Fukushima Health Study Launched

How does exposure to low-level radiation affect a person’s risk of developing cancer or other health problems? Is there a threshold below which there is no effect at all? Can we really understand the effects of prolonged low-level exposure by applying what we’ve learned from one-time blasts like the Hiroshima and Nagasaki atomic bombs? Following the reactor fuel meltdowns at Japan’s Fukushima Daiichi nuclear power plant in the spring of 2011, these unsolved puzzles—long the subject of debate among radiation epidemiologists— have taken on deep personal importance for millions of Japanese potentially exposed to radioactive fallout from the damaged plant. In June Fukushima’s prefectural government launched an ambitious project aimed, in part, at providing some answers—although experts warn the accident’s health impacts may not become clear for decades, if ever. Study leader Seiji Yasumura, an epidemiologist at Fukushima Medical University, says the main goal of the Fukushima Residents’ Health Management Survey is improved health care for those exposed to radiation through ongoing free health screenings and provision of other services should those screenings identify problems. Some residents will also receive mental health questionnaires and related services. “If we put research first, people wonder if they’re being used as laboratory animals, and that’s not our intention,” he says. But Yasumura and colleagues also intend to analyze the data they collect for evidence regarding the health effects of low-level radiation. The researchers plan to combine activity logs for each of the prefecture’s 2 million–plus residents with maps plotting daily radiation levels to estimate the external radiation dose each person may have received in the first four months after the crisis began March 11. Questionnaires distributed to three towns in late June and prefecturewide starting in late August ask residents to recall their whereabouts and activities during the period following the still-unresolved crisis. The survey requires extremely detailed, hour-by-hour activity information through March 25. For the period after that, respondents are asked to fill in their weekly routine, including hours spent outside at specific locations, as well as any major departures from that routine. This method, which also was used after the 1986 Chornobyl nuclear power plant disaster, hinges on the ability of study subjects to remember their activities, hour by hour, after a gap of several months. This raises questions about the reliability of the exposure estimates. The problem is not unique: For both logistical and political reasons, past survey-based studies of radiation exposure have often taken years to get off the ground. “[Given that Japanese officials] have also had to deal with the accident, having questionnaires out in five months is amazing,” says John Boice, scientific director of U.S.-based International Epidemiology Institute and a professor of medicine at Vanderbilt University. There are other complications in estimating exposure for the people of Fukushima. The time lag between the most severe exposure and the start of the study means researchers cannot physically check internal levels of iodine-131. Iodine-131 exposure is a concern in Fukushima because the quick-to-decay radionuclide caused thyroid cancer in thousands of people who, as children, drank contaminated milk following the Chornobyl accident. Although the Fukushima project will include free life-long thyroid cancer screening for all 360,000 residents who were under 18 years of age at the time of the accident, and the health of all residents will be tracked for at least 30 years, data on internal iodine-131 exposure exist only for 1,150 children tested in mid-March. Kagoshima University cancer epidemiologist Suminori Akiba says that won’t be enough to determine the relationship between future thyroid cancer rates and radiation from Fukushima Daiichi.