Global health. The current scenario and future perspectives

81 Ozone forms a layer in the stratosphere (10 to 48 kilometers above the Earth). This layer protects the planet from 95-99% of the harmful ultraviolet rays from the sun. These rays can cause health effects, primarily on the skin and eyes, and disrupt the balance of ecosystems and alter chemical and physical processes that occur in the cycle of nature. Additionally, the thinning of the ozone layer interacts with the trend of global warming. According to UNEP, since measurements began in the early 1980s, the thinning of the ozone layer over the poles has caused a constant erosion, resulting in “ozone holes” over the Earth. The ozone hole over the South Pole grew to about 2 billion hectares in the early 1990s and, at times, increased to 2.8 billion hectares. In 2001, the ozone layer had thinned by 30% over the North Pole, Europe and other high latitudes. At its maximum size in 2006, the ozone hole in the Antarctic region reached 2.7 billion hectares, while in 2009, the hole reached 2.4 billion hectares, a decrease compared to the previous year and even smaller than the record size in 2006, according to images collected by the National Aeronautics and Space Administration (NASA). By the end of 2012, the area of the ozone hole had reduced to 1.8 billion hectares, the lowest levels observed in over a decade. The main cause of ozone depletion is the emissions of halocarbons produced by humans, especially chlorofluorocarbons (CFCs). Discovered in the early 20 th century, these gases, famous for their industrial properties, were globally used in a wide range of applications, including refrigerators, air conditioning, aerosol cans, solvents and fire extinguishers. The disadvantage of these gases is that they remain in the atmosphere for a long time (50 to 1,700 years) and, thus, cause lasting environmental damage. The chlorine from CFCs chemically reacts with ozone and breaks it down, which reduces the ozone layer’s ability to block ultraviolet rays. The international response to the ozone threat has perhaps been the most successful of all global environmental efforts. In 1985, the Vienna Convention for the Protection of the Ozone Layer (signed by Chile in 1990) committed countries to promoting cooperation through systematic observations, research and exchange of information on the impact of human activities on the ozone layer, and to adopt legislative measures against activities that would have adverse effects on the ozone layer. At that time, the scientific understanding of ozone depletion was still limited, so no specific measures were established, but countries were willing to acknowledge and combat the problem. As scientists developed a precise understanding of how ozone depletion occurs, the parties to the Vienna Convention decided to take specific