THE ELDERLY, young children and asthma sufferers have been advised to keep indoors during the day as temperatures in Lisbon soared to nearly 100 degrees Fahrenheit (35ºc) last week.
Low lying ozone pollution went beyond safe levels for the first time this year between Thursday and Sunday in Greater Lisbon, while temperatures in the interior and Alentejo reached 40ºc.
The worst place affected by general pollution was registered in Vila Real where ozone levels topped 248 to 258 micrograms per cubic metre according to the Environment Institute.
Ozone (O3), which normally exists in the upper atmosphere, is a powerful oxidant that can aggravate respiratory complaints and cause breathing difficulties. It can also irritate the eyes, nose and cause sore throats.
According to the law, it is a government requirement to issue a public health warning when ozone levels exceed 240mg per cubic metre.