Dust and quartz concentrations and alpha quartz percentage
| n | Mean | SD | Median | Range | |
|---|---|---|---|---|---|
| TWA, 8 hour time weighted average; SD, standard deviation. | |||||
| *Following pooling of batches of dust samples by occupation. Alpha quartz fraction for that batch attributed to each sample in the batch. | |||||
| Research dust measurements | |||||
| TWA respirable dust concentration (mg/m3) | 506 | 0.35 | 0.46 | 0.17 | 0.05–3.71 |
| Alpha quartz fraction (%) | 497* | 12.0 | 5.6 | 13.2 | 0–21.3 |
| TWA respirable quartz concentration (mg/m3) | 497 | 0.048 | 0.072 | 0.019 | 0–0.71 |
| Routine dust measurements | |||||
| TWA respirable dust concentration (mg/m3) | 715 | 0.36 | 0.44 | 0.22 | 0.022–4.29 |
| Alpha quartz fraction (%) | 655* | 16.0 | 5.8 | 16.1 | 0.67–39.1 |
| TWA respirable quartz concentration (mg/m3) | 715 | 0.051 | 0.072 | 0.028 | 0–0.71 |