What would cause renal cancer? Is it related to diet, or to smoking, or to pollution?

Mostly unknown. A specific factor in the etiology of rcc is not known, although a number of dietary, environmental factors, hormonal, celllular and genetic factors associated with increased risk. Rcc consists of a number histologically defined entities which may occur either non-hereditary or hereditary, e.g. The influence of genetic factors in vhl disease, in hereditary papillary rcc and familial rcc.
Cigs, chemicals,gene. Kidneys clear variety of chemicals. Tobacco is known cause, some industrial chemicals, some are genetic linked, some are unknown cause. Perhaps link to some diabetes meds.