Ozone may protect the earth but poses a threat to food security: Here's how

Ozone is a well-known and interesting gas. It is thought of as a “good” gas when present in the stratosphere, where it forms the ozone layer sitting 15 to 30 kilometres above Earth that protect life from detrimental ultraviolet radiation.

But when present in the lowest atmospheric layer – the troposphere, which extends 8 to 14 kilometres above Earth – ozone becomes a concern for human and plant health. It is also the third most important greenhouse gas after carbon dioxide and methane. There’s substantial evidence that ozone is one of the most phytotoxic (toxic to plants) air pollutants, causing significant damage to agricultural crops worldwide.

A combination of pollutants

This is partly because ozone is a secondary air pollutant: it is not emitted directly, but is formed when other primary pollutants – mainly oxides of nitrogen (NOx), carbon monoxide (CO) and volatile organic compounds (VOC), which are emitted mainly from the burning of fossil fuels in transport, industry and power generation – undergo photochemical reactions under sunny conditions.