Review Question - QID 214445

A 65-year-old man presents to the clinic with complaints of blood in his urine. The patient reports similar episodes for the past week; however, today he began passing small blood clots and was concerned. He denies dysuria, fever, chills, or discharge. His past medical history includes hypertension, recurrent bladder infections, and rheumatoid arthritis for which he is taking methotrexate. He drinks 3-4 beers a day and denies any history of smoking or drug use. He has worked in a textile factory for the past 45 years. The patient underwent cystoscopy and pathology findings are shown in Figure A. Which of the following is the most significant risk factor in this patient that contributed to his disease?