Figures 2a–2b.

Adjusted mortality rate ratios (MRR) of lung cancer as a function years exposed to biocide with synthetic metalworking fluid (MWF) (2a) and with soluble MWF (2b) as estimated by Cox regression using penalized splines in the full cohort and subcohort. The subcohort is restricted to workers hired on or after start of follow-up. All models were adjusted for straight MWF (mg/m³ per year), soluble MWF (mg/m³ per year) (only in 2a), synthetic MWF (mg/m³ per year) (only in 2b), race, gender, plant, calendar year, and years since retirement. Years exposed to biocide with synthetic and soluble MWF, straight MWF, soluble MWF, synthetic MWF, calendar year, and years since retirement were treated as non-linear terms if degrees of freedom selected by Akaike information criterion (AIC) >1.0 and if P<0.10. Rug plots represent the distribution of exposure for incident hires (top) and the full cohort (bottom).