Hole in the sky

For starters it could cause crop yields to fall, seriously disrupt marine food chains upon which millions of Indians depend and affect delicately balanced ecosystems. Ultimately, everyone on earth is affected by such far-reaching impacts, but too little is understood by the public about this ‘hidden threat'.

Concern over ozone depletion first grew in the early 1970s, when scientists warned that the stratospheric ozone layer could gradually be consumed by chlorofluorocarbons (CFCs) and other ozone depleting substances such as HCFCs, halons (used in fire extinguishers), methyl bromide (a pesticide), carbon tetrachloride, and methyl chloroform. Culprits ranged from aerosol products like perfumes, room fresheners and insecticides to cars, refrigerators, air-conditioners and fire extinguishers. 

An ozone hole over the Antarctic, deodorant spray on a summer day… the challenge is to place these in perspective for the common person on the streets of Delhi or Mumbai. Unknown to most Indians, each molecule of the most commonly used CFC traps 10,000 times as much infrared radiation as a single molecule of carbon dioxide. The consequent overheating of the planet, increased risk of cataracts and skin cancer, weakened immune systems and effects on agriculture and food would pose a serious problem to millions in the subcontinent. Besides, increased ultraviolet radiation can also lead to reduced crop yield and disruptions in the marine food chain. Substances used in agriculture such as methyl bromide, five metric tonnes of which are annually imported by India for use in grain and soil fumigation, have been given an Ozone Depletion Potential (ODP) of 0.4. In the US, all substances with an ODP of 0.2 or greater are considered ‘Class I' ozone depleting substances that must be phased out. The persistence of CFCs only exacerbates the problem as they may survive for years, eating away at the ozone layer. 

Ozone in the mid-latitudes and tropics was discussed as a separate issue in the scientific assessment of ozone depletion by the World Meteorological Organisation (Global Ozone Research and Monitoring Project). The Executive Summary Report warns that: “The ozone layer is currently in its most vulnerable state. Release of CFCs would lead to a significant reduction of upper stratospheric ozone, with the peak percentage decline occurring around 40 km. Total stratospheric loading of ozone depleting substances is expected to maximise and the current ozone losses (as compared to the values observed in the 1970s) are estimated to be about six per cent at Northern Hemisphere mid-latitudes (winter/spring), three per cent at Northern Hemisphere mid-latitudes (summer/fall); five per cent at Southern Hemisphere mid-latitudes (year-round); about 50 per cent in the Antarctic (spring); and about 15 per cent in the Arctic spring."

On September 16, 2000, the International Day for Preservation of the Ozone Layer, representatives from the Union Environment Ministry and industry met in New Delhi to discuss ozone depleting substances, rules and phase-out projects to work in accordance with the Montreal Protocol. The health of the ozone layer, over the tropics, they agreed had registered a dip and alternatives were to be explored. According to the US Environmental Protection Authority, the earth is experiencing an ozone depletion of approximately three to six per cent at mid-latitudes, but if no action had been taken to limit CFCs, ozone depletion at mid-latitudes would eventually have reached 20 per cent or more. 

Ozone formation and depletion continue to occur every second and attention now has to also focus on the other ozone depleting substances. Are we keeping pace?

By Priya Raja

First published in Sanctuary Asia, Vol. XXI. No. 3., June 2001