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Table 1 Baseline characteristics of the subjects and distributions of pollutants according to antibody outcomes

From: Long-term exposure to a mixture of industrial SO2, NO2, and PM2.5 and anti-citrullinated protein antibody positivity

ACPA outcome

Positive

Negative (< 20 units/ml)

Strong (≥60 units/ml)

Moderate (40–59 units/ml)

Weak (20–39 units/ml)

Number of subjects (%)

134 (1.8)

158 (2.1)

494 (6.5)

6788 (89.6)

Mean agea(standard deviation)

55.1 (7.5)

53.8 (7.8)

54.6 (7.6)

54.0 (7.7)

Female, N (%)

76 (56.7)

88 (55.7)

247 (50.0)

3441 (50.7)

Ancestry, N (%)

French Canadian

96 (71.6)

103 (65.2)

330 (66.8)

4571 (67.3)

Other

38 (28.4)

55 (34.8)

164 (33.2)

2217 (32.7)

Smokersb,N (%)

Never

45 (33.6)

68 (43.0)

225 (45.5)

2710 (39.9)

Occasional

69 (51.5)

67 (42.4)

208 (42.1)

3141 (46.2)

Daily

20 (14.9)

23 (14.6)

59 (11.9)

913 (13.5)

Annual income level, N (%)

(Canadian $)

< 25,000

13 (9.7)

19 (12.0)

44 (8.9)

631 (9.3)

25,000 to 49,999

29 (21.6)

34 (21.5)

94 (19.0)

1363 (20.1)

50,000 to 74,999

32 (23.9)

29 (18.4)

111 (22.5)

1447 (21.3)

75,000 to 149,999

38 (28.4)

49 (31.0)

151 (30.6)

2233 (32.9)

> 150,000

15 (11.1)

15 (9.5)

64 (13.0)

782 (11.5)

Range, mean, and standard deviation of exposure variables

Industrial SO2(ppb)

0.64–19.57, 2.89, 2.34

0.62–71.19, 2.91, 5.71

0.61–17.14, 2.69, 1.94

0.34–60.98, 2.56, 2.15

Industrial NO2(ppb)

0.16–3.01, 1.14, 0.56

0.27–6.05, 1.25, 0.73

0.26–4.06, 1.13, 0.57

0.12–7.76, 1.16, 0.52

Industrial PM2.5(μg/m3)

0.06–2.87, 0.27, 0.39

0.05–14.09, 0.28, 1.14

0.05–3.12, 0.23, 0.32

0.03–11.17, 0.21, 0.36

Overall PM2.5(μg/m3)

5.27–14.85, 11.24, 3.06

5.58–14.85, 11.55, 2.97

5.22–14.85, 11.44, 3.02

5.13–14.85, 11.76, 2.90

  1. a Age is a continuous numeric variable in the standard logistic and Weighted Quantile Sum (WQS) regression models
  2. b Missing data existed for the covariates smoking and income, and thus the summed number of daily, occasional, and never smokers is slightly smaller than the total number of population subjects involved in the analysis