A WARNING has been issued after a toxic smog cloud is heading to the UK - causing problems for asthma sufferers. 

Health experts say the deadly pollution could put thousands of people with health problems at risk. 

The north of the country will be worst affected but the south East of England, including Essex, will also be covered with the huge cloud. 

Pollution in Essex will be level 4 - moderate. 

Defra, which measures air pollution, says when 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.

The warning was issued by the Met Office at 4am today and says there is a northeasterly breeze so the smog should have cleared by Friday afternoon.

Pollution forecast for Saturday is low.