Why air quality is about more than just cutting carbon

Cutting carbon will improve health, but when it comes to poor air quality, other pollutants are also responsible. How do they contribute to respiratory and heart conditions in towns and cities, how are they generated, and what action is being taken to cut them out? We share the findings from a webinar.

Enda Hayes is Professor of Air Quality & Carbon Management and Director of the Air Quality Management Resource Centre at the University of the West of England, Bristol. Prof Hayes explains, ‘when we think about traditional air pollution, the pollutants in our urban environment that interest us are nitrogen dioxide and particulate matter. Nitrogen dioxide predominately comes from road traffic, whereas particulate matter has a number of different sources such as traffic, industrial sources and domestic solid fuel burning. Depending on where you are around the world, there are other concerns as well, such as ground-level ozone, sulphur dioxide, and carbon monoxide.’

Measurement methods and standards vary

Prof. Hayes explains that there several different ways to measure these pollutants: ‘We have reference methods – which are the best but are quite expensive to maintain and run. We also have passive methods such as diffusion tubes that we can use for nitrogen dioxide. What we are seeing now in the air quality profession is a growing number of low-cost sensors that can be used for engagement programmes. While there are some question marks over the robustness of their data, they are fantastic tools for empowering and engaging the public in the air quality debate.’

The World Health Organization (WHO) has health-based air quality guidelines (AQGs) for different pollutants. At the same time, each country sets its own air quality standards and objectives, but these are often less ambitious than the WHO guidelines. For example, since 2021 the WHO’s annual mean AQGs for nitrogen dioxide and PM10 (one kind of particulate matter) have been 10µg/m3 and 15µg/m³ respectively. In the UK, though, the annual mean air quality objective is 40µg/m3 for both pollutants.

Pollution presents health threat in multiple ways

Dr Shyamala Rajan, National Director of Policy, Healthy Air, at the American Lung Association, notes: ‘There are conventional pollutants and then we have carbon emissions. Carbon dioxide and methane are climate change drivers, which have a significant impact on human health in multiple ways. We consider climate change to be a health emergency.’

For example, climate change is driving more frequent and extreme wildfires that generate large amounts of particulate matter. This then causes or exacerbates a variety of respiratory, cardiovascular, developmental, neurological and immunological illnesses, including asthma and lung cancer, as well as increasing the risk of heart attacks.

Air pollutants have also been finding their way into the food chain. ‘A prime example of this would be mercury, a toxic air pollutant that accumulates in fish and other aquatic animals that are sources of food,’ says Dr Rajan. ‘Another more recent example is airborne microplastics, which have been found in human lung tissues and are now prevalent in both terrestrial and aquatic food systems.’

She adds: ‘All of us are affected by air pollution to a different degree. The most vulnerable populations are children, because their lungs are still developing; the elderly, because their lungs are not so robust; people with existing medical conditions, such as respiratory illnesses; pregnant women; and people who spend a lot of time outdoors.’

Cities take action despite political constraints

According to Prof. Hayes, we are excellent at diagnosing the problem but struggle to solve it. There are several reasons for this.

• A lack of political will, because of the nature of the four- to six-year political cycle. The interventions we need to successfully address air pollution and work towards net-zero carbon are not easy to achieve, and politicians perhaps shy away from that.
• Insufficient funding, given that many interventions can be quite expensive for cities and local authorities to implement.
• There is also an issue with taking responsibility for air pollution responses at a local authority level.

There are also positive examples. For instance, Paris is doing great work in encouraging people to walk, cycle and make use of public transport rather than drive. In the UK, we are also seeing the introduction of clean air zones, from which certain types of car and other vehicle are restricted. In terms of research, the American Lung Association publishes several research and analysis reports on air quality issues affecting human health, such as State of the air and Zeroing in on healthy air.

Deprived areas suffer disproportionate impact

Dr Rajan points out that major highways, power plants and industrial clusters are often located in economically deprived areas, leading to poor local air quality. She says: ‘In the US there is a history of red-lining, in which communities of colour were systematically denied loans and investment, among other economic opportunities. These red-lined urban areas tend disproportionably to affect people of colour and the economically deprived, and normally have poorer air quality. The richer you are, the more likely you are to create pollution, but the less likely you are to be exposed to it; and conversely, the poorer you are the less likely you are to create pollution, and the more likely you are to be exposed to it.’

Indoor air faces distinct quality issues

Chris Rush, Associate Director and Air Quality Group Lead at engineering consultancy Hoare Lea, states that the ‘outdoors affects the indoors massively, to the point that they are intrinsically linked – needing to be considered together to improve air quality.’

Depending on the location of development in relation to sources of pollution such as roads, relying on distance alone to protect the end user by allowing for the pollutants to disperse may have limited potential, especially in an urban environment where space is restricted. ‘From an intervention perspective, what can be done in that case?’ asks Rush. ‘Well, the building itself can protect the end user from outdoor pollutants by including mechanical ventilation systems.’

Older buildings present a challenge where no such measures have ever been installed. In these cases, external pollutants will come directly inside, resulting in the same concentrations indoors as outdoors for certain pollutants.

Pollutants also arise indoors, with sources including particulate matter in the form of dust from rugs and carpets, heating systems when first turned on, and ventilation systems that are not serviced effectively. Homes meanwhile can be affected by cooking activities such as burning toast or using gas stoves, gas appliances and wood burners, all of which significantly increase the amount of particulate matter and nitrogen dioxide. Volatile organic compounds (VOCs) are another pollutant specific to the indoor space, originating from cleaning products and materials such as paints, mentions Rush.

In response to a question about how indoor air quality can be improved, Rush explains: ‘We need all parts of the design team – such as architects, sustainability consultants, air quality consultants and mechanical engineers – through to those charged with operating these buildings to help ensure the benefits of clean air.’

Societal innovation proposed to benefit health and environment

Prof. Hayes explains: ‘What I would like to see is more focus on people, on health, on different populations and on understanding exposure signs and the impacts of deprivation. There should be more focus on societal innovation, realising that air quality is about health risk and health management, and bringing more of that science and knowledge into the way local authorities and cities manage their environments. Air quality management is not new; but what we see now is an obsession with technocentric solutions and the need for technical innovation. We need to marry that with societal innovation and understand that it is about people, about their behaviours and practices.’

Rush agrees, and highlights that we need to act now: ‘There is no single action that will solve the issue of poor air quality. Several solutions coming together through a collaborative and consistent approach are required for the ambition of clean air to be achieved and – most importantly – maintained.’