Arithmetic and geometric mean PCM fibre concentrations (fibres >5 μm/ml) by plant, exposure zone and calendar period, North Carolina asbestos textile plants
| Plant | Exposure zone | 1935–1946 | 1947–1970 | 1971–1986 | |||||||||
| No | AM | GM | GSD | No | AM | GM | GSD | No | AM | GM | GSD | ||
| 1* | All combined† | 129 | 65.3 | 23.2 | 4.7 | 419 | 9.5 | 5.9 | 3.1 | * | |||
| 1 | Preparation | 25 | 139.2 | 65.0 | 3.9 | 43 | 15.8 | 10.6 | 2.2 | ||||
| 1 | Carding | 35 | 110.4 | 64.9 | 3.2 | 76 | 13.4 | 11.4 | 1.9 | ||||
| 1 | Spinning | 17 | 18.9 | 14.4 | 2.1 | 106 | 9.7 | 7.1 | 2.4 | ||||
| 1 | Twisting | 18 | 21.6 | 16.2 | 2.2 | 66 | 9.8 | 7.1 | 2.4 | ||||
| 1 | Weaving | 17 | 10.4 | 7.3 | 2.4 | 75 | 3.4 | 2.0 | 3.4 | ||||
| 1 | Winding | 10 | 14.7 | 10.1 | 2.9 | 41 | 7.0 | 4.3 | 2.8 | ||||
| 1 | Finishing | 2 | 5.2 | 5.2 | 1.2 | 2 | 1.7 | 1.6 | 1.4 | ||||
| 1 | All others | 5 | 6.5 | 0.9 | 9.9 | 10 | 7.2 | 3.4 | 4.7 | ||||
| 3 | All combined† | 279 | 100.5 | 39.2 | 4.0 | 767 | 10.1 | 5.3 | 3.1 | 831 | 5.1 | 1.4 | 5.3 |
| 3 | Preparation | 59 | 182.3 | 64.2 | 4.2 | 124 | 11.1 | 6.9 | 2.5 | 116 | 7.0 | 1.1 | 6.1 |
| 3 | Carding | 60 | 128.9 | 72.6 | 3.1 | 158 | 14.7 | 9.9 | 2.4 | 187 | 7.7 | 1.8 | 6.1 |
| 3 | Spinning | 35 | 16.0 | 12.5 | 2.2 | 133 | 4.0 | 2.9 | 2.5 | 99 | 4.2 | 1.9 | 4.6 |
| 3 | Twisting | 21 | 22.4 | 15.1 | 3.0 | 118 | 6.5 | 4.2 | 3.0 | 93 | 4.7 | 2.0 | 4.4 |
| 3 | Weaving | 65 | 104.5 | 47.1 | 3.7 | 153 | 14.4 | 5.9 | 3.3 | 170 | 3.6 | 1.3 | 4.5 |
| 3 | Winding | 18 | 54.2 | 46.3 | 1.8 | 30 | 7.5 | 4.4 | 3.1 | 56 | 4.0 | 2.3 | 3.1 |
| 3 | Finishing | 5 | 31.0 | 18.6 | 3.2 | 16 | 2.1 | 1.0 | 2.8 | 44 | 1.0 | 0.7 | 2.7 |
| 4‡ | All combined† | 16 | 46.0 | 25.8 | 3.7 | 514 | 21.2 | 13.9 | 2.9 | 456 | 3.5 | 1.1 | 5.1 |
| 4 | Preparation | 52 | 25.9 | 17.9 | 2.4 | 52 | 3.1 | 1.0 | 6.0 | ||||
| 4 | Carding | 94 | 21.4 | 14.0 | 3.2 | 119 | 6.1 | 1.7 | 5.4 | ||||
| 4 | Spinning | 83 | 19.5 | 14.9 | 2.1 | 27 | 1.1 | 0.8 | 2.4 | ||||
| 4 | Twisting | 55 | 29.5 | 19.9 | 2.7 | 25 | 6.5 | 5.0 | 2.2 | ||||
| 4 | Weaving | 14 | 47.7 | 25.8 | 4.0 | 147 | 21.3 | 15.0 | 2.5 | 80 | 2.5 | 1.6 | 2.9 |
| 4 | Winding | 39 | 16.5 | 10.2 | 3.3 | 51 | 1.7 | 0.6 | 4.4 | ||||
| 4 | Finishing | 2 | 33.9 | 25.7 | 3.0 | 19 | 9.2 | 4.5 | 4.8 | 15 | 3.6 | 1.6 | 3.5 |
| 4 | All others | 25 | 12.7 | 7.2 | 4.6 | 83 | 2.1 | 0.5 | 5.9 | ||||
*Plant 1 ceased asbestos production in 1970; †all departments combined; ‡plant 3 began asbestos operations in approximately 1942.
AM, arithmetic means; GM, geometric means; GSD, geometric standard deviation; PCM, phase contract microscopy.