This measure directly affects eight municipalities in the Vallès Oriental region: Granollers, La Llagosta, Martorelles, Mollet del Vallès, Montmeló, Montornès del Vallès, Parets del Vallès, and Sant Fost de Campsentelles. The warning was activated after the daily average PM10 level last Tuesday exceeded 50 micrograms/m3 at five measurement stations within the ZPE.

The stations that recorded these high levels are located in L'Hospitalet de Llobregat (Torrent Gornal avenue), Terrassa (Pare Alegre), and three points in Barcelona (Observatori Fabra, Parc de la Vall d’Hebron, and the Eixample district). The weather forecast indicates that dispersion conditions will not improve significantly, keeping levels high throughout Wednesday.

The preventive warning is the phase prior to a possible environmental episode and aims to reduce pollutant emissions generated by human activities. Consequently, citizens are advised to prioritize the use of public transport over private vehicles.

Furthermore, this phase involves notifying industrial activities, public works, and electricity generation facilities to activate their working protocols. Municipalities are also recommended to halt or reduce activities or construction works that generate dusty materials.