Lo smog estivo ha fatto al sua ricomparsa a sud delle Alpi quest’anno a causa delle temperature vicine a 30 gradi di questi ultimi giorni. I livelli medi di ozono erano mercoledi elevati, raggiungendo 190 microgrammi per metro cubo a Mendrisio e 192 a Chiasso. Il limite fissato dall’Ufficio federale dell’ambiente è di 120 (valore medio orario). A Lugano-Pregassona si misuravano 166 microgrammi, 140 a Magadino, 144 a Locarno e 90 a Mesocco.
80 giornate di superamento
In concentrazioni eccessive l’ozono nuoce alla salute di esseri umani, animali e piante. Colpita è soprattutto la popolazione attiva all’aria aperta. Il clima più caldo e più soleggiato nella Svizzera italiana, le valli strette e la vicinanza dei centri industriali della Pianura padana favoriscono la formazione dell’ozono. Mediamente il superamento dei limiti avviene 80-90 giorni all’anno.
RedMM/mas
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