Table 1.
Prevalence of silicosis by demographic and occupational variables (N = 14,221)
| Profusion score ≥ 1/1 | Profusion score ≥ 1/0 | |||||
|---|---|---|---|---|---|---|
| N (column %) | n | Crude prevalence % | n | Crude prevalence % | ||
| Overall | 14,221 (100) | 535 | 3.76 | 730 | 5.13 | |
| Cluster | 1 | 1138 (8.00) | 39 | 3.43 | 54 | 4.74 |
| 2 | 859 (6.04) | 25 | 2.91 | 31 | 3.61 | |
| 3 | 353 (2.48) | 10 | 2.83 | 11 | 3.12 | |
| 4 | 922 (6.48) | 48 | 5.21 | 61 | 6.61 | |
| 5 | 946 (6.65) | 32 | 3.38 | 45 | 4.76 | |
| 6 | 1006 (7.07) | 70 | 6.96 | 81 | 8.05 | |
| 7 | 948 (6.67) | 26 | 2.74 | 40 | 4.22 | |
| 8 | 960 (6.75) | 13 | 1.35 | 22 | 2.29 | |
| 9 | 659 (4.63) | 24 | 3.64 | 36 | 5.46 | |
| 10 | 1085 (7.63) | 71 | 6.54 | 93 | 8.57 | |
| 11 | 1004 (7.06) | 57 | 5.68 | 76 | 7.57 | |
| 12 | 1140 (8.02) | 32 | 2.80 | 59 | 5.17 | |
| 13 | 1013 (7.12) | 9 | 0.89 | 18 | 1.78 | |
| 14 | 1151 (8.09) | 34 | 2.95 | 44 | 3.82 | |
| 15 | 1037 (7.29) | 45 | 4.34 | 59 | 5.70 | |
| Region | Carletonville | 6726 (47.30) | 209 | 3.11 | 307 | 4.56 |
| Orkney | 3104 (21.83) | 150 | 4.83 | 192 | 6.18 | |
| Welkom | 4391 (30.88) | 176 | 4.00 | 231 | 5.26 | |
| Company | A | 5395 (37.94) | 216 | 4.00 | 295 | 5.47 |
| B | 3779 (26.57) | 98 | 2.59 | 140 | 3.70 | |
| C | 5047 (35.49) | 221 | 4.38 | 295 | 5.84 | |
| Gender | Male | 13,894 (97.70) | 534 | 3.84 | 728 | 5.24 |
| Female | 327 (2.30) | 2 | 0.61 | 2 | 0.61 | |
| Age (yrs) | 18–34 | 3361 (23.63) | 9 | 0.27 | 14 | 0.42 |
| 35–39 | 2062 (14.50) | 17 | 0.82 | 30 | 1.45 | |
| 40–44 | 2998 (21.08) | 72 | 2.40 | 103 | 3.45 | |
| 45–49 | 2965 (20.85) | 179 | 6.03 | 253 | 8.53 | |
| 50+ | 2835 (19.94) | 258 | 9.10 | 330 | 11.64 | |
| Racial ascription | Black | 13,790 (96.97) | 530 | 3.84 | 721 | 5.23 |
| Other | 431 (3.03) | 5 | 1.16 | 8 | 1.86 | |
| Country of origin | South Africa | 8062 (56.69) | 261 | 3.24 | 364 | 4.51 |
| Lesotho | 3510 (24.68) | 192 | 5.47 | 256 | 7.29 | |
| Swaziland | 565 (3.97) | 21 | 3.71 | 26 | 4.60 | |
| Mozambique | 1853 (13.03) | 44 | 2.37 | 64 | 3.45 | |
| Botswana | 223 (1.57) | 16 | 7.17 | 20 | 8.97 | |
| Other | 8 (0.06) | 0 | 0.00 | 0 | 0.00 | |
| Years since entry into industry | 0-4a | 2314 (16.27) | 5 | 0.22 | 10 | 0.43 |
| 5–9 | 1276 (8.97) | 7 | 0.55 | 11 | 0.86 | |
| 10–14 | 1724 (12.12) | 12 | 0.70 | 15 | 0.87 | |
| 15–19 | 1956 (13.75) | 39 | 1.99 | 61 | 3.12 | |
| 20–24 | 2479 (17.43) | 90 | 3.63 | 120 | 4.84 | |
| 25–29 | 2113 (14.86) | 143 | 6.77 | 202 | 9.56 | |
| 30+ | 2359 (16.59) | 239 | 10.13 | 311 | 13.18 | |
| Skill level | Unskilled | 12,981 (91.28) | 506 | 3.90 | 694 | 5.35 |
| Skilled/Official | 1240 (8.72) | 28 | 2.26 | 35 | 2.82 | |
| Underground work | Full time | 13,245 (93.14) | 515 | 3.89 | 705 | 5.32 |
| None/part time | 976 (6.86) | 20 | 2.05 | 25 | 2.56 | |
| Tuberculosis | On CXR and/or self-reported treatment | 3046 (21.42) | 194 | 6.37 | 241 | 7.91 |
| Neither | 11,175 (78.58) | 341 | 3.05 | 488 | 4.37 | |
CXR Chest radiograph, N number of subjects in each category, n number of cases of silicosis
aIncluding 202 subjects with “0” years in the industry recorded on the questionnaire