Preparing for the worst while hoping for the best

News in August of the latest nuclear accident - at a power generation facility in Mihama, Japan - was greeted with considerable concern. It is precisely the type of incident that Brenda Howard - a radioecologist and head of research at the Centre for Ecology and Hydrology at Lancaster in the UK - is ready to respond to. "When there's an accident we have to move fast, to know if there is a radiation leak, and which farm products are going to cause concern and pose a potential risk to human health", she says.

Thankfully there was no radiation leak from the ruptured turbine pipe in Japan. However, with the increasing number of nuclear power reactors worldwide, and more than 18,000 radioactive sources in use in healthcare and in industry, the possibility of accidental release of radioactive substances - radionuclides - is ever present.

"Radioecology is the understanding of how radionuclides move in the environment", says Howard. "Through air, water or soil they can very quickly find a pathway, via farming and food, to humans. The reason that so many people developed thyroid cancers after the Chernobyl accident in the former USSR in 1986 was from radioiodine that immediately got into leafy vegetables and the milk of dairy cows."

credit:Dr N.A Beresford

It is possible to block the pathway of contamination via food to consumers provided that farmers are instructed and equipped to adopt appropriate countermeasures. These actions can be as extreme as the immediate prohibition of consumption, or sales, of farm produce but there are other measures that allow farming, and local food production and consumption, to continue. Giving a dairy cow a daily dose of Prussian blue (ferric hexacyanoferrate) stops the absorption of radiocaesium from the gut into the animal's bloodstream. The application of potassium fertiliser to the soil binds and prevents take up of radiocaesium by crops.

Countermeasures - and monitoring to ensure they are in use - may be needed for years. "Radioiodine is shortlived - it has a half-life of 8 days - so within just over a week the problem it presents has already halved", explains Howard. "But radiocaesium, the other major radionuclide released during the Chernobyl accident, has a half-life of 30 years." As a result tens of thousands of farmers from the east Ukraine across north-west Europe are still farming under restrictions, and will continue to do so until radiocaesium no longer presents a threat.

Ensuring that all farmers whose land has been contaminated in the wake of an accident adopt appropriate countermeasures is essential but has proved difficult. The smaller scale, more remote producers are hardest to reach. But, whatever the cost, they all need to receive advice warns Howard. "While the collective farms affected by the Chernobyl release were briefed on the countermeasures and implemented them straightaway, no such effort was directed at the hundreds of private farmers, some with only one cow." Many consumers needlessly received high doses of radioactivity from the milk they drank.

Accidents are not the only source of radioactive pollution. Howard and her team are working to understand the contamination caused by nuclear weapons testing. "Kazakhstan was one of the two major test sites for the former USSR", she says. "Many bombs were exploded in the atmosphere as well as in boreholes and tunnels in the mountains and there was considerable contamination of the environment, the soil and vegetation. Now that area is being used by Kazakh farmers for grazing sheep and horses. Horse meat is very important in the local diet. So it is important to know what contamination there is and how it transfers to the livestock. If the land is to be used sustainably for farming we have to be sure that for all the radionuclides and all the pathways (via grazing or in fodder crops or in hay) we know what levels are going to end up where."

The need for further research, according to Howard, is urgent. "So much of what we understand now about how to deal with nuclear accidents is based on radiocaesium because that was the major contaminant from the Chernobyl accident. But with nuclear waste - now being produced in power generation in 50 countries worldwide - the radionuclides are different and will all behave differently in different environments. So we have to think of each one separately, how it interacts with the environment and which products it's going to contaminate. We all hope there will never be another incident as serious as Chernobyl but we have to face the undeniable fact: accidents do happen."

Article submitted by Susie Emmett