Everything in moderation is the rule my Mother always taught me. Science seems to bear this out as well. The human organism is designed to heal itself and it is remarkable in this regard. As a full-time cancer researcher, I know that the link between cancer and smoking, for example, came in 1984 as a result of the largest medical study ever conducted. What you never hear about is that moderate smokers (less than 1/2 a pack per day) actually scored the same as non-smokers in every category except oral cancer in that same report. Moderate pipe and cigar smokers (less then two pipes or two cigars per day) actually showed slightly better results than non-smokers in that same report. The native Americans of the U.S. have used tobacco in moderation for millennia without ill effect as they sat around their smoky camp fires. The point is not to say smoking is ok, because the 519 additives combust to create over 4,000 chemicals in tobacco smoke, of which more than 100 are known carcinogens, but to suggest that moderation in all things allows the body the opportunity to heal itself. Now, a compromised body immune system can cause even water to become dangerous. As it turns out, and no great surprise here, it's the toxins in the smoke, the water, the air, the food, etc. that cause the cancer to grow out of control, and, even then, only in a compromised body. A seed will grow a tree, but only if it lands in fertile soil with sunlight and water available. Conditions have to be right for any of these things to harm us, and it's almost always a combination of factors that have to be just right. The problem is that 30, 40, 50 years of toxicity, including smoking with its toxins, heavy metals, etc., does tend to compromise our immune systems and prepare the soil accordingly. Even if we have an answer to your question, i.e., yes or no, it still depends on the condition of the person in question. Only one in ten smokers develop lung cancer, but one in 100 non-smokers develop lung cancer, America's deadliest cancer, and the least researched cancer in the last 30 years thanks to the dubious connection to smoking in the 1984 medical studies. Again, I know that smoking is deadly, and vaping is significantly better for us than smoking, but I suspect there will never be an easy answer to your question, as there are an unlimited number of variables and causal factors. Sorry I got off on this tangent, but the question "Is it ok" is pretty broad and I think does encompass the health issue as I suspect the topic was suggesting. Imho, I say vaping IS ok for you compared with smoking. Compared with non-smoking, I would suggest that moderation is once again the answer....generally speaking. I doubt that more studies will be able to answer this question completely.