Ozone levels exceeding permitted levels: study

Source: The Hindu

What is the News?

A Centre for Science and Environment (CSE) study has found that ozone levels are exceeding the permitted levels even during winter in Delhi-NCR. It is making the smog more “toxic”.

Key Findings of the Study:

• Ozone is becoming more widespread in Delhi and the National Capital Region (NCR) across all seasons. It is contrary to the notion that ozone is a summer phenomenon and is produced photochemically from the interaction between gases in the presence of sunlight.
• Increasing Ozone Standards: The number of days not meeting the ozone standards has begun to increase. The city-wide average largely remains within the standard. But the ‘good’ category days have fallen to 115 days in 2020 which is 24 days less than in 2019 in Delhi.
• Pandemic effect: Despite the pandemic and lockdowns, more days and locations witnessed a higher and longer duration of ozone spells.
• Night-time ozone is higher during the pandemic lockdown and night curfews: Ozone generally disintegrates after sunset. It is because, in the absence of sunlight, NOx further reacts with ozone to neutralize it. But elevated ozone levels have been noticed during nighttime.

About Ozone:

• Ozone is a gas composed of three atoms of oxygen. Ozone occurs both in the Earth’s upper atmosphere and at ground level. It can be good or bad, depending on where it is found.
• The stratospheric ozone also called Good Ozone occurs naturally in the upper atmosphere. There, it forms a protective layer that shields us from the sun’s harmful ultraviolet rays.
• On the other hand, Ozone at ground level is a harmful air pollutant, because of its effects on people and the environment, and it is the main ingredient in “smog”.