Is the exhaust smelling air when you wait for airplane takeoff bad?

March 6, 2024 6:27 PM

1: does airplane exhaust have lead in it? 2: would a N95 filter out lead fumes? 3: any studies or thoughts about the experience of slightly exhaust smelling air for 10 minutes before takeoff during taxi? I know in the 90s I would smell exhaust all the time in cars but now it’s so rare it’s surprising to me.
posted by bbqturtle to Travel & Transportation (14 answers total)

Jet A does not contain lead.
posted by wierdo at 6:31 PM on March 6, 2024 [9 favorites]

This happens because the plane's ac system uses bleed air from the engines and some combination of sitting still and the wind leads to fumes going back into the engine.

It's surely not great for you, but everyone working in aviation is exposed to way more of it than you are as a passenger without obvious ill effect, much like you incur extra radiation exposure while flying.

Avgas used by small planes is leaded, however.
posted by hoyland at 6:46 PM on March 6, 2024 [3 favorites]

No, the fuel used in almost every single passenger plane, including those with turboprops, does not have lead in it. It's similar to diesel or kerosene.

Small non-jet or turbojet planes - think 2-8 seats - usually run on leaded gasoline.
posted by CharlesDeP at 7:00 PM on March 6, 2024 [1 favorite]

Jet fuel exhaust may not have lead, but it does contain things like benzene, volatile organic compounds (including aromatic compounds), and fine particles (soot), which is what you are smelling. Very high levels of exposure -- for example, for ground crew personnel or serving in the military in certain careers, not regular passenger exposure -- are associated with increased risk for certain diseases See this literature review and this Dep't of Veterans Affairs fact sheet.

N95 masks, as I understand it, don't fully protect against vapors/fumes like the volatile compounds in jet fuel, though it should filter out most particulates and some compounds.
posted by alligatorpear at 7:06 PM on March 6, 2024 [4 favorites]

Also, for what it's worth, at least if you were in the US in the 90s, you probably weren't smelling leaded gasoline very often. The ban started with cars made after 1975 and was already extremely rare by the time the full ban went into effect on Jan 1 1996.
posted by alligatorpear at 7:15 PM on March 6, 2024 [1 favorite]

A lot of what you're smelling on the airport tarmac is unburned fuel and fumes, as well as exhaust from fully burned fuel. Aircraft engines, especially jet engines, are most efficient at high altitudes and at cruising speed, and very inefficient at low speeds (taking off, landing, taxiing, and especially idling). As hoyland says, the cabin's pressurisation/ventilation system---which includes its own filters---draws air from the outside, and when you're not moving, that includes waste from combusted and uncombusted fuel.

Masks/filters are less effective against most fumes and gases, and more effective against particulates and smoke, and aerosols. But I would not be concerned at all about what you're describing, certainly not for the short times you're exposed to it as a passenger.
posted by Fiasco da Gama at 8:03 PM on March 6, 2024 [1 favorite]

I think you should be very concerned about breathing "that exhaust-smelling air":

BA pilot 'killed by toxic fumes on flightdeck after being constantly exposed to fuel leaks on-board passenger jets'

British Airways pilot who died at 43 after complaining he was being poisoned by toxic fumes may have been right, according to new research.

Richard Westgate, from Edinburgh, suffered years of ill health including severe headaches, mental confusion, sight problems and insomnia before he died in December 2012 at the age of 43.

Just before he died, he instructed lawyers to sue BA for health and safety breaches, convinced his problems were related to his being exposed to toxic chemicals on board the planes he flew.

Now, new scientific research has provided compelling evidence that exposure to cockpit air contaminated with hazardous organophosphates caused his death.

Lawyer Frank Cannon, who was instructed by Mr Westgate before his death, said: 'We believe that constant exposure to fuel leaks in planes contributed to Richard's death.

'This scientific research proves that Richard suffered from chemicals called organophosphates which cause chronic brain and other problems.

'This happens because of constant exposure working aboard aircraft.'

The new findings - the results of a wide-ranging study which took in evidence given by Mr Westgate - have just been published in the Journal of Biological Physics and Chemistry.

They show that scientists found organophosphates did affect Mr Westgate's health.


Mr Westgate, a world record-breaking paraglider, died within days of the death of fellow BA pilot Karen Lysakowska, 43, who also claimed she had been poisoned by contaminated air.
[…]

The organophosphate in question is also responsible for one of the largest and most tragic mass poisonings in American history, the Ginger Jake affair:

Jamaica Ginger extract, known in the United States by the slang name "Jake," was a late 19th century patent medicine that provided a convenient way to bypass Prohibition laws, since it contained between 70-80% ethanol by weight.
...
"Jake" was not itself dangerous, but the U.S. Treasury Department, which administered the Prohibition laws, recognized its potential as an illicit alcohol source, and because of this, it required changes in the solids content of Jake to discourage drinking. The minimum requirement of ginger solids per cubic centimeter of alcohol resulted in a fluid that was extremely bitter and difficult to drink. Occasionally, Department of Agriculture inspectors would test shipments of Jake by boiling the solution and weighing the remaining solid residue. In an effort to trick regulators, bootleggers replaced the ginger solids with a small amount of ginger and either castor oil or molasses.

A pair of amateur chemists and bootleggers, Harry Gross and Max Reisman, worked to develop an alternative adulterant that would pass the tests, but still be somewhat palatable. They sought advice from a professor at MIT who did not realize it was meant for internal consumption. They settled on a plasticizer, tri-o-tolyl phosphate (also known as tri-ortho cresyl phosphate, TOCP, or Tricresyl phosphate), that was able to pass the Treasury Department's tests but preserved Jake's drinkability. TOCP was originally thought to be non-toxic; however, it was later determined to be a neurotoxin that causes axonal damage to the nerve cells in the nervous system of human beings, especially those located in the spinal cord. The resulting type of paralysis is now referred to as organophosphate-induced delayed neuropathy, or OPIDN.

In 1930, large numbers of Jake users began to lose the use of their hands and feet. Some victims could walk, but they had no control over the muscles which would normally have enabled them to point their toes upward. Therefore, they would raise their feet high with the toes flopping downward, which would touch the pavement first followed by their heels. The toe first, heel second pattern made a distinctive “tap-click, tap-click" sound as they walked. This very peculiar gait became known as the jake walk and those afflicted were said to have jake leg, jake foot, or jake paralysis. Additionally, the calves of the legs would soften and hang down and the muscles between the thumbs and fingers would atrophy.

Within a few months, the TOCP-adulterated Jake was identified as the cause of the paralysis, and the contaminated Jake was recovered. But by that time, it was too late for many victims. Some users did recover full, or partial, use of their limbs. But for most, the loss was permanent. The total number of victims was never accurately determined, but is frequently quoted as between 30,000 and 50,000. ...

And jet fuel does contain heavy metal as well, in the form of cerium oxide nanoparticles which aid combustion and were recently found in the placentas of women who lived in London during their pregnancies.
posted by jamjam at 8:31 PM on March 6, 2024 [1 favorite]

I believe the common term is fume events. It's pretty scary. According to this, the 787 is the only airplane which doesn't use bleed air for cabin ventilation.
posted by flimflam at 9:42 PM on March 6, 2024 [1 favorite]

Here is a documentary about a 2016 fume event on a British Airways flight - and its cover up by the airline. Note that his is talking about an in-flight event where there is no alternative to getting the air via the jets. My guess is that you may be thinking about smelling fumes during refueling on the ground - where the fumes may not have come from the jets and where there are other potential sources of uncontaminated air. On health grounds that may be no less harmful - but, in my own experience, it is pretty common.
posted by rongorongo at 12:25 AM on March 7, 2024

Most likely it is Ozone that you are smelling.

While ozone is not emitted directly from automobiles, the unstable compound is formed in the atmosphere through a complex set of chemical reactions involving hydrocarbons, oxides of nitrogen, and sunlight. The rate at which the reactions proceed is related to both temperature and intensity of the sunlight. Because of this, problematic ozone levels occur most frequently on hot summer afternoons.[x]

Long-term exposure risks. Scientific studies warn of serious health effects from breathing ozone over long periods —that is, for periods longer than eight hours, including days, months or years. Long-term ozone exposure is associated with increased respiratory illnesses, metabolic disorders, nervous system issues, reproductive issues (including reduced male and female fertility and poor birth outcomes), cancer and also increased cardiovascular mortality, which is the main driver of total mortality.

Research shows lower levels of ozone can also cause harm. The official national limit on ozone, also called the National Ambient Air Quality Standard, was last strengthened by EPA in 2015. However, newer research shows that ozone can cause serious harm even at much lower levels. For example, in a 2017 study showed that older adults faced a higher risk of premature death even when levels of ozone pollution remained well below the current national standard. [x]
posted by Lanark at 3:19 AM on March 7, 2024

I think you should be very concerned

Your examples are from people suffering from prolonged, consistent exposure. That's a huge difference from what a passenger in the back of a plane experiences. "The dose makes the poison" after all. I'm assuming the poster is not sitting next to a leaking fuel pipe for 2000+ hours a year.

Incidental, occasional exposure to fumes is not something to be worried about. I would be more concerned about the extra cosmic and UV radiation you're exposed to at the flight levels, both of which absolutely pose an increased risk of various cancers for pilots - but, again, as a passenger, your exposure level is so low as to be meaningless.

If you're concerned about safety in commercial aviation, the biggest things you can do to protect yourself:
-Wear sensible shoes and keep them on during taxi, takeoff, and landing
-Wear your seat belt at all times
-Put everything away during takeoff and landing - don't let your phone become a projectile
-Don't drive to the airport
posted by backseatpilot at 5:32 AM on March 7, 2024 [6 favorites]

Since no one here is explaining (guess no more serious sim pilots on MeFi anymore) what you are actually smelling and why it's happening:

In short, you are smelling the exhaust from the plane, in the same way you would if you just ran your car in an enclosed space and ran the A/C. Just like in your car, if you start moving or turn off the A/C, the smell goes away. And if jet fuel didn't have something in you likely don't smell much (kerosene), you probably wouldn't even notice.

Airliners don't have a "starter" like your car. They also don't a battery that can run everything after the ground/truck power is disconnected but before the engines start. Therefore, disregarding situations that require a truck full of compress air to start the engines, something called an Auxiliary Power Unit (APU) is fired up first. This is a tiny jet engine in the tail that starts up and provides air pressure (bleed) to start the engines, and electricity (via the APU generator) to power the plane. When you leave the gate during push back, this is what is powering the plane.

And if it's hot inside the plane, bleed is what is running the A/C systems (Pneumatic Air Cycle Kits or PACKs). Bleed, since it's just pulling air from right outside the plane, can contain Jet-A fuel exhaust. And if your plane isn't moving yet, then you might smell it stronger than other times. And since Jet-A is 30% kerosene/70% gasolne, you notice it more than you would if it was just 100% gasoline like your car.

Eventually, your pilots fire up the engines (which provide their own bleed), turn off the APU, and then start taxing down the runway. If it's warm enough to require the PACKs while taxing around, it might be too warm to have the them on while taking off, since using bleed lowers the available trust. But, in any case, since you aren't sitting around in once place, the bleed is going to have less exhaust in it.

Edits: Oops, someone did mention bleed air. Oh well, leaving my longer explanation up anyway.
posted by Back At It Again At Krispy Kreme at 9:24 AM on March 7, 2024 [2 favorites]

3M sells a P100 respirator for painters. The P100 cartridges for this respirator filter the kinds of organic compounds that painters are exposed to when painting, which would have some overlap with what you would encounter in jet fuel and exhaust. They also sell a P100 respirator with cartridges that filter lead. Both options may offer some additional protection to you while taxiing.
posted by They sucked his brains out! at 11:31 AM on March 7, 2024 [2 favorites]

I wrote a long response to a recent somewhat similar question about air pollution from a burning dump. Interestingly, the general types of air pollution you are talking about here are, in very general terms, similar to that: VOCs, including benzene, and particulates.

So one thing I found out while looking into that issue, is that filters can reduce particulates. But they don't make a dent in VOCs at all.

So particulates are definitely worth filtering out - meaning that something like an N95 mask is worth wearing in such situations. Also, I understand that airliner air filtered pretty well - one reason you don't smell even more of this type of thing while flying.

But to go beyond particulates to reduce the VOC content of air requires something like a charcoal filter.

As They sucked his brains out! mentioned just above, there are masks available that include this kind of activated charcoal element. Here is a sample list. As They sucked his brains out! mentioned, P100 is the most common type available.

So, if you are worried about this type of exposure, or it makes you feel ill etc, you might well find that wearing this type of mask in those situations would reduce the smell substantially.

They are quite large and bulky, so only you can say carrying such a thing would be worth it to you. But if, for example, you just decided to use this type of thing as your go-to mask to use when traveling by air, it would definitely be very effective as a general airborne disease mask - with the added benefit of cutting down strange smells significantly.
posted by flug at 2:48 PM on March 8, 2024