Table I.

Distribution of radon exposure rates by categories of latency in cases and controls from the nested case–control data set^*.

	Age <60 years		Age ≥60 years
	Controls	Cases	Controls	Cases
Number of records†	5360	134	4699	129
Exposure rate during previous 30 years (WL)‡
First quartile	2.7	5.7	2.6	3.8
Second quartile (median)	5.3	8.8	5.1	6.2
Third quartile	9.4	13.3	8.9	10.5
Radon exposure rates during 0–9 years of latency (WL)
No exposure (per cent)	66	57	80	77
Median among exposed	4.1	4.2	3.5	3.3
IQR§	5.7	8.5	4.5	4.0
Radon exposure rates during 10–19 years of latency (WL)
No exposure (per cent)	38	28	47	39
Median among exposed	4.2	7.6	4.5	5.6
IQR	7.0	10.9	6.7	8.2
Radon exposure rates during 20–29 years of latency (WL)
No exposure (per cent)	48	44	35	33
Median among exposed	5.8	9.3	5.4	8.4
IQR	7.5	9.7	7.1	10.6
Radon exposure rates during 30+ years of latency (WL)
No exposure (per cent)	85	78	72	70
Median among exposed	6.6	7.5	7.4	6.1
IQR	10.3	11.7	11.4	15.3

Note: A subject’s rate in a latency interval is computed as total exposure (WLM) within the latency interval divided by the time worked in a mine within the latency interval.

^*Computed up to two years prior to the case’s age at death.

^†Subjects may be controls in multiple case–control sets.

^‡Computed as the total cumulative exposure during the past 30 years divided by the time exposed.

^§Inter-quartile range= third quartile-first quartile.