Scientists: Ozone layer began to be destroyed even before the Freon era

For a long time, freons were considered the main cause of ozone layer depletion, and the scale of the problem became known after the discovery of the ozone hole over Antarctica in the 1980s. However, a new study, reported by Tagesspiegel, shows that anthropogenic destruction of the ozone layer began much earlier.

According to the authors of the work from the Massachusetts Institute of Technology (MIT), if modern observation tools had existed in the mid-1950s, the first signs of ozone loss could have been detected as early as 1957.

Researchers found that the main cause of early ozone layer destruction was not freon, but carbon tetrachloride (CCl₄). This substance was used in the US as an industrial solvent since 1914, and by the 1930s, it had already become widespread. Like freons, carbon tetrachloride releases chlorine, which destroys ozone molecules.

According to the study, carbon tetrachloride was the main source of human-induced ozone layer depletion between 1920 and 1960. However, its scale was not sufficient to cause noticeable health consequences for humans.

Subsequently, the concentration of chlorofluorocarbons (CFCs, or freons) began to rapidly increase in the atmosphere, and soon they became the main cause of ozone layer depletion.

The researchers arrived at their conclusions by combining simulations of the ozone layer's reaction to natural phenomena, including volcanic eruptions, with an analysis of data obtained from ice cores, which preserve traces of chemicals present in the atmosphere in past decades.

The simulation also showed that, given appropriate measurements, the first signs of ozone layer depletion in 1957 would most likely have been noticed over the tropics, where natural fluctuations in ozone levels are small. In high latitudes, losses were greater, but they were more difficult to detect due to significant natural fluctuations in ozone levels. For such an assessment, observations would have had to start as early as 1950 to have sufficient data for comparison.

In 1974, chemists first experimentally confirmed that freons destroy ozone. In the 1980s, satellite observations showed a significant decrease in the ozone layer over Antarctica, after which the Montreal Protocol was signed in 1987. It significantly restricted the production of ozone-depleting substances, including freons and carbon tetrachloride.

According to the World Meteorological Organization, thanks to these measures, the ozone layer is now gradually recovering and could return to its mid-20th century state by the middle of the 21st century. This should significantly reduce the risk of diseases associated with exposure to ultraviolet radiation, as well as reduce harm to ecosystems.

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