Environmental factors are undoubtedly related to the incidence of the disease with smoking causing a two to six fold rise in the risk of the disease. It is thought that the aromatic amines in the tobacco smoke are the carcinogenic agents - absorbed into the blood after inhalation into the lungs and then excreted in the urine, where the contact with the bladder wall lining (epithelium) proves the trigger for the eventual development of the cancer.
Workers in industries involved with work with aromatic amines also have a higher incidence of the disease and once again due the exposure to aromatic amines (particularly the rubber industry and those workers exposed to dye stuffs).
Interestingly, recent data suggest a familial tendency to the disease and it is thought that the genetic expression of genes that metabolise the toxic substances varies between individuals and hence the excretion/concentration of carcinogenic metabolites in the urine.
In countries where the infectious disease: schistosomiasis is endemic/common e.g.Egypt, there is an increased incidence of squamous cancer of the bladder (a type which is otherwise infrequent in the UK.)
