Here's What We Actually Know About Toxic Fumes On Airplanes

Last week, flight attendants sued Boeing for exposure to toxic fumes while flying. Despite decades of worry over these “fume events,” scientists still don’t really know if they’re harmful.

A new lawsuit charges Boeing with exposing flight attendants — and passengers — to dangerous fumes in airplane cabins, reviving a long-running safety debate.

The lawsuit is centered on a 2013 Alaska Airlines flight from Boston to Los Angeles that had to land in Chicago because flight attendants on board passed out.

Despite decades of such incidents (and lawsuits), the industry is only now teaming up with federal scientists to study airplane "fume events" — when engine exhaust bleeds into the pressurized air that passengers breathe.

"Something horrible was happening on the plane," former Alaska Airlines flight attendant Vanessa Woods said last Tuesday at a press briefing on the lawsuit.

Woods filed the suit with three other flight attendants, who had variously passed out, vomited, and required ambulances to get to the hospital after landing. Two have returned to work, but Woods said she still suffers chronic fatigue, confusion, and intestinal ailments after smelling fumes and then passing out in the back of the plane.

Boeing vigorously disputes the lawsuit's claims. "The air in our airplane cabins is safe," Boeing's Paul Bergam told BuzzFeed News. "The current lawsuit distorts and misrepresents the facts and the science," he said by email.

But the facts and the science of cabin air have been disputed since the 1950s, cabin experts said, with notable incidents including a 2008 Alaska Airlines flight in which de-icer fumes sent seven plane crew members to the hospital, and a 2010 U.S. Airways flight where a suspected hydraulic fluid leak sickened crew and passengers.

"There is a lot of concern, unfortunately, over ventilation systems," Ruel Overfelt of Auburn University's Airliner Cabin Environment Research Center told BuzzFeed News. "It's a really difficult issue to try and solve because the cases are so rare and each one is different."

A 2009 analysis by the Federal Aviation Administration (FAA) found fewer than three such incidents of cabin fumes for every million flights. In these rare cases, fuel, oil, or hydraulic fluid leaks into cabin air, creating smelly fumes.

Aside from carbon monoxide, carbon dioxide, and ozone, the FAA doesn't set limits on contaminants in cabin air, and there isn't a requirement to monitor for them in real time during flights. Despite a 2002 National Research Council report calling for sensors to detect engine combustion fumes, research has languished.

Along with looking at what happens when jets suck in volcanic ash, a NASA program called Vehicle Integration Propulsion Research (VIPR) is looking at oil ingestion, Peter Merlin of NASA's Armstrong Flight Research Center at Edwards, California, told BuzzFeed News.

This summer, the program's scientists will test sensors that could detect when engine fumes seep into cabin air.

About 2 million passengers fly every day in the U.S., with the cabin air typically pressurized to the equivalent of the thin air on an 8,000-foot mountaintop.

While Boeing's new 787 Dreamliner provides fresh air directly from outside, older planes rely on "bleed" air from jet engine compressors to provide pressurized cabin air.

Woods is only the latest in a long line of flight crew and passengers complaining of toxic effects from oil or vapors in bleed air incidents dating back to the 1950s.

One of the most alarming filings in the new lawsuit is a series of Boeing memos dating to 2007, in which an environmental engineer warned about failed oil seals in engines, and wrote, "I think we are looking for a tombstone before anyone with any horsepower is going to take interest."

The central health claim in the new case is one made before: that leaks of synthetic oil vaporized in the jet's engines, where temperatures can reach 900 degrees, releasing into the air organophosphates linked to neurological damage. The flight attendants who boarded the plane 45 minutes early were exposed to a bigger dose, the lawsuit suggests, which explains why all four attendants fell ill before any passengers did.

"I came to on the floor of the galley," Woods said, and then suffered the dry heaves, amid an escalating crisis as the other flight attendants aboard grew light-headed and also collapsed. Since the flight, Woods has had trouble speaking and remembering, she said, preventing her from working.

There is duelling science on the organophosphate question. A 2003 Archives of Environmental Health study by Duke's Mohammed Abou-Donia proposed that exposures triggered rapid death of brain cells. This study has been pivotal in the last decade of disputes between the airline industry and the Association of Flight Attendants.

Other aerospace medicine experts are skeptical, however.

"Why are there no reports of ill health from the passengers who were breathing the same cabin air, nor from the pilots on that flight who were also breathing the same bleed air?" aviation medicine expert Michael Bargshaw of King's College London asked BuzzFeed News.

Bargshaw, a consultant to Airbus, wrote a 2013 review of various medical theories about why fumes might cause ill health. The review suggested "hyperventilation" offers a plausible explanation for most reported events.

On organophosphates, Bargshaw concluded that a "worst case" fume incident in an airplane would only be one-quarter of the concentration needed to cause any ill effects — too low for any "medically feasible" injuries.

Some people experience higher-than-normal genetic sensitivity to some chemicals, Bargshaw acknowledged. "This might explain some cases of reported ill-health following cabin air smells."

Regardless of whether they’re dangerous, everyone agrees that these incidents are extremely rare.

In April, the Indoor Air journal released a study finding that reports of engine fume events were very rare and spread across all passenger aircraft, both Boeing and its competitors' models, from 2007 to 2012. That means that thousands of airplanes will need years of monitoring (with the kinds of cheap monitors that NASA is still developing) before we actually know the scope of cases like whatever happened to Woods and her colleagues on that flight two years ago.

"I would go get on an airplane today with no compunctions," Overfelt of Auburn University said. "At the same time, you have some people who really seem to be suffering and have real human stories to tell."