In vitro studies have been widely used to support the toxicological evaluation of chemicals and complex mixtures including cigarette smoke. In this study a variety of test matrices from different tobacco and nicotine delivery products was assessed against a Kentucky reference (3R4F) cigarette.

The mouse lymphoma assay (MLA) is underpinned by OECD guideline 490 and ICH S2(R1) guidance and is a recognised in vitro genotoxicity test battery assay. The aim of this study was to assess the suitability of the MLA with a variety of tobacco and nicotine product test matrices. Testing was conducted in general accordance to OECD Guideline 490 and ICH S2 (R1) test guidance. The same samples were also assessed using the in vitro micronucleus assay; results are reported separately (Part 2).

Total particulate matter (TPM) from a 3R4F cigarette was compared against pad-collected aerosol matter generated from a commercial electronic nicotine delivery system (ENDS), a commercial e-liquid, and TPM from a commercial tobacco-heating product (THP) using the in vitro MLA. Exposures were conducted for 3 h ±S9 metabolic activation and 24 h -S9 conditions at concentrations up to 500 µg/mL.

Under all treatment conditions, 3R4F produced a clear positive response with regard to induction of mutation. In contrast, no marked induction of mutation was observed for the e-liquid, ENDS and THP. Based on the results of this study, the mouse lymphoma assay can be used effectively for the assessment of these test matrices.