In vitro hazard characterization of simulated aircraft cabin bleed-air contamination in lung models using an air-liquid interface (ALI) exposure system

June 21, 2021

Rui-Wen He a,b, Marc M.G. Houtzager c, W.P. Jongeneel a, Remco H.S. Westerink b, Flemming R. Cassee a,b

a National Institute for Public Health and the Environment (RIVM), P.O. Box 1, 3720 BA Bilthoven, the Netherlands
b Institute for Risk Assessment Sciences (IRAS), Toxicology Division, Faculty of Veterinary Medicine, Utrecht University, P.O. Box 80177, 3508 TD Utrecht, the Netherlands
c The Netherlands Organisation for Applied Scientific Research, TNO, P.O. Box 80015, 3508 TA Utrecht, the Netherlands


This unique experimental “Mini-BACS + AES” setup is able to provide steady conditions to perform in vitro exposure under ALI conditions to aircraft engine oil and hydraulic fluid fumes, generated at respectively 350 ◦C and 200 ◦C. Exposure of the Calu-3 monoculture and Calu-3 + MDM co-culture lung cell models to high levels of aircraft engine oil and hydraulic fluid fumes under ALI conditions can reduce TEER and viabilities of the cells, induce cytotoxicity, and increase production of proinflammatory cytokines. Hydraulic fluid fumes are more toxic than engine oil fumes on the mass concentration of fume basis, which may be related to higher abundance of OPs and smaller particle size of hydraulic fluid fumes. The toxicological data clearly reflect the potential health risks during fume events in aircraft cabins.


Contamination of aircraft cabin air can result from leakage of engine oils and hydraulic fluids into bleed air. This may cause adverse health effects in cabin crews and passengers. To realistically mimic inhalation exposure to aircraft cabin bleed-air contaminants, a mini bleed-air contaminants simulator (Mini-BACS) was constructed and connected to an air-liquid interface (ALI) aerosol exposure system (AES). This unique “Mini-BACS + AES” setup provides steady conditions to perform ALI exposure of the mono- and co-culture lung models to fumes from
pyrolysis of aircraft engine oils and hydraulic fluids at respectively 200 ◦C and 350 ◦C. Meanwhile, physicochemical characteristics of test atmospheres were continuously monitored during the entire ALI exposure, including chemical composition, particle number concentration (PNC) and particles size distribution (PSD). Additional off-line chemical characterization was also performed for the generated fume. We started with submerged exposure to fumes generated from 4 types of engine oil (Fume A, B, C, and D) and 2 types of hydraulic fluid (Fume E and F). Following submerged exposures, Fume E and F as well as Fume A and B exerted the highest toxicity, which were therefore further tested under ALI exposure conditions. ALI exposures reveal that these selected engine oil (0–100 mg/m3) and hydraulic fluid (0–90 mg/m3) fumes at tested dose-ranges can impair epithelial barrier functions, induce cytotoxicity, produce pro-inflammatory responses, and reduce cell viability. Hydraulic fluid fumes are more toxic than engine oil fumes on the mass concentration basis. This may be related to higher abundance of organophosphates (OPs, ≈2800 µg/m3) and smaller particle size (≈50 nm) of hydraulic fluid fumes. Our results suggest that exposure to engine oil and hydraulic fluid fumes can induce considerable lung toxicity, clearly reflecting the potential health risks of contaminated aircraft cabin air.

Read article

News overview