Well, any time you pull smoke into your lungs, you're pulling certain levels of the tar, carbon monoxide, (nicotine, if you're using tobacco), etc., in there with it. Those tubes probably help a bit, especially if you can see some of the residual on the tube when you're finished. It is, after all, on the tube and not inside your lungs.

I can't preach about consumption by fire, because I'm guilty of it as well. But I try not to make tobacco an addition to the mix, since there's a whole other list of chemicals that you end up inhaling along with the cannabis smoke. Tobacco smoke irritates your lungs. Period. Some people are just bothered by it more than others. There aren't many ways around that. Perhaps a filter on every tobacco-laced spliff you smoke, but most smokers don't like using any kind of filters. It's up to you to make a health conscious decision, or you'll just have to deal with the harmful side-effects.