Table 3 Mortality rate ratios from Cox proportional hazards models with penalised spline models for silica and lung cancer in the Vermont granite study, 1950–94

Cohort definition	Maximum MRR* (95% CI)	Exposure† at maximum MRR	% Prevalent hires
Original cohort‡	2.50 (1.81 to 3.47)	4.0	50.2
Prevalent hires§	1.97 (1.52 to 2.56)	4.1	100.0
Incident hires¶	2.19** (1.27 to 3.76)	0.6	0.0

MRR, mortality rate ratio.
*Models used age as the timeline and controlled for calendar year and age at hire.
†Cumulative exposure with 15-year lag, in mg-year/m³.
‡Subjects who worked in granite industry anytime between 1 January 1950 (start of follow-up) and 31 December 1982 (includes prevalent hires and incident hires).
§Subjects who were already at work prior to the start of follow-up on 1 January 1950 and still at work on that date.
¶Subjects who started working in granite industry between 1 January 1950 (start of follow-up) and 31 December 1982.
**For incident hires, MRR of 14.89 (95% CI 1.63 to 135.76) was observed at 2.0 mg-year/m³.