Application of a modified gaseous exposure system to the in vitro toxicological assessment of tobacco smoke toxicants

Abstract

Tobacco smoke is a complex mixture of over 6,000 individual chemical constituents. Approximately 150 of these have been identified as 'tobacco smoke toxicants' due to their known toxicological effects. A number of these toxicants are present in the gaseous phase of tobacco smoke. This presents a technical challenge when assessing the toxicological effects of these chemicals in vitro. We have adapted a commercially available tobacco smoke exposure system to enable the assessment of the contribution of individual smoke toxicants to the overall toxicological effects of whole mainstream cigarette smoke (WS). Here we present a description of the exposure system and the methodology used. We use the example of a gaseous tobacco smoke toxicant, ethylene oxide (EtO), a Group 1 IARC carcinogen and known mutagen, to illustrate how this methodology can be applied to the assessment of genotoxicity of gaseous chemicals in the context of WS. In the present study we found that EtO was positive in Salmonella typhimurium strain YG1042, a strain that is sensitive to tobacco smoke. However, EtO did not increase the mutagenicity of the WS mixture when it was added at greatly higher concentrations than those found typically in WS. The findings presented here demonstrate the suitability of this exposure system for the assessment of the mutagenic potential of gases in vitro. Whilst we have focused on tobacco smoke toxicants, this system has broad application potential in studying the biological effects of exposure to a wide range of gaseous compounds that are present within complex aerosol mixtures. Environ. Mol. Mutagen. 55:662-672,

The mutagenic assessment of mainstream cigarette smoke using the Ames assay: A multi-strain approach

“…For each strain, independent chemicals and dose ranges were investigated, demonstrating the responsiveness of these strains in the context of historical data and literature. Gaseous exposure systems exist [12] and could have been employed in this setup to show positive control responses. However, these systems are logistically challenging to employ with numerous EH&S issues.…”

“…These guidelines ensure the uniformity and robustness of data submitted to regulatory agencies for registration or acceptance of many chemicals. Although these guidelines are appropriate and suitable for the testing of compounds as solutions or suspensions, modifications are required to enable the testing of gases, such as individual cigarette smoke toxicants, and complex aerosols including cigarette smoke [9,12,13]. As a result, there is currently a drive by investigators involved in tobacco-related research to ensure the toxicological assessment of cigarette smoke is based on the complete smoke aerosol, and not just a smoke sub-fraction [14][15][16][17].…”

A Case Study for the Comparison ofIn VitroData Across Multiple Aerosol Exposure Studies with Extrapolation to Human Dose

“…T he development of whole aerosol (whole smoke) exposure systems has been driven by the necessity to develop techniques to deliver aerosols in vitro in ways that mimic human exposure to cigarette smoke and other inhaled chemicals with increasingly physiological accuracy. [1][2][3] Cigarette smoke is a complex dynamic aerosol consisting of thousands of chemicals distributed in the particulate and vapor phases, with some transitioning between both phases. 4 Due to the complex nature of cigarette smoke, appropriate analysis and exposure is a challenging multifactorial problem.…”

Cigarette Mainstream Smoke: The Evolution of Methods and Devices for Generation, Exposure and Collection

“…Combining the results of the two studies (494,495) the authors proposed a battery of strains for testing the genotoxicity of TPM generated from (conventional or modified) tobacco containing smoking products using either traditional or air-agar interface Ames methodology. Instrumentation for assessing the contribution of single gaseous components in cigarette mainstream smoke to cytotoxic and genotoxic effects was developed by BREHENY et al (496). Ethylene oxide -a (minor) constituent of fresh tobacco smoke with known direct in vitro and in vivo genotoxicity and a carcinogen in rodents -was chosen as test gas.…”