<prompt> All are risk factors of squamous cell carcinoma exceptUltraviolet radiationTarTobaccoHPV 18  <response>: Ultraviolet radiation, chronic inflammation, and chemical carcinogens arsenicals, tar and infection with HPV 5 and 16.There is also evidence that current and previous tobacco use doubles the relative risk of SCC.Ref: Bailey and Love, 27e, page: 606 