深圳市大气PM10与呼吸系统疾病日门诊量的时间序列分析

目的探讨大气可吸入颗粒污染物（PM10）对医院呼吸系统疾病门诊量的影响。方法2012年1月1日至12月31日疾病资料来源于深圳市2家三级甲等综合性医院逐日门诊病例资料,空气污染物资料来自深圳市环境监测站,气象资料来自气象局。采用广义相加Poisson回归模型的时间序列分析,在控制长期趋势、星期几效应和气象等影响因素后,对大气PM10日均浓度与呼吸系统疾病日门诊量的关系和滞后效应进行分析。结果深圳市2012年全年日均大气PM10浓度为0．052mg／m^3,符合国家二级标准,2家医院全年呼吸系统门诊量为562174人次,平均1535．99人次／d。广义相加模型分析结果发现PM10日均浓度与呼吸系统疾病门诊量存在正相关关系。滞后6d时PM10日均浓度对呼吸系统疾病门诊量的影响最强[相对危险度（RR）为1．0047,95％CI：1．0036—1．0058]。引入CO、O3、NO2、SO2进行多污染物模型分析发现,多污染物模型的RR值相对单污染物模型有升有降（均P〈0．05）,其中以双污染物模型PM10＋SO2和三污染物模型PM10＋CO＋SO2中的PM10的RR值最高,分别为1．0059、1．0067。结论深圳市大气PM10污染与医院呼吸系统疾病日门诊量呈正相关关系,且存在滞后效应。     

Air pollution, weather, and respiratory emergency room visits in two northern New England cities: an ecological time-series study

Daily emergency room (ER) visits for all respiratory (ICD-9 460-519) and asthma (ICD-9 493) were compared with daily sulfur dioxide (SO2), ozone (O3), and weather variables over the period 1998-2000 in Portland, Maine (population 248,000), and 1996-2000 in Manchester, New Hampshire (population 176,000). Seasonal variability was removed from all variables using nonparametric smoothed function (LOESS) of day of study. Generalized additive models were used to estimate the effect of elevated levels of pollutants on ER visits. Relative risks of pollutants are reported over their interquartile range (IQR, the 75th -25th percentile pollutant values). In Portland, an IQR increase in SO2 was associated with a 5% (95% CI 2-7%) increase in all respiratory ER visits and a 6% (95% CI 1-12%) increase in asthma visits. An IQR increase in O3 was associated with a 5% (95% CI 1-10%) increase in Portland asthmatic ER visits. No significant associations were found in Manchester, New Hampshire, possibly due to statistical limitations of analyzing a smaller population. The absence of statistical evidence for a relationship should not be used as evidence of no relationship. This analysis reveals that, on a daily basis, elevated SO2 and O3 have a significant impact on public health in Portland, Maine.     

Air pollution, aeroallergens and cardiorespiratory emergency department visits in Saint John, Canada

Existing studies of the association between air pollution, aeroallergens and emergency department (ED) visits have generally examined the effects of a few pollutants or aeroallergens on individual conditions such as asthma or chronic obstructive pulmonary disease. In this study, we considered a wide variety of respiratory and cardiac conditions and an extensive set of pollutants and aeroallergens, and utilized prospectively collected information on possible effect modifiers which would not normally be available from purely administrative data. The association between air pollution, aeroallergens and cardiorespiratory ED visits (n = 19,821) was examined for the period 1992 to 1996 using generalized additive models. ED visit, air pollution and aeroallergen time series were prefiltered using LOESS smoothers to minimize temporal confounding, and a parsimonious model was constructed to control for confounding by weather and day of week. Multipollutant and multi-aeroallergen models were constructed using stepwise procedures and sensitivity analyses were conducted by season, diagnosis, and selected individual characteristics or effect modifiers. In single-pollutant models, positive effects of all pollutants but NO2 and COH were observed on asthma visits, and positive effects on all respiratory diagnosis groups were observed for O3, SO2, PM10, PM2.5, and SO4(2-). Among cardiac conditions, only dysrhythmia visits were positively associated with all measures of particulate matter. In the final year-round multipollutant models, a 20.9% increase in cardiac ED visits was attributed to the combination of O3 (16.0%, 95% CI 2.8-30.9) and SO2 (4.9%, 95%CI 1.7-8.2) at the mean concentration of each pollutant. In the final multipollutant model for respiratory visits, O3 accounted for 3.9% of visits (95% CI 0.8-7.2), and SO2 for 3.7% (95% CI 1.5-6.0), whereas a weak, negative association was observed with NO2. In multi-aeroallergen models of warm season asthma ED visits, Ascomycetes, Alternaria and small round fungal spores accounted for 4.5% (95% CI 1.8-7.4), 4.7% (95% CI 1.0-8.6) and 3.0% (95% CI 0.8-5.1), respectively, of visits at their mean concentrations, and these effects were not sensitive to adjustment for air pollution effects. In conclusion, we observed a significant influence of the air pollution mix on cardiac and respiratory ED visits. Although in single-pollutant models, positive associations were noted between ED visits and some measures of particulate matter, in multipollutant models, pollutant gases, particularly ozone, exhibited more consistent effects. Aeroallergens were also significantly associated with warm season asthma ED visits.     

2014-2015年合肥市大气PM2.5污染对儿童门诊量影响的时间序列分析

目的 探讨合肥市大气PM2.5日均浓度对合肥市儿童门诊量的影响.方法 分别从合肥市气象局、合肥市环保局获得2014-2015年合肥市全年气象、环保资料,从合肥市滨湖医院、合肥市第二人民医院医院信息系统(HIS)获取同期儿童门诊资料.采用基于Poisson回归的广义相加模型(GAM)控制时间趋势、温度和相对湿度、星期几效应、法定节假日等因素进行PM2.5对儿童门诊量影响的时间序列分析,分析PM2.5浓度对当日、滞后1～7 d效应(lag0～lag7),以及移动平均浓度对滞后1～7 d的累积滞后效应(lag1～7).结果 2014-2015年合肥市PM2.5平均浓度为(73.1±43.5)μg/m3,是GB 3095-2012《环境空气质量标准》二级标准年均值(35 μg/m3)的2.1倍,2年共有267 d(占36.6％)的PM2.5日均浓度超过国家二级标准24 h均值(75 μg/m3).GAM模型发现PM2.5对合肥市滨湖医院、合肥市第二人民医院的儿科门诊均有显著影响,其中对总门诊量当日的影响最大,合肥滨湖医院、合肥市二院的ER分别为0.65％(95％CI:0.49％～0.81％)、0.92％(95％CI:0.70％～1.13％);对合肥滨湖医院儿童呼吸系统当日的门诊量影响最大[ER=0.78％(95％CI:0.58％～0.99％)],对合肥市二院儿童呼吸系统滞后2d门诊量影响最大[ER=0.90％ (95％CI:0.63％～ 1.18％)].采用PM2.5移动平均浓度分析累积滞后效应时发现,PM2.5污染物对儿童的总门诊量和呼吸系统门诊量均有累积滞后效应,两医院的总门诊和呼吸系统门诊量均在累积滞后7 d (lag0～7)时ER最高,总门诊ER分别为1.60％ (95％CI:1.32％～1.87％)、2.62％(95％CI:2.25％～3.00％),呼吸系统门诊ER分别为1.83％(95％CI:1.48％～2.19％)、3.19％(95％CI:2.7％～3.66％).未发现PM25浓度对儿童循环系统门诊量有显著影响.结论 2014-2015年空气污染对合肥地区儿童门诊量有显著影响,PM2.5浓度增加会导致儿童总门诊、儿童呼吸系统门诊的门诊量增加.     

An association between fine particles and asthma emergency department visits for children in Seattle.

Asthma is the most common chronic illness of childhood and its prevalence is increasing, causing much concern for identification of risk factors such as air pollution. We previously conducted a study showing a relationship between asthma visits in all persons < 65 years of age to emergency departments (EDs) and air pollution in Seattle, Washington. In that study the most frequent zip codes of the visits were in the inner city. The Seattle-King County Department of Public Health (Seattle, WA) subsequently published a report which showed that the hospitalization rate for children in the inner city was over 600/100,000, whereas it was < 100/100,000 for children living in the suburbs. Therefore, we conducted the present study to evaluate whether asthma visits to hospital emergency departments in the inner city of Seattle were associated with outdoor air pollution levels. ED visits to six hospitals for asthma and daily air pollution data were obtained for 15 months during 1995 and 1996. The association between air pollution and childhood ED visits for asthma from the inner city area with high asthma hospitalization rates were compared with those from lower hospital utilization areas. Daily ED counts were regressed against fine particulate matter (PM), carbon monoxide (CO), sulfur dioxide, and nitrogen dioxide using a semiparametric Poisson regression model. Significant associations were found between ED visits for asthma in children and fine PM and CO. A change of 11 microg/m3 in fine PM was associated with a relative rate of 1.15 [95% confidence interval (CI), 1.08-1.23]. There was no stronger association between ED visits for asthma and air pollution in the higher hospital utilization area than in the lower utilization area. These findings were seen when estimated PM2.5 concentrations were below the newly adopted annual National Ambient Air Quality Standard of 15 microg/m3.     

Emergency department visits and "vog"-related air quality in Hilo, Hawai'i

Emergency department (ED) visits in Hilo, Hawai'i, from January 1997 to May 2001, were examined for associations with volcanic fog, or "vog", measured as sulfur dioxide (SO(2)) and submicrometer particulate matter (PM(1)). Exponential regression models were used with robust standard errors. Four diagnostic groups were examined: asthma/COPD; cardiac; flu, cold, and pneumonia; and gastroenteritis. Before adjustments, highly significant associations with vog-related air quality were seen for all diagnostic groups except gastroenteritis. After adjusting for month, year, and day of the week, only asthma/COPD had consistently positive associations with air quality. The strongest associations were for SO(2) with a 3-day lag (6.8% per 10 ppb; P=0.001) and PM(1), with a 1-day lag (13.8% per 10 microg/m(3); P=0.011). The association of ED visits for asthma/COPD with month of the year was stronger than associations seen with air quality. Although vog appears influential, non-vog factors dominated associations with the frequency of asthma/COPD ED visits.     

Effects of ambient air pollution on symptoms of asthma in Seattle-area children enrolled in the CAMP study

We observed a panel of 133 children (5-13 years of age) with asthma residing in the greater Seattle, Washington, area for an average of 58 days (range 28-112 days) during screening for enrollment in the Childhood Asthma Management Program (CAMP) study. Daily self-reports of asthma symptoms were obtained from study diaries and compared with ambient air pollution levels in marginal repeated measures logistic regression models. We defined days with asthma symptoms as any day a child reported at least one mild asthma episode. All analyses were controlled for subject-specific variables [age, race, sex, baseline height, and FEV(1) PC(20) concentration (methacholine provocative concentration required to produce a 20% decrease in forced expiratory volume in 1 sec)] and potential time-dependent confounders (day of week, season, and temperature). Because of variable observation periods for participants, we estimated both between- and within-subject air pollutant effects. Our primary interest was in the within-subject effects: the effect of air pollutant excursions from typical levels in each child's observation period on the odds of asthma symptoms. In single-pollutant models, the population average estimates indicated a 30% [95% confidence interval (CI), 11-52%] increase for a 1-ppm increment in carbon monoxide lagged 1 day, an 18% (95% CI, 5-33%) increase for a 10-microg/m(3) increment in same-day particulate matter < 1.0 microm (PM(1.0)), and an 11% (95% CI, 3-20%) increase for a 10-microg/m(3) increment in particulate matter < 10 microm (PM(10)) lagged 1 day. Conditional on the previous day's asthma symptoms, we estimated 25% (95% CI, 10-42%), 14% (95% CI, 4-26%), and 10% (95% CI, 3-16%) increases in the odds of asthma symptoms associated with increases in CO, PM(1.0), and PM(10), respectively. We did not find any association between sulfur dioxide (SO(2)) and the odds of asthma symptoms. In multipollutant models, the separate pollutant effects were smaller. The overall effect of an increase in both CO and PM(1. 0) was a 31% (95% CI, 11-55%) increase in the odds of symptoms of asthma. We conclude that there is an association between change in short-term air pollution levels, as indexed by PM and CO, and the occurrence of asthma symptoms among children in Seattle. Although PM effects on asthma have been found in other studies, it is likely that CO is a marker for vehicle exhaust and other combustion by-products that aggravate asthma.     

Association between particulate matter and emergency room visits, hospital admissions and mortality in Spokane, Washington

There is conflicting evidence regarding the association between different size fractions of particulate matter (PM) and cardiac and respiratory morbidity and mortality. We investigated the short-term associations of four size fractions of particulate matter (PM(1), PM(2.5), PM(10), and PM(10-2.5)) and carbon monoxide with hospital admissions and emergency room (ER) visits for respiratory and cardiac conditions and mortality in Spokane, Washington. We used a log-linear generalized linear model to compare daily averages of PM and carbon monoxide with daily counts of the morbidity and mortality outcomes from January 1995 to June 2001. We examined pollution lags ranging from 0 to 3 days and compared our results to a similar log-linear generalized additive model. Effect estimates tended to be smaller and have larger standard errors for the generalized linear model. Overall, we saw no association with respiratory ER visits and any size fraction of PM. However, there was a suggestion of greater respiratory effect from fine PM when compared to coarse fraction. Carbon monoxide was associated with both all respiratory ER visits and visits for asthma at the 3-day lag. We feel that carbon monoxide may be serving as a marker for combustion-derived pollutants, which is one large component of the diverse air pollutant mixture. We also found no association with any size fraction of PM or CO with cardiac hospital admissions or mortality at the 0- to 3-day lag. We found no consistent associations between any size fraction of PM and cardiac or respiratory ER visits or hospital admissions.     

Young infants' morbidity and exposure to fine particles in a region with two power plants

This study investigated the effect of fine particulate matter (PM2.5) in ambient air on hospital admissions and emergency room (ER) visits among young children (0-3 yr) residing in 4 communities in southern Israel, within an area 5-25 km from the 2 power plants, which operate within 25 km of each other. Daily records of hospitalizations and ER visits for respiratory diseases at the 3 hospitals serving the region were examined for 9 mo, October 1, 2000-June 30, 2001. Mean PM2.5 concentrations for the four communities ranged from 11.6 to 28.1 microg/m3. Time series analysis revealed a statistically significant association (p < 0.05) between the numbers of hospitalizations and ER visits for respiratory symptoms and concentrations of PM2.5. This effect was evaluated for 0-3 lag days, directly, and for interactions with temperatures and seasonal parameters. The respiratory health of young children may be affected by 24 hr concentrations of PM2.5 < 60 microg/m3, the threshold proposed by both Israel and the United States.     

Acute effects of urban ambient air pollution on respiratory symptoms, asthma medication use, and doctor visits for asthma in a cohort of Australian children

We enrolled a cohort of primary school children with a history of wheeze (n=148) in an 11-month longitudinal study to examine the relationship between ambient air pollution and respiratory morbidity. We obtained daily air pollution (ozone, particulate matter less than 10 microm, and nitrogen dioxide), meteorological, and pollen data. One hundred twenty-five children remained in the final analysis. We used logistic regression models to determine associations between air pollution and respiratory symptoms, asthma medication use, and doctor visits for asthma. There were no associations between ambient ozone concentrations and respiratory symptoms, asthma medication use, and doctor visits for asthma. There was, however, an association between PM(10) concentrations and doctor visits for asthma (RR=1.11, 95% CI=1.04-1.19) and between NO(2) concentration and wet cough (RR=1.05, 95% CI=1.003-1.10) in single-pollutant models. The associations remained significant in multipollutant models. There was no consistent evidence that children with wheeze, positive histamine challenge, and doctor diagnosis of asthma reacted differently to air pollution from children with wheeze and doctor diagnosis of asthma and children with wheeze only. There were significant associations between PM(10) levels and doctor visits for asthma and an association between NO(2) levels and the prevalence of wet cough. We were, however, unable to demonstrate that current levels of ambient air pollution in western Sydney have a coherent range of adverse health effects on children with a history of wheezing.     

大气污染对变应性疾病及花粉症就诊人次的影响

目的 研究大气污染物浓度对医院变应性疾病和花粉症日就诊人次的影响.方法 收集2004年4-9月北京市8个国家监测点大气污染物[SO2、NO2、可吸入颗粒物(PM10)]浓度、4个观测点花粉日监测数据、气象资料及北京世纪坛医院变态反应科同时段变应性疾病和花粉症日就诊人次资料,应用时间序列分析的广义相加泊松回归模型进行定量分析,并考虑滞后效应和多种空气污染物的影响.结果 研究期间大气SO2、NO2、PM10日均浓度分别为(20.9±12.9)、(58.6±13.6)、(126.8 ±64.1)μg/m3,花粉日均浓度为(163.8±209.0)粒/1000 mm2,变应性疾病日就诊(16.3±5.3)人次,花粉症日就诊(3.5±5.0)人次.时间序列分析显示,花粉浓度每升高100粒/1000 mm2,第2天的变应性疾病日就诊人次增加2.44%(95%CI:0.75%～4.13%),当天的花粉症日就诊人次增加6.58%(95%CI:3.82%～9.34%).而大气污染物(NO2、SO2和PM10)对变应性疾病和花粉症日就诊人次的影响呈现明显的滞后效应:NO2每升高10 μg/m3,滞后6 d的变应性疾病日就诊人次增加3.14%(95%CI:0.42%～5.85%);S02滞后1 d、NO2滞后6 d、PM10滞后3 d对花粉症日就诊人次影响较大,但差异均无统计学意义[RR值(95%CI值)分别为1.0460(0.9640～1.1280)、1.0325(0.9633～1.1017)、1.0079(0.9942～1.0217)].将4种大气污染物同时引入模型分析时,其效应稍微增强:花粉浓度每升高100粒/1000 mm2,变应性疾病日就诊人次增加2.56%(95%CI:0.80%～4.31%),花粉症日就诊人次增加6.81%(95%CI:3.91%～9.71%).结论 影响变应性疾病和花粉症日就诊人次的环境因素主要为空气花粉浓度,大气污染物的作用不大.     

大气可吸入颗粒物与心脑血管疾病急诊关系的病例交叉研究

目的 探讨北京市大气可吸入颗粒物污染(PM10)对心腩血管疾病急诊的影响.方法 收集北京大学第三医院急诊科心脑血管疾病急诊资料和北京市环境监测中心大气污染物数据,应用时间分层的病例交叉设计研究方法进行数据分析.结果 无滞后单向同顾性1:4配对病例交叉研究的效应值(OR值)最大,在控制所选PM10当日气温、相对湿度影响的情况下,PM10浓度每提高10μg/m3与心脑血管疾病急诊(ICD-10:I00-I99)、冠心病急诊(ICD-10:120-125)、心律失常急诊(ICD-10:147-149)、心衰急诊(ICD-10:150)和脑血管疾病急诊(ICD-10:160-169)的OR值分别为1.006(95%CI:1.003～1.008)、1.003(95%CI:0.996～1.010)、1.005(95%CI:0.997～1.013)、1.019(95%CI:1.005～1.033)、1.003(95%CI:0.998～1.007),其中PM10与总心脑血管疾病急诊和心衰急诊的关联有统计学意义(P<0.05).结论 大气PM10污染物浓度升高可导致总心脑血管疾病急诊和心衰急诊增加.     

Winter Temperature Inversions and Emergency Department Visits for Asthma in Salt Lake County, Utah, 2003�C2008

Background: Winter temperature inversions—layers of air in which temperature increases with altitude—trap air pollutants and lead to higher pollutant concentrations. Previous studies have evaluated associations between pollutants and emergency department (ED) visits for asthma, but none have considered inversions as independent risk factors for ED visits for asthma.Objective: We aimed to assess associations between winter inversions and ED visits for asthma in Salt Lake County, Utah.Methods: We obtained electronic records of ED visits for asthma and data on inversions, weather, and air pollutants for Salt Lake County, Utah, during the winters of 2003 through 2004 to 2007 through 2008. We identified 3,425 ED visits using a primary diagnosis of asthma. We used a time-stratified case-crossover design, and conditional logistic regression models to calculate odds ratios (ORs) and 95% confidence intervals (CIs) to estimate rate ratios of ED visits for asthma in relation to inversions during a 4-day lag period and prolonged inversions. We evaluated interactions between inversions and weather and pollutants.Results: After adjusting for dew point and mean temperatures, the OR for ED visits for asthma associated with inversions 0–3 days before the visit compared with no inversions during the lag period was 1.14 (95% CI: 1.00, 1.30). The OR for each 1-day increase in the number of inversion days during the lag period was 1.03 (95% CI: 1.00, 1.07). Associations were only apparent when PM₁₀ and maximum and mean temperatures were above median levels.Conclusions: Our results provide evidence that winter inversions are associated with increased rates of ED visits for asthma.     

Short-term effects of low-level air pollution on respiratory health of adults suffering from moderate to severe asthma

Only a few studies have been carried out on the health effects of air pollution on patients suffering from severe asthma. We wanted to test the sensitivity of these patients to Paris air pollution. During 13 months, 60 severe asthmatics (62- female; mean age 55 years) were monitored by their physician, who filled in a follow-up form at each consultation and reported any asthma attacks. Daily levels of SO(2), PM10, NO(2), and O(3) were provided by the air quality network. Statistical analysis (generalized estimating equation models that accounted for autocorrelation of responses, temporal, meteorological, and aerobiological variables, and some individual characteristics) revealed significant associations between PM10, O(3), and incident asthma attacks. Odds Ratio (OR) for an increase of 10 microg/m(3) of PM10 was 1.41; 95% confidence interval (CI) [1.16; 1.71]. An increase of 10 microg/m(3) of O(3) was significantly associated with asthma attacks; OR=1.20; 95% CI [1.03; 1.41]. These relations were observed after a delay between exposure and asthma attacks of 3 to 5 days for PM10 and 2 days for O(3), and they tended to differ according to atopic status. The results of our study suggest that ambient Paris levels of PM10 and O(3) affected health of severe asthmatics, despite their treatment.     

Relationships of mortality with the fine and coarse fractions of long-term ambient PM10 concentrations in nonsmokers

In a cohort of 6338 California Seventh-day Adventists, we previously observed for males associations between long-term concentrations of particulate matter (PM) with an aerodynamic diameter less than 10 microm (PM10) and 15-year mortality due to all natural causes (ANC) and lung cancer (LC) listed as underlying causes of death and due to nonmalignant respiratory disease listed as either the underlying or a contributing (CRC) cause of death. The purpose of this analysis was to determine whether these outcomes were more strongly associated with the fine (PM2.5) or the coarse (PM2.5-10) fractions of PM10. For participants who lived near an airport (n=3769), daily PM2.5 concentrations were estimated from airport visibility, and on a monthly basis, PM2.5-10 concentrations were calculated as the differences between PM10 and PM2.5. Associations between ANC, CRC, and LC mortality (1977-1992) and mean PM10, PM2.5, and PM2.5-10 concentrations at study baseline (1973-1977) were assessed using Cox proportional hazards models. Magnitudes of the PM10 associations for the males of this subgroup were similar to those for the males in the entire cohort although not statistically significant due to the smaller numbers. In single-pollutant models, for an interquartile range (IQR) increase in PM10 (29.5 microg/m3), the rate ratios (RRs) and 95% confidence intervals (CI) were 1.15 (0.94, 1.41) for ANC, 1.48 (0.93, 2.34) for CRC, and 1.84 (0.59, 5.67) for LC. For an IQR increase in PM2.5 (24.3 microg/m3), corresponding RRs (95% CI) were 1.22 (0.95, 1.58), 1.64 (0.93, 2.90), and 2.23 (0.56, 8.94), and for an IQR increase in PM2.5-10 (9.7 microg/m3), corresponding RRs (95% CI) were 1.05 (0.92, 1.20), 1.19 (0.88, 1.62), and 1.25 (0.63, 2.49), respectively. When both PM25 and PM2.5-10 were entered into the same model, the PM2.5 estimates remained stable while those of PM2.5-10 decreased. We concluded that previously observed associations of long-term ambient PM10 concentration with mortality for males were best explained by a relationship of mortality with the fine fraction of PM10 rather than with the coarse fraction of PM10.     

Seasonal modification of the association between temperature and adult emergency department visits for asthma: a case-crossover study

ABSTRACT: BACKGROUND: The objective of this study is to characterize the effect of temperature on emergency department visits for asthma and modification of this association by season. This association is of interest in its own right, and also important to understand because temperature may be an important confounder in analyses of associations between other environmental exposures and asthma. For example, the case-crossover study design is commonly used to investigate associations between air pollution and respiratory outcomes, such as asthma. This approach controls for confounding by month and season by design, and permits adjustment for potential confounding by temperature through regression modeling. However, such models may fail to adequately control for confounding if temperature effects are seasonal, since case-crossover analyses rarely account for interactions between matching factors (such as calendar month) and temperature. METHODS: We conducted a case-crossover study to determine whether the association between temperature and emergency department visits for asthma varies by season or month. Asthma emergency department visits among North Carolina adults during 2007-2008 were identified using a statewide surveillance system. Marginal as well as season- and month-specific associations between asthma visits and temperature were estimated with conditional logistic regression. RESULTS: The association between temperature and adult emergency department visits for asthma is near null when the overall association is examined [odds ratio (OR) per 5 degrees Celsius = 1.01, 95% confidence interval (CI): 1.00, 1.02]. However, significant variation in temperature-asthma associations was observed by season (chi-square = 18.94, 3 degrees of freedom, p <0.001) and by month of the year (chi-square = 45.46, 11 degrees of freedom, p <0.001). ORs per 5 degrees Celsius were increased in February (OR = 1.06, 95% CI: 1.02, 1.10), July (OR = 1.16, 95% CI: 1.04, 1.29), and December (OR = 1.04, 95% CI: 1.01, 1.07) and decreased in September (OR = 0.92, 95% CI: 0.87, 0.97). CONCLUSIONS: Our empirical example suggests that there is significant seasonal variation in temperature-asthma associations. Epidemiological studies rarely account for interactions between ambient temperature and temporal matching factors (such as month of year) in the case-crossover design. These findings suggest that greater attention should be given to seasonal modification of associations between temperature and respiratory outcomes in case-crossover analyses of other environmental asthma triggers.     

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.     

Particulate air pollution and respiratory disease in Anchorage, Alaska.

This paper examines the associations between average daily particulate matter less than 10 microns in diameter (PM10) and temperature with daily outpatient visits for respiratory disease including asthma, bronchitis, and upper respiratory illness in Anchorage, Alaska, where there are few industrial sources of air pollution. In Anchorage, PM10 is composed primarily of earth crustal material and volcanic ash. Carbon monoxide is measured only during the winter months. The number of outpatients visits for respiratory diagnoses during the period 1 May 1992 to 1 March 1994 were derived from medical insurance claims for state and municipal employees and their dependents covered by Aetna insurance. The data were filtered to reduce seasonal trends and serial autocorrelation and adjusted for day of the week. The results show that an increase of 10 micrograms/m3 in PM10 resulted in a 3-6% increase in visits for asthma and a 1-3% increase in visits for upper respiratory diseases. Winter CO concentrations were significantly associated with bronchitis and upper respiratory illness, but not with asthma. Winter CO was highly correlated with automobile exhaust emissions. These findings are consistent with the results of previous studies of particulate pollution in other urban areas and provide evidence that the coarse fraction of PM10 may affect the health of working people.     

Association of ambient air pollution with respiratory hospitalization in a government-designated "area of concern": the case of Windsor, Ontario

This study is part of a larger research program to examine the relationship between ambient air quality and health in Windsor, Ontario, Canada. We assessed the association between air pollution and daily respiratory hospitalization for different age and sex groups from 1995 to 2000. The pollutants included were nitrogen dioxide, sulfur dioxide, carbon monoxide, ozone, particulate matter 10 microm in diameter (PM10), coefficient of haze (COH), and total reduced sulfur (TRS). We calculated relative risk (RR) estimates using both time-series and case-crossover methods after controlling for appropriate confounders (temperature, humidity, and change in barometric pressure). The results of both analyses were consistent. We found associations between NO2, SO2, CO, COH, or PM10 and daily hospital admission of respiratory diseases especially among females. For females 0-14 years of age, there was 1-day delayed effect of NO2 (RR = 1.19, case-crossover method), a current-day SO2 (RR = 1.11, time series), and current-day and 1- and 2-day delayed effects for CO by case crossover (RR = 1.15, 1.19, 1.22, respectively). Time-series analysis showed that 1-day delayed effect of PM10 on respiratory admissions of adult males (15-64 years of age), with an RR of 1.18. COH had significant effects on female respiratory hospitalization, especially for 2-day delayed effects on adult females, with RRs of 1.15 and 1.29 using time-series and case-crossover analysis, respectively. There were no significant associations between O3 and TRS with respiratory admissions. These findings provide policy makers with current risks estimates of respiratory hospitalization as a result of poor ambient air quality in a government designated "area of concern."