Exposure to radiation from the Chernobyl disaster did increase the risk of certain thyroid cancer-related mutations. However, it did not cause new mutations in the DNA of children born to parents who participated in the clean-up of the site after the accident.
Researchers recently looked into the genetic legacy of the Chernobyl disaster, recognized as the worst nuclear accident on record. One group focused on genetic changes in thyroid tumors developed in people exposed to radioactive iodine released during the disaster. A second team focused on the children of those assigned to clean up the site.
Radiation and DNA
Epidemiological research has shown that people exposed to the Chernobyl accident had a higher risk of developing a particular type of thyroid cancer called papillary thyroid carcinoma. That said, while we know that radiation can damage our DNA, the precise nature of this damage remains difficult to understand.
As part of this new study, researchers analyzed tissue from thyroid carcinoma tumors held in the Chernobyl tissue bank. They compared the genetics of tumors from 359 people exposed to Chernobyl radiation before adulthood with that of tumors from people in the same region born more than nine months after the accident (so not directly exposed).
These studies revealed that the greater the exposure to radiation, the more the tumor tissues presented high levels of double-stranded DNA breaks, in which the two strands that make up DNA break at the same point. Cells normally develop mechanisms to repair such ruptures. However, these results also highlighted that the tumors presented also errors in these repair mechanisms.
“These errors are not unique to cancer caused by radiation”, underlines Stephen Chanock, of the US National Cancer Institute (NCI) and principal author of this work. “The same mutations occurred in unexposed people with tumors. On the other hand, they occurred at a lower rate ”.
The children of liquidators
For the second study, the researchers looked for possible multigenerational effects radiation exposure.
The study focused on the children of the personnel who intervened at the scene of the disaster from the morning of April 26, 1986, but also the teams involved in the consolidation and cleaning up of the site in the longer term (liquidators). The genomes of 130 children born between 1987 and 2002 of these individuals were sequenced.
For this work, the researchers focused on the mutations again. These are genetic mutations isolated in the DNA of a child, but which were not present in the genome of his parents.
Concretely, the fact of isolating an increase in genetic mutations in these children, but not in their parents exposed directly, would have suggested that the radiations damage the sperm or the ovum. Conversely, finding no increase in de novo mutations would have suggested that children were escaping DNA damage caused by their parents’ exposure.
Usually, it is estimated that between fifty and one hundred de novo mutations occur naturally in each generation. These new results are consistent with this average. In other words, “People who have suffered from radiation at very high doses did not transmit more mutations to the next generation “, note Stephen Chanock. “There is an effect, but it is very subtle and very rare”.
For the researcher, this work is a new step forward in understanding the mechanisms leading to thyroid cancer in humans. They are also reassuring for those who were exposed to radiation during the Fukushima disaster in 2011 who would consider starting a family.