Poor air quality, including high levels of PM, is a prominent health risk worldwide. Establishing cause and effect for many of the associated health impacts of air pollution is difficult, as there are many contributing factors. However, one of the possible pathways of the acute health
effects — arising from PM exposure in the human body — is suggested to be inflammation in the heart and lungs. Inflammation (chronic and acute) is an immune reaction to pathogens, and PM with a high ‘oxidative potential (OP)’ — a particle’s ability to react with other molecules to start a cascade of reactions—may induce this process — increasing the risks of cardiovascular and pulmonary disease.
Europe has many measures in place to reduce air pollution. The National Emissions reduction Commitments Directive imposes reduction obligations for emissions of five key air pollutants, including PM, that harm human health; other legislation targets specific sources, such as air pollution from transport, agriculture and industry; two air quality directives set pollutant concentration thresholds; and the proposed 8th Environment Action Programme has a zeropollution ambition (including for air pollution) as one of its priority objectives, while also defining a route to achieving greenhouse gas emission reduction targets across the region.
PM comes in different size categories (both PM10 and PM2.5 are reviewed in the study), from different sources, with a range of constituent molecules, and with an OP that varies according to source. Currently we have a limited understanding of which sources emit PM that causes an acute oxidative response in the human body; this study aims to identify which sources in Europe contribute most to emissions of PM with a higher OP, so steps can be taken to reduce these emissions to improve air quality and human health.
The researchers combined air quality data from nine sites in Switzerland and Lichtenstein with continent-wide modelling to determine the primary and secondary sources of PM and OP in Europe. They analysed site samples for chemical composition, source and OP content of all PM types (elements, and primary and secondary organic aerosol). The analysis showed that the mass of PM in the air at the sample sites was controlled by soil material and secondary aerosols from the atmospheric oxidation of inorganic and biogenic — from biological sources — organic precursors. In contrast, PM with the highest OP came from two anthropogenic sources: firstly fine PM less than 2.5 micrometres (μm) in diameter — as secondary organic aerosols form in the air from people burning biomass (i.e. from logs) in their homes; secondly, non-exhaust emitted transition metals, such as copper or chromium, as coarse PM greater than 10 μm in diameter, from vehicles ¬(i.e. from brake wear).
The latter type of OP PM was particularly high in cities, where vehicular activity is highest. The researchers’ model matched well with data gathered on OP PM from the field sites. The researchers conclude that strategies which solely aim to reduce the overall mass of PM in the air may not reduce the concentration of PM with high OP. This type of airborne pollution may be linked to a range of negative health impacts, indicating it may be more effective for regulations to target specific major sources of OP-high PM.
Source – European Commission