An international study, published in the journal Nature, has found cutting pollution from road traffic and wood burning may be the most effective way to reduce the harm from air pollution across Europe.
Rather than just looking at the amount of particle pollution in the air, the research team looked at its toxicity, by measuring the way air pollution samples depleted the natural defences in our lungs. To do this, they collected more than 11,000 pollution samples on filters and placed them, one-by one, into artificial samples of the fluid that lines our lungs. This measurement is called oxidative potential (OP).
Dr Steven Campbell from Imperial College London, who was not part of the study, explained: “Measuring OP allows us to identify the sources of particle pollution that are potentially most damaging to our health. This can guide more efficient and targeted policies to reduce the health burden of air pollution.”
The researchers measured the OP of air pollution particles collected from 43 different locations in six countries.
Dr Gaëlle Uzu from the Institute for Research and Development at Université Grenoble Alpes, said: “Once we reached more than 10,000 samples in my laboratory, I thought that was a good number for statistical power to start thinking about trends. Given previous French campaigns, I also had a feeling that OP would help us to discriminate between different types of polluted environments, but would that be the case at EU scale?”
They found that the toxicity of particle pollution was not the same everywhere. For the same amount of particle pollution, some places had much greater OP than others. Air breathed close to roads was about three times more toxic than that collected in rural areas. Places with the most toxic air were generally in valleys, where local pollution struggles to disperse. OP was also worst in winter, when wood burning added to the pollution mixture.
Sarajevo, in Bosnia and Herzegovina, was one city where all of these factors came together.
Dr Katja Džepina of the Paul Scherrer Institute, Switzerland said: “High OP values in Sarajevo are due to unrestricted burning, mainly wood for heating, and an old vehicle fleet. During the cold winter months, air pollution gets trapped in the Sarajevo valley, leading to some of the globally highest particle pollution and the greatest European OP values in our study.”
In a warning to governments and city authorities, the researchers showed that reducing the amount of particle pollution alone may not reduce its toxicity, unless we also focus on the most harmful sources.
Two examples are Grenoble in France and Berne in Switzerland. Both had successes in reducing the amount of particle pollution in their air, but the toxicity of the particles did not improve. In Berne, some of the measurements of OP worsened.
Looking to the future, controlling traffic exhaust may not be enough to reduce the toxicity of our air. Previous studies found that the OP from tyre, brake and road wear was greater than that from exhausts.
Uzu said: “Our mitigation strategies must be tailored to the type of environment if we are to successfully reduce both OP and the amount of particle pollution.”
