17 never-smoker subjects 30-60 years of age , with stable type 2 diabetes but otherwise healthy , inhaled either filtered air ( 0-10 particles/cm3 ) or elemental carbon UFP ( ~ 107 particles/cm3 , ~ 50 ug/m3 , count median diameter 32 nm ) by mouthpiece , for 2 hours at rest , in a double-blind , randomized , crossover study design .