A crooked industry in China has been releasing ozone-depleting chemicals into Earth's atmosphere for years. Now, many of the culprits have been exposed.

CFC-11, an illegal chemical used to make foam insulation used in homes and buildings, has been banned globally for decades. But scientists spotted an uptick in the chemical's abundance in the air since 2012, meaning its overall decline has slowed. Researchers concluded in May that there must be a new source of these pollutants.

Exactly who was annually spewing some 14,000 thousand tons of a chemical that erodes the ozone layer — which keeps life on Earth from getting irradiated by the sun — wasn't known.

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Independent investigators, like the Washington D.C.-based Environmental Investigation Agency (EIA), started snooping around.

"We were immediately on the trail," Avipsa Mahapatra, a climate analyst at the EIA, said in an interview.

"It is a massive environmental crime that’s occurring," she added.

Using undercover sources to film and record at factories in China, the organization confirmed that 18 factories across the country admitted to using CFC-11. The organization released their full report on July 8.

The depleted zone of the ozone layer, in September 2014 Image: nasa/noaa

"What was most egregious to us wasn't only that they knew it was illegal, but they said a majority of the market were using it as well," said Mahapatra, who happened to be speaking from an international meeting in Vienna, Austria, on these very ozone-depleting chemicals.

As of May, scientists suspected the source of CFC-11 to be somewhere in southeastern Asia. "But we weren't able to pinpoint it more precisely," said National Oceanic and Atmospheric Administration scientist Steve Montzka, who led the May study identifying the new CFC emissions, in an interview.

The EIA's report follows a June investigative story by the New York Times, which showed that Chinese factories were knowingly using the illegal chemical, in large part because it's cheaper than the legal — and less environmentally impactful — alternative.

"The benefits far outweigh the risks was the bottom line," said Mahapatra of these companies' choice to use the banned substance. They used it for years without their activity being observed by atmospheric scientists. But eventually, said Motzka, scientists "were able to raise a flag."

It appears the polluters have been outed. But how can they be stopped?

The Chinese government itself is largely responsible for putting a cap on the problem.

China, like every other nation in the world, has signed the Montreal Protocol, which in 1987 sought to phase out the use of ozone-depleting chemicals. This international treaty is widely viewed as one of the most successful international agreements ever, as the use of the chemicals has incrementally dropped, and the ozone layer has begun to mend.

The Montreal Protocol has a scientific body that can study the ozone layer, but it doesn't have a police force meant to stop illegal chemical emitters. That's up to each nation to enforce.

"It is illegal by Chinese law to produce and use these chemicals," said Mahapatra.

In this case, these companies appear to have deceived their own nation. As the EIA report showed, one company had even painted the side of its building to declare it as a "farming plantation."

"I would say these are rogue companies, and they understand it’s an illegal gas," said Mahapatra. "They have engineered a means to circumvent Chinese regulations."

"This environmental crime demands decisive action"

To stop the emitters, the Chinese government "can start with an immediate clampdown of the companies we identified," said Mahapatra.

Luckily, the Chinese government already has a head start. The EIA provided an earlier copy of the report directly to them before releasing it publicly. The penalties for flouting the Montreal treaty, including seizures and arrests, should be severe enough to discourage future violations, said Mahapatra.

NOAA's Montzka cautions that although the EIA's relatively quick turnaround is impressive, it might not explain all the new sources of CFC pollutants recently observed. Even so, cutting off these emissions will likely make a meaningful difference.

"If the emissions were to persist, we could imagine the ozone recovery might be delayed by a decade or so," said Montzka.

Already, the ozone layer's recovery will take decades. Earlier this year, NASA scientists estimated it could take until 2060, 2080, or longer.

And illegal polluting certainly won't help any.

"This is not naivete here," said Mahapatra. "It's widespread and pervasive. This environmental crime demands decisive action."