You can do better than correlations, but do you deny that you can draw from them the conclusions that Yvain does? (ie, the population effect of smoking)

The conclusion he draws is:

Even if we didn't know there was causation, it would at least help us to pick out who needs more frequent lung cancer screening tests.

Sure, standard statistics. No problem, for want of anything better.

On the other hand, if you want to know how the link between smoking and lung cancer works, the epidemiology can do no more than suggest places to look.

The MN scientist is lying. No, I didn't click on the link. Yes, I mean lying, not mistaken.

On closer reading, the actual scientific claim is less than I thought. It's a statistical study correlating the presence of a nitrosamine compound in the urine with lung cancer, and finding a higher correlation than with self-reported smoking. Original paper (full text requires subscription) here and blogged here. So just more statistical epidemiology and not at all epoch-making.

ETA: Extra links, just because these things are worth knowing.