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The Ozone Layer is threatened by Chloroform

While we thought we had solved the ozone problem with the Montreal protocol banning CFCs, a new category of gas was added to the list of threats. The rising emissions of chloroform could thus delay the reconstruction of eight years.

Last November, the United Nations announced good news about the ozone layer. According to experts, it is recovering at a rate of 1% to 3% per year, suggesting a return to its pre-1980s level by the 2030s in the northern hemisphere and 2050 in the ‘southern hemisphere.

This is thanks to the Montreal Protocol, which prohibits the production of CFC and HCFC gases, which are mainly responsible for the destruction of this protective layer of the stratosphere.

But now a new threat is hovering over ozone:

chloroform. An odorless and colorless gas, resulting in particular from the manufacture of Teflon or produced involuntarily during the disinfection of water by chlorine processes.

A new MIT study, published in Nature Geoscience , shows a worrying increase in chloroform emissions into the atmosphere that could delay the reconstruction of the ozone layer, up to eight years, if the rise continues at its current rate .

A short life … but emissions that leap

Chloroform is already known for its effects on ozone. But so far, its lifetime in the atmosphere (about five months) was considered too low to have a significant impact (by comparison, CFCs can have a life span of 100 years).

It had therefore been excluded from the Montreal Protocol like other VSLS ( very short lived susbtances ).

“But while long-lived compounds are declining, the reconstruction of the ozone layer could be delayed by those with a short life span and they are very numerous.”


says Ronald G Prinn, co-author of the study and professor of atmospheric science at MIT.

Emissions from eastern China:

The researchers based on the measurements of 13 stations of the Agage network ( Advanced Global Atmospheric Gases Experiment ), which since 1978 have measured the precise composition of the atmosphere in about fifty greenhouse gases and depletion of ozone.

They thus noted a sharp increase in chloroform emissions between 2010 and 2015, rising from 270,000 tons per year during the previous decade to 324,000 tons in 2015.

Two stations in particular are distinguished by their increases: one in Japan and another in Korea. from South. By modeling the atmospheric fluxes, the researchers concluded that the culprit of the emissions was in fact in the east of China.

“This corresponds with the locations of chloroform plants and other industrial areas.”

Confirms Xuekun Fang, the main author of the article.

This source is not insignificant because the region is particularly subject to monsoon and typhoon , which aggravates the dispersion of chloroform in the stratosphere, where it will degrade into chlorine which destroys ozone under the influence of UV .

In 2017, a Lancaster University study identified dichloromethane , another short-lived gas, as a potential new hazard to the ozone layer. Several researchers are calling for an amendment to the Montreal Protocol to ban VSLS.

“Our study shows in any case that the battle for the preservation of the ozone layer is not over”

warns Ronald G Prinn.

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