Fact check: No evidence airplane contrails are harmful to health

January 11, 2023 chemtrails

The claim: Meme implies contrails cause respiratory illnesses

A Jan. 2 Facebook post (direct link, archive link) features a meme showing Marge Simpson, a character from the animated sitcom “The Simpsons,” staring at an airplane in the sky surrounded by contrails.

“I see respiratory illness is on the rise again!” reads text attributed to Simpson in the image.

The post was shared more than 13,000 times in four days.

Some commenters posted about their belief that contrails were connected to illnesses.

“I always tell people the air is poisonous to me and my kids,” one social media user wrote. “We always have the worst sinus infections.”

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Our rating: Missing context

The implied claim here is wrong. There is no evidence to suggest contrails are harmful to humans, according to the Federal Aviation Administration, which constantly studies their air quality impact.

Agencies that study contrails say they aren’t hazardous

Contrails are the white streaks of condensed water vapor left in the sky in the wake of an aircraft or rocket.

The meme implies contrails cause respiratory illnesses, but they are “absolutely not” dangerous for humans, according to the Federal Aviation Administration’s website.

The site says:

“A major portion of the water to form these particles comes from the atmosphere itself, and a small portion is from the engine exhaust. The engine exhaust contains products of combustion of aviation fuel that are like the exhaust composition of automobile exhaust. Since these combustion products occur high above the ground, their impact is far less than that of automobiles. FAA, with other agencies, is constantly studying the climate and surface air quality impacts of aviation exhaust.”

The U.K. government also states there is no evidence to suggest contrails are connected to respiratory illnesses.

“There is no evidence that contrails cause health problems,” reads a section of the government’s website. “At the altitude that contrails are produced, the oxides of nitrogen and particulate matter which can cause respiratory problems become dispersed.”

USA TODAY has previously debunked an array of false claims about so-called chemtrails, including claims that pictures showed “barrels of chemtrails” on planes and that an Oregon weather broadcast showed proof of chemtrails.

Cold affects both contrails, respiratory illness

The only connection between contrails and respiratory illnesses is that both are linked to cold temperatures.

Respiratory illnesses tend to affect more people during colder months, several studies have found. Researchers believe this is likely due to a combination of human behavior and environmental factors.

People are more likely to spend time indoors in groups during the winter months, creating an environment where viruses and bacteria are more likely to spread.

Cooler weather also impacts the number of contrails in the air, said Mississippi State University meteorology professors Jamie Dyer and Andrew Mercer.

The temperature must be around negative 40 degrees for contrails to form, Mercer said.

In warmer months, contrails will only form behind airplanes at very high elevations where the temperature is lower. In colder months, lower altitudes are more likely to reach the same cool temperature, Mercer said.

This means that in the winter, airplanes at lower altitudes are more likely to produce those white, long clouds of water vapor.

The relative humidity also increases in the winter, Dyer said. Cool air can hold less water vapor than warm air. This means water vapor is more likely to condense into clouds, like contrails, during cold months.

USA TODAY reached out to social media users who shared the post for comment.

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