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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