>>1331478https://academic.oup.com/jnci/article/96/11/853/2520796According to this study, a pipe a day gives you a 25% increase in lung cancer risk (1.25 vs 1.0, which I imagine can vary based on inhalation level), no risk of esophageal and stomach cancer, and strangely, a decreased risk of colorectal cancer. But the figures are all over the place; for no inhalation while smoking, there were 52 deaths due to lung cancer, which makes no sense. Either the subjects were lying, or (most likely) there were confounding variables.
Also, apparently
>The National Youth Tobacco Survey has measured prevalence of pipe smoking among U.S. youth since 1999. The prevalence of current pipe smoking has increased from 2.4% to 3.5% of middle school students and from 2.8% to 3.2% of high school students from 1999 to 2002I have never heard of middle or even high school students smoking tobacco pipes. I find it extraordinarily difficult to believe that 3.5% of all students in either group smoke pipes that aren't filled with pot.
Needless to say, at a couple bowls per week, the cancer risk due to pipe smoking is negligible at best.