The ash cloud looming over Europe as a result of the volcanic eruption in Iceland could be a health hazard if the fine particles in the haze descend below the upper atmosphere, according to World Health Organisation (WHO).
The health agency noted that people with chronic respiratory conditions like asthma, emphysema or bronchitis may be more susceptible to irritation if ash is in the lower atmosphere in high concentrations.
"Particulate matter is identified according to its diameter. The small particulates less than 10 microns in size are more dangerous because they can penetrate deeper into the lungs," said Maria Neira, Director of Public Health and Environment Department at WHO.
So far, it has been estimated that about 25 per cent of the particles are less than 10 microns in size.
"Since the ash concentration may vary from country to country depending on the wind and air temperatures, our advice is to listen to local public health officials for the best guidance for individual situations," said Neira.
"If people are outside and notice irritation in their throat and lungs, a runny nose or itchy eyes, they should return indoors and limit their outdoor activities," she added.
Today, the volcano erupted again to send tremors over Iceland.
In case of increased air pollution, WHO advised normal precautions to avoid strenuous exercise by people with asthma and respiratory symptoms.
"At that point, WHO might recommend that people stay indoors as much as possible, and if they did go outdoors, people with respiratory problems should wear a protective mask," said Daniel Epstein, a WHO official.