The head of the International Civil Aviation Authority says that the organisation plans to convene a group of experts to draw up guidance for the industry in determining what concentration of volcanic ash would deem it unsafe to fly, the Voice of America reported.

Raymond Benjamin's comments, on April 20 2010, came as European airports began gradually resuming flights after a five-day shutdown due to a huge cloud of volcanic ash making its way from Iceland across Europe.

Benjamin said his organisation, which is a specialist UN agency dealing with air safety, held a special meeting on April 19 on the issue of volcanic ash standards. "We are going to convene a group of people - industry, manufacturers, IATA [International Air Transport Association], governments, scientists  - to start working on these standards," he said.

He said no international standards currently exist stating what concentration of volcanic ash could affect a jet's engine. Tiny particles in the ash can cause engines to stall or shut down and do other damage to planes.

Benjamin said the standards would be "guidance material" for countries.

The International Civil Aviation Authority gathers scientific information on volcanic ash at nine centres worldwide, which it then provides to governments. But Benjamin said the decision and responsibility for closing airspace lies solely with individual countries.

Asked if he would fly, Benjamin said he would. "So when you are asking, would you fly? Of course I would fly if the airspace had been re-opened, that means that there is no hazard or risk," he said.

European governments have come in for harsh criticism from groups such as the International Air Transport Association for shutting down airspace after the volcano erupted in Iceland on April 14. Airlines were losing about $200 million a day from cancelled flights and the European economy was suffering staggering losses in lost business.
 
While eruptions from the Icelandic volcano that have disrupted global air travel have recently ejected less ash, that could change at any time, the United Nations World Meteorological Organisation warned on April 20, the UN News Service said.

Regarding public health, the ash has no effect except in the immediate vicinity of the volcano in Iceland, according to the UN World Health Organization.

The WMO said the plume from Eyjafjallajokull volcano was reaching less than 3000 metres, with its whiteness suggesting that it contained mainly steam and little ash. "However, the volcano is liable to revert to explosive eruptions at any time," it said.

The fine ash injected into higher levels of the atmosphere, above 6000 metres, would remain there for some time, as these small particles could only be effectively removed by thunderstorms which were not expected for the next few days.

The particles were slowly descending to lower levels, with measurements showing most ash was between the Earth’s surface and 3000 metres.

The fine particles, if sucked into a jet engine, can erode and destroy fan blades, eventually leading to the engine stalling. They can also ‘blind’ by sandblasting the windscreen, requiring an instrument landing, and damage the fuselage.

The WMO, according to the UN News Service, was working in close co-operation with the UN International Civil Aviation Organisation (ICAO), which runs nine Volcanic Ash Advisory Centres (VAAC) in various regions that issue meteorological warns for aircraft.

As for public health, WHO environmental epidemiologist Carlos Dora told a news briefing in Geneva that the very coarse particles near the volcano in Iceland caused a lot of irritation and people had to take precautions, including using goggles and masks and remaining indoors as much as possible.

In the rest of Europe, the pollution had not arrived at ground level, he said.

There was a very good network of air quality monitoring at ground level in European cities, and so far the range has been within the normal, with no concern for health in European countries.

It was very possible that the plume would disperse in the air without there being any concentration at ground level, he said.