Harmonized source apportionment of atmospheric particulate matter (PM10
) at 5 EU cities (Barcelona, Florence, Milan, Athens and Porto) reveals that vehicle exhaust (excluding nitrate) plus non-exhaust contributes 16–32 % to PM10
and 15–36 % to PM2.5
. Secondary PM represents 37–82 % of PM2.5
. Biomass burning varies from < 2 to 24 % of PM10
, depending on the residential heating fuel. Other sources are local dust (7–19 % of PM10
), industries (4–11 % of PM10
), shipping, sea salt and Saharan dust.