Instead, this is about the air quality aboard commercial airplanes. 

A pair of new scientific studies says it's often polluted with engine oil and other aircraft fluids, and can cause significant health problems for pilots and other crew who breathe it day after day. Maybe also for some frequent passengers.

For many of us, constant business travel is a fact of life. So, below, we'll explain the studies, which were published in the World Health Organization's journal Public Health Panorama. along with what some scientists recommend and others are doing about the air quality.

"Bleed air" and "fume events"

The air we breathe on commercial airplanes, the study authors explain, is a combination of recycled air within the cabin (that we all inhale and exhale), along with outside air that is compressed by the aircraft's engines.

The outside air is known as "bleed air." Most passengers might expect it to be heavily filtered, but the Public Health Panorama article says it's not the case. 

That means that when there is a leak of engine oil, hydraulic fluid, or even deicing fluid, these contaminants can wind up being pumped right into the cabin. The industry term for these kinds of mishaps: "fume events."

To measure the effects of bleed air and fume events, the researchers from three universities (two in the United Kingdom and one in Australia) conducted two studies.

"Full or partial incapacitation of two pilots"

The first study examined how healthy 274 British commercial pilots reported being over time. 

"Almost 65 percent [of pilots] reported specific health effects, while 13 percent had died or experienced chronic ill health," a press release summarizing the article said.

The second study examined maintenance reports that showed "potential cabin air quality incidents," largely oil leakage issues. Then, they tracked reports of health issues such as upper airway problems, vision problems, dizziness, and the like among the flight crew and passengers on board.

"Symptoms ranging from in-flight incapacitation to impairment were reported in 93 percent of events, with the majority (73 percent) involving pilots and 33 percent including full or partial incapacitation of two pilots," according to the article.

"What we are seeing here is aircraft crew being repeatedly exposed to low levels of hazardous contaminants from the engine oils in bleed air, and to a lesser extent this also applies to frequent fliers," said Vyvyan Howard, a professor of pathology and toxicology at the University of Ulster in the United Kingdom, one of the study authors.

"Exposure should be avoided"

While this is a new study, or pair of studies, it's by no means a new issue--and it's often ended up in the courts. 

Two years ago, some Alaska Airlines flight attendants sued Boeing Company, claiming that they'd gotten sick as a result of dirty air, "vomiting and three of them passing out during a coast-to-coast flight that was diverted to Chicago in 2013," according to a press account.

Another 20 passengers sued Boeing in 2007 over the same kind of issue, alleging that, according to The Wall Street Journal, "bleed air contaminated by an oil leak made them sick on a Boeing 767, ... [including] respiratory problems, severe headaches, vomiting, bowel problems, and extreme fatigue."

All of which means you may have no choice to fly--so some scientists think airlines and airplane manufacturers should be doing something about this.

"We know from a large body of toxicological scientific evidence that such an exposure pattern can cause harm and, in my opinion, explains why aircrew are more susceptible than average to associated illness," explained Professor Howard. "However, exposure to this complex mixture should be avoided also for passengers, susceptible individuals, and the unborn."