Correlation between Exposure to Air Pollution and Onset of Acute Coronary Syndrome

Recent evidence suggests that long-term exposure to air pollution contributes to progression of atherosclerosis and the risk of cardiac morbidity and mortality. Short-term exposure may also lead to thrombosis and acute ischemic events. To evaluate the correlation between the levels of major air pollutants (CO and PM10) and hospital admission for acute coronary syndrome (ACS) in Tehran, we performed a casecrossover design and checked whether individual characteristics act as effect modifiers. We selected 250 residents of Tehran who had been hospitalized with ACS from fourth of April through tenth of June, 2007. The individualsʹ data including sex, age, date of hospitalization, and coexisting illnesses (hypertension, diabetes) were gathered. Daily air pollution data were taken from the Air Quality Control Center. Temperature, humidity, stress, physical activity, and weekend days were treated as confounding variables, and a conditional logistic regression model was used for statistical analysis. We found a positive relation between ACS and average 24-hour CO levels. The odds ratio (OR) for each unit increase of the average 24-hour CO was 1.18 (95%CI: 1.03 – 1.34). The correlation between ACS and 24-hour average PM10 did not reach statistical significance (OR for average 24-hour PM 10 was 1.005, 95%CI: 0.99 – 1.01). The association between ACS and 24-hour average CO tended to be stronger in women (OR=1.68 for each unit increase, 95%CI: 1.25 – 2.26). The relation between 24-hour average PM10 and ACS did not change across the layers of the effect modifiers. The results suggest that an increase in average 24-hour CO levels will augment the risk of ACS, and the effect is stronger in females. On the other hand, we were unable to document an relation between ACS and average 24-hour PM 10 levels.