Black lines refer to overall data while colored plots refer to seasonal aggregations. Vertical bars denote the 95% confidence level. The x-axis indicates the N_1–10 threshold values (lowest boundaries) for dust outbreak periods for which ΔO₃ was calculated. Squares denote ΔO₃ calculated for days with African air masses without significant dust loading. At lower N_1–10, ΔO₃ appeared to be almost unaffected by the mineral dust; moving towards higher dust loading (i.e. higher N_1–10) ΔO₃ strongly decreases.