Ground-level ozone: CSE analysis says South Delhi, New Delhi worst affected

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?

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