Table 1.

Description of sample size.

Macro-region	Region	No. of municipal districts	No. of air monitoring stations
Northern	Emilia Romagna	57	111
	Friuli Venezia Giulia	24	38
	Liguria	21	56
	Lombardy	86	116
	Piedmont	30	45
	Trentino-South Tyrol	20	30
	Aosta Valley	6	10
	Veneto	43	67
	Total	287	473
Central	Abruzzo	8	13
	Latium	21	42
	Marches	20	31
	Tuscany	36	71
	Umbria	8	21
	Total	93	178
Southern	Basilicata	7	12
	Calabria	7	9
	Campania	6	20
	Molise	6	11
	Puglia	26	61
	Sardinia	26	65
	Sicily	25	69
	Total	103	247
Total		483	898