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Mean quartz content in dust in German coal mines.
| Particle size | Quartz (% by weight) | Dust concentrations (mg/m3) |
|---|---|---|
| Total dust | 4.1 ± 3.3 | 53.1 ± 29.4 |
| Dust <7 microns | 4.3 ± 3.0 | 25.3 ± 13.0 |
| Dust <5 microns | 2.9 ± 1.9 | 9.2 ± 7.9 |
| Dust <3 microns | 2.2 ± 1.6 | 2.1 ± 1.6 |
