RESULTS.A total of 325 upper respiratory tract (UPT) carcinomas and 821 lung
carcinomas were observed during follow-up. Incense use was associated with a
significantly increased risk of UPT carcinomas other than nasopharyngeal,
whereas no overall effect was observed on lung cancer. The duration and intensity of incense use were associated with an increased risk of squamous cell carcinomas in the entire respiratory tract (Pfor trend 5.004), whereas there was no
significant association noted between incense use and nonsquamous cell carcinomas. The relative risk of squamous cell carcinomas among long-term incense
users was 1.8 (95% confidence interval [95% CI], 1.2-2.6;P5.004) in the entire
respiratory tract