The eastern region can finally expect fresh air today following days of elevated pollution levels, forecasters have said.
It follows a spell of smog caused by dust sweeping in from the Sahara Desert, and winds being too light to shift pollution from cars and industry in the UK.
Defra – the Department for Environment, Food and Rural Affairs – ranks air pollution from one to 10, with 10 the highest.
While many Norfolk towns were ranked at 10 on Wednesday, a westerly wind had carried much of it out to sea by yesterday lunchtime.
Phil Garner, weather forecaster for Weatherquest, said that most of the smog would have cleared by late this morning due to a cold front coming through from the west.
He added this was bringing fresh air through.
The region's ambulance service received a further increase in calls yesterday evening.
An East of England Ambulance Service spokesman said: 'Although we didn't see any particular increases in calls during the day, we did see a rise of about 7% across the evening - with calls about breathing problems up 17%.
'Norfolk and Hertfordshire both seemed to be particularly affected and staff across the ambulance service worked hard to manage the increase.'
The service also saw an increase in 999 calls of 6% on Wednesday, however, air pollution levels are expected to drop today.
For health advice concerning air pollution, visit the DEFRA website.
In Norfolk the increase was of 25%.
Norfolk County Council said a dozen schools had sought health advice yesterday, and in line with Defra advice were urged to pay particular attention to children with breathing conditions, ensure asthma-sufferers had their inhaler with them and consider avoiding outdoor play.
They also said those with existing health conditions such as heart and lung complaints should avoid strenuous activity.
In Norfolk the only hospital to report a slight increase in admissions relating to breathing and cardiac problems was the James Paget University Hospital in Gorleston, with the other two reporting no change at all.
Sotiris Vardoulakis, head of air pollution at Public Health England's (PHE) centre for radiation, chemical and environmental hazards, said most people will not be affected by short-term peaks in air pollution.
But some groups, such as those with existing heart or lung conditions, may experience increased symptoms.
A poll of 532 asthmatics for Asthma UK, conducted overnight from Wednesday to Thursday. found 30% have suffered an attack as a result of the pollution and 84% reported using their blue reliever inhaler more often than usual.
More than half had avoided going outside and 39% had sought advice about managing their asthma.
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