The contribution of wildfires to PM2.5 trends in the Mediterranean and their relation to national-level extreme events

Air quality across Europe has generally improved in recent decades due to stricter regulations. However, the European Environment Agency (EEA) also highlight that the number of premature deaths in Europe due to air pollution is still far too high. Moreover, the impacts of wildfire smoke, often coupled with the combined effects of droughts and heatwaves in the region, are often disregarded. With the projected rise in wildfires due to climate change, wildfire smoke's contribution to air quality degradation in the Mediterranean is likely to grow in the coming years.This study focuses on the Mediterranean region, relying on air quality data (specifically particulate matter PM2.5) obtained from the Copernicus Atmosphere Monitoring Service (CAMS) European reanalysis from 2013 to 2023 at 0.1 resolution to assess the impact of wildfire smoke on PM2.5 concentrations. Additionally, meteorological data from ERA5 were utilized to identify heatwaves and droughts (as depicted by the Standardized Precipitation-Evapotranspiration Index, SPEI). Our findings suggest that wildfire smoke has substantially influenced PM2.5 trends across the Mediterranean. This influence could be eroding past air quality improvements, potentially equivalent to several years of progress lost.The intersection of wildfire pollution and extreme events presents a critical public health challenge, highlighting the need to address these complex relationships when developing comprehensive strategies and regulations to protect human health and well-being in the context of a changing climate.This work was funded by the Portuguese Fundao para a Cincia e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC) UIDB/50019/2020 (https://doi.org/10.54499/UIDB/50019/2020), UIDP/50019/2020 (https://doi.org/10.54499/UIDP/50019/2020) and LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020). This work was performed under the scope of project https://doi.org/10.54499/2022.09185.PTDC (DHEFEUS) and supported by national funds through FCT. DL and AR acknowledge FCT I.P./MCTES (Fundao para a Cincia e a Tecnologia) for the FCT https://doi.org/10.54499/2022.03183.CEECIND/CP1715/CT0004 and https://doi.org/10.54499/2022.01167.CEECIND/CP1722/CT0006, respectively.