Please be aware that I am not at all trying to indicate the I personally need any sort of scientific proof in regards to qi, qigong, the benefits of either or anything of the sort. I have been involved as a practioner/teacher of qigong and various energetic arts for some time now and have all of the evidence/proof that I personally need. My comments concern the community at large (i.e. that outside of the martial arts community) and most specifically the Western medical and/or scientific community. To be able to begin to get them to "see the light" and have the type of funding and research put into this topic that is going to get tangible results is going to require those of us that are already in the "qi camp" to be quite careful in the blanket types of statements that we make.
While on the scientific topic, let's use your example of smoking cigarettes. There is a whole can of worms in and of itself...but I think a good one to illustrate the point. Yes, the cigarette making industry wanted scientific proof. Why (other than for financial motives)? Because the scientists still cannot understand nor show why it is that some folks can smoke 3 packs a day for 50 years and never get cancer or related illnesses and the non-smoking wife or husband of a smoker can get lung cancer after only a couple of years of being exposed to second hand smoke. Much of the reserach now indicates a pre-disposition to such cancers (and other types of illnesses). With the recent breakthrough of decoding human DNA, researchers are now getting close to being able to do a test that will score an individual on their percentile chances of contracting such illnesses. To me, this is excellent on two fronts. First, I think it will possibly lead to some research and is tied to prenatal qi. For those that practice and understand Traditional Chinese Medicine (TCM), we can easily understand and see how it is that some folks can partake of something like smoking and have it not effect them and others get a diluted by product and get the disease...and it goes hand in hand with pre-disposition. Second, I think that this holds tremendous possibilities as to the benefits of qigong. If we get to the point where DNA analysis shows such a predisposition, what would the same DNA analysis of person show after 6 months of qigong work? If we see a verifiable change to the analysis, then we begin to establish "hard" evidence that the qigong had an effect. The next 3 to 5 years should be interesting indeed!
As to the "purification and distillation" issue...you state:
"these were ideas formulated in the days when pollution levels were not as there are today"
My response (without being sarcastic) is so what? This process is built into the human energetic system for just this reason. To deal with the "unknown" environmental conditions. Remember, the "qi process" (using a very simplistic term) happens with every breath that we take. And remember, the pressure/vital points that are on the external meridians serve as a vortex...so, to some degree or another...there is a constant flow in and out of them. With the increased pollutant environs, people should be dropping dead like crazy if this distillation and purification process was not at work...especially with the increased life expectancy we have. Granted, alot of the increase there has to do with advances in medical science in being able to sustain life past where they could in the past...but life expectancy is still many decades longer than it was a few hundred or a thousand years ago. The three burner system of the body is that protection mechanism. Again, some systems may not be the best, but our energetic system is capable of taking all of that into consideration and dealing with it. Know what I mean?
Anyway...enough rambling from me for now. Thanks for the constructive conversation!