The symposium comprised three sessions, focusing on: 

1. Global/Outdoor Air Quality-Climate Interactions; 

2. Convolved Health Impacts of Air Quality and Climate; and

3. Synergies and Trade-offs in Pursuit of Clean Air and Net Zero in Buildings.

In our first session, chaired by Dr James Levine from Cambridge Zero, we explored how air quality and climate are closely connected. Professor Alex Archibald, from the Yusuf Hamied Department of Chemistry, explained how rising temperatures and changes in humidity can affect the levels of air pollutants like ozone, which can irritate our lungs. He also discussed how climate change can influence plant life, which in turn can change the makeup of the air we breathe.

Climate refers not only to the typical weather expected in a place at a certain time of year, but also encompasses broader patterns, such as the direction and strength of winds that transport air over long distances. These wind patterns are important because they help determine which areas end up being affected by air pollution, even if that pollution comes from far away.

Dr Irene Dedoussi, from the Department of Engineering, explained how emissions from aviation can have effects far from where the planes fly. She also discussed how climate change could shift these “source-receptor” pathways, meaning that pollution could end up in new places over time.

In the second session, chaired by Dr James Smith from the Department of Public Health and Primary Care, the focus turned to how air pollution and extreme heat combine to affect our health. This is especially common in cities, where high-pressure weather can lead to both very hot conditions (made worse by the urban heat island effect) and still air, which allows pollution to build up.

Road traffic is the biggest contributor to outdoor air pollution in cities. While electric vehicles (EVs) can play an important role in reaching Net Zero, provided their entire life cycle and the electricity they use are carbon neutral, they only go part of the way toward solving our air quality problems.

60% of the tiny harmful particles (PM2.5) from vehicles no longer originate from the exhaust. Instead, they come from brake dust, tyre wear, and the breakdown of road surfaces. These sources of pollution aren’t reduced by switching to electric cars and may even get worse, since EVs are often heavier due to their large batteries.

Dr Robert Rouse, from the Department of Applied Mathematics and Theoretical Physics, spoke about how climate, and in particular extreme heat, can directly affect our health. His research focuses on developing new ways, using statistics and machine learning, to better predict when and where people are likely to be exposed to dangerous levels of heat. Crucially, he’s working on improving forecasts of exposure to heat that can be life-threatening, not just uncomfortable.

In the final session, chaired by Dr James Levine, the focus turned to indoor environments and the difficult choices we sometimes face when trying to achieve both clean air and Net Zero goals.

Dr Ronita Bardhan, from the Department of Architecture, explained how important good ventilation is for reducing harmful indoor air pollutants, especially the tiny particles (PM2.5) released during cooking. This is particularly urgent in places where people regularly cook indoors over open fires, where daily indoor exposure to PM2.5 can be ten times higher than daily outdoor exposure.

Following this, Dr Lia Chatzidiakou, from the Yusuf Hamied Department of Chemistry, introduced new tools and techniques for measuring people’s personal exposure to indoor air pollution. Her work aims to help design indoor spaces that reduce this exposure in ways that respect local cultures and traditions.

Something as simple as opening a window can help improve indoor air quality, and doesn't increase energy use. But mechanical ventilation systems, while more effective, can come with a trade-off: if they require extra energy that doesn’t come from renewable sources, they may work against our climate goals.

Professor Peter Guthrie, from the Department of Engineering and Chair of the National Engineering Policy Centre’s report on healthy and sustainable buildings, highlighted other trade-offs we must consider. Ventilation is crucial—not just for clearing out air pollution, but also for reducing the spread of airborne diseases like COVID-19. It also helps prevent damp and mould, both of which can harm health. At the same time, efforts to make buildings more energy efficient, such as by sealing them more tightly, can limit airflow.

This creates a challenge: how do we design heating, ventilation, and air conditioning (HVAC) systems that keep us healthy while also being sustainable? The problem is even bigger when we consider that around 80% of the buildings we’ll be using in 2050 already exist today and will need to be retrofitted.

At the University of Cambridge, the Clean Air research community brings together experts in health, environmental science, and engineering to tackle these complex challenges. As we reflect on the insights shared and gather feedback from attendees, it’s clear this interdisciplinary approach has real potential to make a difference, for both people and the planet.

In response to the initial question, ‘Will Net Zero (Alone) Deliver Clean Air?', the answer from a human health perspective is ‘No’: Net Zero is a necessary, but insufficient, condition for Clean Air, and whole systems approaches are needed to realise both. 

(Editing by Annie McKenzie)