Also incidentally the existence of trends in the time

The annual mean PM10 concentrations were calculated from the daily average values, and ranged from 8.5 μg m− 3 (Izki in 2010) to 46.0 μg m− 3 (Nautica in 2006), whereas the averages for the whole period ranged from 10.8 μg m− 3 (Izki) to 35.1 μg m− 3 (Zelaieta). Maxima of the daily average concentrations in the period ranged from 46.0 μg m− 3 (Valderejo) to 209 μg m− 3 (Arrasate).