Investigators at the University of Nebraska Medical Center in Omaha and the University of California San Francisco have published an important study in JAMA Network Open on “Exposure to toxicants associated with use and transitions between cigarettes, e-cigarettes, and no tobacco.”
Hongying Dai and colleagues looked at 55 tobacco exposure biomarkers (mostly toxins) in the urine of adult smokers, vapers and dual users in the first wave of the Population Assessment of Tobacco and Health Study. They compared this data with urine samples from the same participants one year later in Wave 2, when the participants may or may not have changed their tobacco use status.
While Dai and coauthors “found complex patterns and heterogeneous health outcomes associated with transitions between cigarettes and e-cigarettes,” the results can be succinctly summarized. First, “transitions from dual use or exclusive cigarette use to exclusive e-cigarette use and transitions from any tobacco use to no use” were associated with sharp declines in toxins. Second, “transitions from exclusive e-cigarette use to cigarette use or dual use” were associated with “moderate to large effect” increases in toxin levels. And third, “transition from exclusive cigarette smoking to dual use of cigarettes and e-cigarettes” didn’t provide any meaningful change in urinary toxins.
The authors found that “only a small percentage of [Wave 1] exclusive cigarette smokers and dual users transitioned to exclusive e-cigarette use at [Wave 2] (1.2%and 5.6%, respectively), which could limit ben
efits in moving combustible cigarette smokers to less hazardous, noncombustible e-cigarettes.” This is an important statement, because it acknowledges less e-cigarette harm by referencing an FDA press release from 2017 (here). More importantly, it is followed by a solid explanation for the low transition rate to vapor: “low effectiveness in early generations of e-cigarettes in delivering nicotine [the PATH Waves were in 2013 and 2014, when e-cigarettes were not very effective], lack of knowledge among cigarette users to distinguish harmful effects between dual use and exclusive e-cigarette use, or the effects of negative public health messaging [emphasis added, references omitted].”
All of the above is informative, but the real news from this study is demonstrated in the following table. It reports levels of cotinine – a breakdown product of nicotine – in the urine of participants, according to the product they used at Wave 1, and one year later at Wave 2. Cotinine levels are widely used to indicate tobacco use levels. In general, higher cotinine indicates more tobacco use. Higher cotinine, especially with cigarette combustion, also means greater exposure to toxins.
| Urinary Cotinine Levels* at PATH Waves 1 and 2, According to Product Use | |||||
|---|---|---|---|---|---|
| Wave 1 Product (n users) | Wave 1 Cotinine | Wave 2 Product/Cotinine | |||
| None | Cigarettes Only | E-Cigarettes Only | Dual Use | ||
| Cigarettes (247) | 158 | 5 | |||
| Cigarettes (1820) | 2273 | 2265 | |||
| Cigarettes (32) | 1833 | 713 | |||
| Cigarettes (257) | 3068 | 2522 | |||
| E-cigarettes (44) | 16 | 2 | |||
| E-cigarettes (14) | 502 | 1942 | |||
| E-cigarettes (121) | 727 | 470 | |||
| E-cigarettes (31) | 972 | 2569 | |||
| Dual use (42) | 213 | 6 | |||
| Dual use (315) | 2690 | 2628 | |||
| Dual use (36) | 2792 | 1192 | |||
| Dual use (252) | 3179 | 3374 | |||
One can readily see that cotinine levels were high in smokers and/or dual users in both waves. Cotinine levels among e-cigarette users were much lower, confirming that in 2013-14, the products did not deliver nicotine very effectively.
Everyone in the first four rows of the table smoked cigarettes in Wave 1, so one might expect that their cotinine levels in that wave would be the same. Instead, there were huge differences between them, depending on where the smokers ended up at Wave 2. The 247 smokers who had a cotinine level of only 158 ng/ml at Wave 1 quit everything at Wave 2 and had negligible cotinine. The highest Wave 1 cotinine levels were in smokers who continued to smoke at Wave 2, while the smokers who ended up with e-cigarettes went from 1833 ng/ml at Wave 1 to 713 at Wave 2.
The same is true for the other two categories: The e-cigarette users and dual users at Wave 1 who quit completely at Wave 2 started out with much lower cotinine levels.
The take-home message is hugely important. Tobacco users at Wave 1 may have self-selected their Wave 2 product use based on their cotinine status at Wave 1. This says that those who quit completely, switched to e-cigarettes, or stayed with cigarettes were entirely different groups of smokers, each with distinct nicotine needs. Because no one can predict how individual smokers will be able to quit, they should be provided access to all quit-smoking options.
