tag:theconversation.com,2011:/id/topics/organophosphate-5803/articlesOrganophosphate – The Conversation2017-04-11T06:27:49Ztag:theconversation.com,2011:article/760122017-04-11T06:27:49Z2017-04-11T06:27:49ZWhat we know about the April 4 chemical attack in Syria<p>The <a href="https://theconversation.com/the-latest-suspected-chemical-attack-in-syria-brings-destruction-and-deception-75718">April 4, 2017 chemical attack</a> on the rebel-held town of Khan Sheikhoun in Syria led to <a href="https://www.theguardian.com/world/2017/apr/04/syria-chemical-attack-idlib-province">at least 70 deaths and more than 100 people requiring medical attention</a>, prompting an outcry from the international community. It led to the <a href="https://theconversation.com/with-syria-missile-strikes-trump-turns-from-non-intervention-to-waging-war-75917">April 7 US bombing</a> of the Shayrat air base. </p>
<p>It is alleged that sarin was used in the Khan Sheikhoun attack. This particular chemical became famous in 1995 with the <a href="https://theconversation.com/how-should-we-remember-violence-lessons-from-the-tokyo-sarin-attack-39101">Tokyo subway attack</a>, launched by members of the cult movement Aum Shinrikyo.</p>
<h2>Was it sarin?</h2>
<p><a href="https://www.opcw.org/protection/types-of-chemical-agent/nerve-agents/">Sarin</a> is an organophosphorus compound and was first synthesised in 1938 in Germany as part of a pesticide research program. </p>
<p>Sarin is a moderately volatile substance – that is, it readily forms a gas – which can be taken up by inhalation or skin contact. It is an inhibitor of the enzyme acetylcholinesterase, which is critical in regulating nerve function. </p>
<p>When exposed to a low dose of a <a href="https://www.opcw.org/protection/types-of-chemical-agent/nerve-agents/">nerve agent such as sarin</a>, people experience increased production of saliva, a running nose and a feeling of pressure on the chest. The pupils of the eye becomes contracted, so-called “pin-point” pupils.</p>
<p>Pin point pupils, which have been recorded in video footage of the Khan Sheikhoun attack, are a characteristic consequence of acetylcholinesterase inhibitors like sarin. This clinical sign is quite different from the irritating effects of chlorine and mustard gas.</p>
<p><a href="https://www.opcw.org/protection/types-of-chemical-agent/nerve-agents/">Medium to higher dose exposure to sarin and other nerve agents</a> can result in difficulty in breathing and coughing, abdominal cramps and vomiting, and sometimes involuntary discharge of urine and faeces. Increased saliva production, running eyes and sweating may occur, as well as muscular weakness, tremors or convulsions. Loss of consciousness, and death due to respiratory failure may be seen at higher doses. </p>
<p>Survivors of the Tokyo subway sarin attack recovered reasonably well but experienced some clinically detectable <a href="https://www.ncbi.nlm.nih.gov/labs/articles/16962140/">neurological effects</a>, and <a href="http://onlinelibrary.wiley.com/doi/10.1002/ana.21024/abstract">some evidence of brain changes</a>. </p>
<p>Although sarin use is suspected in Khan Sheikhoun, there are many organophosphorus insecticides that would exert the same effect (in sufficient quantity). It is possible that an organophosphate pesticide or a simple organophosphate (not normally classified as a chemical weapon) was used in this attack.</p>
<p>The production of sarin requires special facilities and is expensive, perhaps running into the tens of millions of dollars. <a href="https://www.opcw.org/protection/types-of-chemical-agent/nerve-agents/">Similar chemicals, such as tabun</a>, are less expensive to make. </p>
<h2>Will we ever know what was used?</h2>
<p>In order to establish the identity of the substances used in Khan Sheikhoun, a combination of information needs to be gathered and assessed. In particular the results of chemical tests on wipe samples, soil and clothing samples must be determined and verified. </p>
<p>The Organisation for the Prohibition of Chemical Weapons (<a href="https://www.opcw.org/">OPCW</a>) Fact Finding Team would be the most authoritative source to reveal the nature of the chemical(s) used, and we will await their report. However, in the past these reports have been <a href="http://www.un.org/ga/search/view_doc.asp?symbol=S/2017/45">inconclusive</a> owing to the time taken to gather chemical samples, limits of detection, specificity and the presence of mixtures. </p>
<p>The conflict in Syria involves the government military forces, the rebels, ISIS and the Kurds. It is sometimes hard to know where the chemicals might be coming from (for example, from neighbouring countries), or whether they have been produced or sourced locally.</p>
<h2>Local history of chemical attacks</h2>
<p>This experience in Syria may lead to improved medical responses in the case of future attacks. But in the absence of detailed knowledge of the substances involved, the treatment of casualties is unlikely to be optimal. </p>
<p>With so many individual chemical substances, and improvised mixtures, only generic decontamination and treatment procedures can be used. However, it may be feasible to have chemical specialists attached to hospitals collecting and storing specimens for subsequent analysis.</p>
<p>Sadly, the use of chemicals in Khan Sheikhoun is not an isolated incident. After all, a <a href="http://www.un.org/ga/search/view_doc.asp?symbol=S/2017/45">recent report</a> of the OPCW Fact Finding Mission for the period December 2015 to November 20, 2016, recorded 65 potential incidents of the use of chemical weapons reported in open sources. </p>
<p>The use of chemical weapons has a long history in the region. On <a href="http://news.bbc.co.uk/onthisday/hi/dates/stories/march/16/newsid_4304000/4304853.stm">March 16, 1988</a>, Iraq dropped bombs containing multiple toxic chemicals on the Kurdish city of Halabja, killing thousands.</p><img src="https://counter.theconversation.com/content/76012/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dino Pisaniello receives or has received funding from Australian Research Council, Safe Work Australia, Safe Work SA, Australian Department of Health, Defence Science and Technology Group and indirectly through the US Department of Defence. He has received funding in the past from the mining industry. He is on a committee in the Department of Veterans Affairs relating to veterans health. </span></em></p>The Organisation for the Prohibition of Chemical Weapons Fact Finding Team has not yet revealed the nature of the chemicals used in Khan Sheikhoun.Dino Pisaniello, Professor of Public Health , University of AdelaideLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/743162017-03-14T16:01:00Z2017-03-14T16:01:00ZPhosphorus is vital for life on Earth – and we’re running low<figure><img src="https://images.theconversation.com/files/160487/original/image-20170313-11138-fgimr5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The stuff of life.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/focus-on-phosphorus-chemical-element-mendeleev-380077645?src=0TCLmvir6Yx_ZTdiq0XkrQ-1-8">Shutterstock</a></span></figcaption></figure><p><a href="http://www.rsc.org/periodic-table/element/15/phosphorus">Phosphorus</a> is an essential element which is contained in many cellular compounds, such as DNA and the <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/Biology/atp.html">energy carrier ATP</a>. All life needs phosphorus and agricultural yields are improved when phosphorus is added to growing plants and the diet of livestock. Consequently, it is used globally as a fertiliser – and plays an important role in meeting the world’s food requirements.</p>
<p>In order for us to add it, however, we first need to extract it from a concentrated form – and the supply comes almost exclusively from <a href="https://www.theatlantic.com/science/archive/2016/11/the-desert-rock-that-feeds-the-world/508853/">phosphate mines in Morocco</a> (with far smaller quantities coming from China, the US, Jordan and South Africa). Within Morocco, most of the mines are in <a href="http://www.bbc.co.uk/news/world-africa-14115273">Western Sahara</a>, a former Spanish colony which was annexed by Morocco in 1975. </p>
<p>The fact that <a href="https://minerals.usgs.gov/minerals/pubs/commodity/phosphate_rock/mcs-2016-phosp.pdf">more than 70% of the global supply</a> comes from this single location is problematic, especially as scientists are warning that we are approaching <a href="http://www.americanscientist.org/issues/pub/does-peak-phosphorus-loom">“peak phosphorous”</a>, the point at which demand begins to outstrip supply and <a href="https://theconversation.com/peak-phosphorus-will-be-a-shortage-we-cant-stomach-25065">intensive agriculture</a> cannot continue to <a href="https://theconversation.com/how-the-great-phosphorus-shortage-could-leave-us-all-hungry-54432">provide current yields</a>. In the worst case scenario, mineable reserves could be exhausted within as <a href="http://www.sciencedirect.com/science/article/pii/S095937800800099X">little as 35 years</a>.</p>
<p>So what is going on – and how worried should be?</p>
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<img alt="" src="https://images.theconversation.com/files/160488/original/image-20170313-19256-1j44seb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/160488/original/image-20170313-19256-1j44seb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/160488/original/image-20170313-19256-1j44seb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/160488/original/image-20170313-19256-1j44seb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/160488/original/image-20170313-19256-1j44seb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/160488/original/image-20170313-19256-1j44seb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/160488/original/image-20170313-19256-1j44seb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Here be phosphorous.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/map-western-sahara-blue-pushpin-stuck-471656336?src=vkDq71HKb0RiDbwLKFAtnA-1-8">Shutterstock</a></span>
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<h2>Natural limits</h2>
<p>In nature, phosphorus only exists bound to oxygen, which is called phosphate. It is in this form that it is mined. Chemists can remove the oxygens bound to it to get elemental white phosphorus, which glows in the dark, but it is so unstable that it spontaneously ignites on exposure to air.</p>
<p>Phosphate easily diffuses through soil or water and can be taken up by cells. When phosphate meets free calcium or iron, they combine to give highly insoluble salts. </p>
<p>In the first half of the 19th century, Justus von Liebig popularised the <a href="https://en.wikipedia.org/wiki/Liebig's_law_of_the_minimum">law of the minimum</a> for agriculture, which states that growth is limited by the least available resource. It was soon discovered that this was often some form of phosphorus.</p>
<p>As a consequence, bones – comprised mostly of calcium and phosphate – from old battlefields were dug up to use in farming. <a href="https://www.britannica.com/topic/guano">Guano</a>, large accumulations of bird droppings, also contains high concentrations of phosphorus and was used to fertilise crops. But supplies of this were soon depleted. As demand increased, supplies had to be mined instead.</p>
<p>But this applied inorganic phosphate fertiliser is highly mobile and leaches into watercourses. In addition, phosphate rock weathers and is also ultimately washed into the ocean where it either deposits as calcium phosphate or is taken up by marine organisms who also eventually deposit on the ocean floor when they die. Consequently, terrestrial phosphorous doesn’t really disappear, but it can move beyond our reach.</p>
<h2>Natural wastage</h2>
<p>To complicate matters further, even the phosphorous we can use is largely wasted. Of the phosphorus mined as fertiliser, only <a href="http://www.mdpi.com/2073-4395/3/1/86/htm">a fifth reaches the food we eat</a>. Some leaches away and some is bound to calcium and iron in the soil. Some plant roots have the ability to extract the latter, but not in large enough quantities to retrieve all of it. </p>
<p>In addition to these inorganic forms, phosphate is also converted into cellular compounds, creating organically-bound phosphorus, such as <a href="https://www.reference.com/science/function-phospholipids-c0bbfb78de2b1593">phospholipids</a> or <a href="https://en.wikipedia.org/wiki/Phytic_acid">phytate</a>. After the death of an organism, these organic phosphorus compounds need to be returned into the useable phosphate form. How much organically-bound phosphorus is present in soils depends on the number and activity of the organisms that can do this.</p>
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<img alt="" src="https://images.theconversation.com/files/160489/original/image-20170313-11138-1ohd33y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/160489/original/image-20170313-11138-1ohd33y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/160489/original/image-20170313-11138-1ohd33y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/160489/original/image-20170313-11138-1ohd33y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/160489/original/image-20170313-11138-1ohd33y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/160489/original/image-20170313-11138-1ohd33y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/160489/original/image-20170313-11138-1ohd33y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Phosphorous boosts crop yields.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/corn-field-140658412?src=pm2Y_QViULXrR6JnuICWoQ-1-3">Shutterstock</a></span>
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<p>Agricultural soils are usually rich in inorganic phosphorous while in undisturbed ecosystems, such as forests and long-term pastures, organically-bound phosphorus dominates. But agricultural land is often depleted of phosphorus during harvest and land management practises such as ploughing, hence the addition of phosphate-containing fertilisers. </p>
<p>Spreading manure and avoiding tillage are ways of increasing microbial abundance in the soil – and so keeping more phosphorus in an organically-bound form. </p>
<p>The risks of peak phosphorous can be countered with some simple solutions. Eating less meat is a start as huge amounts are used to rear <a href="http://www.npr.org/sections/thesalt/2013/02/14/172009950/should-you-be-worried-about-your-meats-phosphorus-footprint">livestock for meat</a>. The chances are that agricultural yields are limited by phosphorus availability and will be further stretched as the global population grows. </p>
<p>Humans are themselves wasteful of phosphorous, as most of what we take in goes straight out again. Fortunately, technologies have been developed to <a href="http://iahr.tandfonline.com/doi/abs/10.1080/09593332008616874">mine phosphorus from sewage</a>, but at present are too expensive to be practical. </p>
<p>Peak phosphorus does not mean that phosphorus will disappear, rather that the reserves with mineable high concentrations are depleting. Instead, we are increasing the background concentrations of phosphorus and adding it to the ocean floor. More sustainable phosphorus use requires a greater appreciation and understanding of the many organisms that make up soils – and the part they play in phosphorus distribution – or we may no longer be able to feed the world at an affordable price.</p><img src="https://counter.theconversation.com/content/74316/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Vera Thoss does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>It is essential to maintain global food supply, but the clock is ticking.Vera Thoss, Lecturer in Chemistry, Bangor UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/435952015-06-20T09:40:24Z2015-06-20T09:40:24ZExplainer: is aircraft cabin air toxic?<figure><img src="https://images.theconversation.com/files/85791/original/image-20150620-3380-1925u1g.jpg?ixlib=rb-1.1.0&rect=0%2C3%2C910%2C501&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Debate over potential pollutants calls for better tools to measure air quality.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/imranghaffar/16948377692/sizes/l">Singapore Spotter/flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Following the death of commercial airline pilot Richard Westgate, an inquest was launched into the cause of his death. Westgate <a href="http://www.dailymail.co.uk/news/article-2708365/BA-pilot-killed-toxic-fumes-flightdeck-constantly-exposed-fuel-leaks-board-passenger-jets.html">had previously claimed</a> that his health problems were caused by exposure to on board toxic chemicals and a subsequent <a href="https://www.judiciary.gov.uk/wp-content/uploads/2015/03/Westgate-2015-0050.pdf">coroner’s report</a> raised concerns with the pilot’s employers, British Airways, and the Civil Aviation Authority (CAA), regarding the health effect of aircraft cabin air on aircraft occupants. Both organisations <a href="http://aerotoxic.org/wp-content/uploads/2015/04/BA-and-CAA-responses-to-Coroner1.pdf">have responded to the report and stress</a> that they take the matter of cabin air quality very seriously but that scientific evidence had not established a risk to ill-health. The investigation is ongoing and the inquest has not yet been heard.</p>
<p>This hasn’t stopped at least 17 former and serving cabin crew <a href="http://www.bbc.co.uk/news/business-33008356">from seeking legal action</a> against various British airlines for ill health they allege was caused by pollutants in cabin air. </p>
<p>Whether their claims are successful remains to be seen, but at least one precedent has been set: in 2010 a former flight attendant in Australia was <a href="http://www.flightglobal.com/news/articles/australian-appeal-court-awards-big-compensation-in-toxic-cabin-air-340362">awarded compensation</a> for respiratory damage sustained as a result of exposure to on-board toxic chemicals.</p>
<h2>What are these toxic chemicals?</h2>
<p>Airline crew have been <a href="http://www.researchgate.net/publication/27248026_Survey">reporting ill-health</a> following exposure to contaminated air for many years. Most commonly reported symptoms are: irritation to the eyes, nose and throat; headaches, light-headedness and dizziness; fatigue, weakness; generally feeling unwell; confusion and difficulties in concentration. </p>
<p>While passengers have occasionally complained of similar symptoms, this is a much rarer occurrence (unsurprising perhaps because of the relative infrequency of travel compared to aircrew). Symptoms may be the result of <a href="http://www.publications.parliament.uk/pa/ld200708/ldselect/ldsctech/7/7we05.htm">exposure to the organophosphate known as tricresyl phosphate (TCP)</a>; a flame retardant additive in jet engine oil and hydraulic fluids. As well as acting as an irritant, these substances are a type of neurotoxic compound, <a href="http://www.ncbi.nlm.nih.gov/pubmed/23163581">and can interfere</a> with nervous system functions, resulting in cognitive, emotional and behavioural problems.</p>
<p>Since their use as nerve gas agents in World War II, it is known that organophosphates can cause ill health and death in high doses. However, controversy still surrounds whether low levels are actually harmful. Establishing a link between exposure and chronic ill-health lies in the difficulty we have with establishing an accurate estimation of exposure. The absence of routine air quality monitoring on commercial aircraft make it impossible to determine what chemicals enter the cabin and in what quantities. </p>
<p>In addition, relying on self-reported measures of exposure is notoriously problematic as they depend on memory and a capacity to detect noxious substances (both of which vary enormously in reliability). So, before a causal relationship can be determined, our understanding of how exposure might occur, and the level of this exposure, needs to be improved.</p>
<h2>How would exposure occur?</h2>
<p>Air is supplied throughout the aircraft to allow crew and passengers to breathe. The human body is used to breathing in air of around 15°C, at a pressure of 14.7 pounds per square inch, or psi, (at sea level). However, at an altitude of 35,000 feet the air pressure is only 3.46 psi with temperatures lower than -50°C, so fresh air is pumped into the plane from outside the aircraft but only after it is warmed and pressurised to a safely breathable level.</p>
<p>As part of the propulsion process, aeroplane engines heat and compress air before fuel is added and combusted. On most aircraft this air is then “bled off” and <a href="http://www.lufthansa-technik.com/cabin-air-circulation">pumped into the aircraft</a>, unfiltered. Ordinarily this process is relatively safe. But occasionally faulty seals can result in contamination by allowing heated and broken down engine oil fumes to escape into the airflow.</p>
<p>The incidence of these “fume events” is difficult to quantify, as commercial aircraft are generally not fitted with equipment for monitoring on-board air quality. There is also significant under-reporting of exposure: for example, the Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment estimated that fume events occur on about <a href="https://www.gov.uk/government/publications/cabin-air-quality-faq/cabin-air-quality-main-issues">0.05% of flights</a>. </p>
<p>However, in 2003, a survey of pilots belonging to the <a href="http://www.researchgate.net/profile/Peter_Halkon/publication/27248026_Survey/links/546dce800cf2a7492c5602d5.pdf">British Airline Pilots Association</a> suggested that up to 96% of contaminated air events may go unreported. Collectively, the pilots in the survey claimed to have experienced more than 1,674 smoke or fume events but only 61 instances were formally reported to the CAA, possibly due to lack of awareness, commercial pressure and the perception that exposure to such contaminants is normal and part of their everyday job.</p>
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<img alt="" src="https://images.theconversation.com/files/85045/original/image-20150615-5816-os0qrg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/85045/original/image-20150615-5816-os0qrg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/85045/original/image-20150615-5816-os0qrg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/85045/original/image-20150615-5816-os0qrg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/85045/original/image-20150615-5816-os0qrg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/85045/original/image-20150615-5816-os0qrg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/85045/original/image-20150615-5816-os0qrg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Oxygen masks for all?</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/miikkah/5067446540/sizes/l">'mikkahoo/flickr'</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
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<p>To better establish the incidence of fume events, the UK Department for Transport commissioned <a href="http://www.iom-world.org/pubs/iom_tm1106.pdf">Cranfield University</a> to carry out an air monitoring study of affected aircraft types. They monitored 100 flights, measuring the levels of several chemical compounds that were present in the cabin during different stages of flight. A number of chemicals were detected over the course of this study, including TCP and carbon monoxide. </p>
<p>All levels were reported to be within safe limits – regardless of an absence of aircraft safety standards regarding TCP. While reassuring for routine flight safety, no fume events were observed in this small sample size due to the relative rarity of cabin air contamination. The study reinforced the lack of clarity around possible exposure that aircrew and passengers may face during a fume event.</p>
<h2>So what evidence is there?</h2>
<p>Without accurate measures of exposure, it is very difficult to reliably determine whether there is a relationship between ill-health and exposure to fume events, though there is some supporting evidence. For example, <a href="http://www.researchgate.net/profile/Peter_Halkon/publication/27248026_Survey/links/546dce800cf2a7492c5602d5.pdf">symptom surveys</a> from 2003, and <a href="http://ashsd.afacwa.org/docs/AIAA2011.pdf">case studies</a> of exposed passengers and crew (where subsequent mechanical inspections of the aircraft confirmed oil leaks had occurred) have demonstrated signs of ill-health consistent with organophosphate exposure.</p>
<p>In 2013, biological markers of possible neurotoxicity were found in flight crew with these <a href="http://www.researchgate.net/publication/236112575_Autoantibodies_to_nervous_system-specific_proteins_are_elevated_in_sera_of_flight_crew_members_biomarkers_for_nervous_system_injury">symptom profiles</a>. And in 2012, <a href="http://www.itcoba.net/30MA11A.pdf">a neuropsychological study</a> found that a group of airline pilots had a specific pattern of cognitive impairments similar to that seen in <a href="http://oro.open.ac.uk/32168/1/">organophosphate-exposed farmers</a>. While these studies may provide evidence consistent with exposure, it is still very difficult to claim causation, mainly because of small sample sizes.</p>
<p>It seems there is still a large amount of scientific uncertainty regarding the long-term effects of inhaling pyrolysed engine oil on human health. However, with the growing pressure from lobbyists (such as the <a href="http://aerotoxic.org/">Aerotoxic Association</a>), potential legal suits and inquests, we may soon have a more definitive answer to this question. </p>
<p>The European Aviation Safety Agency has launched a preliminary cabin air quality measurement campaign, which should allow for the development of instruments that may be able to monitor air quality in real time. In addition, <a href="https://theconversation.com/why-single-blood-markers-for-disease-will-become-a-thing-of-the-past-41636">biomarkers</a> for exposure to TCP <a href="http://abrapac.com.br/wdownloads/Imprensa_Maio/Prof.%20Furlong%20research%20update%20and%20funding%20request_24%20April%202014.pd">are being developed</a> by researchers from the universities of Washington and Nebraska.</p>
<p>Given these advancements, we may not be far away from establishing a valid and reliable measurement of exposure. And with that a better answer on whether there is a clear link between ill health and exposure.</p><img src="https://counter.theconversation.com/content/43595/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gini Harrison does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Health effects from contamination on planes is controversial, not least because we don’t measure on-board air quality during ‘fume events’.Gini Harrison, Lecturer in Psychology, The Open UniversityLicensed as Creative Commons – attribution, no derivatives.