The “trio molecule” as protector and hazard

By Dr. Azizi Abu Bakar 

The relentless and concerted efforts by our Malaysian government, alongside scientists and industries, in healing the ozone layer since the ratification of the Vienna Convention and Montreal Protocol in 1989, are highly commendable. The phased reduction of ozone-depleting substances (ODSs), including the decline in imports and consumption of ODS technologies and products, has had a significant positive impact. Industries have been recognized for completing the technology conversion from HCFC to cyclopentane and for their readiness to adopt the latest non-ODS technologies. Additionally, the adoption of technology for the reclamation of refrigerants and other ODSs has further contributed to the healing and preservation of our ozone layer.

This progress is evident in reports from NASA and the US National Oceanic and Atmospheric Administration, which indicate that the hole in the ozone layer above Antarctica is continuing to shrink—from its peak size of 27.5 million square kilometers in 2006 to 23.2 million square kilometers in 2022. This is a promising development, and the World Meteorological Organization reports that the ozone layer is recovering at a rate of up to 3% per decade. With sustained efforts, the hole could be fully closed within 50 years.

Stratospheric Ozone – The Protective Shield

The “trio” or three molecules of oxygen, with a Lewis structure forming a bent shape, are what we call ozone. In the stratosphere, ozone forms a layer that functions as Earth’s sunscreen, though it is only a fragile 3 to 5 mm thick. Stratospheric ozone, found 16 to 50 kilometers above the Earth in low latitudes and 8 to 50 kilometers in high latitudes, acts as a “good gas,” protecting life on Earth from harmful ultraviolet (UV) radiation.

The ozone layer filters out and reduces over 90% of the harmful UV radiation from the sun. However, ozone-depleting substances (ODSs) such as chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) can decompose under UV radiation in the stratosphere, releasing chlorine atoms. Just one chlorine atom from CFC can destroy up to 100,000 ozone molecules. Uncontrolled ozone depletion leads to excessive UV-B radiation exposure, which can cause skin cancers, cataracts, and damage to the human immune system. By protecting the ozone layer, we can balance the positive and negative effects of UV-B. Without the Montreal Protocol, which has been ratified universally by 197 countries, ozone depletion would have exceeded 50% by the end of this century.

Uncontrolled UV radiation not only poses a health risk but also threatens food security by damaging aquatic ecosystems, which form the basis of commercial fisheries. UV radiation can directly harm crustaceans and fish eggs, disrupting aquatic food webs and affecting our food supply. It also damages plants, reducing food availability for herbivores and disrupting entire food webs. Additionally, increased UV radiation accelerates the breakdown of decaying leaves and organic matter, reducing ecosystems’ ability to trap carbon dioxide, including emissions from human activities. Consequently, large-scale ozone depletion would exacerbate the build-up of carbon dioxide in the atmosphere, contributing to climate change.

The Environmental Effects Assessment Panel (EEAP) determined that a 10% reduction in stratospheric ozone, leading to increased UV radiation, could reduce the growth of many crops by about 6%. However, it is worth noting that natural levels of UV radiation can benefit crops by protecting them from pests and diseases.

Surface Ozone – An Emerging Hazard

Surface ozone is a secondary air pollutant formed when primary pollutants like nitrogen oxides (NOx), carbon monoxide (CO), and volatile organic compounds (VOCs) from fossil fuel combustion in transport, industry, and power generation undergo photochemical reactions under sunny conditions. This surface ozone poses a significant threat to crop production by causing strong oxidative stress, which can jeopardize food security.

China and India, for example, are already experiencing the adverse effects of surface ozone pollution on crop production. In developing countries, particularly in South and East Asia, surface ozone levels are rising, and this trend is expected to continue at least until 2030 unless emissions of primary pollutants, particularly NOx and VOCs, are significantly reduced. As industrial development intensifies across Asia, Malaysia, being part of this region, may also face the threat of surface ozone pollution if preemptive monitoring measures are not taken. Additionally, the hemispheric transport of surface ozone can occur, leading to trans-regional pollution, where emissions from one continent can significantly influence surface ozone concentrations in another.

As an abatement strategy, scientists have proposed using milkweed as an indicator to monitor surface ozone pollution due to its leaves’ sensitivity to the pollutant. Ozone damage, visible as black spots on the upper leaf surface, provides early warnings of ozone pollution, which can last from days to weeks. This helps farmers minimize crop loss through sustainable management practices.

Do Not Let Perfect Be the Enemy of Good

Ozone acts as a double-edged sword: high in the atmosphere, it serves as a protective shield, but at ground level, it becomes a threat. Preventing the production and use of ozone-depleting substances (ODSs) and reducing surface ozone from primary pollutants are essential steps toward safeguarding our environment. In honor of the International Day for the Preservation of the Ozone Layer on September 16, individuals can contribute by avoiding products containing CFCs and HCFCs, such as polystyrene and styrofoam, and by reducing single-use plastics. These small actions not only reduce waste but also help mitigate climate change. Healing the ozone layer and preventing surface ozone formation require collective action at all levels, from individuals to international communities.

In conjunction with the International Day for the Preservation of the Ozone Layer on 16 September, let us not underestimate the power of our individual actions. It is crucial to avoid letting the pursuit of perfection hinder meaningful progress in striving to restore ozone levels to pre-1980 values by 2040-2045. Every effort counts, as it can inspire collective and effective action.

Just like the ozone layer —a thin yet vital layer in our atmosphere— individual contributions, though small, are essential to achieving our global goals.

_{The author is the Research Officer at Universiti Malaya Sustainable Development Centre (UMSDC), and may be reached at azizi.bkr@um.edu.my}