carbon monoxide,CO）每增加10 μg/m3,呼吸系统门急诊量增加3.34%（RR=3.34,95%CI:1.57~5.15,P=0.001）,且最强效应期均在第0 d。二氧化硫（sulfur ioxide,SO₂）每增加10 μg/m3呼吸系统门急诊量增加-1.69%（RR=-1.69,95%CI:-1.80~-1.57,P=0.001）,且在第1 d达到最强效应值。臭氧（ozone,O₃）每增加10 μg/m3呼吸系统门急诊量增加-0.12%（RR=0.12,95%CI:-0.15~-0.10,P=0.001）,且在第5 d达到最强效应值。双污染物模型分析中,CO在SO₂的影响下,对呼吸系统疾病门急诊人数影响尤为明显。  结论  本研究结果提示延庆区PM_2.5、PM₁₀、NO₂、CO浓度的增加均会导致呼吸系统门急诊量的增加,且不同污染物之间存在相互作用。     

上海市气温变化对医院急诊人次的影响

目的 研究上海市日均气温与三级医院医保急诊人次的关系.方法 应用广义相加模型分析时间序列资料,并在模型中加入自回归模型AR(P)处理时间序列资料自相关的问题,在控制了与时间有关的中长期趋势、星期效应、节假日效应、SARS事件、大气污染等混杂因素的基础上,拟合二次函数结合导数原理分析上海市2002-2004年间日均气温与三级医院医保急诊人次的关系.结果 当气温低于14.71℃时,气温每升高1℃对应急诊人次增加艘值的95%C/均小于1;当气温高于19.59℃时,气温每升高1℃对应急诊人次增加RR值的95%CI均大于1;而在温度段为14.71～19.59%,气温每升高1℃对应急诊人次增加RR值的95%CI包含1,称之为"最适温度段".结论 目前上海市日均气温偏离最适温度段时,气温变化对三级医院医保急诊人次有影响.     

Homocysteine and cysteine concentrations are modified by recent exposure to environmental air pollution in São Paulo, Brazil

Millions of people worldwide are affected by anthropogenic air pollution derived from the combustion of fossil fuels. In this work, we tested the effects of fetal, lactation and post-weaning ambient air pollution exposure on total homocysteine (tHcy) concentrations and on a downstream pathway element, the plasma cysteine (Cys) concentration. Two similar exposure chambers (polluted and filtered chamber) were located near an area with heavy traffic in São Paulo, Brazil, and male Swiss mice were housed there from the pre-natal period until 3 months of age. Groups during fetal, lactation and adult periods of exposure were apportioned, and tHcy and Cys plasma concentrations were assessed when the animals were 3 months old. In our study, both the tHcy and Cys concentrations were decreased in groups that spent their final stage of life in polluted chambers, suggesting recent alterations in tHcy and Cys concentrations due to air pollution exposure. The possible relationship of these data with cardiovascular dysfunction is still a matter of controversy in animals; nevertheless, epigenetic mechanisms emerge as a possible issue to consider in the investigation of the link between air pollution and Hcy measurement.     

Associations between outdoor air pollution and emergency department visits for stroke in Edmonton, Canada

Inconsistent results have been obtained from studies that have examined the relationship between air pollution and hospital visits for stroke. We undertook a time-stratified case-crossover study to evaluate associations between outdoor air pollution and emergency department visits for stroke among the elderly according to stroke type, season, and sex. Analyses are based on a total of 12,422 stroke visits among those 65 years of age and older in Edmonton, Canada between April 1, 1992 and March 31, 2002. Daily air pollution levels for SO₂, NO₂, PM_2.5, PM₁₀, CO and O₃ were estimated using data from fixed-site monitoring stations. Particulate matter data were only available from 1998 onwards. Conditional logistic regression was used to estimate the odds ratios (ORs) and their 95% confidence intervals in relation to an increase in the interquartile range (IQR) of each pollutant. ORs were adjusted for the effects of temperature and relative humidity. We found no association between outdoor measures of air pollution and all stroke visits. In contrast, elevated risks were observed between levels of air pollution and acute ischemic stroke between April and September. During this season, the ORs associated with an increase in the IQR of the 3-day average for CO and NO₂ were 1.32 (95% CI = 1.09–1.60) and 1.26 (95% CI = 1.09–1.46), respectively. CO exposures in the same season, lagged 1 day, were associated with an increased risk of hemorrhagic stroke with ORs was 1.20 (95% CI = 1.00–1.43). Our results suggest it is possible that vehicular traffic, which produces increased levels of NO₂ and CO, contributes to an increased incidence of emergency department visits for stroke.