UC Irvine-led study links low-dose radiation to higher cancer risk

Irvine, Calif., Aug. 16, 2023 — Long-term exposure to low-dose radiation is linked to an increased risk of cancer, according to a study led by the University of California, Irvine. In the U.S., radiation exposure for the average person doubled between 1985 and 2006, mainly from medical imaging procedures such as CT scans, highlighting the need for its judicious use.

Published online today in The British Medical Journal, the research found that the cancer death rate grew by more than 50 percent per Gy, or gray, the unit of absorbed dose of ionizing radiation. This is larger than estimates currently underlying radiation protection. The paper marks another milestone in the International Nuclear Workers Study, which has followed 309,932 industry workers to study their causes of death.

“We wanted to strengthen the scientific basis for radiation protection by directly studying settings where low-dose exposures occur,” said corresponding author David Richardson, Ph.D., professor of environmental and occupational health with UCI’s Program in Public Health. “Understanding those associations is essential to inform decisions about medical and commercial uses of ionizing radiation, exposure limits for the public, and workers.”

The study cohort included workers who were hired in the early years of the Manhattan Project and were employed at nuclear sites in France, the United Kingdom and the U.S. They were monitored with radiation badges that measured their exposures, enabling researchers to examine the association between dose and deaths due to cancer. Of the 103,553 deaths, 28,089 were due to solid cancers, with an estimated 52 percent higher mortality rate per Gy of cumulative dose.

Currently, studies of atomic bomb survivors are the primary basis for establishing protection measures. But their exposure differs greatly from that typically encountered by workers, patients and members of the public. This long-term study provides estimates of the association between low-dose exposure and cancer based on some of the world’s most informative cohorts of radiation workers.

“Contrary to the trend of reducing or removing exposure to carcinogens once we have recognized them, the public’s exposure to ionizing radiation has increased over the past few decades and remains elevated,” Richardson said. “Understanding the risks associated with low-dose radiation is crucial for guiding policy.”

The study team included research scientists from the U.S. National Institute for Occupational Safety and Health; the U.K. Health Security Agency; France’s Institute for Radiological Protection and Nuclear Safety and International Agency for Research on Cancer; and Spain’s Barcelona Institute for Global Health.

This work was supported by the U.S. National Cancer Institute under award R01CA242852.

About the University of California, Irvine: Founded in 1965, UCI is a member of the prestigious Association of American Universities and is ranked among the nation’s top 10 public universities by U.S. News & World Report. The campus has produced five Nobel laureates and is known for its academic achievement, premier research, innovation and anteater mascot. Led by Chancellor Howard Gillman, UCI has more than 36,000 students and offers 224 degree programs. It’s located in one of the world’s safest and most economically vibrant communities and is Orange County’s second-largest employer, contributing $7 billion annually to the local economy and $8 billion statewide. For more on UCI, visit www.uci.edu.

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