3 things to know about the NRC’s proposed dose limit changes

New occupational dose limits proposed by the Nuclear Regulatory Commission (NRC) would have the greatest impact on physicians and pregnant nuclear medicine workers, according to a recent study published by the Journal of the American College of Radiology.

The changes would reduce dose limits for lens dose equivalent (LDE), embryo/fetus dose, and administrative control levels (ACLs) related to deep dose equivalent (DDE), bringing the standards of the NRC, an agency of the U.S. government, closer to what is currently supported by the International Commission on Radiological Protection (ICRP).

William F. Sensakovic, PhD, of Florida Hospital in Orlando, and colleagues examined the overall impact of the NRC’s proposed changes in the study. The team gathered radiation badge data for more than 1,000 workers from 2013-2014 and 180 pregnancies from 2009-2014, comparing the data with the proposed regulations.

These are three of the biggest takeaways from the team’s research:

1. Some physicians could have decreased workload

The data showed interventional radiologists, pain medicine physicians, and cardiologists working in cath labs would be most affected by the new LDE limits and ACLs.

“Although proposed regulatory changes would be applied to all workers who wear badges, physicians will be affected disproportionately by changes to those limits,” the authors wrote.

For example, the NRC proposed changing the yearly LDE limit from 150 to 50 mSv, aligning it more with the ICRP’s own limits. The authors found that 15 of the 16 workers who exceeded this limit were physicians.

Sensakovic and colleagues said training could possibly limit the impact to some degree, but “a decreased workload is more likely to be necessary.”

“The workload of workers who exceed the limit would likely need to be reduced, presenting a substantial burden to the worker and possibly the hospital,” the authors wrote.

2. Pregnant workers should not be affected ... with one exception

The NRC proposed a reduction of the annual dose limit for a “declared embryo or fetus” from 5 mSv over the course of the worker’s pregnancy to 1 mSv, and the overall impact appears to be minor. Just 1 percent of pregnancies exceeded the proposed limit, and the pregnancies that did were carried out by nuclear medicine workers.

“The proposed limit seems to mainly affect nonphysician nuclear medicine workers who handle high-energy isotopes regularly,” the authors wrote.

Sensakovic and colleagues noted that pregnant hospital workers can choose to declare or not declare their pregnancy; pregnant workers could technically delay declaring their pregnancy if the NRC’s limits became too burdensome, though that does not appear likely.

3. Some proposed changes could result in a significant amount of time and effort

“The proposed ACLs that include a cumulative (lifetime) dose component could represent a substantial burden to the radiation safety program, not because of the number of workers who potentially exceed the limit (0.0%-0.6%), but because efficiently and accurately tracking cumulative dose using current methods is extremely difficult,” the authors wrote.

According to Sensakovic et al., hospital officials should only be responsible for knowing an individual’s dose history for the time they are employed at that hospital and “the individual worker should be responsible for gathering and tracking their cumulative dose across their employers and lifetime.”

The team said their study did have noteworthy limitations, including the fact that all information was all from a single hospital. Also, worker age was not part of the data, making it impossible to assess certain ACLs.