A new international study warns that the recovery of the ozone layer may be delayed by several years due to continued emissions of “feedstock” chemicals—substances still permitted for industrial use.

The research was led by a team from the Massachusetts Institute of Technology (MIT), in collaboration with international institutions including NASA, the University of Bristol, and research centers across Europe and Asia.

The findings indicate that emissions of ozone-depleting “feedstock” chemicals have been underestimated in previous international agreements, despite their ongoing use in industries such as refrigerant and plastic production.

Global measurements show that between 3% and 4% of these substances leak into the atmosphere during production—significantly higher than earlier estimates that informed environmental policies.

While the ozone layer had been projected to recover to its 1980 levels by 2066, the study—published in Nature Communications—suggests this timeline could be delayed until 2073 if current emission rates continue.

Researchers also noted that the exemption of these chemicals under the Montreal Protocol was based on inaccurate assumptions. Rather than declining, their use has increased, particularly in sectors tied to modern technologies.

The team emphasized that reducing these emissions would offer a dual benefit: helping restore the ozone layer while also mitigating global warming. They cautioned that if current trends persist, emissions could increase by hundreds of millions of tons annually by mid-century.