Much of what is known about cancer caused by radiation exposures from nuclear power plant accidents comes from research on the April 1986 nuclear power plant disaster at Chernobyl in Ukraine (Chornobyl in Ukrainian) (1, 2). The radioactive isotopes released during the Chernobyl accident included I-131, Cs-134, Cs-137, and Sr-90.
Power plant workers on-site at the time of the accident. Approximately 600 workers at the power plant during the emergency received very high doses of radiation and suffered from radiation sickness. All of those who received more than 6 grays (Gy) of radiation became very sick right away and subsequently died. Those who received less than 4 Gy had a better chance of survival. (A Gy is a measure of the amount of radiation absorbed by a person’s body.)
Cleanup workers. Hundreds of thousands of people who worked as part of the cleanup crews in the years after the accident were exposed to average external doses of ionizing radiation that ranged from approximately 0.14 Gy in 1986 to 0.04 Gy in 1989. Studies conducted in this group of people have found an increased risk of leukemia (3–5).
Residents near Chernobyl. From 1986 through 2005, approximately 5 million residents of the contaminated areas surrounding Chernobyl received an accumulated whole-body average dose of around 0.01 Gy (6). Studies that have followed children and adolescents exposed to I-131 from the Chernobyl accident showed an increased risk of developing thyroid cancer (7–9).
Recent studies have used genomic analysis of people affected by the Chernobyl accident to better understand how radiation exposure leads to cancer. In a 2021 study, investigators found that thyroid tumors in children who were exposed to fallout from the Chernobyl accident had higher levels of a particular kind of DNA damage that involves breaks in both DNA strands than tumors in unexposed individuals born more than 9 months after the accident (10). The more radiation the children had been exposed to, the more of this type of DNA damage was seen. This association was stronger the younger the children were at the time of exposure.
Another way in which radiation exposure could lead to cancer is through transgenerational effects, in which people exposed to ionizing radiation develop new genetic changes in their gametes (sperm or eggs) that are passed on to their future offspring, increasing cancer risk in those offspring. Transgenerational effects have been observed in some animal studies. However, genomic analysis of children born to people exposed to radiation at Chernobyl indicates that this exposure did not lead to an increase in new genetic changes in the children of exposed parents (11).