A chemical that has been banned internationally for the last three decades has reappeared on a global scale, the main country we have to thank for it is China, according to National Post.

In the 1980’s, countries from all corners of the map came together to sign the Montreal Protocol on Substances that Deplete the Ozone Layer, a treaty designed to reduce the production of chlorofluorocarbons (CFC) and similar chemicals, typically used in fridges and foams that had the side effect of destroying Earth’s ozone layer.

That treaty was signed by 197 countries, including China. That treaty is credited with aiding in the slow heal of the damaged ozone layer.

Sadly though, scientists from the National Oceanic and Atmospheric Association found that global emissions of Trichlorofluoromethane (CFC-11) have actually been increasing since 2013. Meaning that someone, somewhere was violating the Montreal treaty.

Unfortunately, scientists were only able to attribute the pollution to somewhere in East Asia. Now, in a study by University of Bristol, Kyungpook National University, and the Massachusetts Institute of Technology found that over half of the total CFC-11 emissions were coming from eastern China, to the tune of 60 percent.

Thanks to the aid of international networks of measuring devices, specifically designed to find gases in the atmosphere, the team behind the study found that data from their devices in Korea and Japan had spiked since 2013. After taking a closer look at weather and wind patterns, it led them to eastern mainland China, near the Shandong province.

Though the lead author of the study Matthew Rigby didn’t find it overly surprising that Mainland China was at fault for the emissions, he did say that the sheer amount that China was emitting was a shock.

“That’s more than double the emissions we were expecting from China at the time,” he said. “Was this enough to account for a substantial fraction of the global emissions rise that we saw? What we’ve found in this study is that, yes, it is globally significant.”

Rigby also mentions that CFC-11 is a greenhouse gas, about “5,000 times more potent than carbon dioxide at warming the climate.”

The Chinese government has been cracking down on illegal CFC-11 manufacturers and shutting down production facilities and Rigby hopes this new study will help law enforcement officials in their search for illicit producers.

Rigby also says that the team cannot say with confidence where the rest of the emissions are coming from, stating that there is little information on regions such as South America and India.

With the increased emissions from China seemingly not ending any time soon, Rigby states that the healing process could be delayed by “potentially decades.”