Hydraulic Oil Infiltration into Potable Water through Aircraft Pneumatic Systems: A Qualitative Assessment of Chemical Contamination

Potable water on aircraft is currently monitored for microbiological contaminants of water quality such as E. coli, but because the source water for aircraft is pre-treated water from municipalities, chemical contaminants are not assessed. This neglects the possibility of aircraft pneumatic systems, interconnected with other systems such as the engines and hydraulic oil reservoirs, from becoming fouled and contaminating the potable water onboard with organophosphate esters and other contaminants of concern. In this novel initial qualitative study potable water samples were taken on twenty domestic and international flights on various commercial aircraft. The samples were analyzed with high-resolution liquid chromatography mass spectrometry and compared against 18 Mohm ultrapure water and tap water blanks drawn from departing airports. Suspect compounds were identified using safety data sheets for commonly used aircraft oils and compounds previously identified in aircraft cabin contamination research. Tributyl phosphate, the primary component in aircraft hydraulic oil, was confirmed to be present in the potable water of the majority of flights sampled (11 of 20 flights). Other organophosphates were also identified in the water on a high percentage of flights (tris (chloropropyl) phosphate (TCPP): 20%; triphenyl phosphate (TPhP): 10%; tris (butoxyethyl) phosphate (TBEP): 10%). The qualification of the compounds is supported by mass accuracy, fragment, isotope abundance, and adduct data. This work suggests that as there is currently a potentially unaddressed occupational and public health risk. Detailed quantitative chemical monitoring of aircraft potable water is therefore recommended to fully establish the magnitude of this risk.