What Is the Ozone Hole?

The ozone hole refers to a phenomenon in which halogenated hydrocarbons and other anthropogenic pollutants enter the stratosphere, where—through photochemical reactions and catalytic decomposition—ozone is massively depleted, causing total ozone column values to fall significantly below normal levels.

In 1985, scientists from the British Antarctic Survey first published observations of severe ozone depletion over Antarctica. Today, ozone layer depletion has become an environmental issue of global concern, directly threatening the balance of the biosphere and human health. The reduction of stratospheric ozone allows more solar ultraviolet radiation to reach the ground, particularly in the UV-B band (280–315 nm), which has strong damaging effects on biological cells and poses risks to ecosystems and all living organisms, including humans.

Ozone is primarily formed when solar ultraviolet radiation dissociates oxygen molecules, and the resulting oxygen atoms combine with O₂. It is mainly generated over the equator, where solar radiation is intense, and then transported worldwide by atmospheric circulation. The total atmospheric ozone reservoir is approximately 3.3 billion tonnes; if spread evenly over the Earth's surface, it would form a layer only about 3 mm thick—roughly the height of a mung bean.

Ozone absorbs the vast majority of solar ultraviolet radiation harmful to life. Wavelengths shorter than 280 nm are almost entirely blocked by stratospheric ozone, while most UV-B radiation (280–315 nm) is also absorbed, significantly reducing the intensity of ultraviolet radiation reaching the surface. If stratospheric ozone declines, surface UV-B exposure increases correspondingly. Just as life depends on water and oxygen, the atmospheric ozone layer is an essential protective shield upon which all living creatures on Earth rely.

However, as human activities have intensified—especially through the widespread use and emission of manufactured halogenated compounds such as chlorofluorocarbons (CFCs) and halons—the ozone layer has suffered continuous destruction. Total atmospheric ozone has declined markedly, with the most severe depletion occurring over the polar regions. Over Antarctica, an ozone-depleted area exceeding 20 million square kilometres has developed. In the lower stratosphere (approximately 14–21 km), average ozone loss can exceed 90%, and in extreme years, ozone in this altitude range may be nearly completely depleted—hence the evocative term "ozone hole" coined by scientists.

Continued ozone depletion will expose humanity to excessive solar ultraviolet radiation, significantly increasing the incidence of skin cancer, cataracts, and other diseases. It will also damage crop growth, disrupt marine phytoplankton community balance, and ultimately affect the stability of the global ecosystem.