How to Safely Use Flavorings in E-Liquids
When it comes to the risks of vaping, flavorings are the big unknown. We may know that the flavors used in e-liquids are generally recognized as safe for ingesting as part of food, but we can’t say the same when it comes to inhalation. If diacetyl and acetyl propionyl have taught us anything, it’s that “safe to eat” doesn’t mean “safe to inhale.” The problem is that such evidence on the potential risks of inhaling flavorings is not available for most food flavorings used in e-liquid. So how can e-liquid mixers go about making sure that they use flavorings in a safe way? A recently-published guide from British American Tobacco’s Nicoventures aims to offer the solution.
The Recommendations – Keeping Vapers Safe By Doing Your Research
The advice from the report can be summarized most simply by saying “find out exactly what flavoring chemicals you’re using and do your research on them,” but of course, there are a lot of complexities to consider. The main issue with flavorings is that the evidence often just isn’t there on the risks for inhalation, so how can you stay safe?
1. Only Use Food-Grade Flavorings
This should be obvious to any e-liquid company, but it’s worth repetition, regardless. To provide some re-assurance that there are no contaminants in your flavorings (or at very least, that any present are only in very low levels), only food-grade flavors should be used in e-liquids. The reasoning behind this is that although food flavorings haven’t been tested to make sure they’re safe to inhale, they have been looked at more generally to ensure they aren’t particularly toxic. Finding out about each of the individual chemicals in a flavor can be difficult, but the Perfumer’s Apprentice provides spec sheets for each of its flavorings with full listing of components.
2. Avoid Any Flavorings With Known Risks
Although using food-grade flavorings should ensure that the included flavors aren’t carcinogenic, mutagenic (mutation-causing) or a reproduction toxin, it’s worth checking the chemicals out specifically for this purpose. The problem is that some chemicals are classified as food-safe in some places and not others, and some are riding on the coat-tails of their historic use “without known issues” despite not being specifically subjected to the same criteria. The authors recommend excluding chemicals classed in group 1 or 2 by the International Agency for Research on Cancer or included on various other lists of chemicals of concern, such as the FDA’s harmful and potentially harmful constituents list. Additionally, if any ingredients are classed as respiratory sensitizers – like known allergens – these also flavorings shouldn’t be used.
3. Look for Existing Evidence on Toxicity
After weeding out any potentially risky ingredients through the above two steps, mixers should then look for specific evidence relating to the toxicity of the chemicals, ideally for exposure through inhalation. As an example of some flavorings that shouldn’t be used and would be ruled out at this stage, the authors point to diacetyl and acetyl propionyl, two chemicals commonly used in food without problems but which have been shown to cause lung damage when inhaled.
However, there is a problem because many flavors have been tested for ingestion but not for inhalation. The authors point out, though, that many flavorings have been tested for inhalation, because a large amount of flavor chemicals are added to cigarettes (some tests reported here and here).
These investigations are somewhat limited because they were examined as part of smoke, but if the flavors made the effects substantially worse they can be identified from this data. The authors use spearmint oil as an example: when this was added in substantial amounts (about 10 percent of the total) to a cigarette, the mice used in the experiments developed problems in their airways, so this ingredient should be avoided in e-liquids (although all oils should really be avoided due to the risk of lipoid pneumonia).
When there is no inhalation-specific information available, the authors advise using available information on the toxicity of the chemical in question through other routes of exposure. This isn’t a definitive assessment, but it’s reasonable to expect that if something is an irritant to the skin or eyes, for example, it will probably have a similar effect on the lungs.
4. Use Toxicological Thresholds of Concern
Already-established toxicological thresholds of concern (shortened to TTC) can also be used as a guide in the absence of other information. These have been developed for many specific applications, including inhalation of many different types of products (including cigarettes and consumer aerosol products), and provide a guideline daily amount, above which there would likely be health concerns. This is useful when, for example, you can’t find reliable information about the risks of inhaling something. The specific guidelines the authors suggest are those designed for consumer aerosol products (because of a very close similarity with vaping), which are based on the Cramer Classification Scheme (which basically grades chemicals from 1 to 3 according to their likely toxicity).
The authors’ conservative estimate suggests that vapers shouldn’t be exposed to class 1 compounds at levels over 0.98 mg per day, and for class 2 and 3 compounds, no more than 0.17 mg per day. This may be difficult to work out, but it can be done based on the amount of a chemical present in the e-liquid and assuming a consumption of 5 ml of e-liquid per day, as has been done in other studies.
5. Test for Thermal Breakdown Products
The main thing left out so far is the fact that e-liquid is heated prior to being inhaled, and this can lead to changes in the chemical composition of the vapor in comparison to the liquid. In short, the heating will lead some of the constituent chemicals to break down, so what you put in the e-liquid will be slightly different from what ends up in the vapor (which is why e-liquids taste slightly different in different devices and with different settings).
The authors suggest that this should be tested using gas chromatography and mass spectrometry (GC-MS), and mixers should use the same TTC approach as above to determine that vapers should be exposed to no more than 1.8 mg per day of class 1 compounds and no more than 0.09 mg per day of class 2 and 3 compounds.
Based on general guidelines and the assumption of 300 puffs per day for vapers, they suggest that such breakdown products should be tested using GC-MS with a minimum detection limit of 5 ng per puff.
They suggest that these unavoidable breakdown products could also be compared to levels in cigarettes, since almost all vapers are using e-cigs to replace smoking. However, they crucially point out that intentionally added ingredients shouldn’t be held to this (relatively low) standard, because any flavor ingredient can be replaced altogether if it’s potentially risky.
With Some Work, All Mixers Can Keep Vapers Safe
The guidelines laid down by this paper aren’t the last word on how to safely use flavorings in e-liquid, but they offer a general set of rules that health-conscious mixers can follow to ensure that they keep their customers as safe as possible. It might take a little research and a bit of expense to conduct testing, but in an industry on the verge of regulation and where we value the health of our customers, it’s the least we can do.
Here at Black Note, we had our juices independently tested to ensure freedom from ingredients like diacetyl, acetyl propionyl, diethylene glycol, acrolein and acetoin, and we don’t add any artificial colors or flavors, but the information contained within this paper could be absolutely invaluable for mixers who do.
- Costigan, S. and Meredith, C. (2015) An approach to ingredient screening and toxicological risk assessment of flavours in e-liquids
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