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Breakthrough Magazine

Q&A with Tim Mousseau, College of Arts and Sciences

Biological Sciences professor Timothy Mousseau has made more than 30 trips to the Chernobyl nuclear disaster site in Ukraine since 1999. In the past few years, he has traveled a dozen times to the Fukushima Dai-ichi nuclear site in Japan to study the aftereffects of that catastrophe.

Biological Sciences professor Timothy Mousseau has made more than 30 trips to the Chernobyl nuclear disaster site in Ukraine since 1999. In the past few years, he has traveled a dozen times to the Fukushima Dai-ichi nuclear site in Japan to study the aftereffects of that catastrophe. Mousseau, as a part of USC’s Chernobyl Research Initiative, is focused on the health and environmental outcomes of radiation effects in wildlife.

What do you hope comes out of your research?

Initially, our work was motivated by a basic interest in the genetic, ecological and evolutionary consequences of elevated mutation rates in natural populations. The landscape scale of these disasters leads to population and community level impacts that have not been possible to study in the past. Our findings to date suggest that these impacts are significant, widespread and much larger than would have been predicted by conventional laboratory-based approaches to such questions.

For example, recent studies by others suggest that the sensitivities of natural populations in Chernobyl to radiation effects are at least eight-times larger than expected based on the conventional modeling approaches used by most risk analysts. It is too soon to determine how Fukushima will compare, but our preliminary results suggest persistent negative effects for many species with no signs of any positive changes so far.

Some of our latest results from studies of Chernobyl birds suggest that because of the intensity of some of these negative effects, some species are actually adapting by adjusting their allocation of antioxidants in their bodies towards the defense of radiation in ways that have not been observed before. So in many ways, this research is helping to push basic science forward.

What is the goal of your research?

More recently, our goals have expanded to include the development of a better appreciation of the risks and hazards of nuclear accidents for human populations living in these regions. Can the effects observed for plants and animals be extrapolated to predict possible long-term outcomes for people? Humans are just animals, and there is no reason to expect qualitative differences in their responses to mutagens in the environment. Anything we can do to help refine predictions of these risks will be of great interest and potential importance for people living in the face of nuclear hazards.

What’s the latest at the Fukushima site?

We don’t know yet how things are changing at Fukushima. The government there has invested billions into removal of contaminated dirt from towns. It is too early to say if this will have a positive or no effect. It is a big experiment. Certainly there will continue to be significant consequences for the wildlife living in the areas of contamination deemed too high to be worthy of clean up. Actual cleanup is only feasible for the slightly contaminated areas as the best they can do is drop the ambient radiation levels by a half or so. This leaves vast areas that will require decades to centuries before cleanup is feasible.

Is the Fukushima site becoming less dangerous?

A significant part of the initial dispersal of radioactive materials has now dissipated. Perhaps the most dangerous radioisotope was iodine-131, which is extremely dangerous for mammals and can lead to thyroid cancers relatively quickly in exposed populations. More than 9,000 thyroid cancers were reported for Chernobyl victims. Currently it is believed that there are more than 40 cases of thyroid cancer among children who were living in the Fukushima region, a frequency that is believed to be much higher than what would normally be expected. It is still early to say what the final rates will be as such cancers normally have about a five-year latency period, and it has only been three years since the disaster. Fortunately, Iodine-131 has a relatively short half life so pretty much all of it disappeared within months of the disaster. Similarly, many of the other highly radioactive gases dissipated very quickly and are no longer a threat to the people and animals living there.

That said, a massive amount of radioactive cesium, mostly Cs-137 and Cs-134, was also released and they have half-lives of about 30 and two years respectively, and thus are still very much part of the local environment. Most of the ongoing cleanup efforts are aimed at removing these cesium isotopes. Unfortunately, because cesium is water soluble and a potassium analog, it tends to be taken up by plants and redeposited onto the topsoil every fall and so it is not disappearing very quickly. We have now measured radiation levels at 400 locations across Fukushima for four years in a row and after an initial drop, we are now finding that levels have stabilized and may even be increasing in some areas because of movement with water and the effects of plants on redistribution. So the short answer is that although things are much less dangerous now than they were during the weeks and months following the disaster, current conditions are expected to persist for decades to centuries in many areas.

Will the new cover for the Chernobyl reactor site help to alleviate the problems in Ukraine?

The new reactor cover at Chernobyl will certainly reduce the potential impacts of the collapse of the old containment shelter.  The concern has been that the reactor contains tons of unspent nuclear fuel, i.e. plutonium and uranium, that is in the form of nano-particles that could be jettisoned into the atmosphere should the old structure collapse, leading to another environmental disaster that could rival the initial explosion in terms of potential health and environmental impacts. Also, it has been impossible to decommission the old reactor as the basement is full of water.  The new structure should help to dry out the old building, allowing workers to begin a cleanup of the area. Hence the urgency for the new shelter structure, or safe confinement building as it is called in Ukraine.

When did you first become interested in studying the impact of nuclear fallout?

I first developed an interest in doing research in Chernobyl while on sabbatical in Paris. I wanted to work in a new system — birds — in some unusual places. Many folks have studied how variation in natural selection can drive evolutionary responses in natural systems, but no one had ever looked at how evolution might work along a variably mutagenic landscape such as can be found in Chernobyl and now Fukushima. Also, I had had a long-standing interest in how maternal effects shaped adaptation, and I believed that maternal effects (i.e., things that mothers can do to enhance the survival and success of their offspring) could play a significant role in dealing with the stress of a radioactive environment. So we started studying barn swallows in Chernobyl and Spain.

In summary, what have you found at these sites?

These findings clearly demonstrate landscape-scale individual, population and ecosystem consequences of these nuclear disasters, with many examples of developmental abnormalities and deformities that likely contribute to the depressed abundances and biodiversity seen in radioactive parts of the Chernobyl and Fukushima regions. These findings contrast starkly with the optimistic, unsupported claims made by the United Nation’s Chernobyl Forum and UNSCEAR committees. Continued study will be required to determine not only the time-course for population and community adaptation to this perturbation, but also if and when these regions will ever again be suitable for human habitation.