In an extensive study of children exposed to varying levels of fallout from the 1986 Chernobyl Nuclear Power Plant accident, Israeli researchers have found that Attention Deficit/Hyperactivity Disorder (ADHD) scores are higher among those who were in-utero at the time of the accident -- regardless of their actual level of radiation exposure.
The study conducted at the Technion-Israel Institute of Technology appears in the August 30, 2004 issue of the American Journal of Epidemiology.
The researchers tested ADHD levels in both radiation-exposed and non-exposed children who emigrated from the former Soviet Union. There were no significant differences between the scores of children with high radiation exposure levels when compared with those who had moderate or very low exposure levels. The researchers therefore hypothesize that the cause of the ADHD lies not in the radiation exposure itself; rather, they say, it might stem from a heightened level of anxiety transferred to these children by their mothers.
"Immigrants to Israel from the Chernobyl region manifested high levels of anxiety and concern about radiation exposure," explains lead researcher Dr. Gad Rennert of the Technion Faculty of Medicine. "This resulting anxiety could have been transferred to the children."
The researchers also concluded that exposure to radiation does not affect children's cognitive abilities. Using a battery of non-language-dependent tests, the researchers found no relationship between the children's intelligence scores and their radiation exposure level.
"Children with higher levels of radiation exposure showed no significant differences in intellectual or neurophysical functioning when compared to those who had little or no exposure," notes Rennert.
These findings contradict those from studies of survivors of the atomic bombs in Hiroshima and Nagasaki, which showed that fetal exposure to high doses of radiation increased the risk of mental retardation, small head size, subsequent seizures, and poor performance on conventional tests of intelligence.
The researchers also found that the mothers -- especially those who were pregnant at the time of the accident -- showed inaccurate preconceptions about the physical and mental-health risks of radiation exposure. They sought extensive health care for what they feared would be long-term illnesses. While physical manifestations of radiation exposure -- such as a higher incidence of thyroid cancer among exposed children -- have been documented, the researchers found no differences in cognitive and neurofunctioning of exposed children when compared to those from non-contaminated areas.
The subjects of the study were 1,629 children who immigrated to Israel from the former Soviet Union between 1989 and 2000. A total of 667 (41%) of the children were from areas with high radiation exposure, and 408 (24%) from areas with low radiation exposure. The control group was composed of 554 (34%) children from non-contaminated areas. All were in-utero or up to 14 years of age at the time of the accident.
The Technion-Israel Institute of Technology is Israel's leading science and technology university. It commands a worldwide reputation for its pioneering work in computer science, biotechnology, water-resource management, materials engineering, aerospace and medicine. The majority of the founders and managers of Israel's high-tech companies are alumni. Based in New York City, the American Technion Society is the leading American organization supporting higher education in Israel, with more than 20,000 supporters and 19 offices around the country.