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.
