Table 2.
Results of logistic regression for the association between exposure to air pollution and thyroid nodules a .
| Model | Sample size | Model 1 | Model 2 | Model 3 | Model 4 b | |
|---|---|---|---|---|---|---|
| PM2.5, μg/m3 | ||||||
| Per 10 units | 4,920,536 | 1.04 (1.04, 1.04) | 1.04 (1.04, 1.04) | 1.06 (1.06, 1.06) | 1.06 (1.06, 1.06) | |
| 10–29 | 573,013 | 1.00 (ref) | 1.00 (ref) | 1.00 (ref) | 1.00 (ref) | |
| 30–49 | 1,793,520 | 1.27 (1.26, 1.28) | 1.25 (1.25, 1.26) | 1.14 (1.13, 1.15) | 1.16 (1.15, 1.17) | |
| 50–69 | 1,824,227 | 1.15 (1.14, 1.16) | 1.13 (1.13, 1.14) | 1.21 (1.21, 1.22) | 1.24 (1.23, 1.25) | |
| 70– | 729,776 | 1.43 (1.42, 1.45) | 1.39 (1.38, 1.40) | 1.46 (1.45, 1.47) | 1.52 (1.51, 1.54) | |
| PM10, μg/m3 | ||||||
| Per 10 units | 4,920,536 | 1.02 (1.02, 1.02) | 1.02 (1.02, 1.02) | 1.03 (1.03, 1.03) | 1.04 (1.03, 1.04) | |
| 20–39 | 75,311 | 1.00 | 1.00 | 1.00 | 1.00 | |
| 40–59 | 795,836 | 1.20 (1.18, 1.22) | 1.20 (1.18, 1.22) | 1.11 (1.09, 1.13) | 1.08 (1.06, 1.10) | |
| 60–79 | 1,382,917 | 1.47 (1.44, 1.49) | 1.44 (1.42, 1.47) | 1.12 (1.10, 1.14) | 1.13 (1.11, 1.15) | |
| 80–99 | 1,362,765 | 1.36 (1.34, 1.38) | 1.34 (1.32, 1.37) | 1.20 (1.18, 1.23) | 1.22 (1.20, 1.24) | |
| 100– | 1,303,707 | 1.53 (1.51, 1.56) | 1.49 (1.46, 1.52) | 1.37 (1.35, 1.39) | 1.38 (1.36, 1.41) | |
| NO2, μg/m3 | ||||||
| Per 10 units | 4,920,536 | 1.05 (1.05, 1.05) | 1.05 (1.05, 1.05) | 1.09 (1.09, 1.09) | 1.10 (1.09, 1.10) | |
| <20 | 98,703 | 1.00 (ref) | 1.00 (ref) | 1.00 (ref) | 1.00 (ref) | |
| 20–29 | 804,180 | 1.43 (1.41, 1.46) | 1.42 (1.40, 1.44) | 1.21 (1.20, 1.23) | 1.24 (1.22, 1.26) | |
| 30–39 | 1,281,162 | 1.33 (1.31, 1.35) | 1.32 (1.30, 1.34) | 1.17 (1.15, 1.18) | 1.15 (1.14, 1.17) | |
| 40– | 2,736,491 | 1.46 (1.44, 1.48) | 1.45 (1.43, 1.47) | 1.39 (1.37, 1.41) | 1.41 (1.39, 1.43) | |
| SO2, μg/m3 | ||||||
| Per 10 units | 4,920,536 | 1.10 (1.09, 1.10) | 1.09 (1.09, 1.09) | 1.12 (1.10, 1.12) | 1.11 (1.11, 1.12) | |
| <10 | 579,116 | 1.00 (ref) | 1.00 (ref) | 1.00 (ref) | 1.00 (ref) | |
| 10–19 | 2,192,717 | 0.98 (0.97, 0.98) | 0.98 (0.98, 0.99) | 1.06 (1.05, 1.06) | 1.14 (1.13, 1.14) | |
| 20–29 | 1,188,411 | 1.21 (1.21, 1.22) | 1.19 (1.18, 1.20) | 1.21 (1.21, 1.22) | 1.31 (1.29, 1.32) | |
| 30– | 960,292 | 1.36 (1.35, 1.37) | 1.33 (1.32, 1.34) | 1.47 (1.46, 1.48) | 1.55 (1.54, 1.57) | |
| CO, mg/m3 | ||||||
| Per 1 units | 4,920,536 | 1.20 (1.19, 1.21) | 1.17 (1.16, 1.18) | 1.46 (1.45, 1.47) | 1.50 (1.49, 1.52) | |
| 0.40–0.79 | 676,838 | 1.00 (ref) | 1.00 (ref) | 1.00 (ref) | 1.00 (ref) | |
| 0.80–1.19 | 2,898,208 | 1.001 (0.998, 1.002) | 1.001 (1.001, 1.002) | 1.17 (1.16, 1.17) | 1.19 (1.19, 1.20) | |
| 1.20– | 1,345,490 | 1.14 (1.13, 1.15) | 1.12 (1.11, 1.13) | 1.41 (1.40, 1.42) | 1.43 (1.42, 1.44) | |
| O3, μg/m3 | ||||||
| Per 10 units | 4,920,536 | 1.21 (1.20, 1.21) | 1.20 (1.20, 1.20) | 1.20 (1.18, 1.20) | 1.151 (1.149, 1.154) | |
| <50 | 738,472 | 1.00 (ref) | 1.00 (ref) | 1.00 (ref) | 1.00 (ref) | |
| 50–59 | 2,327,055 | 1.17 (1.16, 1.17) | 1.16 (1.16, 1.17) | 1.15 (1.15, 1.16) | 1.17 (1.16, 1.18) | |
| 60–69 | 952,216 | 1.43 (1.42, 1.44) | 1.40 (1.40, 1.41) | 1.42 (1.41, 1.42) | 1.43 (1.42, 1.44) | |
| 70– | 902,793 | 1.60 (1.59, 1.62) | 1.58 (1.57, 1.59) | 1.56 (1.55, 1.57) | 1.43 (1.42, 1.44) | |
Data are OR (95% CI), unless indicated otherwise. ORs are presented for the following increments: 10 μg/m3 for PM2.5, PM10, NO2, SO2, and O3, and 1mg/m3 for CO. OR, Odds ratio.
Model 1 included only age, and sex. Model 2 added individual level variables: fasting blood glucose, body mass index, triglyceride, low density lipoprotein, and high density lipoprotein. Model 3 added city-level variables including Gross Domestic Product, and O3 concentration (except for O3 itself). Model 4 added province-level variables including average urine iodine level, average years of education and average smoking rate.
P-values for trend in Model 1 to Model 4 were all less than 0.05.