Evaluation of the performance of receptor statistical methods for quantifying desert dust contributions to ambient particulate for health studies and policy

There is a body of evidence on the risk to human health posed by the exposure to desert dust. However, results from epidemiological studies from different regions are inconsistent. Among possible causes of inconsistency is the scarcity of daily desert dust contributions to PM 10 and PM 2.5 levels recorded in populated areas in order to conduct rigorous epidemiological studies, but also the lack of robust and harmonized methodologies to deliver airborne desert-dust concentrations. This study evaluated the performance of the main statistical methods currently used by European countries to estimate the net load of desert dust on PM 10 and PM 2.5 levels during the occurrence of desert dust outbreaks. To this end, long-term data series (2010-2023) on PM 10 and PM 2.5 levels and composition obtained in a regional background (Montseny) and an urban background (Barcelona) monitoring site, in Northeast Spain, were used. The results identify the most appropriate method for determining the regional daily PM 10 background concentration, excluding dust-days. This involves applying a moving 50 th percentile with a 30-day time window to data from nearby regional background environments. Such PM 10 background is essential for calculating the daily net dust contribution (PM 10 net-dust ). However, applying this procedure to data from urban or industrial environments causes an overestimation of PM 10 net-dust values, which intensifies with higher local PM 10 levels. On the other hand, in the case of low PM 10 net-dust values(