Author Affiliations: Division of Epidemiology, Chinese University of Hong Kong, Hong Kong SAR, China (firstname.lastname@example.org).
To the Editor: Dr Mustafić and colleagues studied the association between exposure to air pollutants and the risk of myocardial infarction (MI) in a meta-analysis.1 It may not be appropriate to combine data from different studies because the increases in air pollutant concentrations and lag patterns differ in each study.
For increases in air pollutant concentrations, the authors selected 1 mg/m3 as a standard increase in pollutant concentration for carbon monoxide and 10 μg/m3 for other air pollutants when calculating relative risks.1 However, the studies used 0.9 mg/L, 0.1 mg/m3, and 0.23 mg/m3 for carbon monoxide and 7.5 μg/m3, 10 μg/m3, and 9.1 μg/m3 for particulate matter with an aerodynamic diameter of 10 μm (PM10).2- 4
Huang Y, Mao C. Exposure to Air Pollutants and Myocardial Infarction Risk. JAMA. 2012;307(22):2370. doi:10.1001/jama.2012.4116