Getting to the roots of a global health problem

Mr. El Haddad, for its 20th anniversary, the journal Atmospheric Chemistry and Physics asked 20 leading atmospheric researchers to write an article about what they see as the biggest challenges in their field now. What was your answer?

Imad El Haddad: Our group pointed out that the existing regulations and laws for reducing particulate pollution may no longer be sufficient. Particulate matter can be described as tiny particles suspended in the air.

So, these rules have not led to an improvement in air quality?

Yes, they have. Regulations in Europe and the U.S. have significantly reduced particulate pollution from industrial and traffic emissions. However, the issue isn’t just the quantity of particles in the air, but also their chemical composition. For example, breathing exhaust fumes behind a truck is vastly different from inhaling fresh, salty air at the beach, even if the particle levels are similar. That's why it’s crucial to distinguish which types of aerosol particles are most harmful. This distinction is increasingly important as global warming is causing a rise in natural particulate matter.

What kind of particulate matter comes from natural sources?

These particles include dust from deserts and soot from forest fires. Additionally, emissions from plants releasing hydrocarbons like terpenes are increasing due to climate stress. It is crucial to quantify these particles and assess their health impacts, especially in developed countries, where their contribution is becoming more prevalent compared to anthropogenic particulate matter emissions. In contrast, in developing regions such as Eastern Europe, Asia, and Africa, anthropogenic emissions remain the primary concern. Globally, particulate pollution still causes around seven million deaths each year, with 90% of those occurring in China and India. 

Doesn't the size of particles also play a role, because smaller particles can penetrate deeper in the lungs?

That’s right, particle size is crucial—smaller particles, especially those under 2.5 micrometres, can penetrate deeper into the lungs and thus pose significant health risks. However, size is closely linked to composition. By understanding the chemical makeup of particles, we can also estimate their size. Chemical composition also gives us information about the sources: For example, sulphate comes from power plants, while nitrate is from traffic. This is why targeting chemical composition in regulations is so important— so we can address the causes of pollution. This way, we can tackle the problem at its root and may have to invest less money in medicine to deal with the consequences. Especially since expensive medicine is not equally accessible to everyone. Particulate regulations, on the other hand, help everyone.

Is this social aspect also a motivation for you to conduct this research?

Absolutely. The social dimension is a key driver of my work. By deepening our understanding of the composition of particulate matter, we can improve public health and well-being, particularly by preventing diseases early on through cleaner environments for all. That is why we focus on addressing root causes like air pollution. We also conduct significant research in places like India, particularly in Delhi, a city of over 20 million people where air quality can be dangerously bad. At times, particulate levels exceed WHO-recommended limits by as much as 15 times. Our research shows that much of this pollution comes from organic compounds released by incomplete combustion. By understanding these sources, we can work towards solutions that protect vulnerable populations from the harmful health impacts of air pollution.

Were you able to identify the sources?

Aside from traffic and agricultural burning, a significant source of organic emissions in India is household combustion. Many people, due to poverty, burn whatever they can find—such as dried cow dung—for cooking or heating during the winter. These fuels burn inefficiently, leading to high emissions of organic compounds.

How could this problem be solved?

As is often the case, the solution requires financial investment. Gas stoves or electric cars, for example, remain too expensive for most people in India. Here it is crucial that strategies to reduce air pollution also benefit the climate. Currently, the carbon footprint of the average Indian is five times lower than that of an average European. Given India’s large population, it is vital that the energy sector develops sustainably to improve both air quality and climate conditions. This requires us to examine the energy-air quality-climate-health nexus as an interconnected whole. Strong collaboration between global and local scientists, along with substantial financial support, will be key—especially as the benefits of a solution extend to the entire world.