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How clean is the air in your city, neighbourhood, or street? Dutch researchers are mapping this out, with and for citizens. They develop new measurement methods, combine them with existing techniques, and create detailed air quality maps at local, regional, and (inter)national levels. Their ambition? To make the living environment healthier through smart interventions.

You probably don't think about it often, but almost every European breathes unhealthy air daily. That has an impact. "Air pollution is one of the biggest causes of illness in the Netherlands and is about as significant a risk factor as being overweight and lack of exercise combined," says Professor Roel Vermeulen. His team focuses on mapping air pollution. "We track the concentrations of substances such as black carbon, nitrogen dioxide, and (ultra)fine particles. Our biggest concern is the ultrafine particles. These can penetrate deep into the lungs and bloodstream, increasing the risk of respiratory, cardiovascular diseases, cancer, and brain disorders."

Capture everything

"To map air pollution, we use models, among other things. We do this because fixed measurement stations can only measure at a few locations," says Jules Kerckhoffs, junior assistant professor at Vermeulen's team. "The National Air Quality Monitoring Network, managed by the , measures the concentrations of certain substances in the air at about a hundred locations in the Netherlands. To get a complete picture of air quality everywhere, we use computational models. We incorporate datasets such as population density and traffic characteristics. But specific and local features of a road, neighborhood, or city also influence air quality. This is where our mobile measurement data comes in."

Let It flow

Since 2019, the research team has had two Air View cars. In collaboration with various partners, such as urban developers, public health organizations (GGDs), companies, and residents, they map air quality in cities. "We've equipped the cars with modern measuring devices that can detect nitrogen dioxide, black carbon, and ultrafine particles every second while driving."

These measurements allow researchers to compare different street types. For instance, variations in traffic speed impact air quality. In Rotterdam, they also examined the influence of roadside trees. The findings? Streets without trees had lower pollution levels than those with trees. The most polluted streets were those where trees were in the middle of the road. Kerckhoffs explains: "Trees hardly absorb air pollution but (especially in summer) reduce ventilation, leading to less dispersion of pollutants. As a result, pollution gets trapped under the trees. While greenery and trees are essential in cities, we need to carefully consider where and how we place them."

Wood smoke in the neighborhood

The researchers are also studying neighborhood-level issues, such as wood smoke. Wood smoke contributes to fine particulate matter in the air, sometimes as much as industry and road traffic. However, its health effects are not fully understood. Kerckhoffs says: "With local measurements in specific neighborhoods, we can better determine the contribution of wood-burning stoves to overall air pollution. The measurement vehicle can distinguish between black carbon from traffic and black carbon from biomass (wood)."

At the city level, the research team investigates major sources of air pollution, such as industry and airports. "In Amsterdam and Copenhagen, we found a significant increase in ultrafine particles around airports," Kerckhoffs notes. "It turned out that even in the city centers, traces of this pollution could still be detected."

The researchers are collaborating with citizens and the municipality of Son en Breugel to assess the impact of Eindhoven Airport. "This airport will close for several months in early 2027, providing us with a unique opportunity to conduct an intervention study. In 2025, we will take measurements in various locations in Son en Breugel and repeat them in 2027 when there is no air traffic."

Citizens play a crucial role

The research team has also launched a large citizen science project: the Exposome Panel Study. Nearly 500 Dutch citizens participate by measuring air quality in and around their homes using fine dust sensors for two weeks each year. Additionally, they keep a diary and fill out a questionnaire. Vermeulen is impressed by the high level of engagement among participants. "It provides a wealth of data and enhances our measurements."

Vermeulen and Kerckhoffs aim to further promote their mobile Air View car and citizen science project. "Air quality in European cities has improved in recent years but still falls short of World Health Organization recommendations. Together with policymakers, companies, and citizens, we want to reduce the negative effects of air pollution and create a healthier living environment."

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