NEW YORK (Reuters Health) - People who lived near a nuclear test site
in the former Soviet Union during active above-ground and atmospheric testing
have nearly twice as many inheritable DNA mutations as their countrymen
and women who were not exposed to radiation, according to the results of
a new study.
But once atomic testing was forced underground by a US-USSR treaty,
the international team of researchers found, the mutation rate in later
generations of test-site neighbors began to drop.
Dr. Yuri E. Dubrova of the University of Leicester, UK, and colleagues
investigated the effects of nuclear testing at Semipalatinsk nuclear test
site in Kazakhstan, formerly part of the Soviet Union and now an independent
Between 1949 and 1989, 470 nuclear tests were performed at the Semipalatinsk
site, some of which resulted in relatively high contamination of surrounding
territories with radioactive fallout, Dubrova explained in an interview
with Reuters Health.
The study "provides us with the first solid experimental evidence of
an elevated mutation rate in the germline of families exposed to ionizing
radiation," Dubrova said. "Germline" refers to the genes contained in a
man's sperm and a woman's eggs, which are passed on to their children.
From 1949 to 1963, nuclear tests at Semipalatinsk took place in the
atmosphere or on the ground, while tests after 1963 were conducted underground.
Up to 85% of the radiation exposure to nearby residents came from four
surface tests, conducted in 1949, 1951, 1953 and 1956.
The investigators evaluated the germline mutation rate in 40 three-generation
families living near the nuclear test site, who were compared with 28 three-generation
families from another rural region of Kazakhstan who had not been exposed
The researchers divided the radiation-exposed families into two groups:
those born before 1949, who had likely received the heaviest doses of radiation,
and those born in 1950 and later. Individuals in the second group who were
born between 1950 and 1956 were also exposed to a significant amount of
radiation, while those born later were not.
People born before 1949 near Semipalatinsk had 1.8 times as many germline
mutations as their counterparts who had not been exposed to radiation,
Dubrova and colleagues found. Those born in 1950 and afterwards had 1.5
times the number of mutations seen in the unexposed group, according to
the report in the February 8th issue of the journal Science.
"This means that exposure to ionizing radiation has resulted in (an)
elevated mutation rate in the germline of the affected families," Dubrova
told Reuters Health.
"The most interesting finding is that in the less-contaminated group,
a negative correlation between germline mutation rate and the parental
year of birth was found," he said. "This decrease in mutation rate perfectly
reflects the improvement of the radiological situation in the area around
the site after the cessation of atmospheric and ground nuclear tests in
According to Dubrova, the findings show that the Limited Test Ban Treaty,
which banned atmospheric and above-ground nuclear tests and was signed
by the US and USSR in August 1963, has been effective in reducing the genetic
risks for the exposed population.
As far as health consequences due to the exposure, "an elevated incidence
of cancer has been reported for this area, but these data are still preliminary,"
"The message is straightforward," Dubrova said. "The testing (of nuclear
weapons) in the atmosphere and above the ground was not the best idea,
and the Soviet and American governments were clever enough to ban this
testing in 1963."
SOURCE: Science 2002;295:1037.