Ashes to ashes: A car in Iceland which has been coated in dust after the volcano eruptionPeople were today warned to stay inside if the ash from the volcanic eruption in Iceland settles on the ground.
In a extraordinary move, the World Health Organisation (WHO) said they did not know the exact risks presented by the cloud, which is currently moving south across the UK.
But David Epstein, a spokesman for the UN agency, said the microscopic dust is potentially dangerous to people if it starts to 'settle' on the earth.
'We're very concerned about it,' he added. 'These particles when inhaled can reach the peripheral regions of the lungs and can cause problems - especially for people with asthma or respiratory problems.'
Mr Epstein said for the most part the cloud remained high in the atmosphere. 'But when they do settle ... we would recommend that people stay indoors as much as possible.'
'Those who venture outside might want to consider a mask.'
British health officials have limited themselves to less strident advice, instead stating that only people with breathing difficulties should stay inside if the ash settles.
Lunar landscape: The ash cloud is now over Britain and health officials have warned people to stay indoors if the dust starts to settle on the groundDust has fallen in northern parts of Britain, including Shetland and Aberdeen, and is expected to progress southwards later today.
It has already blanketed the ground in parts of rural southern Iceland. The ash is not toxic.
Last night, health bosses in Britain said that people with breathing conditions should stay inside
The Health Protection Agency (HPA) said the ash should not cause serious harm but could cause irritation, particularly to those with respiratory conditions.
It advised people with conditions including asthma and chronic bronchitis to carry inhalers and medication with them and those who noticed symptoms, including itchy or irritated eyes, runny nose, sore throat or dry cough, should either return to their homes or 'limit their activities outdoors'.
But the Met Office said any ash which did reach ground level would be barely visible and the public should not be concerned.
The HPA said weather patterns indicated a 'small fraction' of the volcanic plume in the UK's airspace, which could include low levels of sulphur dioxide, was likely to reach the ground
Eerily quiet: A near-deserted Terminal Two at Birmingham International Airport where passengers stayed away
Exhausted: Passengers stranded at Stansted resort to sleeping on the floor after all flights were cancelled for a second dayIn a statement, the HPA said: 'It is important to stress that the concentration of particles which may reach ground level is likely to be low and should not cause serious harm.
'If people are outside and notice symptoms such as itchy or irritated eyes, runny nose, sore throat or dry cough, or if they notice a dusty haze in the air or can smell sulphur, rotten eggs, or a strong acidic smell, they may wish to limit their activities outdoors or return indoors.
'Those with existing respiratory conditions such as chronic bronchitis, emphysema and asthma may notice these effects more than others and should ensure they have any inhalers or other medications with them.
'Any such health effects are likely to be short term. The Health Protection Agency, Health Protection Scotland and the Met Office will continue to monitor the situation and issue any further advice or updates as necessary as the weather changes.'
'Low concentrations of volcanic dust, which may contain low levels of sulphur dioxide, are also expected to ground with the plume, although this is not expected to be a significant threat to public health,' the spokesman added.
Met Office forecaster John Hammond: 'There's always been a small chance of it reaching the ground.
'Over the next few days or so, with winds as they are, there is a chance we will see some small deposits but these will be quite difficult to see.
'It might be easiest to see anything that comes out of the sky on cars because the amounts will be very small.'
source: dailymail