Global surveillance of oral tobacco products: total nicotine, unionised nicotine and tobacco-specific N-nitrosamines

Objective Oral tobacco products contain nicotine and carcinogenic tobacco-specific N-nitrosamines (TSNAs) that can be absorbed through the oral mucosa. The aim of this study was to determine typical pH ranges and concentrations of total nicotine, unionised nicotine (the most readily absorbed form) and five TSNAs in selected oral tobacco products distributed globally. Methods A total of 53 oral tobacco products from 5 World Health Organisation (WHO) regions were analysed for total nicotine and TSNAs, including 4-(methylnitrosamino)- 1-(3-pyridyl)-1-butanol (NNAL), using gas chromatography or liquid chromatography with mass spectrometric detection. Unionised nicotine concentrations were calculated using product pH and total nicotine concentrations. Fourier transform infrared spectroscopy was used to help categorise or characterise some products. Results Total nicotine content varied from 0.16 to 34.1 mg/g product, whereas, the calculated unionised nicotine ranged from 0.05 to 31.0 mg/g product; a 620-fold range of variation. Products ranged from pH 5.2 to 10.1, which translates to 0.2% to 99.1% of nicotine being in the unionised form. Some products have very high pH and correspondingly high unionised nicotine (eg, gul powder, chimo, toombak) and/or high TSNA (eg, toombak, zarda, khaini) concentrations. The concentrations of TSNAs spanned five orders of magnitude with concentrations of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) ranging from 4.5 to 516 000 ng/g product. Conclusions These data have important implications for risk assessment because they show that very different exposure risks may be posed through the use of these chemically diverse oral tobacco products. Because of the wide chemical variation, oral tobacco products should not be categorised together when considering the public health implications of their use.