Answer to Question #12317 Submitted to "Ask the Experts"

My daughter is pregnant and works for a company that had her go out and check sealant drums which were hot. She told them she was not comfortable doing this and her boss told her to do it anyway. She had not started the survey and had just walked through and her dosimeter went off. What is the limit dosage for a pregnant woman in a hot area?

Thank you for your question. There are two limits for persons occupationally exposed to radiation. Let me explain each.

The first limit is 50 millisievert (mSv) in a year. This limit applies to a pregnant worker who has not formally declared her pregnancy to her employer. This limit applies to any radiation worker. When a pregnant worker does not formally declare her pregnancy, the employer can do nothing to force her to change her job (job discrimination).

The second limit is 5 mSv during the gestation period. This limit applies to a pregnant worker who formally (in writing) declares her pregnancy to her employer. The employer needs to assess the potential radiation dose to the fetus up to the point of declaration then continually assess any additional dose after declaration and until the end of the pregnancy.

There is another limit for a pregnant member of the public who is possibly exposed to radiation (for instance, living next to a nuclear power plant or working for FedEx and transporting boxes containing radioactive materials for medical use). That limit is 1 mSv per year and is kept in check by the organization that uses the radiation or creates the radiation source. In the case of a nuclear power plant, they limit their emissions so someone living right on their property boundary does not receive more than 1 mSv in a year. In the case of a FedEx shipment, the organization that delivered the material to FedEx for shipment has to be sure that the shipping box is of the appropriate type and measured radiation levels are below applicable limits. Those are only two examples, but I'm sure you get the idea.

I don't know what your daughter's dosimeter was set at—a guess on my part would be 0.02 mSv per hour (mSv/h) because that's a common alarming point. If the reading was 0.02 mSv/h, and she stood in that spot for an hour, she'd receive 0.02 mSv, well below any limit.

Some of the lower radiation dose numbers in literature that are suggested to cause harmful effects are 60–100 mSv. Most studies suggest at least 150 mSv.

I hope this is helpful.

Kelly Classic
Certified Medical Health Physicist