Ground-level Ozone

News:

According to CSE analysis, parts of Delhi NCR is experiencing ground-level ozone levels above the national standards on 87/ 92 days in summer (March-May).

What:

• Also known as tropospheric ozone
• It is a colourless irritating gas that forms near the surface i.e. up to 2 miles above ground.
• It is a secondary pollutant formed by interaction between primary pollutants.

Concern:

• Can travel long distances and pollute regions far away from source i.e. even rural areas could be affected.
• Has serious health consequences:
  • Inflammation and damage of airways
  • Increased susceptibility of lungs to infections
  • Aggravates conditions like:
    • Asthma
    • Emphysema
    • Chronic bronchitis
• Negatively impacts:
  • Sensitive vegetation
  • Sensitive ecosystems

How:

• Formed by reaction between:
  • NOx- nitrogen oxides
  • VOCs- volatile organic compounds
• These two primary pollutants are emitted by natural and anthropogenic sources.
• 95% of NOx comes from anthropogenic activities like burning of coal and oil.
• VOCs are emitted by:
  • Gasoline combustion and marketing
  • Upstream oil and gas production
  • Combustion of wood
  • Evaporation of liquid fuels and solvents

When:

• Ground-level ozone usually breaches safety levels on hot summer days, especially in urban areas.
• It could also reach high levels in colder months.