Five monitoring stations in Belgium exceeded the European ozone information threshold on Monday, including four in Flanders and one in Brussels, according to the Interregional Environment Unit (IRCEL).
The information threshold is set at 180 micrograms per cubic metre of air, the level at which the public must be informed. The higher alert threshold of 240 micrograms per cubic metre was not reached anywhere.
The highest hourly average concentration was recorded in Schoten, at 192 micrograms per cubic metre. In Brussels, Neder-Over-Heembeek peaked at 181 micrograms, while Rixensart in Wallonia reached 169 micrograms.
Ozone levels are expected to remain relatively high on Tuesday, particularly in the north of the country, although no new exceedances are expected.
Peak concentrations are expected to range between 100 and 130 micrograms per cubic metre.
Air quality is expected to improve from Wednesday, as ozone concentrations should fall to between 60 and 80 micrograms per cubic metre, which is considered normal for this time of year.
High ozone concentrations can reduce lung function and cause eye irritation and irritation of the upper airways.
They can also trigger respiratory symptoms and worsen both the severity and frequency of symptoms in people with chronic obstructive pulmonary disease.
People who are particularly sensitive to air pollution, including children, older people and those with breathing problems, are advised to avoid unusual physical exertion outdoors between 12:00 and 22:00 when ozone levels are high.
