( CNN ) -- Inside a freezer in a research laboratory at the University of Washington are blood and blood plasma samples from 92 people who suffer from mysterious illnesses , including tremors , memory loss and severe migraine headaches . Terry Williams hugs her two boys -- Jake , left , and Zack -- in 2006 , before she says toxic cabin air made her sick . They are mostly pilots and flight attendants who suspect they 've been poisoned in their workplace -- on board the aircraft they fly . Clement Furlong , University of Washington professor of medicine and genome sciences , leads a team of scientists who have been collecting the samples for 2 ½ years . Furlong said his team is a few months away from finalizing a blood analysis test that will be able to definitely confirm whether the study participants were indeed poisoned by toxic fumes . Results of Furlong 's research could expand recognition of what a select group of researchers believes is a largely unrecognized risk of flying : the chance that poisonous fumes enter the cabin . `` There 's a danger of inhaling compounds that are coming out of the engine , '' said Furlong in his laboratory . See a diagram of how the air is circulated » . The air we breathe on board a plane is a 50-50 mix of filtered , recirculated air and so-called `` bleed air '' -- which bleeds off the engines , and then is pressurized and cooled before being sent into the cabin through vents . If an engine oil seal leaks , aviation engineers and scientists say , the bleed air can become contaminated with toxins . In 2002 the National Academies of Sciences ' National Research Council reported `` contaminant exposures result from the intake of chemical contaminants ( e.g. , engine lubricating oils , hydraulic fluids , deicing fluids and their degradation products ) into the Environmental Control System and then into the cabin . '' Of particular concern are toxic anti-wear agents in the oil , designed to prolong an engine 's life , called tricresyl phosphates . `` The engine seals fail and there 's very potent toxins that can come on board , '' said Furlong . Neuropsychologist Sarah Mackenzie Ross of University College London studied 27 British pilots who claimed they had inhaled contaminated air and subsequently had difficulty processing information and slowed reaction times . Her testing confirmed their symptoms . `` They did appear to underperform on tasks that required attention , processing speed , reaction time , and what we call executive functioning , which is high-level decision making , '' said Ross . Former flight attendant Terry Williams believes she is a victim of such a `` fume event . '' She complains of debilitating migraine headaches , tremors , and blind spots in her field of vision . `` It 's been so constant and just continues to worsen so it 's extremely frustrating , '' said Williams , who is suing Boeing , the owner of McDonnell Douglas , which made the MD-82 aircraft on which she worked . `` I 'm frustrated that I do n't feel any better and it 's over two years after the exposure . '' Boeing told CNN , `` It is our belief that air quality on airplanes is healthy and safe . '' In its response to Williams ' suit , the company said : `` The potential for bleed air contamination has been known through the aviation industry for many years . '' But Boeing denies any responsibility for Terry Williams ' illness . While Williams ' symptoms appear to be quite rare , it appears that fume events occur with regularity . A British study for the House of Lords found fume events in 1 of every 2,000 flights . In the U.S. , airlines are required to report `` fume events '' to the Federal Aviation Administration . There were 108 such reports last year . So why would n't more flight attendants , pilots and passengers suffer symptoms ? Furlong said a small percentage of people ( how small is not known ) appear to be highly sensitive to the most toxic chemicals . They may be genetically disposed to a strong reaction , possessing multiple genes of metabolizing proteins in their livers , or temporarily have high enzyme levels ( which can be triggered by prescription drugs ) that will act on the inhaled chemicals to magnify their toxicity . `` If you happen to be taking a medication that turns on the protein that converts pre-toxin to very potent toxin , you 've got an issue , '' said Furlong . As a result , someone sitting next to a victim may have inhaled the same contaminated fumes , but not suffer the same reaction . How might you know that you may have been exposed to a `` fume event '' while flying ? Experts say the telltale sign is a `` dirty sock '' smell . That 's butyric acid from engine oil , which itself is not highly toxic . But along with it comes the deadly nonodorous compounds tri-ortho-cresyl phosphate and mono-ortho-cresyl phosphate . Boeing 's new plane , the 787 Dreamliner , has been designed so that air entering the cabin from outside will not `` bleed '' off the engines . The company says that 's only for fuel efficiency purposes , not because of any concern about the quality of bleed air in its current fleet of aircraft . Indeed , Boeing and the FAA say the air quality on airplanes is as good or better than that of the average office building or home . CNN 's Jessica Ravitz contributed to this report .
Results of scientist 's research could expand recognition of `` bleed air '' Bleed air is air that passes through the engines of a plane , then into cabin . Boeing and FAA say air quality on airplanes is as good as in office or home . Flight attendant Terry Williams believes she is a victim of fumes in cabin air .