A comprehensive evaluation of the toxicology of cigarette ingredients: heterocyclic nitrogen compounds.

Three heterocyclic nitrogen compounds, 2,3-diethylpyrazine (DEP), 2,3,5,6-tetramethylpyrazine (TMP), and 2-acetyl pyridine (AP), are naturally present in tobacco and are also added to tobacco as flavor ingredients. A battery of tests was used to compare the toxicity of mainstream smoke from experimental cigarettes containing the three heterocyclic nitrogen compounds added individually at three different levels. The lowest target inclusion level of the ingredient was 10 ppm, and the highest was 10,000 ppm. Smoke from experimental and control cigarettes was evaluated in analytical smoke chemistry, in vitro cytotoxicity, and mutagenicity assays. The cigarettes with added DEP produced some minor (approximately 10%) changes in smoke chemistry when compared with the cigarettes containing no DEP. Smoke chemistry was effectively unchanged by the addition of either AP or TMP. Cytotoxicity, assessed by the neutral red uptake assay using both gas-vapor and particulate phases of smoke, was unaffected by the addition of any of the test ingredients. Mutagenicity, assessed in five strains of Salmonella treated with mainstream cigarette smoke condensate, also was unaffected by any of the test ingredients. Despite the exaggerated ingredient levels relative to commercial-use levels, there was a lack of a toxicological response for the three heterocyclic nitrogen compounds in the test systems used.