The DGS states that, "due to their greater vulnerability to the effects of this phenomenon", these groups, in addition to following the recommendations for the general population, should, whenever possible, remain indoors and, preferably, with the windows closed.

For the general population, the health authority recommends not making prolonged efforts, limiting outdoor physical activity and avoiding exposure to risk factors, such as smoking tobacco and coming into contact with irritating products.

In a note published on its website, the Directorate-General for Health says that "a mass of air coming from the deserts of North Africa, carrying suspended dust, is expected to cross mainland Portugal" today, and could continue for the following days.

"Poor air quality is expected to occur on the continent, with an increase in the concentrations of inhalable particles of natural origin in the air," it highlights.

According to the Department, this pollutant (inhalable particles -- PM10) has effects on human health, especially on the most sensitive population, children and the elderly, which is why health care should be redoubled during these situations.

In keeping with this forecast, the DGS also recommends that chronically ill patients continue their medical treatments and, in the event of worsening symptoms, contact the Health Line 24 (808 24 24 24) or seek medical care.