Why in News?

• According to the Centre for Science and Environment (CSE), parts of the Delhi-NCR region witnessed ground-level ozone readings exceeding the safe standards (50 ppb over an 8-hour average) between March and May.
• Moreover, the region is seeing a rare phenomenon where ozone levels remain elevated even at night (should ideally become negligible during the night) and has become a yearlong problem.

What’s in Today’s Article?

• What is Ground-level Ozone?
• What are the Harmful Effects of Ground-level Ozone?
• What is the Situation of Ground-level Ozone in India?

What is Ground-level Ozone?

• Also known as tropospheric ozone, ground-level ozone is a colourless and highly irritating gas that forms just above the Earth’s surface (up to 2 miles above the ground).
• Ground-level ozone is a “secondary” pollutant - not directly emitted into the air but rather produced when two primary pollutantsreact in sunlight and stagnant air.
• These two primary pollutants are nitrogen oxides (NOx) and volatile organic compounds (VOCs).
  • NOx and VOCs come from natural sources as well as human activities.
  • About 95% of NOx from human activity comes from the burning of coal, gasoline and oil in motor vehicles, homes, industries and power plants.
  • VOCs from human activity come mainly from gasoline production and combustion, residential wood combustion and from the evaporation of liquid fuels and solvents.
• Ground-level ozone is likely to breach safety standards on hot summer days in urban areas, but can also reach unhealthy levels during colder months.
• The pollutant can also travel long distances due to wind and affect rural areas

What are the Harmful Effects of Ground-level Ozone?

• On human health:
  • As ground-level ozone is a highly reactive gas, it has serious health consequences.
  • Those with respiratory conditions, asthma, chronic obstructive pulmonary disease and particularly children with premature lungs and older adults are at serious risk.
  • This can inflame and damage airways, make lungs susceptible to infection, aggravate asthma, emphysema, and chronic bronchitis leading to increased hospitalisation.
• The pollutant can affect sensitive vegetation and ecosystems: Including forests, parks and wildlife refuges. Significantly, it can harm sensitive vegetation during the growing season too.

What is the Situation of Ground-level Ozone in India?

• In recent years, ground-level ozone has become a serious public health issue in India.
• According to the 2020 State of Global Air report,
  • Seasonal 8-hour daily maximum concentrations have recorded one of the highest increases (17%) in India between 2010 and 2017.
  • Age-standardised rates of death attributable to ground-level ozone are among the highest in the country.