A Comparison of Fresh and Used Aircraft Oil for the Identification of Toxic Substances Linked to Aerotoxic Syndrome Chemosphere
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Chemosphere 158 (2016) 116e123 Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere A comparison of fresh and used aircraft oil for the identification of toxic substances linked to aerotoxic syndrome David Megson a, *, Xavier Ortiz b, Karl J. Jobst b, Eric J. Reiner a, b, Michel F.A. Mulder c, Jean-Christophe Balouet d a Department of Chemistry, University of Toronto, Toronto, ON, Canada b Ontario Ministry of the Environment and Climate Change, 125 Resources Road, Canada c Aviation Medical Consult, Karbouwstraat 14, 1402 VC Bussum, The Netherlands d Environnement International, Orrouy, France highlights High resolution mass spectrometry was used to identify toxic compounds in jet oil. Ortho substituted TCP was not detected in jet oil. Alkylated TCP was detected in used jet oil at 0.13e0.69%. w/w. Previous air quality studies may have underestimated the risks from OPs. article info abstract Article history: Fresh and used aircraft engine lubricants (Mobil Jet Oil II) were analysed using a Fourier Transform Ion Received 18 March 2016 Cyclotron Resonance Mass Spectrometer (FTICRMS) and comprehensive two dimensional gas chroma- Received in revised form tography with high resolution time of flight mass spectrometry (GCxGC-HRTOFMS). The composition of 16 May 2016 the fresh oil was established, with special focus to its tricresyl phosphate (TCP) content as this has Accepted 21 May 2016 formed the focus for most investigations into aerotoxic syndrome. The results showed that only four TCP isomers were present at detectable levels in the fresh oil: mmm-TCP, mmp-TCP, ppm-TCP and ppp-TCP. Handling Editor: J. de Boer The results indicate that the formulation of Mobile Jet Oil II does not contain the more toxic ortho substituted TCP isomers at concentrations above 0.0005%. The temperatures of jet engines during Keywords: operation are greater than 200 C which creates the potential to alter the composition of the original oil Aerotoxic and create other toxic compounds. The results show there may be a significant risk from alkylated cresyl Multidimensional chromatography phosphates, which were identified in the used oils at concentrations calculated in the range of 0.13 High resolution mass spectrometry e0.69%. w/w. Several xylenyl and ethylphenyl phosphates have been shown to exhibit a similar toxicity Cresyl phosphates to ortho substituted TCP isomers which makes there discovery in used oil significant. These compounds Organophosphates should be included in future aircraft air quality studies and when assessing the risks and causes of aerotoxic syndrome. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction exposure to toxic fumes and organophosphates (Abou-Donia et al., 2013; Harrison and Mackenzie Ross, 2016; Liyasova et al., 2011; Due to their widespread use as pesticides, plasticizers and flame Payne, 2015). There have been reports of headaches, loss of bal- retardants organophosphates are routinely detected in environ- ance, numbness and neurobehavioral abnormalities such as mental samples. However, a specific concern has arisen in recent emotional instability, depression and cognitive dysfunction, decades as aircraft crew have developed symptoms consistent with including impaired short term memory, blurred vision and speech, altered coordination (de Ree et al., 2014; Abou-Donia et al., 2013). Organophosphates are not just used as pesticides on crops in fields but are also used in aircraft as flame retardants, in engine oil and * Corresponding author. hydraulic fluids, and on material surfaces. This has resulted in their E-mail address: [email protected] (D. Megson). http://dx.doi.org/10.1016/j.chemosphere.2016.05.062 0045-6535/© 2016 Elsevier Ltd. All rights reserved. D. Megson et al. / Chemosphere 158 (2016) 116e123 117 link to aerotoxic syndrome by Winder and Balouet (2002). The term Many crew members who have reported conditions consistent with Aerotoxic Syndrome was first published in 1999 by an international organophosphate poisoning recover and return to their flight scientific team to describe the symptoms and exposure conditions duties, however some staff have lost their jobs, and several have reported by aircraft crew from Australia, US, Europe. Whilst aero- even passed away. When individuals are grounded they are no toxic syndrome has not been fully accepted as a medical syndrome longer exposed to aircraft air their reported symptoms can gradu- (Wolkoff et al., 2016) it is commonly used to refer to air quality in ally reduce. The underlying mechanism that caused the ill health aircraft and the associated exposure of crew and passengers to toxic may be an active auto immune reaction, set into motion by compounds. Aerotoxic syndrome is understood to be caused by repeated low dose exposure to organophosphates, causing actual long term and repeated exposure to chemicals released from smoke damage to the Blood-Brain-Barrier and apoptosis inside the brain. and fume events in aircraft. Protein filaments of these decaying cells are able to re-enter the During a flight the air cabin pressure and temperature are bloodstream, causing a secondary auto immune response. Memory maintained with outside air that is passed through the jet engine. B cells can recognise certain antigens for a long duration of time, Cabin air is recycled for 50%, whereas the flight deck air is comparable to a status after vaccination and can lead in rare in- comprised in most aircraft types of a continuous stream of bleed air stances to an anaphylactic shock (Banks and Lein, 2012), also (de Boer et al., 2015). Engine seals in use are known as “wet-seals”, known as “incapacitation”, or sudden heart failure due to lym- an inherent design feature, whereby a thin film of oil prevents phocytic myocarditis. UK Coroner Payne, recently issued a report to rotating surfaces to come into mechanical contact with each other. prevent further deaths following the death of a pilot, which was Pressure differentials over the seals cause a constant loss of oil and linked to OP poisoning (Abou-Donia et al., 2014; Payne, 2015). The vapours into the core engine. These enter the inlet of the high post mortem investigations gave the cause of death of either pressure compressor and contaminate the bleed air which is taken pentobarbital toxicity or lymphocytic myocarditis, individually or downstream. Oil leaks can result in odd smells in the cabin and in in combination. Hair analysis had shown the use of pentobarbital more extreme cases smoke events. The tricresylphosphate chemi- during the 4 weeks prior to his death, as a form of self medication cal fingerprint from wipe samples taken from a cockpit showed a against severe headaches. Pentobarbital is not known for causing statistically significant correlation (p value 0.039) with used engine the widespread infiltration of T-lymphocytes in the brain, heart and oil (Houtzager et al., 2013), indicating that this can be a significant neurological damage otherwise observed. Testing of samples taken source of exposure. Estimates of how often these events occur both prior to and after death disclosed symptoms consistent with varies depending upon whether the information is sourced from exposure to organophosphate compounds. regulatory authorities such as the UK Civil Aviation Authority (CAA), Due to the sporadic occurrence of smoke/fume incidents it is from airlines or from trade unions who represent aircrew (Harrison particularly difficult to obtain worst case air samples for analysis. and Mackenzie Ross, 2016). Reported values for the frequency of No fume events were observed on any of the flights that were smoke/fume events include 0.5% of flights (Murawski and Supplee, monitored by Crump et al. (2011) and de Ree et al. (2014). Although 2008), 0.05% (COT, 2007) and 0.02% (Shehadi et al., 2015). Lubri- this is hardly surprising as they only involved analysis on 100 and cating oil is applied to gas turbines in aeroplanes as anti-wear 20 flights respectively. Using the estimates of the frequency of fume agents. However, there have been several studies that have iden- events from Murawski and Supplee (2008), and Shehadi et al. tified subchronic neurotoxicity of aviation oils (Freudenthal et al., (2015) a sample size of between 200 and 5000 flights would be 1993; Daughtrey et al., 1996; Mackerer et al., 1999). Aircraft lubri- required to identify one event. Interestingly nine smoke/odour cating oils have remained relatively unchanged since the 1960s and events were recorded in 78 samples taken by De Nola et al. (2011). are comprised of approximately 95% synthetic esters with 3% tri- de Boer et al. (2015) used data from De Nola et al. (2011) and Craig cresyl phosphates and 1% phenyl-a-naphthalamines (Winder and and Barth (1999) to calculate that even using worst-case scenarios Balouet, 2002). Tri-cresyl phosphates (TCPs) are a group of organ- they cannot explain a relation of TCP in flight deck air to the ophosphates which contain 10 structural isomers. The ortho complaints of pilots and air crew, a similar conclusion was also substituted congeners are considered to be the most toxic and reached by de Ree et al. (2014) and Schindler et al. (2012). Available therefore the proportions of these compounds in oil have been data was reviewed by Ramsden (2013) who used jet oil consump- reduced in recent decades (Craig and Barth, 1999). Most of the focus tion as a surrogate to measure chemical contamination in aircraft of investigations in aircraft air quality and aerotoxic syndrome has cabin air. Those results show that the oil concentration in a fume been focused on tri-ortho-cresyl phosphate (ooo-TCP or ToCP), event, in which visible smoke appears in the cabin, was estimated however the mono-ortho and di-ortho isomers are also highly toxic at 50 mg/m3. The concentration of TCP was approximately 1.5 mg/ with omp-TCP the most toxic (de Boer et al., 2015; De Nola et al., m3 and using the ratio of ToCP to total TCP from Crump et al.