Is PM similar to PM? A new insight into the association of PM and PM with children's lung function.

Experimental data suggests that PM is more toxic than PM although the epidemiologic evidence suggests that the health associations are similar. However, few objective exposure data are available to compare the associations of PM and PM with children lung function. Our objectives are a) to evaluate associations between long-term exposure to PM, PM and children's lung function, and b) to compare the associations between PM and PM. From 2012 to 2013, we enrolled 6,740 children (7-14 years), randomly recruited from primary and middle schools located in seven cities in northeast China. We measured lung function including forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), peak expiratory flow (PEF), and maximal mid-expiratory flow (MMEF) utilizing two portable electronic spirometers. We dichotomized continuous lung function measures according the expected values for gender and age. The spatial resolution at which PM and PM estimated were estimated using a machine learning method and the temporal average concentrations were averaged from 2009 to 2012. A multilevel regression model was used to estimate the associations of PM, PM exposure and lung function measures, adjusted for confounding factors. Associations with lower lung function were consistently larger for PM than for PM. Adjusted odds ratios (OR) per interquartile range greater PM ranged from 1.53 for MMEF (95% confidence interval [CI]: 1.20-1.96) to 2.14 for FEV1 (95% CI: 1.66-2.76) and ORs for PM ranged from 1.36 for MMEF (95%CI: 1.12-1.66) to 1.82 for FEV1 (95%CI: 1.49-2.22), respectively. PM and PM had significant associations with FVC and FEV1 in primary school children, and on PEF and MMEF in middle school children. Long-term PM and PM exposure can lead to decreased lung function in children, and the associations of PM are stronger than PM. Therefore, PM may be more hazardous to children's respiratory health than PM exposure.