TEN years ago parents were rushing to the laboratories at University College Cork with samples of water their children had played in and milk that they had drunk. They wanted them checked.
A Soviet nuclear reactor at Chernobyl had exploded and radioactive material had drifted across Europe to come down in rain showers on Irish soil.
"People were bringing water samples and saying their children had been swimming at Douglas. They wanted to know if they were in danger. They were panicking, understandably," said Dr William Reville, a lecturer in biochemistry.
"No country in Europe was prepared to deal with what happened," he continued. "It was unbelievable. This was the accident that could not have happened but it did and we were not prepared."
He said the levels remained acute for two weeks.
The explosion in Ukraine happened on Saturday April 26th. The first indication of radioactivity came on Friday May 2nd from an air filter sample collected at Glasnevin, Dublin.
Widespread radioactive contamination was detected around Ireland in the following days, with deposits heaviest in the midlands, Border areas and Ulster. There were reports that radioactivity around Dublin increased by 30 per cent.
Much of the contamination was the result of heavy rain, which washed radioactive material out of the atmosphere and into the soil. The most significant elements were iodine 131, caesium 134 and caesium 137.
The plume dissipated around May 5th, when a westerly wind from the Atlantic turned the cloud back towards Europe.
Prof Ian McAulay, associate professor of physics at Trinity College Dublin, said the radiation dose to Irish people was overestimated.
"The average dose to the Irish people was estimated at the time as about 0.1 millisievert. I would now consider this to be an overestimate. There were no detectable radiation effects on health," he said.
The Radiological Protection Institute of Ireland estimates that global fallout and nuclear discharges currently account for 0.3 per cent of radiation absorbed by the Irish population, compared with about 90 per cent from natural sources.
But Dr Mary Dunphy, formerly of the Irish Medical Campaign for the Prevention of Nuclear War, still believes adverse health effects did occur as a result of the fall out.
She said it was impossible to prove because no base line - such as a register of miscarriages - existed before Chernobyl. In 1986 her organisation advised young children and pregnant women against drinking fresh milk and suggested intervention stocks of pre Chernobyl dairy products should be released.
The Nuclear Energy Board, which later became the RPII, saw no need for such action. It began monitoring milk on Sunday May 4th, almost 48 hours after the plume had reached Ireland.
Readily concentrated in milk, radioiodine accumulates in the thyroid gland in the body. This in turn concentrates the radiation dose delivered to the thyroid.
The highest radioiodine level was detected on May 5th in Kilkenny when 441 becquerels per litre (bq/l - a becquerel is a measure of radioactivity) were recorded.
By May 13th this had fallen to 30 bq/l as radioiodine breaks down rapidly. But traces of caesium - which breaks down much more slowly - in the milk lingered until at least October.
The assistant chief executive of the RPII, Mr John Cunningham, said it set a limit of 500 bq/l of milk after the accident, and this was not exceeded.
"I would say that if we had a situation where the levels persisted at 300 or 400 bq/l, we would have considered advising restrictions on milk. But that was not the case," said Mr Cunningham.
IN June 1986 the EC ruled that caesium radioactivity in milk must not exceed 370 bq/l kg for milk and baby food and 600 bq/kg of all other foodstuffs.
The RPII advised baby food manufacturers to avoid using more highly contaminated milk powders.
Dried milk powder produced in Munster between April and September 1986 contained peak levels of 1,400bq/kg. On reconstitution this would have meant a level of 150 bq/l. As reconstituted milk, the powder complied with EU regulations.
However, countries such as Mexico and Brazil accused Ireland of sending them radioactive milk powder between 1986 and 1988.
Once tile iodine threat to the milk dissipated, the attention turned to sheep grazing in high areas where the soils are peaty and poor, and so cannot bind radioactive particles.
In Derry and Antrim today there are 57 farms with almost 15,000 sheep still branded "Chernobyl restricted areas". In Wales 220,000 sheep are still affected by restrictions on over 170 farms. In Scotland, 36 farms carrying about 76,000 sheep remain subject to statutory controls because of radiation.
Prof Jack Pearce of the Department of Agriculture in Northern Ireland said all sheep in restricted areas are tested for radioactivity before going on sale. Any sheep with recordings in excess of 1,000bq/kg are not released.
Measurements at these levels are still recorded in the Republic in sheep grazing on high ground in certain parts of the State.
Mr Cunningham said radiation levels sometimes reached heights of 3,000 to 4,000 bq/kg, even higher than those recorded in Northern Ireland, where the maximum was around 3,000 bq/kg.
The areas most affected in the Republic include Donegal, Sligo, Leitrim, the Cooley peninsula, Roscommon, and the Knockmealdown mountains.
The Department of Agriculture said there was no need to restrict the movement of sheep. The RPII says recent readings in butchers' shops show sheep meat, containing less than 10 bq/kg a level which it says poses no threat.
According to the RPII, the number of fatal cancers in Ireland as a result of exposure to Chernobyl will not exceed 25 over the next 69 years. They will not be identifiable among the 450 000 cancers which arise from other causes over the same period.