Tackling the ‘unknowns’ of air pollution

Improving our understanding of its impact on our health.

Global Air Quality Guidelines

The recently updated Global Air Quality Guidelines (AQGs) issued by the World Health Organisation (WHO) means that air pollution is again at the forefront of our conversations. These new AQGs provide clear evidence of the damage that air pollution has on human health and in lower concentrations than previously understood. They also emphasise that any decrease in exposure in areas with both high and low concentration levels will lead to better health of the population. This means that governments around the world must revise their clean air policies and strategies if they are to implement the lower levels of key air pollutants recommended by WHO. Collectively adhering to the new guidelines could save millions of lives as well as mitigating climate change. National and local policymakers are now faced with the unenviable yet critical challenge of responding.

What exactly is air pollution and what are the main causes?


Air pollution consists of gases, chemicals or particles in the air that can harm the health of humans, other living beings, and the climate. Sources of air pollution are either natural or anthropogenic (caused by humans). Natural sources include natural forest fires and sand dust, and anthropogenic sources include transport, industry, energy, and heating. Particulate matter (PM) is divided into categories by size in microns e.g., PM10, PM10-2.5, PM2.5 and ultrafine (PM0.1) particles. Particulate matter is made of many different components e.g., black carbon or metals such as copper or iron, and can change over time and by places.


Size matters: The size of the particulate determines where in the body they can travel to. Larger particles only travel as far as the nose and throat, but ultrafine particles can reach the bloodstream and therefore all organs in the body.


Air pollution has two kinds of effects: acute effects happening hours or days after exposure to very high concentrations, and chronic effects that happen after years of exposure, even at low levels. The current worldwide public health burden of air pollution is driven by long term exposures.

Improving our understanding

While we understand a lot about how air pollution affects our health, there are still many unknowns.  In the LongITools project, of which Beta is a partner, researchers are trying to answer some of the unknowns by studying the effect of air pollution, mainly from traffic, and its interaction with other exposures, on cardiometabolic and cardiovascular health. Importantly, the researchers do know that people or populations exposed to air pollution are often living in complex environments, with social and psychosocial disparities, that also include periods of susceptibility during the life-course.


For example, the project is studying the effect of exposure to air pollutants such as PM and nitrogen dioxide (NO2) on the risk of developing and living with obesity. These studies will answer whether the effect of exposure on obesity is independent from other risk factors or is modified through interaction with other related environmental factors, such as noise pollution, food borne and built environment exposures. Critically they must also analyse when and where the risk develops to identify the most vulnerable populations and the opportunity for prevention.


The LongITools project is part of the European Human Exposome Network (EHEN), the world’s largest network of projects studying the impact of environmental exposures across a lifetime – the exposome – on human health. It is vital we understand how numerous environmental exposures, including air pollution, interact with one another to impact our health and wellbeing. LongITools and EHEN aim to do just that.

Acting on the findings

It is important that the LongITools research findings can be turned into action. This is why we are already talking to policymakers about the project’s research – to raise awareness of the unknowns its research questions hope to address. One of the ways Beta is doing this is by holding regular policy forums on different topics relating to the research.


During our recent LongITools policy forum on air pollution, Dr Kevin Cromar, program director at the Marron Institute of Urban Management, New York University, shared his experience of working at the interface of scientific research and public policy. He explained the importance of considering the health risks that occur due to both long- and short-term exposures when designing solutions to reduce harmful emissions. Although air pollution affects all of us, ambient concentrations can vary dramatically within the same airshed, with hot-spot locations of elevated pollutant concentrations. It is therefore crucial to consider potential environmental justice issues in designing specific remediation policies to address areas with elevated exposure levels.  In the short-term educating people to take protective measures to reduce their own exposure can also be an effective approach to reducing health risks, but risk communication should be secondary to efforts to decrease emissions.


One of the key issues to consider in designing policies to improve air quality is to identify the largest modifiable sources of air pollution, taking into account jurisdictional, technological, and economic considerations. This may or may not include the largest emissions sources overall but will be the sources in which the largest reductions can be realised.  This way of thinking can be greatly enhanced using economic analysis that considers both the costs and the benefits the of proposed policy actions.  They should therefore not only take into account any direct economic benefits, but also consider the health benefits arising from improved air quality, and in some cases can even also include climate related benefits.