About

• Ozone (O3) is a highly reactive gas composed of three oxygen atoms.
• It is both a natural and a man-made product that occurs in the Earth’s upper atmosphere ozone molecule (the stratosphere) and lower atmosphere (the troposphere).  Depending on where it is in the atmosphere, ozone affects life on Earth in either good or bad ways.
• Stratospheric ozone is formed naturally through the interaction of solar ultraviolet (UV) radiation with molecular oxygen (O2).  This “ozone layer,” approximately 6 through 30 miles above the Earth’s surface, reduces the amount of harmful UV radiation reaching the Earth’s surface.
• However, this beneficial ozone has been partially destroyed by chemicals used for refrigeration purposes, such as chlorofluorocarbons (CFCs) and hydrofluorocarbons (HFCs), causing what is sometimes called a “hole in the ozone.”
• Areas with ozone concentrations less than 220 Dobson Units are called “holes” in the layer.
• Tropospheric ozone is a harmful air pollutant, because of its effects on people and the environment, and it is the main ingredient in “smog.” Tropospheric ozone is a harmful pollutant that causes damage to lung tissue and plants.
• Tropospheric ozone is not emitted directly from anthropogenic sources. It is a “secondary” pollutant formed by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC). This happens when pollutants emitted by cars, power plants, industrial boilers, refineries, chemical plants, and other sources chemically react in the presence of sunlight and heat.
• It can be curtailed only if gases from all sources are controlled.

What are the health effects of ozone?

• Ozone in the air we breathe can harm our health. People most at risk from breathing air containing ozone include people with asthma, children, older adults, and people who are active outdoors, especially outdoor workers.
• In addition, people with certain genetic characteristics, and people with reduced intake of certain nutrients, such as vitamins C and E, are at greater risk from ozone exposure.
• Breathing ozone can trigger a variety of health problems including chest pain, coughing, throat irritation, and airway inflammation. It also can reduce lung function and harm lung tissue. Ozone can worsen bronchitis, emphysema, and asthma, leading to increased medical care.

What are the environmental effects of ozone?

• Ozone affects sensitive vegetation and ecosystems, including forests, parks, wildlife refuges and wilderness areas.  In particular, ozone harms sensitive vegetation during the growing season.

Measures related to ozone depletion

• The Montreal Protocol, a landmark international environmental treaty that took effect in 1988, has reduced chlorofluorocarbons (CFCs) emissions worldwide. It is termed as one of the most successful international agreements.
• In 2016, Parties to the Montreal Protocol adopted the Kigali amendment to phase down production and consumption of hydrofluorocarbons (HFCs) worldwide.

Why in the news?

• In an analysis by the Centre for Science and Environment (CSE), it was found that Ozone pollution has increased during the lockdown. This is in contrast with other pollutants because other pollutants levels have fallen during the lockdown.
• Scientists are seeing this pandemic-led change in air quality as an opportunity to study summer pollution which is different from winter pollution as the climatic conditions are different.
• The characteristics of summer pollution are different: there are high winds, intermittent rains and thunderstorms, and high temperature and heat waves.
• This is in contrast to winter — with its inversion, lower mixing height of air, and cold and calm conditions that trap the air and the pollutants in it.

Centre for Science and Environment

• Centre for Science and Environment (CSE) is a public interest research and advocacy organisation based in New Delhi.
• CSE researches into, lobbies for and communicates the urgency of development that is both sustainable and equitable.
• They publish Down To Earth magazine.

https://www.epa.gov/ozone-pollution-and-your-patients-health/what-ozone

https://www.thehindu.com/sci-tech/energy-and-environment/ozone-pollution-spiked-in-several-cities-during-lockdown-cse/article31917957.ece