What is wrong with ecig particulate claims – the simple version

by Carl V Phillips

One of the two blogs (excluding this one — I will leave that judgment to others) you should read every word of, if you are interested in understanding the sciences surrounding THR, is Clive Bates’s. So I suspect most of my reader have already seen this impressive piece he wrote about the series of nonsense claims about e-cigarettes producing dangerous exposure to tiny airborne particulates. However, I found myself thinking “that is so long and goes into so much detail that I think the point might be lost.” You know that you are being wordy if you provoke that from me! :-) Clive joked that I was going to write a haiku version of it, but I don’t think I could pull that off, so here is merely a shorter summary of the main point and an additional fatal flaw that he did not address.

I will assume readers have read Clive’s piece or are familiar with the issue. To summarize the ANTZ position on this: “Inhaling a lot of fine particles has been shown to be a health hazard. Modern e-cigarettes produce a lot of fine particles.” You might expect a “Therefore….” statement at the end of that passage, but it turns out they seldom actually finish the thought. I suppose they are so used to trafficking in innuendo that it does not even occur to them to finish their syllogism.

There are two fundamental problems with this. The first is the one that Clive emphasized: The claims about harms from fine particles are about tiny little solid bits (and, indeed, specifically those created by a few particular combustion processes), whereas the “particles” produced by e-cigarettes are liquid — properly called droplets rather than particles for those who are trying to avoid rather than create confusion. (To the extent that some e-cigarettes are needlessly throwing some solid particles from the hardware, that is a different story, but that is not what is being claimed.) Burstyn and I wrote about this previously.

It is quite simple to explain why it is absurd to make claims about fine droplets based on evidence about fine solid particles. It is not necessary to go into any discussion about surface chemistry, reactivity, or cytotoxicity. Claims about particle exposure — as opposed to claims about simply taking onboard some quantities of the chemicals — are based on the physical form itself having an effect. For example, it could be that inhaling very tiny particles of carbon soot is harmful even though eating millions of times that quantity of soot is harmless. Moreover, it could be that a 2.5 micron particle (often called ultrafine) is more harmful than a 10 micron particle (often called fine), even though it has less than 2% of its mass.

There are a few obvious reasons why ultrafine particles might cause harm disproportionate to their tiny volume of chemicals:

1. They get deeper into the lung passages, on average, and so if they harm the lung surface tissue they contact, they can harm it in more places or where it might be more sensitive. If the particle or droplet is a serious lung tissue carcinogen or irritant, the finer particles might do harm that is disproportionate to their volume.

(Note that it is easy to understand why this works. The smaller the particle, the more likely it can “take the corners”, following the flow of gas into the lungs, rather than having its inertia carry it into a wall. For the largest particles, few of them will make the sharp turn from the mouth into the trachea, so most are deposited in the oral cavity. The smaller the particle, the greater the chance it travels as deep into the lungs as the gasses (air). You can witness this phenomenon when you drive: You smash relatively few mosquitos and other tiny bugs (they are pulled around your car following the slipstream of air) but smash a lot of grasshoppers or other large bugs (their inertia is greater so the airflow is not enough to get them out of the way).)

2. Similarly, when they get deeper into the lung passages they might lodge there, resisting the lung’s self-cleaning mechanisms, doing harm over time.

3. They are small enough to pass into the bloodstream intact, and so possibly lodge somewhere else, doing harm there. This could be because they are chemically harmful where deposited, but it could also just be purely physical.

The latter of these is often overlooked in these discussions, but is potentially huge. Particle deposition could partially explain why smoking is so bad for your cardiovascular system (despite billions spent on smoking research, we do not actually know why it is quite so bad — but that is another story).

The key point here is that only the first of the three could apply to liquids. It is theoretically possible that a droplet could do damage on contact with deep lung tissue that does not happen when a larger particle contacts tissue higher in the airway. Of course this is merely a hypothesis, and there is no reason to believe it happens with e-cigarette aerosol. Indeed, larger particles might be worse because the local concentration of the chemical before dilution is complete is enormously higher. But it is possible. The other two pathways are simply impossible with liquids (or with highly-soluble solids either — like the salt spray that Clive mentioned) because they just dissolve and dilute.

Thus, it is clearly absurd to extrapolate from claims about ultrafine solid particles to claims about ultrafine droplets.

This led me to make this observation about Glantz, the leading liar…er…proponent of the particulate claims:

This perhaps explains why he had to leave mechanical engineering (where not knowing the difference between liquids and solids can be rather disastrous) and go into anti-tobacco extremist activism (where it is not such a problem to not know… well, anything).

That is the first problem with the claims. The second problem is just as bad, and is generally overlooked: The claims about ultrafine particles are pretty sketchy to start with.

It is easy to understand why this is overlooked in discussion of e-cigarettes, where few involved are familiar with the underlying claims and evidence about particulates and health. Science depends on being able to trust that inputs from outside your leading area of expertise are valid; each of us can only have real expertise on a tiny fraction of science we need to move forward. So when we hear that particulates from combustion (vehicles, power generation, etc.) are a proven important health hazard, we are inclined to trust it.

The problem is that those claims are almost as politicized and tenuous as most of the claims about tobacco. They are not necessarily blatantly dishonest — no field is quite like tobacco “research”, where the majority of those involved in academic writing and publishing are trying to mislead people. But they are based on over-concluding from really tricky epidemiology. Basically it is necessary to try to detect a tiny elevated risk for each of the millions of exposed people (basically everyone), which is far harder than detecting the same total effect in the form of highly-elevated risk for a few exposed people. This is made far harder because the comparisons are massively confounded. People in Beijing and San Francisco have very different particulate exposures, but also a lot of other very different exposures. If you try to compare within a particular population across time, there is confounding by other factors, particularly weather (high particulate days are hot days, and high temperatures kill an order of magnitude more people than is claimed for particulate exposure, so the noise dwarfs the signal).

Particulate research is the source of perhaps that most notorious error in the history of high-tech epidemiology methods, in which a coding error — resulting from accepting a default in the software that works fine for 99.999% of all studies, but does not work for this research that pushes the boundaries of what is knowable —  doubled the estimated effect in one of the most important studies in the field. (We know this, of course, because it was caught and corrected by the authors. This shows the contrast with anti-tobacco research, where errors are basically never corrected.) The point is that even when trying to do this research honestly, it is still very tenuous and assumption laden.

Cherrypicking results is always a problem, but it is a far greater problem under these circumstances. Since this is a political issue — attracting the interest of those who are anti-industry, anti-car, anti-coal, generally “green”, etc., to say nothing of the usual tendency of researchers wanting their work to be important — plenty of cherrypicking takes place. There are many results out there that suggest there is far less of a hazard than the dire statistics that appear in the sensationalist news or WHO reports, or in paper introductions written by researchers who want this to be important.

In short, the claims about particulate impacts from e-cigarettes start with some very tenuous claims and then extrapolate them to an exposure that is not actually similar.