Two Landmark Studies Examine the Effects of Chernobyl Radiation on the Body

When the Chernobyl nuclear power plant in northern Ukraine exploded, radioactive materials spilled across the country and throughout much of Europe. The 1986 accident directly killed 30 people and exposed millions to contamination from ionizing radiation, a known carcinogen.

In a landmark effort to understand how this radiation exposure impacts human health, an international team of researchers undertook two large studies. The first examined genetic mutations in children of people with high radiation exposure following the accident. They found that there were no transgenerational mutations. The second investigated thyroid cancer in people who were exposed to radiation. The work provides insight into the ways radiation damages DNA, causing cancerous tumors.

The eight-year effort was led by researchers at the National Cancer Institute (NCI), part of the National Institutes of Health. The studies were published in the journal Science on April 22, close to the 35th anniversary of the disaster.

“We really had a very remarkable and distinctive opportunity to ask this question of ‘how does radiation cause cancer and what can we learn from that that could be important for future issues related to radiation and cancer itself?’” Stephen Chanock, MD, director of NCI’s Division of Cancer Epidemiology and Genetics, tells Verywell.

Tools for Studying Nuclear Incidents

In the aftermath of the accident, scientists collected biospecimen samples from people involved in the immediate clean-up efforts and collected information about people who agreed to be studied long-term. This included careful tracking of people’s exposure levels so researchers could match their experience with changes in their DNA. In addition to direct exposure, some people were indirectly exposed through environmental factors, like drinking milk from cows that grazed on polluted pastures. 

Recent improvements in genome sequencing technology and scientific advancements allowed the researchers to analyze materials in ways that weren’t previously possible. For the transgenerational study, for instance, they sequenced each gene 80 to 90 times—two to three times more than is typical for such projects.

“We didn't want to miss anything—we felt that this was a very unique opportunity,” Chanock says.

These tools may be useful for studying more recent nuclear incidents involving nuclear radiation, like the Fukushima nuclear disaster in 2011.

“By better understanding the nature of the damage caused by such accidents we can hope to improve how we treat and monitor those affected by high ionizing radiation exposure in the future,” Alex Cagan, PhD, a postdoctoral fellow at the Wellcome Sanger Institute, a British genomics research institute, writes in an email to Verywell.

Genetic Effects on Children

For the first study, researchers set out to answer the long-standing question: does radiation exposure lead to genetic mutations in children? Some animal and cellular studies previously indicated that this is possible.

The team analyzed the complete genomes of 130 people born between 1987 and 2002 and their 105 mother and father pairs. The children were all born between 46 weeks and 15 years after the disaster, and one or both parents were involved with clean-up efforts after the accident or lived close to the site.

The researchers looked for germline de novo mutations in the now-adult children. These are genetic mutations that appear randomly in egg or sperm cells and are seen in children but not their parents. These mutations, Chanock says, are “sort of the building blocks of evolution.” Most people have 50 to 100 de novo mutations during conception.

If the researchers observed an increase in the number of de novo mutations in the individuals, compared with their parents, it might indicate that radiation exposure could affect the genome of subsequent generations. But they found the children had no excess mutations. In fact, the main factor in determining how many de novo mutations they carried was the age of their father at conception.

“There are terrible psychological and social and other kinds of health-related issues that the next generation are experiencing, but no genetic ones,” Chanock says.

The Root Causes of Radiation-Induced Thyroid Cancer

Researchers used genome sequencing with what Cagan calls “unprecedented detail” to show how radiation exposure acts on DNA in more than 350 people who had developed thyroid cancer after being exposed to the radiation as children.

Radioactive iodine can damage individual bases of DNA, which causes minor mutations. Breaks in both strands of the double helix—called “double-stranded breaks”—can cause more severe damage.

By comparing the DNA damage from after the meltdown to that of unexposed people who developed thyroid cancers, researchers found that exposed people tended to have more double-stranded breaks than others, who mostly expressed single-point mutations. Plus, the more radiation a person was exposed to, and the younger they were when exposed, the more double-strand DNA breaks they had.

Still, radiation-induced thyroid cancer doesn’t appear very different from randomly occurring thyroid cancers, and it appears that they may be treated in the same way.

“Unfortunately, as the authors recognize, the DNA damage they identify can also be caused by other processes, meaning we still lack a way to definitively prove that an individual's cancer was caused by radiation exposure,” Cagan says. “Nevertheless, this work greatly advances our understanding of the molecular damage caused by ionizing radiation.”

Looking Ahead

There are many remaining questions about how ionizing radiation affects the body. Chanock says scientists have yet to understand why radiation ends up where it does—it tends to travel more easily to the blood than to the testes, for instance.

“By better understanding the nature of the damage caused by such accidents, we can hope to improve how we treat and monitor those affected by high ionizing radiation exposure in the future,” Cagan says.

As scientists look toward studying other nuclear disasters, especially those where the amount of radiation exposure was much lower, Chanock is optimistic that the findings will be similarly encouraging.

“There's a relatively good and reassuring story here,” he says.