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Chernobyl and Fukushima radioactive contamination research unveils future threats

25 March 2014

Professor Tim Mousseau of the University of South Carolina set up the Chernobyl Research Initiative (CRI) 15 years ago to explore the ecological and evolutionary consequences of the radioactive contamination around the Chernobyl nuclear power plant in Ukraine, scene of the 1986 meltdown and radiation release.

Wildfires around Chernobyl could cause further contamination
Wildfires around Chernobyl could cause further contamination

With frequent collaborator Dr. Anders Pape Møller of the University of Paris-Sud, the CRI began formal research activities in Ukraine in 2000, Belarus in 2005, and Fukushima, Japan, in July 2011, four months after the earthquake and tsunami there also caused a meltdown and massive radiation release. To date, the group has conducted more than 30 research expeditions to Chernobyl and 10 expeditions to Fukushima.

Their research suggests that many species of plants and animals experience direct toxicity and increased mutational loads as a result of exposure to radionuclides stemming from the Chernobyl and Fukushima disasters. In many species, data suggests that this mutational load has had dramatic consequences for development, reproduction and survival, and the effects observed at individual and population levels are having large impacts on the biological communities of these regions.

Key results published in 2013 include the discovery of tumours, cataracts and damaged sperm in birds from high radiation areas of Chernobyl, and impacts on biodiversity in Fukushima.

These two disasters differ in the time since the events, and the amount and diversity of radionuclides that were released, although the predominant source of radiation is caesium-137 in both locations.

A recent paper has shown that radioactive damage to microbes around Chernobyl slows decomposition of plant matter, with the potential for future contamination outside currently affected zones a possible result.

On a visit to the Red Zone, the most contaminated area near the nuclear plant, Mousseau and Møller noticed that trees on the ground killed by the initial blast were still largely intact, when they would have decomposed in a normal environment.

In an effort to assess the rate of plant decomposition relative to background radiation, the researchers placed hundreds of mesh bags containing uncontaminated leaf litter in different areas representing a range of radioactive contamination.

Nine months later, analysis of the samples showed that the degree of decomposition was inversely related to the level of radioactive exposure. In the most contaminated areas, decomposition was 40% less than in control regions with normal levels of background radiation.

The result is a build-up of biomass that presents not just a local wildfire hazard, but could potentially spread further radioactivity if carried aloft by smoke.

"There’s been growing concern by many different groups of the potential for catastrophic forest fires to sweep through this part of the world and redistribute the radioactive contamination that is in the trees and the plant biomass," Mousseau said. "That would end up moving radio-caesium and other contaminants via smoke into populated areas."

Other highlights from research published by the CRI include the following:

• Population sizes and numbers of species (i.e. biodiversity) of birds, mammals, insects, and spiders are significantly lower in areas of high contamination in Chernobyl.

• For many birds and small mammals, life spans are shorter and fertility is depressed, in areas of high contamination.

• In Fukushima, only birds, butterflies, and cicadas showed significant declines during the first summer following the accident. Other groups were not negatively affected.

• There is considerable variability among species in their sensitivity to radionuclides. Many species are not affected, and a few species even appear to increase in numbers in areas of high contamination in both Chernobyl and Fukushima, presumably in response to competitive release (i.e. more available food and shelter) and fewer predators.

• Many species show evidence of genetic damage stemming from acute exposures and the differences observed between Fukushima and Chernobyl suggests some species may show the consequences of mutation accumulation over multiple generations.

• Some individuals and species show no evidence of genetic damage in relation to radiation exposure and some even show evidence of evolutionary adaptation to the effects of radiation through increased antioxidant activity, which may provide protection against ionizing radiation.

• The bird species that are most likely to show declines in numbers in response to radiation are those that historically have shown increased mutation rates for other reasons possibly related to DNA repair ability or reduced defences against oxidative stress.

• Deleterious effects of radiation exposure seen in natural populations in Chernobyl include increased rates of cataracts, tumours, growth abnormalities, deformed sperm, and albinism. 

• Neurological development is impacted as evidenced by depressed brain size in both birds and rodents and consequent effects on cognitive ability and survival have been demonstrated in birds.

• Tree growth and microbial decomposition in the soil are also depressed in areas of high radiation. 

• In Fukushima, the first signs of developmental abnormalities have been observed in birds in 2013, although significant genetic damage has not yet been documented for birds or rodents.

Other recent unpublished results include the discovery that some species of birds may have developed resistance to the effects of radiation in both Chernobyl and Fukushima.

A previous CRI study reported last year that, compared with the bird populations near the site of the Fukushima nuclear disaster in Japan, the birds around Chernobyl seemed able to tolerate the effects of radiation better. This finding hinted that natural selection was already under way and that birds unable to cope with high radiation levels had already been culled from the Chernobyl population, leaving behind only those most suited for survival.

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