Table 1 Comparison of population characteristics by site

Male sex^a, n (%)

71 (49)

43 (54)

34 (62)

0.262

Age^b, year, median [25–75^th]

12 [11–13]

12 [11–13]

12 [12–13]

0.978

SES index^a, n (%)

0.466

     Low

29 (20)

19 (24)

6 (11)

     Medium

79 (55)

42 (53)

34 (62)

     High

37 (25)

19 (24)

15 (27)

Maternal asthma^a, n (%)

15 (10)

6 (8)

5 (9)

0.779

Residence in urban area^a, n (%)

130 (95)

64 (89)

40 (83)

0.040

Mother smokes^a, n (%)

33 (23)

20 (25)

9 (16)

0.457

PM₁₀ ^b (μg/m³), median [25–75^th]

63.1 [48.5–88.8]

65.7 [51.8–88.9]

52.1 [37.6–71.3]

0.004

Mn^b (ng/m³), median [25–75^th]

33.4 [19.7–91.8]

22.9 [10.9–44.3]

14.7 [7.61–28.9]

0.000

Ni^b (ng/m³), median [25–75^th]

3.70 [2.10–6.66]

3.36 [1.67–6.90]

1.97 [1.15–3.84]

0.001

Cr^b (ng/m³), median [25–75^th]

8.06 [4.86–14.3]

5.56 [3.29–10.7]

7.25 [3.66–11.0]

0.030

Fe^b (ng/m³) median [25–75^th]

346 [220–629]

559 [278–1058]

305 [173–479]

0.002

Zn^b (ng/m³), median [25–75^th]

80.9 [47.0–118]

56.1 [27.7–107]

57.6 [36.0–92.9]

0.061