Airborne dust, originating in Africa's Sahara Desert, is descending on England, and government officials have warned those with breathing problems to avoid strenuous activity. Britain's Department for Environment, Food and Rural Affairs said certain areas would experience a rating of 10 on its one-to-10 scale of air cleanliness Tuesday and Wednesday. When levels reach seven to nine, adults and children with breathing problems and adults with heart problems are advised to reduce exertion. The elevated pollution levels are brought by a combination of southeasterly wind, the continental air flow and dust blown into the atmosphere from the Sahara Desert. Last weekend many people across Wales and southern England, including Prime Minister David Cameron, found their cars coated with a layer of red dust. Britain's Norfolk region is expected to experience the highest level of air pollution Tuesday, as will East Anglia and the Humber region. Meteorologists expect "high" or "very high" levels across England and Wales Wednesday. It is expected to diminish by Friday.