Yes, yes, “we don’t know”, but it is necessary to put a context on this negative assessment. In particular, we need to challenge rhetorical arguments using this lack of knowledge as an argument to oppose THR.

We don’t know in absolute terms, we might never know it with full precision, as the complexity of human biology makes it a daunting problem given the diversity of individual responses and potentially affected biological systems. However, we can make very robust estimates and inferences from the existing short and mid-term knowledge,  which is substantial: hundreds of well-designed experiments on emissions testing, biomarkers, pre-clinical and even clinical studies clearly indicate in about 10 years of rigorous observation that risks (understood as potential for harm) of vaping are dramatically reduced in comparison with smoking. This long-term inference is one of the main pillars of THR (and of many other issues addressed by science). It is important to understand and defend it.   

There is nothing outlandish in making long-term (decades-long) modeling and forecasts based on what we know now and from past evolution, it is common practice in many scientific disciplines. 

If vaping is to be rejected or harshly restricted and over-regulated because “we don’t know long-term effects”, then we should also reject or drastically restrict promoting green policies to counter climate change from global warming since we cannot be assured that these policies will succeed, we cannot go 30-50 years into the future and come back with thorough measurements showing global temperatures rising 1.5 or 3 degrees or not rising at all. 

Looking at the long-term thermal evolution of the earth’s atmosphere is a daunting problem, just like looking at the evolution of long-term biological effects of vaping. However, the lack of pristine absolute knowledge on long-term effects does not detract governments and institutions from the effort to promote green energies and policy changes. The main argument is that whether global temperatures grow 1.5 or 3 degrees, we would be much worse off if we were “doing nothing” because “we don’t know”.  

Yet, like climate change deniers, many vaping detractors suggest “doing nothing (or opposing or over restricting) it because we don’t know long-term risks”. This common attitude is potentially disastrous (how many smokers will get ill and live shorter lives during the decades it would take “until we know”?). 

In both cases of inferring long-term effects (THR and climate change), all modeling and forecasts strongly depend on assumptions on what happens on the way. Global warming scenarios depend on the policies that may be implemented in the short or medium term; there is a spectrum from “optimistic” to “pessimistic” assumptions. There is no absolute blueprint and many unknowns and uncertainties remain, but all this does not paralyze the efforts.

Likewise, any modeling of long-term biological effects from THR products will also depend on what happens along the way. Bans or over-regulation will deter many smokers from switching and stifle the necessary technological development to produce vapes emitting even less toxic content. Institutional acceptance of THR (even if very critical) would set better conditions for these improvements. 

Besides climate change, pharmaceutical research developing medication and vaccines also relies on long-term forecasting based on previous medical and biological knowledge and a short testing period. Practically all medication is released after up to 10 years of randomized control trials. Of course, it is important to keep a watchful eye and examples exist of medication taken off the market once there is evidence of unforeseen or unexpected harm. No supporter of THR opposes keeping the same watchful eye on vapers. However, it is always necessary to bear in mind that it might be very hard to disentangle detected harms in vapers from previous, ongoing harm after long smoking histories (as most vapers are former or current smokers).   

Another flawed argument around the lack of knowledge of long-term effects is that “it took us decades to find out the harms from smoking, it will take decades to know the harms from vaping”. This argument reveals scientific illiteracy. Yes, it took humans many centuries to be able to fly safely (finally in the early 1900s), but it took humans only a couple of decades to develop means to be able to reach the moon (1969). If smoking cigarettes were invented today, actual knowledge of analytic chemistry, aerosol physics and chemistry, human biology and medical science would make its harmful effects absolutely evident in a matter of months or even weeks. We wouldn’t know the harms in absolute pristine and precise terms, but we would know it is harmful.  

Finally, next time some THR detractor voices the “we oppose it because we don’t know long-term effects”, tell them that the same argument would reject recognizing global warming and promoting changes in energy policies to respond to it. By the same logic, this person should not take any medication or vaccine until decades-long testing.


Dr. Roberto A. Sussman
Institute of Nuclear Sciences

National Autonomous University of Mexico

UNAM