Table IV.
Pneumoconiosis in Coal Mines Regression Results
| Estimate | Std. Error | t Value | p Value | Incident Risk Ratio (IRR) |
IRR 95% CI Lower Bound |
IRR 95% CI Upper Bound |
|
|---|---|---|---|---|---|---|---|
| Base Models: Control variables | |||||||
| Miner age | 0.08** | 0.03 | 2.83 | 0.005 | 1.08 | 1.02 | 1.14 |
| Mining tenure | 0.13*** | 0.03 | 4.92 | <.001 | 1.14 | 1.08 | 1.20 |
| Model 1: Management practices | |||||||
| Miner age | 0.05 | 0.04 | 1.15 | 0.25 | 1.05 | 0.99 | 1.14 |
| Mining tenure | 0.06 | 0.04 | 1.59 | 0.11 | 1.06 | 0.99 | 1.15 |
| U.S. region | 1.22*** | 0.42 | −2.89 | <.001 | 3.40 | 1.48 | 7.78 |
| Mine type | 2.08*** | 0.24 | −8.69 | <.001 | 8.00 | 5.00 | 12.80 |
| Management practices | 0.12** | 0.04 | 2.86 | 0.004 | 1.12 | 1.04 | 1.16 |
| Model 2: Engineering controls | |||||||
| Miner age | 0.07 | 0.04 | 1.54 | 0.12 | 1.07 | 0.98 | 1.16 |
| Mining tenure | 0.07 | 0.04 | 1.68 | 0.09 | 1.07 | 0.99 | 1.15 |
| U.S. region | 1.00** | 0.41 | −2.44 | 0.01 | 2.73 | 1.22 | 6.12 |
| Mine type | 2.28*** | 0.24 | −9.60 | <.001 | 9.78 | 6.14 | 15.58 |
| Engineering controls | 0.10*** | 0.03 | 3.40 | <.001 | 1.10 | 1.04 | 1.16 |
Note: n = 1,634.
***
p < 0.001;
**
p < 0.01;
*
p < 0.05. For U.S. region, the Appalachian region is contrasted with the rest of the United States with the rest of the United States as the reference group. For mine type, underground coal is contrasted with surface coal with surface coal mines as the reference group. The interaction terms between workplace practices and conditions from 1996 to 2005 and mining type and U.S. region were not significant.