A team of researchers has discovered that genetic damage caused by ionizing radiation after the Chernobyl nuclear disaster in 1986 can also be seen in the children of those exposed, marking for the first time a clear transgenerational link between radiation and DNA changes.
The damage produced by the ionizing radiation released following the Chernobyl catastrophe continues to leave subtle traces in DNA, including in the next generation, according to a new study by researchers led by a team from the University of Bonn, Germany.
Previous studies have not been able to clearly establish whether genetic changes caused by radiation can be passed from parents to children. Instead of simply looking for new mutations, the researchers focused on so-called clustered de novo mutations (cDNMs) – that is, two or more mutations in close proximity to each other, present in the children but absent in the parents. They can occur as a result of breaks in the parental DNA caused by radiation exposure.
“We found a significant increase in the number of cDNAs in the offspring of irradiated parents and a possible association between dose estimates and the number of cDNAs in those offspring“, the researchers wrote in the published work, according to the publication Science Alert.
At the same time, they emphasize that, “despite uncertainty regarding the exact nature and amount of ionizing radiation involved, the present study is the first to provide evidence for a transgenerational effect of prolonged paternal exposure to low doses of ionizing radiation on the human genome”.
How the study was conducted
The results are based on whole-genome sequencing of 130 children of Chernobyl cleanup workers, 110 children of German military radar operators likely exposed to residual radiation, and 1,275 children of parents not exposed to radiation, used as a control group.
On average, the researchers identified 2.65 clustered de novo mutations per child in the Chernobyl group, 1.48 in the radar operator group and 0.88 in the control group. Although the study authors caution that these values may be slightly overestimated due to “noise” in the data, the differences remained significant even after statistical adjustments.
Furthermore, a higher dose of radiation in the parents was generally associated with a higher number of mutation clusters in the children. This observation supports the hypothesis that radiation generates molecules called reactive oxygen species, which can break DNA chains; if these breaks are imperfectly repaired, such clusters of mutations can occur.
The health impact appears to be low
The relatively reassuring news is that the health risk appears to be small. The researchers found no evidence that the offspring of exposed parents had a higher risk of disease. One possible reason is that many of these mutations occur in the DNA “FTA”, not in the genes that make proteins directly.
“Given the overall low increase in cDNA after paternal exposure to ionizing radiation and the small proportion of the genome that encodes proteins, the likelihood that a disease in the offspring of exposed parents is triggered by a cDNA is minimal,” the researchers note.
To put things into perspective, experts remind that older fathers tend to pass on more DNA mutations to their children, and the risks associated with the parents’ age at conception are greater than those related to the radiation exposure analyzed in this study.
Limitations and implications
The authors also acknowledge some limitations of the research. The original radiation exposure was decades ago, so levels had to be estimated based on historical records and old devices. Also, participation in the study was voluntary, which could have introduced some bias, as people who suspected they had been exposed to radiation would have been more willing to sign up.
Even under these conditions, the findings indicate that prolonged exposure to ionizing radiation can leave subtle genetic traces that are passed on to future generations, underscoring the importance of safety measures and careful monitoring of exposed individuals.
“The possibility of transmission of radiation-induced genetic changes to the next generation is of particular concern to parents who may have been exposed to higher doses of ionizing radiation and potentially for longer periods than considered safe“, the researchers concluded.
