More than 30 years after the meltdown at the Chernobyl nuclear power plant, there is little human activity for nearly 30 kilometers around the site and it has become a haven for wildlife. But as for the so-called Exclusion Zone, different scientists disagree about the continuing effects of the remaining radiation on animal populations. Now, researchers have conducted a new analysis based on the actual radiation doses to animals at different locations in the region, which supports the hypothesis that the populations of mammals are the least in the regions with the highest doses of radiation.
“The effects we’re seeing are in line with the conventional view of radiation,” said Timothy Mousseau, a biologist at the University of South Carolina and a co-author of the study. “What’s surprising is that it’s taken us so long to start looking at this in a rigorous, holistic way.”
The study, published in Scientific Reports, reanalyzed data collected in 2009. At the time, the same researchers estimated that 12 species of mammals, including rats, horses and wild pigs, were abundant, based on 161 wildlife footprints in the exclusion zone’s nearly 800 square kilometers. They found that there were fewer mammals in areas with higher background radiation. However, two subsequent studies showed no significant association between radiation levels and mammal populations. But Musso and his colleagues believe the three studies oversimplified their analysis of radiation exposure.
Previous studies have relied entirely on measurements of environmental radiation. In the new analysis, the researchers used 2009 estimates of the number of mammals in the exclusion zone, but reassessed the total amount of radiation the animals could be exposed to over a lifetime, taking into account data for each species, including range, diet and lifespan. References were made to radiation levels in soil samples and how animals were exposed to radioactive chemicals.
Again, they found that the more radioactive areas had fewer mammals. Many past studies have linked estimated radiation exposure to harmful genetic, physiological and reproductive effects, Musso said.
“This work is very important and well done,” said Carmel Mothersill, a radiobiologist at McMaster University in Canada (who was not involved in the study). “My own laboratory has used this method to reanalyze data from Fukushima and Chernobyl and found a more meaningful association between radiation exposure and the risk of harm.”
But James Beasley, a wildlife ecologist at the University of Georgia, said the paper was “seriously flawed,” mainly because of the way the authors estimated animal populations. Beasley, who has published with other scientists in the past, has long been opposed to the idea. He said their initial survey locations were not properly spaced or wide enough to draw conclusions about the entire area.
Karine Beaugelin-Seiller, A radioecologist at the Institute for Radiation Protection and Nuclear Safety in France, the study’s corresponding author, said the uncertainty remained. But she also said the study provides a more accurate way to establish a link between radiation exposure and effects, which could guide future research.