A construction force numbering more than 38,000 built the Savannah River Site in the early 1950s. The SRS eventually produced materials used in nuclear weapons. Workers with long-term exposure to radiation there had higher-than-expected rates of leukemia. Photo courtesy of the U.S. Department of Energy.
Radiation on the Job
by Sheila Read
(filed under: public health)
Each time you’re X-rayed or get a CT scan, you’re exposed to radiation. How does the government decide what level of radiation is safe? For many decades the United States has relied on data from the Japanese survivors of atomic bombs to set the safety standards for radiation exposure.
Steve Wing contends that a better source of information exists: the data on death rates and cancer incidence among workers at nuclear facilities. Wing says that his work and that of other researchers suggests that long-term exposure to low levels of radiation is more dangerous than we thought.
For twenty-five years UNC researchers have tracked the effects of radiation on nuclear workers. In a study of nearly 19,000 workers hired between 1950 and 1986, Wing and his coauthor David Richardson found that workers at South Carolina’s Savannah River Site had higher-than-expected rates of leukemia.
More importantly, they found an increase in the rate of deaths from leukemia as the radiation doses to which workers were exposed increased. On average, for every additional 130 millisieverts (mSv) of radiation exposure in their jobs, workers’ death rates from leukemia (other than chronic lymphocytic leukemia) doubled. Researchers knew the levels of radiation that workers had been exposed to because the workers’ employer required them to wear badge dosimeters that measured radiation.
By comparison, the typical patient undergoing a CT diagnostic study receives two to three CT scans, resulting in a radiation dose between 30 and 90 mSv, according to an article in the New England Journal of Medicine. A chest X-ray exposes a patient to 0.1 mSv of radiation, according to the U.S. Food and Drug Administration.
Despite the increase in leukemia deaths associated with increased exposure to radiation, the overall risk remains small.
The results are consistent with a growing body of evidence that studies of A-bomb survivors understate the risk of radiation, Wing says. He believes the U.S. government should consider lowering the maximum limit it has set for yearly exposure to radiation, based on the long-term effects on nuclear workers.
Sheila Read is a master’s student in journalism at Carolina.
Steve Wing is an associate professor of epidemiology in the School of Public Health. David Richardson is an assistant professor of epidemiology in the School of Public Health.
