Good news about Antarctic’s ozone hole
EVEN as the goal of limiting global warming to below 1.5° C by the turn of the century does not seem achievable, there is some news to cheer about.
During the peak of ozone depletion season this year—from September 7 to October 13—the ozone hole was ranked the seventh smallest since recovery began in 1992, when the Montreal Protocol, a landmark international agreement to phase out ozone-depleting chemicals, the chlorofluorocarbons (CFCs), began to take effect. The ozone-rich layer high in the atmosphere acts as a planetary sunscreen that helps shield the earth from harmful UV radiation from the sun.
Sources of CFCs include coolants in refrigerators and air conditioners and aerosols in hairspray, antiperspirant, and spray paint. Harmful chemicals are also released while manufacturing insulating foams and components for industrial fire suppression systems.
But the CFCs already in the air will take many decades to break down. As existing CFC levels gradually decline, the ozone in the upper atmosphere will rebound globally, and ozone holes will shrink. Scientists with NASA and the US’ National Oceanic and Atmospheric Administration (NOAA) project claim that the ozone layer could fully recover by 2066.
The monthly average ozone-depleted region in the Antarctic this year was about 20 million km2. The hole reached its greatest one-day extent on September 28 at 22.4 million km2. “The 2024 Antarctic hole is smaller than ozone holes seen in the early 2000s,” said Paul Newman, leader of NASA’s ozone research team. The improvement is due to a combination of continuing reductions in harmful CFCs, along with an unexpected infusion of ozone carried by air currents from north of the Antarctic, the NASA release said.
Researchers rely on a combination of systems to monitor the ozone layer, including instruments on NASA’s Aura satellite, the NOAA-20 and NOAA-21 satellites, and the Suomi National Polar-orbiting Partnership satellite, jointly operated by NASA and the NOAA.
NOAA scientists also release instrumented weather balloons from the South Pole Baseline Atmospheric Observatory to observe ozone concentrations directly overhead in a measurement called Dobson units. The lowest value ever recorded over the South Pole was 92 Dobson units in October 2006. The 2024 concentration reached its lowest value of 109 Dobson units on October 5. “That is well below the 225 Dobson units that was typical of the ozone cover above the Antarctic in 1979,” said NOAA research chemist Bryan Johnson. “So, there’s still a long way to go before atmospheric ozone is back to the levels before the advent of widespread CFC pollution.”
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Slit-lamp microscopic photographs of all four treated eyes before and 52 weeks after iPSC-derived corneal epithelial cell sheet transplantation. | Photo Credit: The Lancet/Takeshi Soma et al.
Vision restored in four in Japan after stem cell implants
THE corneal limbus is the border between the cornea and the sclera (the white of the eye). The dark ring around the iris, the limbal ring, is the source for limbal stem cells, which have the ability to regenerate the entire corneal epithelium, the thin layer covering the cornea. But damage to the limbus, which can be due to autoimmune diseases, trauma, genetic disorders, or cancer, can lead to deficiency in these stem cells. This medical condition is known as limbus stem cell deficiency (LSCD), and it causes scarring of corneal tissues, which eventually leads to blindness.
Typically, LSCD is treated using corneal cells derived from stem cells obtained from the patient’s healthy eye, a surgical procedure with uncertain results. When both eyes are affected, the option is similar transplants from eyes donated by the dead. However, frequently these are rejected by the patient’s immune system.
Now, in a first-of-its-kind trial, Kohji Nishida, an ophthalmologist at Osaka University, and his colleagues turned to induced pluripotent stem cell (iPSC)-derived corneal epithelial cell sheets as the source to generate corneal cells that could be used as transplants.
The technique of creating embryonic stem cells like iPSCs from somatic cells was invented and perfected by the Nobel laureate Shinya Yamanaka over a decade ago (see Frontline May 18, 2012, and June 01, 2012). Since his pioneering efforts, several trials have been ongoing the world over in using iPSCs to treat intractable anatomical disorders. One of the first trials that Yamanaka himself did involved treating age-related macular degeneration, a medical condition that results in loss of vision in the centre of the visual field (the macula) because of damage to the retina.
In the Osaka University trial, four participants, two women and two men aged between 39 and 72 with severely impaired corneas due to LSCD in both eyes, were enrolled between June 2019 and November 2020 and observed for 52 weeks after the transplants. Over a further 52-week period, the participants were monitored for adverse events. None of them experienced serious side effects. The grafts did not show any signs of rejection by the hosts’ immune system even in the two who were not administered immunosuppressant drugs, and notably, soon after the transplants, a significant improvement was seen in the vision of all four recipients and a decrease in the corneal area affected by LSCD. While the improvements persisted in all, one recipient showed slight reversals in the first 52-week period.
The researchers plan to begin clinical trials in March to assess the treatment’s efficacy. Their work was reported in a recent issue of The Lancet.
