The ozone layer has recovered quite impressively ever since various programs and initiatives have been launched in the past few years. But a recent study that appeared in Nature journal recently, discovered that some of the pollutants that were banned 30 years ago are still present in the air. And as of now, no one has any idea about the culprits.

According to the study, a spike has been observed for a chemical which was banned by an international treaty. Stephen Montzka, lead author of the study and a scientist at the National Oceanic and Atmospheric Administration couldn’t contain his shock.

The ozone pollutant, CFC-11, belongs to a subclass of chlorofluorocarbons or CFCs, which were widely used in the 20 century. From refrigerators to aerosol cans to all other kinds of solvents, CFCs were present almost everywhere. As consumption increased, scientists observed that CFCs had caused the gaping hole in the ozone layer to widen.

Ozone is essential for protection against the harsh UV rays of the sun. The chlorine molecules present in CFCs cause various chemical reasons which destroy ozone layer, and allow UV radiation to pass through with full force.

In the year 1987, the entire world signed Montreal Protocol,which banned the use of all substances that could harm ozone, including CFCs. Every single nation signed the pact at UN headquarters. According to Durwood Zaelke who established, and now presides, the Institute for Governance and Sustainable Development, Montreal Protocol is the most successful treaty to date that has prevented destruction to the climate system.

Viewing our atmosphere from space, you can really get a sense of how delicate it is.

Considering the observations made by this research, the treaty is being violated. It’s still not known if this is accidental or intentional, but in any case, the parties behind the Montreal Protocol are on alert now.

Susan Strahan, at atmospheric scientist at NASA’s Goddard Space Flight Center stated that violation of the treaty is something we should all be concerned about. We all want ozone to recover and not get damaged further.

CFC-11 was used in building insulations and several appliances in the 1980s. Other chlorine-containing fluorocarbons are also dangerous, but CFC-11 holds significance because it is among the most abundant CFC. CFC-11 comprises of three molecules of chlorine whereas other compounds usually feature only two molecules. The extra molecule increases the life of this compound to 52 years, which is more than for most of the ozone damaging chemicals. CFC-11 can also contribute to changing climate because it’s a greenhouse gas and even causes global warming according to some studies.

The Montreal Protocol was put into effect two years after it was signed, and since then, the presence of CFC-11 has significantly decreased in the atmosphere. By 2010, production supposedly stopped completely.

The scientists at NOAA regularly measure the percentage of pollutants in the air. They claim that CFC-11 levels have fallen down, but the rate isn’t as rapid as should be. New emissions can now be detected and have increased by almost 25% since 2012.

Montzka is hopeful that the new emissions wouldn’t really impact ozone depletion by themselves. But if emissions are sustained in future, the damage would delay the ozone recovery date, which is currently between 2050 and 2070.