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  “Nobody really knows what to expect because there haven’t been studies of large groups of people exposed to low doses of radiation.”

  Randolph Carter

  Professor of Biostatistics

By ELLEN GOLDBAUM

Published: Aug. 4, 2011

As the 66th anniversaries of the Hiroshima and Nagasaki bombings approach on Aug. 6 and 9, a UB biostatistics and public health expert says that studies of health effects from those events provide some clues to the potential, long-term health impacts of this year’s Fukushima nuclear disaster in Japan.

At the same time, he says, the Fukushima power plant disaster underscores how little is yet known about the health effects of low-dose radiation.

Since 1989, Randolph Carter, professor and associate chair of the Department of Biostatistics in the School of Public Health and Health Professions, has worked with the Radiation Effects Research Foundation (RERF) in Japan, which conducts population-based studies of the survivors of the Hiroshima and Nagasaki atomic bomb detonations. Carter used RERF data to develop the Cardiovascular Metabolic Risk Index to study correlations between radiation dose and the incidence of cardiometabolic risk factors among survivors.

He says the first and most noticeable health effects expected to emerge in people exposed to the highest radiation doses during and after the Japanese nuclear disaster are thyroid disorders, such as hypothyroidism, some thyroid cancer cases and leukemia.

“I’d expect that the power plant workers who received high doses would be at increased risk of the same diseases that were seen among atomic bomb survivors,” says Carter, “such as thyroid diseases first and leukemia, to be followed in subsequent years by small increases in risk factors for cardiovascular and metabolic diseases, such as hypertension.“

But because the amount of exposure that the general population received was so much lower than what the power plant workers experienced, he says it isn’t certain that they will present the same kinds of diseases seen in the bombing survivors.

“Since the doses were so much lower, it may be that we will see nothing in terms of elevated disease levels in the population living near the Fukushima Daiichi plant,” he says.

Part of the problem in trying to forecast what kinds of health effects will occur in the general population as a result of radiation exposure is that so little is known about how low-dose radiation affects human health.

In fact, Carter says, the Fukushima nuclear disaster provides researchers with an important new opportunity to gather data on how low-dose radiation, in particular, affects the health of those exposed to it.

While radiation specialists note that cumulative doses of 500 millisieverts, a unit of measurement of radiation, raise cancer risks, Carter says that based on his own research and research by colleagues in the field, there is evidence that doses of radiation lower than 500 millisieverts raise cancer risk as well.

“These data indicate that doses below 500 millisieverts and perhaps as low as 160 millisieverts carry an increased risk of leukemia,” says Carter.

“Our research at UB shows that both cardio-metabolic risk and the proportion of lymphocytic blood cells with genetic damage increase the risk of cancer in atomic bomb survivors as radiation doses exceed 240 millisieverts.”

He adds that debate over the effects of low-dose radiation ranges from an argument that low doses may pose even more significant threats to human health than do higher doses, per unit of dose, to arguments that low-dose radiation can be beneficial because of the possibility that when radiation kills cells in the body, it kills cells that are precancerous.

“Nobody really knows what to expect because there haven’t been studies of large groups of people exposed to low doses of radiation,” he says. “Most of the information we have on radiation health effects comes from the atomic bomb studies and those didn’t involve low doses. That’s why I think it’s important that studies be initiated now, in the aftermath of this disaster, to assess the dose that individuals received. These data will be very useful in the future in assessing the impacts of low doses of radiation.”