In a case-crossover study conducted by Li et al. in eight major cities in China, a 10 μg/m
3 increase in the 2-day moving average of PM10, SO
2, and NO
2 concentrations was significantly associated with an increase in daily cardiovascular disease mortality (
5). Another study examined 12 years of time series in the United States. The results showed that daily changes in PM10-2.5 were associated with emergency room admissions due to cardiovascular disease among the elderly (over 65 years of age) (
6). In a case-crossover study in ten southern European cities, results showed that forest fires and PM10 were associated with increased cardiovascular disease mortality in city dwellers (
7). In a time-series study by Zhao et al., 56,940 outpatients in China were examined. Results showed that a 10 μg/m
3 increase in present-day PM10, SO
2, and NO
2 concentrations was associated with a 0.56%, 2.07%, and 2.90% increase in outpatient visits for arrhythmia (
8).
A study conducted on 5,973 cases between 2000 and 2010 in Stockholm showed that exposure to moderate levels of O
3 increased the risk of cardiac arrest in patients (
9). In a study conducted in a region in northeastern China, the results indicated that air pollution increases cardiovascular disease in overweight and obese individuals (
10). Increasing the amount of nanograms per cubic meter caused an increase in coronary events (
11). Another study that examined data from 22 European groups found that 0.1% of air pollutants were associated with mortality from heart disease (
12). In another study, results showed that short-term exposure to fine particle air pollution was mainly associated with the onset of acute ischemic events (myocardial infarction and stroke) (
13).