Derivation of tolerable daily intakes (by inhalation) for three e-liquid ingredients


A major e-cigarette manufacturer.


In addition to nicotine, electronic cigarettes contain select organic chemicals as ingredients in the liquid formulation. Bibra was asked to review the toxicity data and to establish tolerable inhalation doses of three such ingredients that may be used in e‑cigarette formulations in the future.

Project Goals

To establish tolerable daily intakes (by inhalation) for three ingredients that may be used in e-liquid formulations.


We searched for, collated and critically assessed the hazard data and key existing HCVs (where available) for each ingredient, focusing on the inhalation route of exposure. In the absence of reliable repeated dose toxicity data on any of the three potential constituents, route-to-route extrapolation from the existing oral dataset was considered appropriate. Existing Expert Group reports and comprehensive reviews were used as the basis as far as possible, though primary literature papers were consulted where necessary.

We derived systemically-tolerable inhalation doses and assessed the associated peak concentrations for the potential to induce local effects using a specific e-cigarette vaping scenario as agreed with the client.

Project Outcome

Bibra was able to provide a robust justification for the proposed tolerable intake (by inhalation) in terms of systemic effects for each of the three ingredients. Two of the chemicals lacked appropriate short-term inhalation data for a local effects assessment and hence the proposed tolerable intakes were suggested as “tentative”. For the third chemical, the calculated peak concentration was considered highly unlikely to be capable of causing significant respiratory tract irritation.

Project Leader

Daniel Threlfall
Pete Watts
Richard Young



More recent work Info about us Meet our team