Exposure to PM2.5 at level near or below existing National Ambient Air Quality Standards was associated with increased hospital admissions in a population of Medicare enrollees. Analyzing records of 32,119 people in 5,138 ZIP codes in the Medicare Current Beneficiary Survey between 2002 and 2010, researchers part of the Harvard ACE Center found that average exposures at levels over 12 mg/m3 of PM2.5 (the current standard) were associated with increases in all-cause admissions rates of 7%, and of 6% for circulatory health issues, compared to exposures below the standard. Limiting the analysis to people whose average exposures were below the standard, exposures above just 8 mg/m3,compared to those with lower exposures, were associated with a 15% increase in all-cause admissions, 18% increase for circulatory cause, and 21% increase for respiratory illness. Results were robust after controlling for a large number of individual confounders.