Scientists with the European Union's climate monitoring service warned of "very high ozone pollution" for a large region of Europe stemming from heatwaves.
"Very high levels of ozone pollution in southern Europe caused by the heatwave could now affect northwestern regions in the coming week," said a statement on Tuesday by the Copernicus Climate Change Service (CAMS).
Scientists anticipate that after "extremely high surface ozone pollution" was observed across western and southern Europe, ozone pollution might affect the "northwestern regions."
"In mid-July, daily maximum values of surface ozone, which peak during the middle of the day, reached unhealthy levels in Portugal, Spain and Italy with some locations measuring in excess of 200 μg/m3," it said.
Ozone pollution is expected to reach its highest in Europe on July 18 - 20, according to CAMS scientists.
While the heatwave in Spain and Portugal killed more than 330 people last week, the UK recorded its hottest temperature ever Tuesday.
In southwestern France, wildfires have devoured thousands of hectares of forests and lands.
