The Influence of a Particulate Trap on the in Vitro Lung Toxicity Response to Continuous Exposure to Diesel Exhaust Emissions 1999-01-2710

Recent improvement in exhaust after-treatment technologies allows particle removal up to 95% with traps and NOx removal up to 40% with reduction catalyst from diesel exhausts. The efficiency of the technology is mainly based on the rate of regulated pollutant emission reduction but very few information is available in term of health hazard potential which may be related to interactions with several of the hundreds of chemical species present under different phases (liquid, gas, solid). It is therefore necessary to develop useful tools to evaluate the global toxicity of Diesel exhaust. A model of bi-compartimental gas/liquid organotypic culture of lung tissue has been specifically developed and used for continuous in vitro exposure to the exhaust gas of a direct injection 1.9 l turbo-charged engine. Regulated emissions (CO, HC, NOx and particles) were measured in raw exhaust. Exhaust gases are continuously sampled through a dilution tunnel after and before a ceramic particle trap and brought on rat or rabbit lung slices after O₂ and CO₂ concentrations corrections to 21% and 5% respectively, in order to avoid any hypoxia and medium pH adverse effects on the biological material. The impact of several parallel dilution rates and exposure duration are investigated on cell viability parameters namely intracellular ATP (marker of cellular energy status)and Glutathione (marker of oxidative stress). A concentration dependent depletion of intracellular glutathione was observed after a 1 hour exposure to whole exhausts while this effect was only minimal after exposure to filtered exhausts. Intracellular ATP level decreases were of minimal amplitude and were more marked after exposure to filtered than to whole exhausts. This newly designed system may be a very useful tool for the study of the global toxicological impact of after-treatment technologies.