Measuring Radioactivity in the Environment

26 years after Chornobyl, researchers found significant decreases in biodiversity in the Chornobyl exclusion zone, apparently directly correlated to the degree of radioactivity in the environment.

| November 2014

Cooling towers

Nuclear power plants endanger the environment surrounding them; in the case of a meltdown, radioactivity in the environment can remain at unlivable levels for thousands of years.

Photo by Fotolia/Aneese

The effects of nuclear power have been influencing the environment for decades now, but they remain poorly understood at best. In the wake of the Fukushima Daiichi disaster, Helen Caldicott has collected essays from medical and biological scientists, nuclear engineers, and policy experts from Japan, the United States, and other nations to create Crisis Without End (The New Press, 2014), an unprecedented look at the profound effects of radioactivity in the environment. The following excerpt is from chapter 9, “The Biological Consequences of Chornobyl and Fukushima,” by Timothy Mousseau.

A number of years ago, prior to March 11, 2011, my colleagues and I worked on the impact of radioactive contaminants in Chornobyl. Our interest was driven by evolutionary ecology and genetics, not radioecology, nor nuclear medicine, nor antinuclear activism. At first, we worked primarily with birds because they were easy to catch, identify, and count. Not discouraged by the fence around Chornobyl, birds entered the most contaminated areas of the site, and tracking them has allowed us to study the long-term health impact of this radioactive contamination.

We have studied biodiversity at Chornobyl since 2000 and Fukushima since 2011. Most organisms that we have examined showed significantly increased rates of genetic damage in direct proportion to the level of exposure to radioactive contaminants. Many organisms showed increased rates of deformities, developmental abnormalities, eye cataracts, and even tumors and cancers. Reduced fertility rates were also common. We found that about 40 percent of male birds in the more contaminated parts of Chornobyl are completely sterile, with no sperm or only a few dead sperm. Many of the birds have reduced life spans. As a consequence, many of these populations are small and have reduced growth rates. Some of these species have actually died out in the most contaminated areas. Individuals of species that are surviving well now may accumulate mutations that will be passed on to the next generation. Some of these individuals live long enough to migrate out of the area, carrying these mutations and their potential effects to populations that have never been exposed to radiation.

Calculating Radioactivity in the Environment

Understanding the effects of radioactivity in the environment is not easy. All of us are different. Some of this is the result of genetic mutations that, even if they are expressed (most are not), probably do not influence our survival or ability to reproduce. The natural world is a complicated heterogeneous place. Every point in space and time is slightly different, for instance, with respect to the amount of sunlight it receives, the temperature, the plants and animals that are there, the birds that might fly by. In order to ascertain the effect of radioactivity or radioactive contamination on an individual, a population, or a species, this variability must be factored into the equation. We have accomplished this by employing a massively replicated biotic inventory design, which involves counting every last organism in hundreds of places in both Chornobyl and Fukushima repeatedly through time.

At Fukushima, as of July 2012, we had made 700 biotic inventories. At Chornobyl, we stopped at 896. We measured the number of birds, the species of birds, the number of spiders, and so forth. We measured many of the environmental variables that might be relevant in determining the presence or absence of a given group of organisms—the meteorology, the hydrology, the species of plants, the presence of water. We set up about half a kilometer of mist nets to catch thousands of birds to obtain blood and feather samples for analysis of their DNA and their overall health. We measured radiation levels, too, first using a very simple measure of radiation levels—the Geiger counter. We then calculated the partial effects of radioactive contaminants on populations while statistically controlling for the many other environmental factors that can influence abundance and diversity. Such an approach had not ever been previously taken by any team of scientists.

We also made use of a radionuclide identifier system to identify the source of radiation in any given area, and we have developed miniature dosimeters using TLDs—tiny crystal chips that capture radiation. By placing a TLD on a bird, releasing the bird, and then recapturing the bird, we can verify how much radiation it is exposed to and accurately estimate the external dose to an individual. We have also measured internal radiation dose by taking birds, putting them in a lead enclosure in the field, and measuring the amount of radioactive material inside their bodies to estimate internal dose. As a result, we have discovered a good relationship between our simple Geiger counter measures of background radiation in a certain location and how much radiation organisms in that same location are experiencing both externally and internally.