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EXPERT REACTION: More lead and uranium found in teens who vape often

Embargoed until: Publicly released:
Peer-reviewed: This work was reviewed and scrutinised by relevant independent experts.

Observational study: A study in which the subject is observed to see if there is a relationship between two or more things (eg: the consumption of diet drinks and obesity). Observational studies cannot prove that one thing causes another, only that they are linked.

People: This is a study based on research using people.

In a new US study, teens who vape frequently had twice as much uranium, and 30% more lead in their urine, than teens who only vape occasionally. The researchers also found higher uranium levels in teens who preferred sweet vape flavours, over menthol ones. The study canvassed 200 teens who vape but don't smoke, which makes it less likely these toxic chemicals were coming from tobacco. However the researchers say their observational study can't prove a direct link between vaping and the toxic compounds, and the relatively small sample size means that more research is needed to make definitely conclusions.

Journal/conference: Tobacco Control

Research: Paper

Organisation/s: University of Nebraska, USA

Funder: Research of HD reported was partially supported by the National Institute on Drug Abuse under Award Number R21DA058328 (PI: HD). The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.

Media release

From: BMJ Group

Frequent teen vaping might boost risk of toxic lead and uranium exposure

Potentially harmful to brain and organ development, suggest researchers
Findings underscore need for implementation of regulations and targeted prevention

Frequent teen vaping might boost the risk of exposure to lead and uranium, potentially harming brain and organ development, suggests research published online in the journal Tobacco Control.

The findings underscore the need for implementation of regulations and prevention efforts targeting teens, emphasise the researchers.

Vaping is popular with teens. In 2022, an estimated 14% of US high school students—around 2.14 million—and more than 3% of middle school students—around 380,000—reported vaping in the preceding month, note the researchers.

Certain metals have been identified in e-cigarette aerosols and liquids. Their absorption is especially harmful during periods of development, say the researchers, citing research showing that increased levels of exposure are linked to cognitive impairment, behavioural disturbances, respiratory complications, cancer, and cardiovascular disease in children.

The researchers wanted to find out whether potentially toxic metal levels might be associated with vaping frequency and whether flavour might be influential.

They drew on responses to the nationally representative Wave 5 (December 2018 to November 2019) of the PATH Youth Study, involving 1607 teens between the ages of 13 and 17. After exclusions, 200 vapers were included in the final analysis. 

Their urine samples were tested for the presence of cadmium, lead, and uranium, and vaping frequency was designated as occasional (1–5 days/month), intermittent (6–19 days), and frequent (20+ days).

Vape flavours were grouped into four mutually exclusive categories: menthol or mint; fruit; sweet, such as chocolate or desserts; and others, such as tobacco, clove or spice, and alcoholic or non-alcoholic drinks.

Among the 200 exclusive vapers (63% female), 65 reported occasional use, 45 intermittent, and 81 frequent use; vaping frequency information was missing for 9. 

The average number of recent puffs per day increased in tandem with vaping frequency: occasional = 0.9 puffs; intermittent = 7.9 puffs; frequent = 27 puffs.

In the preceding 30 days 1 in 3 (33%) vapers said they used menthol/mint flavours; half (50%) favoured fruit flavours; just over 15% opted for sweet flavours; and 2% used other flavours.

Analysis of the urine samples showed that lead levels were 40% higher among intermittent vapers, and 30% higher among frequent vapers than they were among occasional vapers. Urinary uranium levels were also twice as high among frequent vapers than among occasional vapers 

Comparison of flavour types indicated 90% higher uranium levels among vapers who preferred sweet flavours than among those opting for menthol/mint. 

No statistically significant differences were found in urinary cadmium levels between vaping frequency or flavour types.

This is an observational study, and as such no definitive conclusions can be drawn about toxic metal levels and vaping frequency/flavours, acknowledge the researchers, who also caution that the levels of toxic metals in vapes will vary by brand and type of vaporiser used (tank, pod, mod).

Although urinary levels indicate chronic exposure, they were assessed at just one point in time, added to which the presence of uranium in the urine may be attributable to various sources including environmental exposure from natural deposits, industrial activities, and dietary intake, they add.

“None the less,these compounds are known to cause harm in humans,” they write. Of particular concern were the increased uranium levels found within the sweet flavour category, they add. 

“Candy-flavoured e-cigarette products make up a substantial proportion of adolescent vapers, and sweet taste in e-cigarettes can suppress the harsh effects of nicotine and enhance its reinforcing effects, resulting in heightened brain cue-reactivity.” 

And they conclude: “E-cigarette use during adolescence may increase the likelihood of metal exposure, which could adversely affect brain and organ development.

“These findings call for further research, vaping regulation, and targeted public health interventions to mitigate the potential harms of e-cigarette use, particularly among adolescents.”

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Expert Reaction

These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.

Associate Professor Kelly Burrowes, Auckland Bioengineering Institute, University of Auckland

While vaping is thought to be a safe alternative to smoking, the aerosol still contains a range of chemicals, including heavy metals, that – with chronic exposure - may lead to long-term health effects. Several studies, including our own, have found metals in vape aerosols, either from the e-liquid itself or due to the metal components used, and resultant heating, within the vape device.

This study measured levels of three metals (cadmium, lead, and uranium) in urine and found that increased vaping frequency resulted in higher levels of lead and uranium in urine.

Cadmium and lead are often found in vape aerosol from the vape heating coil and soldering components, however Uranium has not typically been reported in e-liquids or vape aerosol but is an interesting finding due to its high toxicity. Typical sources of uranium exposure are due to natural drinking water sources or from the soil, which could include food exposure, or the tobacco leaves used for nicotine production. Interestingly, uranium levels were significantly higher in those who preferred sweet vape flavours which may indicate a link between variable nicotine levels in different flavours, if the source of uranium is from tobacco leaves.

Last updated: 29 Apr 2024 10:33am
Declared conflicts of interest:
No conflict of interest.
Associate Professor George Laking, Director of the Centre for Cancer Research, University of Auckland

It doesn’t look like this paper has had a critical peer review. So far as I can tell, the authors are primarily interested in public health datasets. I can’t see that there has been a laboratory scientist on the authors’ team. I think that could explain a lot about their work. Journal editors have an important role to think about the larger context. I see this as a significant lapse on the part of the publishing journal.

I would classify it as yet another report intended to promote free-floating anxiety about vaping. To the extent it gets picked up, it is likely to cause active harm by scaring people back to smoking. One has to question the ethics of publication. It reminded me of the adage, widely used in public health ethics, about shouting ‘fire’ in a crowded theatre, just because someone lit a match.

The authors adopt the non-controversial view that young people should not vape. If you’ve already made up your mind on the topic, you don’t need to read this paper. If you haven’t made up your mind, this paper is of no value for your decision, because it does not contextualise the actual risk from the exposures. Sure there is no safe level of lead exposure but it still takes time to cause harm and there is a dose-response relationship.

The authors have not thought critically about scientific inference from the data. For example, they note the limitation of a cross-sectional design. Their endpoint is a proxy for a whole body exposure burden. Urine is a route of excretion. What is going on with the participants? Are their urine metal levels at steady-state? Are they on the way up? Or the way down? Could it be possible that vaping is actually causing people to unload metals from other body compartments? Is this just noisy data in a smallish sample?

Incidentally they report the ratio of metal to creatinine. They don’t say the tissue origin of the creatinine. For biomarker studies both blood and urine creatinine can be reported. Creatinine is used to control for renal function. This report indicates some of the challenges in using creatinine. It recommends “collection of timed urine specimens to estimate the actual excretion rate, provided that the biomarker is stable over the period of collection.” It says “This ideal must be balanced, however, against practical considerations.” If the authors were more interested in the science, they would have used a more rigorous method, especially given the public policy interest.

Also check out this review of biomarkers. It says, right at the top “Urine is the most commonly used biomarker of exposure across metals but it should not be used to assess lead exposure.” The authors don’t engage with this literature, the actual literature to support the validity – or otherwise – of their methods.

The problem with vaping is it is addictive. Anxiety about addiction has spawned an industry that is trying to discover actual physical harms, so far without success. Meanwhile people are dying from smoking while they are scared away or even prohibited from vaping. Vaping is a far safer alternative way to deal with nicotine addiction.

Last updated: 29 Apr 2024 10:39am
Declared conflicts of interest:
“I Chair End Smoking New Zealand, an organisation that supports vaping to quit smoking. I’m also involved in research for vaping to quit smoking, and for nicotine replacement to quit vaping.”

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