Ozone is a paradoxical element — it shields life from harmful UV radiation in atmosphere but is also a big pollutant on the ground

People often think of two different things when they hear the word "ozone": on the one hand, an essential shield in the atmosphere that protects life on Earth from the Sun's dangerous ultraviolet radiation; on the other, a pollutant that causes health problems and damage to the environment. Ozone is indeed a double-edged sword because its effect on human life depends on where it is and how much of it there is.

The "good" ozone in the upper atmosphere is significant, but the "bad" ozone at ground level is very bad for people and the world. This dual nature needs immediate care, new ideas, and cooperation worldwide so that people can continue to live.Ozone creates the well-known ozone layer high in the stratosphere, between 10 and 30 miles  (16-48 km) above the surface of the Earth. This protective layer absorbs the bulk of the Sun's harmful ultraviolet (UV) radiation UV-C and UV-B. Ecosystems would almost certainly be unable to survive as they do now without this natural shield, which exposes life on Earth to hazardous radiation levels.

Although life depends on the ozone layer in the stratosphere, ground-level ozone, found in the troposphere, is a hazardous contaminant. This ozone, created by sunlight-induced chemical interactions between nitrogen oxides (NOx) and volatile organic compounds (VOCs), is mainly caused by human activity, including certain chemicals, industrial processes, and automobile emissions.

This ozone will affect crop productivity and ecosystem dynamics. In the mid-20th century, scientists discovered that chlorofluorocarbons (CFCs) were causing the systematic depletion of the ozone layer. In response to the pressing need, a global accord,  the Montreal Protocol, was adopted in 1987 to gradually eliminate the manufacturing of chemicals that cause the depletion of the ozone layer. The main objective of this accord was to eliminate progressively chemicals that cause erosion of the ozone layer, notably chlorofluorocarbons (CFCs), which are extensively used in refrigeration, aerosols, and other industrial uses.

India is also a signatory to this accord. Indian industries, especially those in the refrigeration, air-conditioning, and foam production sectors, were compelled to transition to ozone-friendly alternatives. The phasing out of CFCs initially led to the adoption of hydrofluorocarbons (HFCs), but attention soon shifted toward more environmentally friendly solutions, such as natural refrigerants, hydrofluoroolefins (HFOs), with lower global warming potential.

Since the implementation of the Montreal Protocol, global emissions of ozone-depleting substances (ODS)  have dramatically decreased. The ozone layer has shown signs of recovery, particularly over Antarctica, where the famous "ozone hole" is gradually closing. This recovery is essential for shielding the planet from harmful UV radiation.

In addition, the phase-out of CFCs and other ODS has had a measurable impact on global temperature regulation. This is significant when considering the urgency of limiting temperature rise to avoid catastrophic climate impacts. The Protocol has become a symbol of what international cooperation can achieve if people unite and work together to protect the environment.  

The illegal production of CFCs and incomplete phase-outs in some regions could slow progress. While ozone protects life and poses risks, its dual nature demands vigilant global action. Striking the right balance between preserving the protective ozone layer and mitigating harmful ground-level ozone is essential for humanity's and the planet's health. We can ensure a safe future only through international cooperation and innovative solutions.

(The writer is an adjunct faculty at the National Institute of Advanced Studies; views are personal)