Table 1. Characteristics of the Study Population according to the Exposure Concentration of PM2.5 and Chemical Constituentsa.
| mean ± SD |
|||||||
|---|---|---|---|---|---|---|---|
| characteristic | n (%) | PM2.5 | BC | Cl– | NH4+ | NO3– | SO42– |
| total subjects | 33,234 (100.0) | ||||||
| total samples | 78,952 (100.0) | 43.69 ± 21.90 | 3.89 ± 1.81 | 1.78 ± 1.63 | 5.43 ± 2.98 | 8.31 ± 5.53 | 9.21 ± 3.44 |
| Ages, years | |||||||
| <30 | 56,879 (72.0) | 43.31 ± 21.57 | 3.83 ± 1.77 | 1.74 ± 1.60 | 5.37 ± 2.93 | 8.28 ± 5.50 | 9.13 ± 3.39 |
| 30–39 | 19,470 (24.7) | 44.80 ± 22.70 | 4.06 ± 1.90 | 1.88 ± 1.71 | 5.59 ± 3.10 | 8.45 ± 5.61 | 9.44 ± 3.56 |
| ≥40 | 2603 (3.3) | 43.78 ± 22.69 | 4.03 ± 1.84 | 1.79 ± 1.65 | 5.40 ± 3.10 | 7.92 ± 5.64 | 9.29 ± 3.40 |
| Ethnicity | |||||||
| Han | 77,007 (97.5) | 43.90 ± 22.03 | 3.90 ± 1.82 | 1.79 ± 1.65 | 5.46 ± 3.00 | 8.36 ± 5.55 | 9.25 ± 3.46 |
| Other | 1945 (2.5) | 35.53 ± 13.75 | 3.31 ± 1.04 | 1.25 ± 0.82 | 4.2 ± 1.78 | 6.27 ± 4.04 | 7.73 ± 1.92 |
| Abstinence Period, days | |||||||
| 2–3 | 22,072 (28.0) | 42.76 ± 21.53 | 3.89 ± 1.70 | 1.76 ± 1.59 | 5.25 ± 2.94 | 7.90 ± 5.49 | 9.11 ± 3.37 |
| 4–5 | 40,617 (51.4) | 42.62 ± 21.03 | 3.80 ± 1.75 | 1.71 ± 1.56 | 5.28 ± 2.86 | 8.11 ± 5.37 | 9.00 ± 3.27 |
| 6–7 | 16,263 (20.6) | 47.63 ± 23.99 | 4.10 ± 2.08 | 1.97 ± 1.84 | 6.04 ± 3.23 | 9.37 ± 5.85 | 9.88 ± 3.83 |
| Region | |||||||
| Guangdong | 34,219 (43.3) | 31.39 ± 7.52 | 3.36 ± 0.54 | 1.28 ± 0.68 | 3.64 ± 1.12 | 4.92 ± 2.44 | 7.42 ± 1.38 |
| Henan | 12,953 (16.4) | 76.91 ± 23.47 | 6.92 ± 2.10 | 4.38 ± 2.25 | 10.19 ± 3.03 | 15.59 ± 5.53 | 15.30 ± 2.81 |
| Hubei | 2655 (3.4) | 55.00 ± 23.38 | 4.44 ± 1.41 | 1.27 ± 0.76 | 6.62 ± 2.37 | 10.17 ± 5.83 | 11.70 ± 2.47 |
| Shanxi | 938 (1.2) | 47.18 ± 15.06 | 3.87 ± 1.38 | 2.21 ± 1.44 | 7.40 ± 2.54 | 8.09 ± 2.98 | 11.11 ± 3.33 |
| Sichuan | 1150 (1.5) | 50.74 ± 19.60 | 6.25 ± 2.19 | 1.88 ± 0.81 | 6.87 ± 2.41 | 8.53 ± 3.13 | 9.80 ± 2.59 |
| Zhejiang | 27,037 (34.2) | 41.82 ± 15.77 | 2.95 ± 0.86 | 1.18 ± 0.81 | 5.16 ± 1.89 | 8.92 ± 4.73 | 8.22 ± 1.87 |
| Year at Semen Examination | |||||||
| 2014 | 9103 (11.5) | 70.64 ± 19.25 | 5.44 ± 2.05 | 3.14 ± 2.14 | 9.02 ± 2.62 | 14.34 ± 5.04 | 13.97 ± 3.26 |
| 2015 | 7176 (9.1) | 71.04 ± 25.78 | 5.52 ± 2.42 | 3.15 ± 2.40 | 8.99 ± 3.31 | 13.96 ± 5.81 | 13.30 ± 3.71 |
| 2016 | 21,386 (27.1) | 37.05 ± 15.48 | 3.63 ± 1.46 | 1.63 ± 1.27 | 4.53 ± 2.26 | 6.25 ± 4.51 | 8.34 ± 2.43 |
| 2017 | 15,825 (20.0) | 39.46 ± 17.41 | 3.71 ± 1.42 | 1.44 ± 1.21 | 4.78 ± 2.47 | 7.45 ± 4.97 | 8.42 ± 2.53 |
| 2018 | 13,507 (17.1) | 35.83 ± 12.16 | 3.40 ± 1.15 | 1.30 ± 1.01 | 4.29 ± 1.72 | 6.58 ± 3.74 | 7.89 ± 1.74 |
| 2019 | 7590 (9.6) | 36.90 ± 16.21 | 3.35 ± 1.71 | 1.40 ± 1.30 | 4.84 ± 2.22 | 8.02 ± 4.45 | 7.87 ± 2.02 |
| 2020 | 4365 (5.5) | 26.58 ± 5.98 | 2.30 ± 0.69 | 0.69 ± 0.51 | 3.45 ± 1.27 | 5.47 ± 2.96 | 6.09 ± 1.05 |
| Season at Semen Examination | |||||||
| Spring (Mar, Apr, May) | 22,545 (28.6) | 53.87 ± 23.51 | 4.50 ± 1.93 | 2.48 ± 1.88 | 6.89 ± 3.01 | 11.67 ± 4.92 | 10.14 ± 3.17 |
| Summer (Jun, Jul, Aug) | 22,620 (28.7) | 34.27 ± 14.66 | 3.35 ± 1.04 | 1.15 ± 0.80 | 4.17 ± 2.14 | 5.57 ± 3.03 | 8.24 ± 3.42 |
| Autumn (Sep, Oct, Nov) | 18,675 (23.7) | 33.49 ± 12.04 | 3.21 ± 1.26 | 1.11 ± 0.88 | 4.14 ± 2.17 | 5.03 ± 3.57 | 8.49 ± 3.51 |
| Winter (Dec, Jan, Feb) | 15,112 (19.1) | 55.22 ± 25.13 | 4.63 ± 2.42 | 2.49 ± 2.09 | 6.73 ± 3.30 | 11.45 ± 6.56 | 10.16 ± 3.1 |
a
Abbreviation: SD, standardized deviation; PM2.5, particulate matter ≤ 2.5 μm in aerodynamic diameter; BC, black carbon; Cl–, chloride; NH4+, ammonium; NO3, nitrate; SO42–, sulfate.