[russholmes]

This is specific to tobacco: firstly that the tobacco leaves pick up trace amounts of polonium-210, and secondly that inhaling tobacco smoke concentrates the Po-210 into localised deposits within the lung. Because Po-210 is a short range alpha emitter, these deposits deliver a significant radiation dose to small areas of lung epithelium. This dose is believed to contribute to the carcinogenic effect of tobacco smoke.

Eating vegetables does not lead to tissue irradiation in this manner. You are not at risk from eating tomatoes (or other fruit and veg) whether or not they are fertilized with rock phosphate.