American journal of respiratory and critical care medicine 2017 12 15() doi 10.1164/rccm.201706-1267OC
Short and long-term fine particulate matter (PM2.5) pollution is associated with asthma development and morbidity, but there is little data on the effects of long-term exposure to coarse PM (PM10-2.5) on respiratory health.
To understand the relationship between long-term fine and coarse PM exposure and asthma prevalence and morbidity among children.
A semi-parametric regression model that incorporated PM2.5 and PM10 monitor data and geographic characteristics was developed to predict two-year average PM2.5 and PM10-2.5 exposure during the period 2009-2010 at the zip-code tabulation area level. Data from 7,810,025 children aged 5-20 years enrolled in Medicaid from 2009-2010 were used in a log-linear regression model with predicted PM levels to estimate the association between PM exposure and asthma prevalence and morbidity, adjusting for race/ethnicity, sex, age, area-level urbanicity, poverty, education, and unmeasured spatial confounding.
MEASUREMENTS AND MAIN RESULTS
Exposure to coarse PM was associated with increased asthma diagnosis prevalence (RR for 1µg/m3 increase in coarse PM level: 1.006, 95%CI: 1.001-1.011), hospitalizations (RR: 1.023, 95%CI: 1.003-1.042), and emergency department (ED) visits (RR: 1.017, 95%CI: 1.001-1.033) when adjusting for fine PM. Fine PM exposure was more strongly associated with increased asthma prevalence and morbidity than coarse PM. The estimates remained elevated across different levels of spatial confounding adjustment.
Among children enrolled in Medicaid, exposure to higher average coarse PM levels is associated with increased asthma prevalence and morbidity. These results suggest the need for direct monitoring of coarse PM and reconsideration of limits on long-term average coarse PM pollution levels.