Table 9 Difference Test of Symptom Frequency in Respiratory system before and after Matching.
| Â | Â | Before matching | After matching | ||||||
|---|---|---|---|---|---|---|---|---|---|
Low exposure | High exposure | χ2 | P | Low exposure | High exposure | χ2 | P | ||
Cough and expectoration | Â | Â | Â | 2.251 | 0.325 | Â | Â | 0.968 | 0.616 |
| Â | Nothing | 830 | 323 | Â | Â | 334 | 323 | Â | Â |
| Â | Light | 127 | 57 | Â | Â | 49 | 57 | Â | Â |
| Â | Middle | 19 | 12 | Â | Â | 10 | 12 | Â | Â |
Shortness of breath | Â | Â | Â | 2.993 | 0.224 | Â | Â | 1.442 | 0.486 |
| Â | Nothing | 906 | 353 | Â | Â | 363 | 353 | Â | Â |
| Â | Light | 62 | 34 | Â | Â | 27 | 34 | Â | Â |
| Â | Middle | 8 | 5 | Â | Â | 3 | 5 | Â | Â |
Chest tightness and shortness of breath | Â | Â | Â | 1.936 | 0.38 | Â | Â | 0.755 | 0.685 |
| Â | Nothing | 889 | 347 | Â | Â | 354 | 347 | Â | Â |
| Â | Light | 74 | 38 | Â | Â | 33 | 38 | Â | Â |
| Â | Middle | 14 | 7 | Â | Â | 5 | 7 | Â | Â |
Unexplained hemoptysis |  |  |  | — | 0.054 |  |  | 10.473 | 0.001 |
| Â | Nothing | 960 | 391 | Â | Â | 379 | 391 | Â | Â |
| Â | Middle | 16 | 10 | Â | Â | 13 | 1 | Â | Â |
