E-cigarettes and other vaping products contain a nicotine-based liquid that is vaporised and inhaled. There is no combustion so the user inhales vapour, not smoke. This means that e-cigarettes deliver nicotine without smoke toxicants. However, some in the public health community still have expressed concerns over the potential health impacts of flavourings used in e-cigarettes.
This is why the British Standards Institute (BSI) are developing product standards for e-cigarettes to provide guidance on manufacturing, testing and safety requirements. 'These guidelines, lay out the 'what' - which includes toxicological risk assessment of flavours,' says Dr Sandra Costigan, 'and our guide explains the 'how'.' Costigan is Principal Toxicologist at Nicoventures, a nicotine company established by British American Tobacco. She is also a member of the BSI steering committee on e-cigarettes.
The flavourings typically used in e-cigarettes are food grade, which means that they have been traditionally ingested rather than inhaled. 'This means that the data available is oral and there are large data gaps. Safe to eat is not the same as safe to inhale,' says Costigan. 'The data gaps need to be filled,' she says. 'In the meantime, what are the kinds of data sources, approaches and scientific rationale that will allow us to determine if we can use a flavour and at what level? This guide explains how to do that.'
The first step is to ensure that any flavourings are food grade and to screen out any potential carcinogens or respiratory allergens. 'At this stage, in the absence of inhalation data we make quite a lot of use of what are called TTCs or Toxicological Thresholds of Concern,' explains Costigan. TTCs are used by agencies like the WHO and FDA and they basically help define how much of something can be used in the absence of other toxicity data.
'We use TTCs to determine how much of any particular flavour ingredient can be used. The next step is to assess the compounds produced as a result of heathing these flavour molecules, as it is the 'vapour' (ie the aerosol produced on heating the e-liquid) that consumers are exposed to, not the e-liquid itself. Here we are dealing with new compounds and potential thermal breakdown products, rather than ingredients,' and so our approach to acceptable levels will be different,' says Costigan.
'None of the draft standards and regulations tell us how to do such a risk assessment, and the scientific literature thus far has focused on problems, such as lack of inhalation data, rather than solutions,' says Costigan. 'Ours is the first sensible and practical guide to help actually conduct such a risk assessment on the flavours, based on sound toxicological principles.'