Humans used to release harmful chemicals that thinned Earth's protective ozone layer, putting life at risk. But laws banning these substances have started helping the ozone recover. The chemicals, chlorofluorocarbons (CFCs) and bromine-containing gases, caused severe ozone loss, especially at the poles, seen in the 1980s. Laws like the Montreal Protocol limited this damage, especially in crowded areas. Though it'll take time to fully heal as these chemicals linger in the air, signs of recovery for upper ozone levels are being seen. However, the biggest threat to the ozone now comes from greenhouse gas emissions.