Table 1.

Spanish city, province (PROV), population (POP, on January 1, 2019), and longitude (LO) and latitude (LA) of the air quality stations (QS) selected for the study

SPANISH CITY	PROV	POP	QS	LO	LA
Bilbao	Biscay	346,843	Europa	-2.9024	43.2549
Madrid – capital city	Madrid	3,266,126	Escuelas Aguirre	-3.6823	40.4217
San Sebastián	Gipuzkoa	187,415	Avenida Tolosa	-2.0109	43.3094
Santiago de Compostela	A Coruña	97,260	S. Caetano	-8.5311	42.8878
Valladolid	Valladolid	298,412	La Rubia II	-4.7406	41.6300
Vigo	Pontevedra	295,364	Coia	-8.7421	42.8548
Vitoria	Álava	251,774	Avenida Gasteiz	-2.6807	42.8548