Table 2 Annual average concentration of air pollutants in Suzhou City in 2014–2016

PM2.5

66.38 ± 22.22

57.51 ± 23.40^ab

45.41 ± 22.04^a

PM10

89.94 ± 26.25

80.51 ± 26.77^ab

71.27 ± 24.96^a

NO₂

51.72 ± 13.74

50.58 ± 14.37^b

48.71 ± 13.91^a

SO₂

23.06 ± 7.68

21.23 ± 7.65^ab

16.84 ± 5.30^a

CO

0.93 ± 0.18

0.93 ± 0.21

0.94 ± 0.19

O₃

55.98 ± 22.03

57.44 ± 23.63

60.07 ± 22.86

Number of patients

1959

1812^a

1716^a