It is expected to prevent 280 million cases of skin cancer, approximately 1.6 million skin cancer deaths, and more than 45 million cases of cataracts in the United States alone. Without it, the sun would burn skin in minutes and our climate would be so hot that there would be a marked increase in natural disasters. Yet the strides made by the Montreal Protocol in repairing our ozone layer may be undone thanks to dangerous chemicals that are making their way into the upper atmosphere, says a new study from the European Geosciences Union (EGU).

This year marks the 30th anniversary of the Montreal Protocol, an international agreement that limited the use of chemicals, like chlorofluorocarbons, that were found to deplete the ozone layer, a protective area of the Earth's stratosphere that shields us from most of the sun's UV radiation. By all accounts, the accord has been successful and our ozone layer is on the mend. Yet the new study warns that dangerous chemicals are being swept into the upper atmosphere where they may undo some of the good that has come from the Protocol.

The researchers involved in the study collected air samples on the ground in Taiwan and Malaysia between 2012 and 2014 and had them analyzed in the UK. They also looked at data that was collected by commercial aircraft between the same years. They found alarming levels of ozone-depleting chemicals, particularly one substance known as dichloromethane, which has many industrial uses including the creation of pharmaceutical drugs and fumigating crops.

At the time of the original Montreal Protocol in 1987, such chemicals were thought to not have an impact on the ozone layer as they are too short-lived to make it very high in our atmosphere. The new research proves that this was an incorrect assumption. It turns out that pockets of cold air in Asia can push the chemicals into tropical areas where rapidly rising warm air can carry them to the stratosphere. In fact, previous work from the EGU suggested that pollution could travel about 1,000 km per day (621 mi), making its way across the South China Sea and to the equator in just a few days.

"We found that elevated concentrations of these same chemicals were present at altitudes of 12 km over tropical regions, many thousands of kilometres away from their likely source, and in a region where air is known to be transferred into the stratosphere," said team leader David Oram from the University of East Anglia.

In fact, the researchers found that while dichloromethane decreased in our atmosphere during the 1990's and early 2000's, it has now become 60 percent more plentiful. In addition to the dichloromethane, the researchers also found large amounts of 1,2-dichloroethane, a chemical that is used in making PVC that depletes ozone.

"This was a major surprise to the scientific community and we were keen to discover the cause of this sudden increase," said Oram. "We expected that the new emissions could be coming from the developing world, where industrialisation has been increasing rapidly. Our estimates suggest that China may be responsible for around 50-60 percent of current global emissions (of dichloromethane), with other Asian countries, including India, likely to be significant emitters as well."

China is world's largest producer of PVC.

Oram and his team regularly monitor the atmosphere for about 50 different ozone-depleting chemicals, and warn that if the newly discovered compounds continue to build up in the higher levels of the atmosphere, an amendment to the Montreal Protocol might be needed. To date, five such amendments have been enacted, most recently in 2016 when the Kigali amendment limits the use of hydrofluorocarbons (HFCs) , which were largely used as replacements for chlorofluorocarbons.

The following video details the results of the study, which has been published in the journal Atmospheric Chemistry and Physics.