Research hot topics
Air pollution in a changing climate
By Samuel Y Cai, Lecturer in Environmental Epidemiology
Air pollution is the single biggest environmental hazard across the world, claiming nearly 9 million lives annually according to recently updated scientific models. The quality of air that we breathe, for over 90% of the world populations, is deemed to be poor against the guidelines set by World Health Organization. In the forms of particles and gases, air pollution comes from both man-made and natural sources, such as road transport, industry, farming, domestic burning, and wildfires, just to name a few. There is already a large body of scientific evidence suggesting that air pollution, even at a relatively low level, could harm our health, in both short-term and long-term timeframe.
Another critical challenge that facing humanity and our planet is the changing climate. Climate change is primarily driven by emission of greenhouse gas (notably CO2) that can trap the heat in the atmosphere and cause the planet’s temperature to rise more rapidly. Yet, climate change is not a future problem. It is now directly impacting our health via more frequent extreme weather events (e.g. heatwaves, wildfire, drought, storms, floods) or indirectly through changing the ecosystems (e.g. increased concentrations of certain air pollutants, prolonged pollen season) and inciting social and economical unrest (e.g. climate migration and conflict, food shortage, occupational risk dur to heat).
It is a no-brainer that air pollution and climate change are closely linked. The debated question is: are they the two sides of the same coin? The answers are not always straightforward.
Burning of fossil fuel lies at the heart of these two problems. The combustion of fuel emits both long-lived and short-lived pollutants into the atmosphere, including CO2, particulate matter (PM), and other pollutants such as NOx, volatile organic compounds (VOCs) which serve as precursors to Ozone. CO2 can remain in the atmosphere for hundreds of years and is a key climate-forcer heating up the planet. Other climate pollutants are generally short-lived, including methane, ground-level Ozone and black carbon (i.e. soot, a PM component), lasting in the atmosphere from hours to years. However, these short-lived climate pollutants (SLPC) has a stronger warming potential as compared to CO2. For example, black carbon can absorb heat due to its dark-colour surface, and thus increasing local temperature more effectively. PM can also alter cloud properties and therefore potentially change the rainfall patterns. Reducing these short-lived climate pollutants are key to protect both our health and that of the planet.
Climate change is also contributing to air pollution in many ways. The altered weather patterns could impact the formation, chemical compositions, and spatial and temporal distributions of air pollutants. Higher temperatures contribute to more rapid formation of Ozone as well as occurrence of wildfires, toxic smoke from which can travel thousands of miles away from the original spot. Climate change can also impact the emission patterns of other so-called naturally occurring air pollutants, such as pollen, VOCs from trees, and windblown dust.
For a long time, air pollution and climate change has been viewed as separate issues by governments around the world, where policies were devised and implemented by different governmental departments. In fighting against this battle, we need integrated and coordinated mitigation policies, by bringing expertise from different scientific disciplines and key stakeholders, to ensure a win-win outcome and maximise public health benefits. For instance, policies aim to reducing ambient NOx and SO2 need to consider the nature and magnitude of the so-called ‘climate penalty’, as these pollutants also hold the ability to cool down the climate.
Now is the time to act. Ambitious policy responses and strong political will to tackle climate change could improve the air quality, bring enormous benefits to health of the people and ecosystems, and create a sustainable, more liveable planet for future generations to enjoy.