Chernobyl's Radioactive Voles

Decades after the infamous Chernobyl nuclear power plant disaster, some surprises have emerged: their wildlife seems to be thriving, with little evidence of increased mutation rates. NPR aired a fascinating interview with biologist Robert Baker. What are the implications for Japan?

Robert Baker is:

a biologist at Texas Tech, who co-directs the Chernobyl Project, has been studying mammals in Chernobyl for two decades. Baker tells Linda Wertheimer his group has found next to no signs of radiation poisoning or cancer in subsequent animal generations there.

You can listen to the NPR story, "Chernobyl's Hot Zone Holds Some Surprises" here:

Below is Robert Baker's interesting commentary, published in 2000 {[Environmental Toxicology and Chemistry, Vol.19, No.5, pp.1231-1232, 2000]}

Letter to the Editor

To the Editor:

Following a recent research expedition to the Chernobyl region, a U.S. Department of Energy official asked us to assess the ecological impacts of the April 1986 Chornobyl disaster on populations of animals. We replied that, although a quantitative assessment is difficult, the net ecological impact has been positive. After a long pause, the perplexed official asked how it could be possible that the worst nuclear power plant accident in history, releasing between 100 and 200 million Curies of radiation into environment, could produce positive ecological consequences. The answer was simple - humans have evacuated the contaminated zone.
Mention of the Chernobyl nuclear disaster usually brings thoughts of death, destruction, cancer, massive economic loss, and other negative images. Clearly, the economic impacts have been devastating for the Ukrainian economy, and the harmful effects such as elevated cancer rates in humans [1-3] and the killing of the pine trees in the Red Forest are real [4,5].

However, the sum effect for the flora and fauna in the highly radioactive, restricted zone has been overwhelmingly positive in favor of biodiversity and abundance of individuals [6]. Our 12 expeditions to the most radioactive areas of these zones reveal that animal life is abundant. Parts of the 10-km zone exclusion zone around Reactor 4 are strikingly, yet deceptively, beautiful (Fig.1). Only the clicks and whistles of our electronic equipment indicated that the habitat was contaminated with radioactivity.

During recent visits to Chernobyl, we experienced numerous sightings of moose (Alces alces), roe deer (Capreol capreolus), Russian wild boar (Sus scrofa), foxes (Vulpes vulpes), river otter (Lutra canadensis), and rabbits (Lepus europaeus) within the 10-km exclusion zone. We observed none of those taxa except for a single rabbit outside the 30-km zone, although the time and extent of search in each region is comparable. The top carnivores, wolves and eagles, as well as the endangered black stork are more abundant in the 30-km zone than outside the area. Trapping of small rodents in the most radioactive area within the 10-km zone has yielded greater success rates than in uncontaminated areas [7]. Diversity of flowers and other plants in the highly radioactive regions is impressive and equals that observed in protected habitats outside the zone.

In reality, radioactivity at the level associated with the Chornobyl meltdown does have discernible, negative impacts on plant and animal life [4,5]. However, the benefit of excluding humans from this highly contaminated ecosystem appears to outweigh significantly any negative cost associated with Chornobyl radiation [8]. Therein lies the often paradoxical relationship between ecological and human health risk considerations. Our observations support the contention that regulatory limits of contaminant exposure to plant and animal populations should remain higher than those set for humans. Such a disparity ensures that removal or relocation of humans will most often facilitate a natural recovery of ecosystems even in the face of deleterious radioactive and chemical challenges. The observation that typical human activity (industrialization, farming, cattle raising, collection of firewood, hunting, etc.) is more devastating to biodiversity and abundance of local flora and fauna than is the worst nuclear power plant disaster validates the negative impact the exponential growth of human populations has on wildlife. If the world cannot afford to experience more nuclear disasters comparable to Chornobyl, then how much more significant is the implication that the world cannot afford to experience additional human population growth? We discussed such matters with Dr. Victor Baryakhtar, Vice President for Ukraine's Academy of Sciences. When comparing the ecological consequences of the Chornobyl region to those in the highly industrialized heavily populated areas of eastern and southern Ukraine, he observed, "Northern Ukraine is the cleanest part of the nation. It has only radiation."

Traditional paradigms of the relative impacts to natural systems by human land use and pollutants are not compatible with the dogma concerning chronic exposure exposure to radioactivity. A proposal was circulated to remediate the Chernobyl environment by burning trees and vegetation from contaminated regions to collect the radionuclides while creating electricity [9]. If enacted, this project would cost $30 million (U.S. dollars) and would likely increase the man-dose when compared to no remediation action. Additionally, this remediation process would result in the total destruction of a vibrant ecosystem while creating at least a temporary technological desert far exceeding any current ecological damage caused by fallout from the Chornobyl accident. Scientific evidence indicates that 1 or 2% of the radionuclidesis present in plant biomass at any given time [10]. In this case, burning vegetative biomass is an ineffective means of remediating radiation, and such actions may exacerbate the mobilization of the significant quantities of radionuclides from soils and sediments. There is a critical need for quality scientific information concerning the environmental and health risk decisions associated with nuclear accidents. We concur with Volodymer Kholosha, Deputy Minister of Emergencies and Protection of the Population from the Consequences of the Chornobyl Nuclear Accident, on the relationship between science and the political processes regulating management decisions in the Chornobyl Exclusion Zone in his statement, "Science is the eyes of the people."

Clearly, our data document a vibrant ecosystem in the most radioactive areas at Chornobyl that in many ways is what we expect from a park dedicated to conservation. Less well documented are possible costs to the species living in this highly radioactive environment. Some of the small mammals living in this environment are experiencing doses from internally deposited 137cesium and 90strontium in excess of 10 rads/d and an external dose at least half that high [11]. Several publications imply significantly elevated detrimental effects from living in the environment. Some of these are anecdotal; however, some are based on modern molecular biology and accepted experimental design [12-14]. The most important question may be 'Is there a build up of genetic (mutational) load that is masked by outbreeding that is generally characteristic of mammalian species?" For humans, any increase in genetic load would be unacceptable. Detailed long-term studies on genetic load, population genetics, demography, mutation rate, life expectancy, fertility, fitness, radioresistence, etc., are needed to understand how the populations exposed to chronic radiation differ from unexposed populations. From a human and wildlife risk perspective, understanding the genetic and population dynamics of wildlife at Chernobyl is not trivial. Chornobyl is no nuclear desert, but the issues raised above concerning latent and long-term effects must be resolved before the total significance of this disaster to native wildlife and to humans can be understood.

Robert J.Baker
Texas Tech University
Lubbock, Texas, USA, and
International Radioecology Laboratory
Slavutych, Ukraine
Ronald K.Chesser
Svannah River Ecology Laboratory
Aiken, South Carolina, USA, and
International Radioecology Laboratory
Slavutych, Ukraine

REFERENCES
1. Jacob P, et al. 1998. Thyroid cancer risk to children calculated. Nature 392:31-32
2. Kazakov VS, Demidchik EP, Astakhova LN. 1992.Thyroid cancer after Chornobyl. Nature 359:21-22
3. Kikhtarev IA, et al. 1995. Thyrod cancer in Ukraine.
Nature 375:365
4. Izrael YA, et al. 1988. Ecological consequences of the radioactive pollution of natural environment in the regions of the Chernobyl APP. Atomnaya Energiya Publ 64:28-40 (in Russian)
5. Medvedev Z. 1994. Chernobyl: Eight years after. TREE 9:369-371
6. Sokolov VE, Rjabov IN, Ryabtsev IA, Tikhomirov FF, Shevchenko VA, Taskaev AI. 1993 Ecological and genetic consequences of the Chernobyl atomic power plant accident. Vegetatio 109:91-99
7. Baker RJ, et al. 1996. Small mammals from the most radioactive sites near the Chernobyl nuclear power plant. J Mammal 75:155-170
8. Chesser RK, Baker RJ. 1996 La Vie Sauvage A Tchernobyl, Analyse d'une prospere mais genetiquement alteree. La Recherche 268:30-31
9. Biomass Workshop. 1998. Proceedings, Chornobyl Phytoremediation and Biomass Energy Workshop. February 23-25. Slavutych Laboratory for International Research and Technology, Slavutych, Ukraine. DOE Publication.
10. Shevchenko VA. 1994. Ecology of the Chernobyl disaster. Man and Biosphere. Pergamon, New York, NY, USA
11. Chesser RK, et al. 2000. Concentrations and dose rate estimates of 134,137 cesium, 90 stroncium in small mammals in Chernobyl, Ukraine. Envion Toxicol Chem 19:305-312
12. Ellegren H, Lindgren G, Primmer CR, Moller AP. 1997. Fitness losss and germline mutations in barn swallows breeding in Chernobyl. Nature 389:593-596
13. Dubrova YE, Nesterov VN, Krouchinsky NG, Ostapenko VA, Neumann R, Neil DL, Jeffreys Al. 1996. Human minisatellite mutation rate after the Chernobyl accident. Nature 380:683-686
14. Baker RJ, DeWoody JA, Wright AJ, Chesser RK. 1999. On the utility of heteroplasmy in genotoxic studies: An example from Chernobyl. Ecotoxicology 8:301-309