Air pollution and emergency department visits for cardiac and respiratory conditions: a multi-city time-series analysis

Abstract

BackgroundRelatively few studies have been conducted of the association between air pollution and emergency department (ED) visits, and most of these have been based on a small number of visits, for a limited number of health conditions and pollutants, and only daily measures of exposure and response.MethodsA time-series analysis was conducted on nearly 400,000 ED visits to 14 hospitals in seven Canadian cities during the 1990s and early 2000s. Associations were examined between carbon monoxide (CO), nitrogen dioxide (NO2), ozone (O3), sulfur dioxide (SO2), and particulate matter (PM10 and PM2.5), and visits for angina/myocardial infarction, heart failure, dysrhythmia/conduction disturbance, asthma, chronic obstructive pulmonary disease (COPD), and respiratory infections. Daily and 3-hourly visit counts were modeled as quasi-Poisson and analyses controlled for effects of temporal cycles, weather, day of week and holidays.Results24-hour average concentrations of CO and NO2 lag 0 days exhibited the most consistent associations with cardiac conditions (2.1% (95% CI, 0.0–4.2%) and 2.6% (95% CI, 0.2–5.0%) increase in visits for myocardial infarction/angina per 0.7 ppm CO and 18.4 ppb NO2 respectively; 3.8% (95% CI, 0.7–6.9%) and 4.7% (95% CI, 1.2–8.4%) increase in visits for heart failure). Ozone (lag 2 days) was most consistently associated with respiratory visits (3.2% (95% CI, 0.3–6.2%), and 3.7% (95% CI, -0.5–7.9%) increases in asthma and COPD visits respectively per 18.4 ppb). Associations tended to be of greater magnitude during the warm season (April – September). In particular, the associations of PM10 and PM2.5with asthma visits were respectively nearly three- and over fourfold larger vs. all year analyses (14.4% increase in visits, 95% CI, 0.2–30.7, per 20.6 μg/m3 PM10 and 7.6% increase in visits, 95% CI, 5.1–10.1, per 8.2 μg/m3 PM2.5). No consistent associations were observed between three hour average pollutant concentrations and same-day three hour averages of ED visits.ConclusionIn this large multicenter analysis, daily average concentrations of CO and NO2 exhibited the most consistent associations with ED visits for cardiac conditions, while ozone exhibited the most consistent associations with visits for respiratory conditions. PM10 and PM2.5 were strongly associated with asthma visits during the warm season.

Global Associations between Air Pollutants and Chronic Obstructive Pulmonary Disease Hospitalizations: A Systematic Review

“…Of the 12 studies included in the metaanalysis (Figure 3), a positive association was found in 10; however, the association was significant in only 4. Studies in which researchers collected measurements of both PM 2.5 and PM 10 fractions, similar associations between COPD hospital admissions and these fractions were found (21,22,(26)(27)(28)(29)(30)(31). However, overall, a stronger association was found with PM 2.5 (OR, 1.03; 95% CI, 1.01-1.05) than with PM 10 , which might be explained by the fact that smaller particles may penetrate deeper into the lungs.…”

“…That approach has the potential for including a large number of days over several years for a large population, with advantages of improving the precision of estimate of effect of exposure-response relationships. The researchers in the vast majority of these studies analyzed exposureresponse relationships at a single-city level, and we found only six time-series multicity investigations (17)(18)(19)(20)(21)(22).…”

“…However, seasonal differences were estimated in a 5-year European study (37), with a very small but insignificant association observed in winter and no relationship seen in the summer. Most studies estimated acute effects for SO 2 (21, 34) or 2-day lagged effects (21,30,38). In only one study (35) did researchers estimate longer lagged effects of up to 13 days.…”

“…Researchers in studies done in Europe estimated an overall stronger association (OR, 1.04; 95% CI, 1.02-1.06; I 2 = 47.3%) than in North America (OR, 1.02; 95% CI, 1.01-1.03; I 2 = 37.5%), possibly because CO concentrations in Europe were higher (2.1 6 0.7 mg/m 3 ) than in North America (1.5 6 0.2 mg/m 3 ), and the metaregression indicated that there is a nonlinear association between effect and ambient concentrations ( Figure E5). Researchers in most studies found significant associations with acute (25,34) or lagged effects of up to 3 days (21,30,31,35).…”

“…The rescaled ORs for this study were 1.67 (95% CI, 1.37-2.04) in the warm season and 2.70 (95% CI, 2.04-3.58) in the cool season. Apart from two European casecrossover studies (21,30) in which researchers found a strong positive association, all included studies were time-series investigations. There was some evidence of small-study bias in the trimand-fill funnel plot, supported by the nonsignificant negative association estimated by the only multicity investigation, which was done in seven Canadian cities (21).…”