Portable emissions toxicity system: Evaluating the toxicity of emissions or polluted air by exposure of cell cultures at air-liquid interface in a compact field-deployable setup

Exposure of cell cultures at air-liquid interface (ALI), mimicking i.e. human lung surface, is believed to be one of the most realistic means to model toxicity of complex mixtures of pollutants on human health. The complexity of the close cooperation of "emissions source" and toxicology groups and of the instrumentation are among the limiting factors of ALI. In this work, the concepts of ALI exposure and real-world emissions monitoring using portable emissions monitoring systems (PEMS) are combined into a portable emissions or air toxicity system, for field deployment, including operation in moving vehicles. Cell cultures grown on 6 mm inserts are placed in an airtight 17x13x9 cm exposure box, where the sample is symmetrically distributed into 8 wells of a standard Transwell 24-well holder at 25 cm³/min/insert. In a 40x35x45 cm inner dimensions incubator, sample and control air are conditioned to 5 % CO₂, 37 °C and >85 % humidity and drawn through 2-4 exposure boxes. Characterization with silver nanoparticles revealed 50 % particle losses at 15 nm and deposition rate of approximately 1.5 % at both 10 and 21 nm mean diameter. The system has undergone an extensive field validation, including 4 h of exposure and 2 h transport in a vehicle each day for 5 days, 5-day operation outside in vans and tents at -7 to +32 °C, long transport and test on a heavy-duty truck, during which cells were exposed to the diluted exhaust from the truck, this being the first known use of ALI exposure chamber as PEMS. The portable exposure chamber, along with a field-deployable auxiliary mobile base including a small laminar flow box, additional incubator and freezer, can be easily used to study the toxicity of various emissions, effluents and polluted air, aiming for a more relevant toxicity measure than chemical composition alone.