Air pollution from particulate matter remains a major public health issue. While mass concentration levels are already regulated in Europe, the new European Air Quality Directive (2024/2881) now recommends monitoring the oxidative potential (OP) of particles as well. This parameter indicates the capacity of particles to induce oxidative stress in the human body—a key mechanism in the development of respiratory and cardiovascular diseases. However, no limit values have yet been defined for OP. This international study proposes, for the first time on a large scale, exposure scenarios that could serve as a basis for setting future European standards.


The researchers compiled and analysed nearly 11,500 oxidative potential measurements from 43 sites across Europe (urban, industrial and rural). Two standardised methods for measuring particulate oxidative potential (the OP-AA and OP-DTT assays, based on pulmonary antioxidants) were applied. This constitutes the most comprehensive database ever assembled on the subject.

Results underline the importance of reducing emissions from road traffic and wood burning

A strong spatial variability in oxidative potential was observed: urban roadside sites exhibited levels up to three times higher than rural ones. Particles from road traffic and wood burning emerged as major contributors to the oxidative potential measured in the European atmosphere. Simulations show that a reduction of at least 15% in emissions from each of these two sources would be needed to lower average urban OP levels to those observed in the least polluted urban areas. However, to approach World Health Organization (WHO) guidelines (PM10 = 15 µg/m³ annual mean), projected mass concentration values would require a reduction of at least 65% in emissions from traffic and wood burning, respectively.

A landmark study to guide public health policies across Europe

This research provides the first large-scale harmonised database on the oxidative potential of ambient particles in Europe. The study suggests that monitoring oxidative potential, alongside particulate mass concentration, could significantly improve the assessment of population exposure to air pollution and help guide emission reduction policies more effectively. By proposing realistic exposure scenarios, the study lays a scientific foundation for establishing future regulatory values for oxidative potential. It represents a crucial milestone for implementing the revised European directive and shaping public health policies addressing the impacts of air pollution.