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Chernobyl Radiation Still Harming Animals

Jennifer Viegas, Discovery News The Chernobyl disaster, a nuclear reactor explosion and subsequent fire on April 26, 1986, which spewed highly radioactive fallout into the atmosphere, continues to harm animal populations in the Ukraine, according to a new study.

The study, published in the latest Royal Society Biology Letters, presents the most extensive data set ever compiled on the abundance of animals at and around the Chernobyl site. "Abundance" is relative in this case, however, since scientists Anders Moller and Timothy Mousseau determined that insect, bird and other animal populations have dramatically diminished there in the two decades following the disaster. "Chronic, continuous exposure to low dose radiation appears to be the cause," Mousseau, director of the Chernobyl Research Initiative at the University of South Carolina, told Discovery News.

For three years, he and Moller conducted population censuses on invertebrates at more than 700 sites near Chernobyl. At each site the researchers measured radiation levels, using Geiger counters and aerial scan data. They also counted numbers of bumblebees, butterflies, grasshoppers, dragonflies and spider webs. "Our prior work on bird populations at Chernobyl inspired this insect study," Mousseau explained. "While collecting birds, we noticed that grasshopper populations were down. Fruit production was also significantly lowered, and even as we walked through the forest, we noticed few spider webs." Throughout this latest study, the researchers controlled for natural population reduction factors, such as soil type, habitat and height of vegetation. They found that the abundance of invertebrates decreased with increasing radiation. The radiation wasn't just higher right at the plant site, either.

Due to factors such as wind direction, the nuclear blast released radiation "in a very patchy manner, so while the highest areas of contamination are closest to the plant, there are also areas of higher radiation quite a ways away from the reactor," Mousseau said. He and Moller are currently analyzing wolf, fox, rabbit, squirrel and other animal populations. The scientists are not yet ready to release those findings, but the insect population study and the earlier bird surveys suggest that many species "are either absent or in very low numbers in the Chernobyl region." "Brightly colored and migratory species of birds appear to be particularly sensitive to radioactive contaminants," Mousseau added. Two processes appear to keep the Ukraine animals in a downward cycle. The first is that radiation could be accumulating within certain species over many generations, through ingestion of contaminated dirt, water and food. Secondly, as one animal or insect population diminishes, another one might take its place.

This "niche replacement" species might then become contaminated too, reducing its later survival rates. As a result, the ecosystem at Chernobyl has never fully recovered and remains in distress, suggest the recent studies. The findings are a far cry from those made by University of Georgia researchers a little more than a decade after the accident. At that time, Cham Dallas, who is now interim head of Health, Policy and Management at UGA, said that when he held a Geiger counter over rodents, the clicks grew to a roar. "You wouldn't want to handle an animal like that, and yet they are surviving," Dallas then said. He and his colleagues found that although animal populations had "changed," he would not use the word "damaged" because, "We found no deformed animals.

None at all." Mousseau and Moller have since identified high mutations in many different species of birds, plants and animals, including humans. Children living near the plant continue to be monitored, as many suffered from thyroid cancer right after the nuclear blast. More recent tests "show significant negative impacts" on the blood cell counts of local children. "The truth is that accidents do happen, so there likely will be a future nuclear accident somewhere," Mousseau warned. "We also face the threat of nuclear terrorism, so I'm hopeful our studies can shed light on the long-term consequences of radiation exposure.

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dsc.discovery.com

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