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. Author manuscript; available in PMC: 2015 Jan 29.
Published in final edited form as: Occup Environ Med. 2014 Apr 2;71(7):507–513. doi: 10.1136/oemed-2013-101874

Figure 1.

Figure 1

Histograms and Density Curves of Changes in Annual Air Pollution Levels over the Study Period. The four panels depict distributions of changes in levels of NO2, PM2.5, PM10 and O3 between Years 5 and 6.