Figure 2From: PM2.5 in Beijing – temporal pattern and its association with influenza Distribution of PM 2.5 concentrations and days with 24-hr averages exceeding the standards. Top – frequency distribution of days with varying 24-hr average concentrations for the whole study period; black line – the WHO standard (25 μg/m3), redline – the EPA standard (35 μg/m3), green – the SEPA standard (75 μg/m3). Bottom – distribution of days each month with the 24-hr averages exceeding the standards by the WHO (red), the EPA (green) and SEPA (blue). The gap between December 2008 and February 2009 was due to missing measurements.Back to article page