Table 2.

Mean (± SD) concentrations of PM_2.5 (μg/m³) from 2006 to 2011 in the northern and central/southern areas

Area	n	2006	2007	2008	2009	2010	2011
Northern	18	27.43 ± 5.03	28.69 ± 5.39	27.33 ± 5.48	25.96 ± 5.32	25.98 ± 5.37	26.61 ± 5.30
Central/southern	23	37.69 ± 3.59	38.03 ± 4.05	37.48 ± 4.59	38.44 ± 3.67	35.46 ± 3.14	36.75 ± 4.97

SD standard deviation, n number of monitoring stations