How is tobacco smoking a risk factor for developing renal cell carcinoma?

How? Or: Wny? I should distinguish that there is an "association" of smoking" and all urothelial, and maybe renal parenchymal cancers. . . Not the same as cause. Epidemiologists study populations that smoke and match with those that do not smoker, try to "adjust" for other variables. Tobacco produces carcinogens, and that could be the "how", but the science of that is not as well described as with lung.

Increased risk.: Smoking introduces many very carcinogenic compounds into the bloodstream, which is filtered by the kidney. These carcinogens, along with the decreased tissue oxygenation caused by smoking, is theorized to increase the risk of renal cell carcinoma. A meta-analysis of 24 studies (hunt, int j cancer 114:101-108, 2005) showed this significantly increased risk, & it is considered causal by the ussg.