Answer to Question #585 Submitted to "Ask the Experts"

Q

What is the permissible dose of radiation from a natural radiation that can be within the healthy limits?

A

There really is no dose limit on radiation from natural sources, unless you're exposed to it as part of your job. So, for example, I have no dose limit from the uranium that occurs naturally in soil but, if I work in a uranium mine, I'll have a dose limit of 5 rem per year (5000 mrem per year) from radiation in the mine.

The US Environmental Protection Agency (EPA) has suggested guidelines for allowable levels of radon in the home, but these are guidelines and not limits. You can have any level of radon in your house and the EPA can't force anyone to reduce the levels, UNLESS the elevated radon levels are due to uranium mill tailings or some other MAN-MADE factor. Similarly, some have suggested limiting cosmic radiation exposure to flight crews, even though this radiation exposure is natural. However, passengers are not subject to these limits because their exposure is not considered to be occupational.

As far as I know there is no serious attempt to restrict cosmic radiation exposure to business travelers, presumably because their job doesn't require that they fly, as opposed to flight crews. The bottom line seems to be that if your job requires you to be exposed to higher-than-normal levels of natural radiation then you may be subject to the same exposure limits as any other radiation worker. If you're just incidentally exposed, then there are no current limits.

Andrew Karam, CHP
University of Rochester