Assessing Exhaust Toxicity with Biological Detector: Configuration of Portable Air-Liquid Interface Human Lung Cell Model Exposure System, Sampling Train and Test Conditions

Air pollution remains to be one of the leading causes of premature death worldwide, with significant share attributed to particulate matter and reactive nitrogen compounds from mobile sources. Due to discrepancies between legislative metrics and health effects, and between laboratory tests and real driving, health-relevant metric applicable to real driving conditions are sought to evaluate the effects of emerging legislation, technologies and fuels. Models of human lung air-liquid interface have been recently explored to simulate effects of exposure to the whole exhaust. In this study, a compact exposure system, utilizing commercially available inserts with 3D in-vitro model of human lung cells, has been designed and fabricated in-house with the vision of mobile use, minimizing size and power consumption. Preliminary tests were done on a Euro 6 direct injection spark ignition engine operating at speeds and throttle positions corresponding to the WLTC cycle. A sample of diluted exhaust was taken from two systems offering dynamic variation of dilution ratio to account for variable exhaust flow: a proportional sampling gravimetric system and from a rotating disc diluter. As expected, nucleation of ~10 nm particles took place at lower (10:1) dilution ratios, however, low dilution ratios may be necessary as the exposure duration is limited to a maximum of hours to several days. The highest particle losses - around 40 % - were in a membrane humidifier, a part of the effort to maintain incubator conditions of 37 C, 80-95 % relative humidity and around 5 % CO₂ at the cells. Two types of cell cultures have been exposed over a period of 5 days, with daily exposure consisting of two runs of WLTC, first with a cold start, active cooling of the engine for two hours, and two additional runs of WLTC, with acceptable rate of cell survival. The compact design and choice of components offers a promise for implementation during common laboratory tests and also on the road.