I like facts.
There are some very plausible, and possibly real ideas about the relationship between second-hand smoke and human health. It is still necessary to untangle other factors. The earliest smokers: where they lived, access to health care, where they worked, etc. The next generations of smokers: were these the ones who, in statistically significant numbers, moved out of cities, mines, and congested traffic? For at least a few years, they lived in somewhat cleaner air of suburbs. They also may have worked in sick buildings. The current generation? These people are more likely to pick up "smoking" of vaping and similar products and to work in newer buildings. Is the newness of buildings making a difference because the buildings contain materials that are less hazardous for human health?
If some studies are reflecting some people's truth, some smokers are plagued by conditions which are eased by smoking, tobacco, nicotine, the kinetic acts of smoking, or something related to that. Will future studies link these conditions to some trigger for cancers and other health conditions which may be related less to smoke than to internal, ongoing stress or something that the future researchers will be able to identify?
Fortunately, my other organs are free of negative or unwanted effects of second-hand smoke. This is known. But why is this so? I do not know. I am grateful for overall great health. Is gratefulness itself a health-protecting act or condition? Some studies suggest that it might, but I do not claim that as an explanation for me. Is there something else in my lifestyle that is health-protective or at least an offset for occasional exposures to second-hand smoke? I follow the doc's suggestions and my health is great. However, no one has designed a proper study of lifestyle factors and me and second-hand smoke. Unless/until that happens, we will never be absolutely certain why exposure to second-hand smoke in my formative years (such as in places where smoking was nearly constant and third-hand smoke also was present) has not caused me to experience what has been predicted for me. We would probably need another study to find out why occasional exposure now is not affecting me in the dire predicted ways.
In order to substantiate broad claims about populations and the three or more types of smoke, we would need vast studies of many people and hundreds if not thousands of factors in order to pinpoint why each person experiences health challenges. We need retroactive data in order to rule out all confounding information. Unless/until that happens and someone knows anything for certain, we know nothing and there is only hype.
I don't like hype.
Bach is not noise, Madam. (Robert, in Two's Company)