Exposure to very low levels of ionizing radiation is common—medical procedures, air travel, and industrial processes expose people to such radiation every day. But the health implications of these very low doses are not well understood. A bipartisan bill passed 7 January by the U.S. House of Representatives seeks to alter that landscape by revitalizing an existing Department of Energy (DOE) low-dose radiation research program.

The bill—motivated in part by concerns raised by the Fukushima nuclear disaster in Japan—calls for a study by the National Academies and would require DOE to produce a 5-year research plan. But it doesn’t provide any new funding, and so far the bill doesn’t have a champion in the Senate, which will also to have to pass the legislation in order for it to become law.

Still, supporters of the DOE program, which has seen its funding and visibility decline since it was first created in the late 1990s, are pleased by the House move. “Unfortunately, this program has not been a priority at DOE over recent years and has seen systematic de-emphasis,” said Representative Lamar Smith (R–TX), the chair of the House Science, Space, and Technology Committee, in statement before the House’s voice vote on the bill. It will, he said, ensure “the continuance and enhancement of this important research program.”

The nuclear energy industry also welcomed the move. “Given the pervasiveness of nuclear technologies in our modern world … it just makes sense that we better understand the health effects of low doses of radiation,” said the Washington, D.C.–based Nuclear Energy Institute, the industry’s main trade group, in a statement.

The human health effects of low-dose radiation have long been a puzzle. “We know that high doses of radiation cause cancer,” says biophysicist David Brenner, director of Columbia University’s Center for Radiological Research, “but as you go down lower and lower in dose it becomes less and less clear what’s happening.” Detecting slight increases in cancer risk, for instance, is difficult. Some scientists have proposed that there is a threshold level, below which exposure to radiation is not dangerous, but there is no consensus on whether such a threshold exists, or what the safe exposure level would be, Brenner says.

Radiobiologist William Morgan, director of radiation biology and biophysics at Pacific Northwest National Laboratory in Richland, Washington, says that researchers are split between multiple theories about low-dose radiation—some say it is good for you, others say it has no effect, and the rest think it's terrible for you. “Herein lies the confusion in the low-dose radiation field,” he says.

Congress aimed to help answer such questions in creating DOE’s low-dose radiation research program in 1999. In particular, researchers and policymakers say solid science is necessary to set appropriate exposure regulations for radiation workers, nuclear power infrastructure, and evacuation plans in the event of a nuclear accident or terrorist attack. But the program’s funding has generally declined over the years; low-dose research sits within a larger DOE funding pool that has gone from a high of some $28 million in the mid-2000s to less than $16 million in recent years.

The 2011 Fukushima accident helped revive low-dose concerns, however, and in 2013 eight prominent researchers in the field, including Brenner and Morgan, wrote to White House science adviser John Holdren asking for a National Academies report on the issue. They also gave presentations to the House Energy Committee. The efforts, Brenner says, were inspired in part by a 2009 road map for systematic low-dose radiation research produced by the European Commission and experts from Europe's low-dose radiation research community.

The result was the Low-Dose Radiation Research Act of 2015 (H.R. 35), backed by both Democrats and Republicans. It initially passed the House last year, but the Senate took no action, meaning the legislation died in December at the end of the 113th Congress. (The leading sponsor of that version was Representative Paul Broun [R–GA], who is no longer in office after losing in a U.S. Senate primary.)

Last week, voting on the noncontroversial bill was one of the first bits of business conducted by the newly seated 114th Congress. This time, the lead sponsor was Representative Randy Hultgren (R–IL), a member of the science committee who represents a district that includes DOE’s Fermi National Accelerator Laboratory. It again passed on a voice vote.

“While there is little doubt that there is a threshold above which humans should avoid exposure to radiation, this legislation will ensure that the Department of Energy’s Office of Science prioritizes the research necessary to understand what that level actually is,” Hultgren said in a speech made on the House floor before the vote.

The bill defines a low radiation dose as an exposure of less than 100 millisieverts. For comparison, a person living in the United States receives an average annual dose of about 6 millisieverts, half of which comes from natural background sources. A chest x-ray contributes a dose of about 0.1 millisieverts, and a full-body CT scan about 10 millisieverts.

The National Academies report required by the bill would follow in the footsteps of the 2009 European Commission report. Lawmakers want it to outline the current status of research, address remaining challenges and scientific goals, and recommend a long-term research agenda. The bill says the report should consider the cost-benefit effectiveness of the proposed research. DOE would then produce a 5-year research plan that responds to the findings of the study. The bill does not authorize any additional funding for DOE, meaning the agency would have to use existing funds unless congressional appropriators say otherwise.

The House bill’s supporters are now looking for senators willing to take up the cause. “We are optimistic” about getting the bill approved by the Senate, a Hultgren press aide wrote ScienceInsider in an e-mail. The White House has taken no position on the bill.

Correction, 11:33am, 1/12/2015: The article misstated the designations of the current and past Congress. Those numbers have been corrected.