I am grateful to Drs. Mortazavi and Bevelacqua for sending their letter to the editor and I read it with interest. Prior to this, I was unaware of Dr. Cameron’s work on background equivalent radiation time (BERT). From reading the letter and researching BERT, I find BERT and flight-time equivalent dose (FED) to be quite similar.

BERT is equivalent to one day’s worth of exposure to average background radiation. FED is typically measured in hours of time spent in an airplane at altitude. Both units are contextual rather than exact, as annual natural background dose and the dose rate at flight altitude can vary significantly with location. In my opinion, both approaches attempt to do the same thing: to provide context that helps the layperson understand radiation. Both units have their own idiosyncrasies.

Drs. Mortazavi and Bevelacqua state that the galactic and terrestrial radiation sources are different and that the...

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