Some alarming news from the stratosphere.

Chinese foam manufacturers are releasing an ozone-destroying chemical into the air that goes against an international agreement meant to fix the ozone layer, scientists announced in a study Wednesday.

The chemical is a chlorofluorocarbon known as trichlorofluoromethane (CFC-11), which the world agreed to phase out starting in 2010. But just in the past six years, emissions of CFC-11 have increased by around 7,000 tons each year, and the source is eastern China, the study suggests.

Located up in the stratosphere, the ozone layer acts like a sunscreen, blocking potentially harmful ultraviolet energy from reaching our planet's surface. Without it, humans and animals can experience increased rates of skin cancer and other ailments such as cataracts.

(The naturally occurring ozone high up in the atmosphere is the "good" ozone and is in contrast to the "bad" ozone near the surface, which is man-made pollution that can cause respiratory problems.)

"It was unexpected when we saw that, starting around 2013, global emissions of one of the most important CFCs suddenly began to grow,” said study lead author Matt Rigby, an atmospheric chemist at the University of Bristol in England.

The new study said that two provinces in eastern China – Hebei and Shandong – appear to be a major source of the CFC-11 emissions. Researchers used air-monitoring equipment in Japan and South Korea to detect the Chinese emissions.

Scientists first discovered the dramatic thinning in Earth's protective ozone layer in the 1970s and also the infamous "ozone hole" over Antarctica. They determined the production of chlorofluorocarbons (CFCs), used in refrigerators and aerosol sprays, caused the problem.

In the late 1980s, 196 countries signed the Montreal Protocol, a treaty that limited production of CFCs around the world. Businesses soon came up with safer alternatives for spray cans and refrigerators.

But any increase in emissions of CFCs will delay the time it takes for the ozone layer, and the Antarctic ozone hole, to recover.

The study is “very definitive,” providing “firm evidence” that there is a continuing problem with emissions from China, Ian Rae, a chemist at the University of Melbourne in Australia who was not involved in the study, told Science magazine.

There are other sources out there, scientists say, since the Chinese emissions account for less than half of the banned chemical.

“It is now vital that we find out which industries are responsible for the new emissions,” Rigby said. “If the emissions are due to the manufacture and use of products such as foams, it is possible that we have only seen part of the total amount of CFC-11 that was produced. The remainder could be locked up in buildings and chillers and will ultimately be released to the atmosphere over the coming decades.”

Study co-author Sunyoung Park, a geochemist at Kyungpook National University in Daegu, South Korea, told Science that "we hope that the information that this new study provided helps the Chinese government take steps to address the issue."

The new study was published in the peer-reviewed British journal Nature.