Distribution of exposure metrics for respirable coal mine dust and quartz in this inception cohort of 1369 coal miners.

Table 2: Distribution of exposure metrics for respirable coal mine dust and quartz in this inception cohort of 1369 coal miners.

	mean	sd	1.Q	median	3.Q	min	max
Respirable coal mine dust
long-term average concentration (mg/m³)	2.48	0.65	2.01	2.34	2.88	0.84	5.04
duration of exposure (dust-years)	14.97	6.78	10.08	16.89	20.38	0.51	28
cum. exposure (mg/m³-years)	37.06	19.8	23.37	36.87	48.5	1.13	100.15
Respirable quartz
long-term average concentration (mg/m³)	0.09	0.03	0.06	0.09	0.11	0	0.26
duration of exposure (quartz-years)	11.32	5.89	6.38	12.81	15.9	0	22.86
cum. exposure (mg/m³-years)	1.04	0.67	0.48	0.98	1.52	0	3.76

sd: Standard deviation; 1.Q: Lower quartile; 3.Q: Upper quartile; min: Minimum; max: Maximum.