I'm not saying smoking is a good thing here... take this example:
The cancer sticks I smoke deliver on average 20mg of carbon monoxide and 0.2mg of hydrogen cyanide, the partial pressure of both of these compounds is effectively zero in clean blood - so generaly all that is inhaled is taken into the blood. (depending on how emphesemic the lungs already are)
The molecular mass of Carbon monoxide is ~28g/mol and hydrogen cyanide is ~27g/mol
there are 6.022x10^23 molecules per mole (Avogadro's number)
so
20mg CO >> 0.020g/28g = 7.14x10^-4 moles = 4.30x10^20 molecules of CO
0.2mg HCN >> 0.0002g/27g = 7.41x10^-6 moles = 4.46x10^18 molecules of HCN
~= 4.34x10^20 molecules of CO and HCN in total
Both CN- and CO are irreversibly adsorbed by hemoglobin.
Hemoglobin has four heme planes with each site binding more easily than the last.
The average red blood cell contains roughly 150 000 hemoglobin molecules.
So one of my cigarettes will kill (4.34x10^20/4)/150000 = 7.24x10^18 blood cells
That's 7.24 trillion blood cells dead from one cigarette - its no wonder two flights of stairs leaves me winded.
(now this assumes that each red blood cell takes up four CO or CN- but of course not all will, but will be reduced in function. This is an overestimate or worst case scenario. I'm not 100% on these calculations but I think they're roughly correct - feel free to find an error!)
Undoubtedly the bilirubin will be much higher in the stool of smokers. It's gotta wear on the liver removing all that dead weight in blood.
Best of luck with your studies, you've got some good support there. Work hard and stay away from the campus pub!