The release of ozone-depleting chemicals such as HFCs has actually been banned since the 1980s. However, the use and production of some gases that are required as raw materials in the chemical industry are excluded from the Montreal Protocol. Now a study shows: The production and release of these ozone-depleting and climate-damaging industrial gases has increased significantly in recent decades. Three to four percent of the produced amounts of carbon tetrachloride and other “ozone killers” now end up in the atmosphere – in 1980 it was only 0.5 percent. If left unchecked, the recovery of the Earth’s ozone layer could be delayed by seven to ten years. Because these ozone-depleting compounds also act as greenhouse gases, they also heat up the climate.
The earth’s ozone layer is our most important protection against harmful UV radiation. But halogen-containing chemicals such as chlorofluorocarbons (CFCs) trigger a chain reaction in the stratosphere that depletes ozone. Since the 1980s, extensive ozone holes have been forming over Antarctica and partly the Arctic. In order to stop ozone depletion, the international community decided in 1987 in the Montreal Protocol to ban ozone-depleting substances containing chlorine and bromine or at least to significantly reduce their production. However, so-called feedstock chemicals are excluded from this – halogen-containing, ozone-depleting compounds that are required by the chemical industry as raw materials for modern refrigerants and chlorine-containing plastics such as PVC. “It was assumed at the time that only around 0.5 percent of the feedstock chemicals produced were released and that the production of these substances would decline in the future anyway,” explain Stefan Reimann from the Swiss Federal Materials Testing and Research Institute Empa in Dübendorf and his colleagues.
Production of ozone-depleting feedstock chemicals is increasing
The researchers have now checked whether these assumptions were justified – and also what consequences the emissions of these ozone-depleting gases have for the ozone layer and the climate. Atmospheric measurement data from international networks such as the Advanced Global Atmospheric Gases Experiment (AGAGE), which also includes a measuring station in the Swiss Alps, served as the database. “We measure the concentrations of these substances in the atmosphere,” explains co-author Martin Vollmer from Empa. The researchers compared these values with the production figures of these ozone-depleting chemicals officially reported by individual countries – such reporting to the UN environmental program UNEP is required by the Montreal Protocol. “Based on the lifespan of these gases, we can calculate how much they should actually decrease. If they don’t, there must still be emissions,” says Vollmer.
It turned out that, contrary to expectations, emissions of ozone-depleting substances have not decreased globally, but have increased. “Today, feedstock chemicals are released to an increased extent during production, transport and further processing, and the quantities currently produced are significantly larger than was assumed 30 years ago,” reports Reimann. Specifically, the analyzes showed: “The global production of feedstock chemicals increased by 163 percent between 2000 and 2024 alone,” the researchers report. The reason for this is, on the one hand, the use of these ozone-depleting halogen compounds in the production of refrigerants such as hydrofluorocarbons (HFCs) and hydrofluoroolefins (HFO). In addition, there is a sharp increase in the use of chemicals in the polymer industry – for example for the production of fluoropolymers such as Teflon (PTFE) or polyvinylidene fluoride (PVDF), an important material in lithium-ion batteries in electric cars.
(Video: Empa)
More and more emissions – with consequences for the ozone layer and the climate
“The feedstock quantities are not decreasing, but will continue to grow at least in the coming years,” says Reimann. At the same time, more and more of these ozone-depleting substances are being released into the atmosphere – for example through leaks or inadequate exhaust gas cleaning in production plants. This particularly applies to carbon tetrachloride (CCl4but also trichloroethane CH3CCl3), cryofluorane (CFC-114a) and trichloro-trifluoroethane (CFC-113a). Reimann and his colleagues determined that around three to four percent of the production volume of each of these substances ends up in the atmosphere. In 1980 the share emitted was still 0.5 percent. According to the researchers, measurement data also suggests that the trend will continue to be upwards rather than downwards in the future. Reimann and his team used a model simulation to determine what this could mean for the long-term development of the ozone layer up to the year 2100 for various future scenarios. They compared the recovery of the ozone layer by 2066, originally predicted based on decreasing emissions, with a scenario based on emissions measured today.
The simulations showed that if feedstock emissions remain at current levels, the recovery of the ozone layer will be postponed by around seven years. The stratospheric ozone layer would therefore not fully recover until around 2073. Depending on the model, the delay could be up to eleven years. But that’s not all: “These substances not only deplete the ozone layer, but are also extremely harmful to the climate,” explains Reimann. Because the halogen-containing compounds act as strong greenhouse gases. If their release continues, these emissions could amount to around 300 million tonnes of CO₂ equivalents per year by 2050. “This corresponds to around 0.8 percent of global anthropogenic CO2 emissions in 2024,” write the researchers. In their opinion, it is therefore advisable to regulate more closely the production and release of ozone-depleting feedstock chemicals. “The Montreal Protocol was successful because science, politics and industry worked closely together. Such collaboration is again crucial today in order to tackle new challenges,” says Reimann.
Source: Stefan Reimann (Empa – Federal Materials Testing and Research Institute, Dübendorf) et al., Nature Communications, doi: 10.1038/s41467-026-70533-w