New studies analyze ozone layer depletion and its effects on human health – 02/10/2021 – Science

The ozone layer is not one of the most debated environmental issues today, but that does not mean that it has been forgotten or, on the contrary, everything is fine. Scientists are still struggling to measure the damage caused by human activity.

Two articles published this Wednesday (10) in the journal Nature even point to the decline in the production of molecules responsible for depleting the ozone layer, such as trichlorofluoromethane, also known as CFC-11, which is used in the Foam production is used.

Between 2018 and 2019 alone, emissions were reduced by 18 thousand tons, which corresponds to 26% of total emissions. The measurement, which was carried out by analyzing gases from the atmosphere, was measured in remote places, far from large centers of pollution.

The result of the work led by scientists from Noaa (the American agency responsible for monitoring the atmosphere and oceans) and other institutions is that the rapid decline was only possible because of a large production of unreported CFC-11 and the resulting emission of CFC-11 must be present in these gases.

The hope is that if the decline in emissions is sustained and irregular production does not increase, the damage to the ozone layer can park, which favors its regeneration.

Another analysis published in the same issue shows a significant decrease in CFC-11 production in eastern China. The study included measurements in China, Japan and South Korea as well as an analysis of the atmospheric dynamics of the Asian continent.

The decrease was around 10,000 tons per year between 2014 and 2017 and reached 5,000 tons in 2019. This decrease corresponds to 60% of the decrease in global pollutant emissions over the same period.
Despite estimating that there is still a large bank of CFC-11, that is, gas that is trapped in ducts and foams and has not yet been released into the atmosphere, the authors attribute the improvement in emissions to the policy of the Chinese government and the actions of back the country’s industry. Scientists from South Korea, Great Britain, Japan, Switzerland, China, the USA and Australia were involved in this work.

USP Professor Carlos Menck embarked on an expedition to Antarctica in late 2017 to study how the loss of the layer affects DNA, in order to study the effects of the destruction of the ozone layer on the various forms of life on earth – including humans. The results were recently published in the journal Photochemistry and Photobiology.

The experiment consisted of exposing a type of gelatinous capsule containing DNA to the sun on the frozen continent, while another capsule was protected under control with a sheet of aluminum foil. This gel is known as a “DNA Lesion Dosimeter” and enables experiments outside of the laboratory.

It may seem easy, but besides the icy weather there were challenges too.

One of them was the skuas, migratory birds that normally roam around Comandante Ferraz Antarctic Station, the Brazilian base on the continent. “They’re like big chickens, but they fly,” says Menck. And the problem is, they tried to steal material from the scientist’s experiments. “I tried taping a rock down, but it wasn’t even 15 minutes and there was the skua again.”

Advised by a colleague, he developed an invention: he fitted the dosimeter onto a squeegee that he had found to give soup to the Brazilian base. He stuck the cord in the snow and used the ground as a support.

Officially, in the scientific article, it is a “tilted prop” or angled prop that actually made the task easier, as it was enough to follow the sun to turn the apparatus.

Ozone is a very unstable gas, made up of three atoms of oxygen (the molecular oxygen we breathe is made up of two atoms), and is mainly found in the stratosphere at an altitude of around 15 km or more.

This ozone forms a kind of scatter cloud that prevents the incidence of ultraviolet rays, especially type C, the most intense, and also type B on the surface of the earth. Interestingly, these atoms combined would form a layer only about 3mm (or 300 DU, Dobson units), which reveals this fragility.

(There is also ozone in the troposphere, the layer of the atmosphere we are immersed in, but there it is mainly linked to pollution in large cities and causing health problems.)

During the Antarctic Spring, the ozone layer can reach less than 1 mm (100 DU). If the value is below 220 UD (corresponds to 2.2 mm), a hole is already taken into account. And whoever is under the hole can suffer from the severity of the solar radiation.

“Even without the hole, there was very strong radiation. And our experiments have already shown a correlation between the thickness of the ozone layer and DNA damage, particularly from the action of type B ultraviolet. [que deixa de ser bloqueado pela camada]”Says Menck.

Injuries and mutations in DNA are among the main factors contributing to the development of cancer. Ultimately, life on earth could be wiped out without the protection of the ozone layer.

On September 20, 2020, the hole reached the size of 25 million square kilometers, almost twice the area of ​​the entire Antarctic continent and even larger than the area of ​​Russia, the largest country with territorial expansion NASA.

Since the negotiations that led countries to sign the Montreal Protocol in the late 1980s, emissions of so-called CFCs (chlorofluorocarbons) have been reduced, gases have been used for applications such as refrigeration and aerosols, which accelerate ozone depletion, and the stratospheric layer has stabilized.

The expectation is that recovery to pre-1980 levels, if all goes well, will take between 60 and 100 years, reports Paulo Artaxo, professor at USP and student of atmospheric physics.

However, there has been a slowdown since the middle of the last decade as gases continue to be emitted that deplete the ozone layer. According to researchers from MIT and the universities of Sussex and the state of Colorado, they defend themselves in an article published in 2020 in the journal Nature Communications. Despite the success achieved so far, it is time to update the Guidelines to Protect the Ozone Layer, boasting longer an accomplishment of the last century.

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