This section of the chernobyl irradiated forest wildfire project is intended to describe the project as it unfolded.

unlike the other sections, it is not written in THE detached, analytical style of most scientific research and analysis.

Effects of catastrophic wildfire in the western United States. (photo courtesy of Yakama Indian Nation)

Effects of catastrophic wildfire in the western United States. (photo courtesy of Yakama Indian Nation)

In 2004-2005, Dr. Sergiy Zibtsev (See “Major Participants”) resided as a Fulbright Fellow at the Yale University School of Forestry and Environmental Studies (Yale FES). Sergiy had done research in the forests contaminated with radiation from the Chernobyl nuclear reactor disaster of 1986. The most contaminated 260,000 hectares had been cordoned off to exclude the public for health concerns, including moving people who lived in villages in the area. Known as the “Chernobyl Exclusion Zone,” the area was primarily accessible to scientists from the Ukraine Institute of Agricultural Radiology, foresters, and other technical people. Sergiy was an expert on forest fires; he and his colleagues had studied relatively small fires that occurred in the Chernobyl Exclusion Zone. During his Fellowship, he studied and visited the large, burned forests of the western United States. His reaction was: “What if such a catastrophic fire occurred in Chernobyl Exclusion Zone?”

Highly flammable, overly crowded pine forests on sandy soils in the Chernobyl Exclusion Zone

Highly flammable, overly crowded pine forests on sandy soils in the Chernobyl Exclusion Zone

Sergiy and I visited the Chernobyl Exclusion Zone in the summer of 2005, and I had the same reaction: “What if a catastrophic fire occurred in the Chernobyl Exclusion Zone?” There are a lot of world experts on radiation, but few of them were familiar with catastrophic forest fires; and, there are a lot of forest fire experts, but few are aware of the Chernobyl irradiated forests. Catastrophic forest fires can be averted with appropriate activities. We felt responsible for alerting the appropriate leaders to the impending danger and opportunities for avoiding them.

We gained the strong backing of Rector Melnychuk (“Major Participants”), Rector of the National University of Life and Environmental Sciences (NULES) in Kiev where Sergiy is a faculty member. Johan Goldammer (“Major Participants”) and the Global Fire Monitoring Center (GFMC) joined our efforts.

Maps of management opportunities to reduce fire danger in the Chernobyl Exclusion Zone. (Red = more flammable forests)

Maps of management opportunities to reduce fire danger in the Chernobyl Exclusion Zone. (Red = more flammable forests)

We first wanted to be certain of our initial impressions, so we proposed to analyze the fire danger of large areas of the Chernobyl Exclusion Zone using computer models (“Analyses: Fire Danger”). We received support from the Chopivsky Family Foundation (“Major Participants“) and assembled a team of NULES and Yale FES graduate students and Jim McCarter, developer of the Landscape Management System at Yale University. Using Ukraine Forestry Department data and LMS, we found the present and future likelihood of fire to be very high, but could be reduced by appropriate thinning of trees. We then developed a plan and budget for fire avoidance, detection, and fighting.

Based on this information, we then felt we could present the concern to the world community who would take responsibility for the next steps. So, we held a meeting at NULES in Kiev with over 80 participants from nine countries representing governments and environmental organizations. The attendees listened, agreed that it was a serious problem and that someone should alert the proper people. Unfortunately, none of the attendees offered to take action.


Meetings at the National University of Life and Environmental Sciences, Kiev, to try to draw administrative attention to the concern.


The next few years were very frustrating for us. During the 1990’s, I had participated in two scientific studies, including multiple Congressional hearings, warning the United States Congress and Executive Branch of the impending wildfires in the United States western forests, only to watch helplessly as no action was taken and the forests burned. I felt we now had an international repetition of the situation, only this time the fire’s smoke would be radioactive. Sergiy was also frustrated, keeping me informed of the fire danger during the northern Ukrainian fire seasons.

We tried vigorously to find someone willing to take responsibility for the issue. However, we did not want to make public announcements for fear of enticing pyromaniacs or terrorists to burn the CEZ. During this time, we held multiple formal meetings (“Meetings“) to try to get someone to take responsibility, as well as private meetings with members of the European Union, the International Bank for Reconstruction and Development, and the World Bank as well as Ministers and Ambassadors of various countries. Among others, Rector Melnychuk contacted President Viktor Yushenko of Ukraine; and I indirectly contacted President George W. Bush of the United States. With the exception of President Bush (who brought up the issue with President Yushenko), the people we contacted recognized the issue, admitted something needed to be done, but declined to take action.

We were looking for some government organization to investigate the potential, risk, and mitigation opportunities—essentially to relieve us of the responsibility of addressing the issue. Instead, in 2009 we were asked how seriously a radioactive fire in the CEZ would affect people. We checked with various radiation scientists and got varied opinions. As scientists, we unhesitatingly decided that question needed to be answered.

Schematic of the model developed to analyze a worst case scenario of a catastrophic wildfire in the CEZ, whose smoke blew to Kiev.

Schematic of the model developed to analyze a worst case scenario of a catastrophic wildfire in the CEZ, whose smoke blew to Kiev.

Although we could find many experts on radiation in the forest, fire and smoke movement, smoke uptake, or radiation and human health, we could not find one who felt comfortable integrating the components and analyzing the entire system—from forest to health. A strength of Yale FES is its ability to integrate; consequently, with further support from the Chopivsky Family Foundation, we assembled a team of scientists from Yale and Ukraine and developed an analysis. First Andrew Niccolai and then Aaron Hohl led the analysis, getting detailed information from Ukraine. Volodymyr Gulidov is fluent in both English and Ukrainian, and proved instrumental in the technical translations. At one point in the analyses, Andrew telephoned me and said: “If there’s a big fire, I think the smoke’s radiation will be very serious for Kiev.” After a pause, he said: “Wait a minute, I’ll call you back.” He called back after ten anxious minutes and said: “I misplaced a decimal point in my analyses. It won’t be as bad as I thought!” For the first time in a long time, I breathed deeply. This, and subsequent analyses, indicated that the fires would be locally very harmful, but as far away as Kiev, they would be less so—although we do not recommend inhaling the smoke. And, eating food that the smoke had covered would also be dangerous. We did not analyze radioactive depots scattered within the forest; these may be more dangerous if burned.

Aaron getting feedback on his analysis of a worse case wildfire scenario

Aaron getting feedback on his analysis of a worse case wildfire scenario

Aaron continued the analyses when Andrew left Yale for another position. Aaron gave presentations to receive scientific input at meetings at NULES and Seoul, Korea (August_2010_IUFRO_abstract). With these inputs and reviews by the coauthors, we obtained recommendations of experts in the various parts of the analysis from various sources (e.g., the U.S. National Academy of Sciences). We requested reviews from these experts and have posted their reviews on the web (“Analyses: Worst Case…”). Aaron then considered and incorporated their comments, and posted his response on the web. The final analysis was accepted for publication in the scientific journal: Earth Bioresources and Quality of Life.


In summary, the findings are:

The analysis showed that the estimated exposure of populations 25 or more kilometers from the source of the fire through inhalation, immersion, and surface exposure pathways is below the critical thresholds that would require evacuations by greater than an order of magnitude.

On the other hand, the potential dosage derived from the consumption of contaminated foodstuffs could exceed acceptable levels set by the Ukrainian government—a prevented internal irradiation dose exceeding 5 mSv or a prevented average annual dose exceeding 1 mSv. For both adults and infants these levels could be almost met or exceeded by consuming food produced at distances as great as 150 km from the center of the CEZ. These highest levels of contamination would occur directly along the trace of the plume. As one moved away from the trace, contamination levels would decline, so the actual amount of agricultural land that would need to be taken out of production would be limited.

From an epidemiological standpoint, the worst case scenario would be if the trace of the plume intersected with a major population center, such as Kiev. If we assume:

  1. the entire population of Kiev (2.7 million) was exposed to the trace;

  2. the population had a sex ratio of 1:1 at the time of the fire; and

  3. the average age of the population was 20 at the time of the fire; and

  4. residents successfully avoided exposure through ingestion;

then we would expect 168 additional cancers to be diagnosed over the lifetime of the residents based on the exposure during the first year after the fire. We would expect 81 additional cancer deaths to occur.

(In 2005, 11% of deaths among females in Ukraine and 13% of deaths among males were attributable to cancer. Calculated for Kiev, this means 324,000 deaths attributable to cancer.)

Even before the analyses were complete, an intense fire season in eastern Europe brought our work to the forefront. Hot fires were burning in Russian and Belarus forests that had radioactive contamination. Alexa Chopivsky (See Major Participants) knew of our work, contacted us, and wrote a story for the Kiev Post. This story proved very popular because it was NOT alarmist; rather, it calmed the Kiev residents because if gave a deliberate, balanced view of the issue. Other news media began reporting the irradiated forest issue (See News Reports), especially around April 26, 2011–the 25th anniversary of the original Chernobyl Nuclear Accident.

A high level conference in Kiev acknowledging the 25th anniversary of Chernobyl brought more attention to the fire risk in the irradiated forest (See April_20_21_2011_Agenda). In 2013, the United Nations Environmental Program has begun addressing a management program in the Chernobyl Exclusion Zone.

The “lessons learned” from the activities are summarized in a paper of October, 2009. In general, the international scientific community worked seamlessly and cooperatively on this potential international threat; however, the world’s political and administrative leaders had difficulty identifying responsibilities and addressing how to respect a country’s sovereignty while addressing a potential disaster that could spread beyond the country’s borders.

Awarded for his work on the humanitarian and environmental impacts of wildfires.

Awarded for his work on the humanitarian and environmental impacts of wildfires.

On September 2, 2013, Sergiy Zibtsev was awarded the Green Star Award for his activities relative to fires in the Chernobyl Exclusion Zone.

During the last 20 years of his professional career, Sergiy Zibtsev, professor at the National University of Life and Environmental Sciences of Ukraine, devoted his efforts for preventing wildfires of catastrophic dimensions in forests contaminated by radioactivity, as a consequence of the failure of the Chernobyl Nuclear Power Plant in 1986. He assessed the effects of a worst-case scenario of a wildfire burning in contaminated terrain and mobilized political awareness to take appropriate action. Scientific studies carried out by an international group of prominent scientists, coordinated by Dr. Sergiy Zibtsev, proved that a high radioactive wildfire hazard exists in the Chernobyl Exclusion Zone.
— Green Star Statement (in part)