On April 26, 1986, reactor number 4 of the Chernobyl power plant (Ukraine) exploded during a safety test. This accident, the most serious in nuclear history along with happened in Fukushima (Japan), caused about 30 direct victims and more than three decades of deaths caused by radioactive aftermath of the catastrophe.
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Despite the past years, many questions remain about how the incident affected the survivors and their children. To date, there have been several studies examining the genetic risks in offspring, but the results have not been conclusive.
Now, two studies published in the journal Science analyze the effect of ionizing radiation, a potential carcinogen, in these generations who experienced an event that shocked the world and forever changed a region. The results were achieved thanks to the whole genome sequencing of the analyzed samples.
“Scientific questions about the effects of radiation on human health have been investigated since the atomic disasters of Hiroshima and Nagasaki, and they have been raised again with Chernobyl and with the nuclear accident that followed the tsunami in Fukushima (Japan) “, he explains to SINC Stephen J. Chanock, director of the Division of Epidemiology and Genetics of the National Cancer Institute from USA
His team leads the first of the articles on whether radiation exposure causes genetic changes that can be passed from parent to child, as some work on animals has suggested. The good news is that no evidence of this was found, that is, children whose parents had been exposed to radiation in 1986 did not have an excess of germline mutations.
“This is one of the first investigations to evaluate alterations in mutation rates in humans in response to a man-made catastrophe, such as accidental exposure to radiation,” the authors state.
The researchers compared the genomes of the children in search of increases in a particular type of inherited genetic changes, known as mutations. de novo. These are genetic variations that arise randomly in the gametes (sperm and eggs) of a person and that can be transmitted to their offspring, but are not observed in the parents.
To do this, they analyzed the genomes of 130 children and their 105 mothers or fathers in which one or both had experienced Chernobyl-related gonadal radiation and in which the children were conceived after the incident (all were born between 46 weeks and 15 years later, between 1987 and 2002).
“Our study does not support a transgenerational effect of ionizing radiation on germline DNA in humans. The incidence was comparable to that in the general population,” they state. Consequently, they suggest that such exposure “had minimal, if any, impact on the health of the subsequent generation.”
“These results are very reassuring for people who they lived in fukushima at the time of the accident in 2011, “says Chanock to SINC.” The radiation doses in Japan were lower than those registered in Chernobyl. ”
Thyroid cancer increase
One of the causes of prolonged exposure to ionizing radiation in survivors of the Chernobyl accident was the radioactive fallout, the accumulation of airborne radioactive particles that are deposited on the ground during and after a nuclear explosion.
These can be inhaled directly and reach the lungs, but also reach the sea and the ground through rain, so it can contaminate crops and pastures, marine fauna and water. This phenomenon is known to be behind the increased risk of cancer in the area, in particular papillary thyroid carcinoma, one of the most important adverse effects observed after the event.
The energy from ionizing radiation breaks chemical bonds in DNA, causing different types of damage. However, detailed molecular knowledge of these tumors is still lacking, and there are no established markers of radiation-induced cancers.
In the second study, researchers from the US National Institutes of Health (NIH, for its acronym in English) provide more data on the process of this carcinoma after examining the effects of such radioactive fallout on survivors.
The authors looked at thyroid cancers that developed in 359 people exposed in infancy or in utero to ionizing radiation from released radioactive iodine (I-131) and in 81 unexposed individuals born more than nine months after the accident.
As indicated to SINC Lindsay M. Morton, director of the work, “genetic changes were observed in the tumors of people who developed papillary thyroid cancer after being exposed as a child or fetus to the radiation released. Among those with cancer, a greater number of ruptures were found in the DNA in the youngest exposed to I-131, and in higher doses, compared to those who had lower doses of I-131 or were not exposed. ”
Hence, experts suggest that the development of thyroid tumors in these cases is a consequence of the DNA double strand breaks in the genome: “Such breaks may be an early genetic change after exposure to radiation in the environment that subsequently allows the growth of these cancers.”
Applications of these studies
These data add to preliminary reports on the characteristics of radiation-related human tumors by integrating data from multiple platforms with a large sample size and detailed figures on proportions.
The researchers believe that their findings provide the basis for future studies on cancer-induced cancers, particularly those involving differences in risk based on dose and age. “Our conclusions have implications for the radiation protection and public health, particularly for exposure to low amounts, “says Morton.
“Since other mutagens can cause DNA double strand breaks, our results suggest that a reliable biomarker to distinguish radiation-induced tumors from those of other causes. Finding such a biomarker could be important for the prevention or early diagnosis of these cancers, “he adds to SINC.
“In addition, we have seen a linear relationship between dose and DNA double strand breaks in the range examined in our analysis. This is in line with the extensive scientific evidence on DNA damage and cancer risk after exposure to ionizing radiation “, emphasizes the specialist. “Therefore, the best prevention of related tumors is to minimize exposure to ionizing radiation, even in small doses.”