An annual maximum occupational exposure for radiation workers in the US is 5,000 millirems. When you spread low doses out over a period for time, it is not as destructive to the body because it has time to recover. To help put this in perspective to dental X-Rays, you would need to have 2,000 dental x-rays to equal the radiation in 1 mammogram. To reach that maximum safety dose, you would need to have taken approximately 10,000 dental X-Rays. On average people receive 3 dental bite wings work of radiation a day just from being outside in the sun or around concrete building and road.