If you actually read the entire study you'll notice that they control for numerous factors and than lump everything together to reach their averages.
The statistics in the abstract therefore at the average from 1-2 bowl a day, non inhaling smokers whose bowls last 30 minutes, all the way up to 10 bowl a day, inhaling, 1 hour plus duration per bowl, who are also drinking 5+ alcoholic beverages a day.
If you read the entire thing and compare it to the 1964 surgeon general's report, which concluded that very moderate pipe smoking was a negligible/acceptable level of risk, the statistics from the sub groups in this study who only smoked 1-2 bowls per day, didn't inhale, and and didn't consume alcohol on a daily basis, the risks are, again, tangible but fairly negligible.
the "safe level of alcohol" 1 drink per day for women/2 for men also increases head and neck cancer risks by 30-40 percent according to many studies. This is similar to pipe smokings impact on the same cancers amongst pipe smoking non regular drinkers, according to this study.
The cultural precedent has been set for acceptable risk, as regards moderate alcohol. A pipe or two a day is fairly analogous.
Read the whole study, and make an informed decision regarding the risk. There is some risk, but other people, often the same ones who berate and chastise you for smoking a pipe, almost certainly have habits that carry similar levels of risk.
It is also worth noting that a baby aspirin a day lowers head and neck cancer rates by 30%+, in addition to it's cardiovascular benefits. The effect is most pronounced in moderate drinkers/smokers. Something to think about for risk mitigation.