MODERATE air pollution is set to affect parts of Merseyside tomorrow prompting advice for people with medical conditions to be cautious.
The Department for Environment, Food and Rural Affairs (Defra) has warned people in England to be braced for "very high" levels of air pollution over the next few days.
Defra ranks air pollution from one to 10, with one being the lowest and 10 the highest.
Across most of England and Wales, moderate to high air pollution levels are forecast, with level 4 to 6 (moderate) expected in St Helens.
The elevated pollution levels have been caused by a combination of light south-easterly winds, the continental air flow and dust which has blown up from the Sahara desert, a Defra spokeswoman said.
Health advice states that when air pollution is moderate adults and children with lung problems, and adults with heart problems, who experience symptoms, should consider reducing strenuous physical activity, particularly outdoors.