TSNAs in nicotine: where they come from and what synthesis changes
Tobacco-specific nitrosamines (TSNAs) are the best-known impurities linked to tobacco. This guide explains how they form, how much cured leaf contains, which limit the snus industry applies, and what changes when nicotine is made without leaf.
For anyone buying nicotine, TSNAs raise two questions: how much can tobacco-derived nicotine contain, and what does a synthetic route change?
The four TSNAs
- NNN (N′-nitrosonornicotine) and NNK (nicotine-derived nitrosamine ketone) are classified by IARC as carcinogenic to humans (Group 1)12.
- NAT (N′-nitrosoanatabine) and NAB (N′-nitrosoanabasine) are in IARC Group 3, not classifiable as to carcinogenicity1.
How they form
TSNAs form mainly when nicotine and the related tobacco alkaloids react with nitrite as the leaf is cured and stored1. How much forms depends on the type of tobacco, the curing method and storage: air-cured burley typically carries far more than flue-cured Virginia.
How much: cured leaf against an industry limit
| Material | Measure | Level |
|---|---|---|
| Flue-cured leaf | NNN, dry weight | 240–1,700 ng/g1 |
| Burley leaf | NNN, dry weight | 1,070–8,620 ng/g1 |
| Snus, industry limit (GOTHIATEK) | NNN + NNK, wet weight | at most 950 ng/g3 |
Nicotine extracted from leaf is purified, and purification lowers TSNA levels. How much remains depends on the extraction and refining, which is why buyers ask for nitrosamine data batch by batch.
What synthesis changes
Synthetic nicotine is made without tobacco leaf. There is no curing and no storage of leaf, the stage at which TSNAs form in tobacco. ESSENZ builds (S)-nicotine from defined synthetic precursors by chiral catalysis.
That does not make nitrosamines impossible by definition. Nitrosamines can form wherever suitable amines meet nitrite or nitrogen oxides. In a synthetic process, the risk comes from precursor impurities and nitrite, and both are things a specification can control and testing can verify.
What to ask a nicotine supplier
- Which nitrosamines are tested: at least NNN, NNK, NAT and NAB.
- The method and its limit of quantification; LC-MS/MS is the usual technique.
- Results for the batch you receive, not only for a reference batch.
- How nitrite and amine precursors are controlled in the process and the specification.
Talk to us about nitrosamine testing for our (S)-nicotine.
Sources
- IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Vol. 89: Smokeless tobacco and some tobacco-specific N-nitrosamines (2007); NNN in cured leaf, Table 1.
- IARC Monographs Vol. 100E: Personal habits and indoor combustions (2012); NNN and NNK reaffirmed in Group 1.
- GOTHIATEK industry standard for snus (2025): NNN + NNK at most 0.95 mg per kg of snus, wet weight.