Ozone levels exceeding permitted levels: study

Subject : Geography

Context : A Centre for Science and Environment study on ozone levels in Delhi-NCR.

Concept :

Contrary to the notion that ozone is predominantly a summer phenomenon, the study found ozone levels exceeding the permitted levels even during winter in Delhi-NCR.
The study notes that despite the lockdown, more days and locations witnessed a higher and longer duration of ozone spells.

Ozone:

While stratospheric ozone protects living things from ultraviolet radiation from the sun, ground-level ozone is considered a pollutant given the adverse health problems it gives rise to.

Ozone formation:

Ozone is a secondary pollutant. Tropospheric, or ground-level ozone, is not emitted directly into the air, but is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight (photochemical reaction).
Emissions from cars, power plants, refineries, chemical plants, and other sources are the major sources of NOx and VOC.
Ozone is most likely to reach unhealthy levels on hot sunny days in urban environments.

Harmful effects:

Ozone is a highly reactive gas and when inhaled it can damage the lungs. Relatively low amounts of ozone can cause chest pain, coughing, shortness of breath and, throat irritation. It may also worsen chronic respiratory diseases such as asthma as well as compromise the ability of the body to fight respiratory infections.
Elevated exposure to ozone can affect sensitive vegetation and ecosystems. In particular, ozone can harm sensitive vegetation during the growing season.