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Radiation exposure in millirems

	5000	The current yearly limit for exposure for adults who work with radioactive materials.
	500	The current yearly limit for minors working with radiation. Set at 10 percent of the adult limit.
	400	Natural background radiation in Denver each year.
	330	Highest dose received by subject of iron experiment at Fernald school.
	300	Natural background radiation in Boston each year.
	230	Average dose of subject in Fernald iron experiment.
	170	Lowest dose of subject in Fernald iron experiment.
 	 30	Approximate exposure from radioactive elements occurring naturally in the body.
	 12	Greatest exposure caused by Fernald calcium experiments.
	 10	Exposure received during flight from Boston to California.
	  2	Dose the body receives from a chest X-ray; the chest receives a higher dose.
The radiation exposure of youths at the Walter E. Fernald School -- as a result of experiments conducted by MIT researchers -- was calculated by Dean for Research J. David Litster PhD '65 from the researchers' published findings.

The table below lists the approximate exposure caused by the experiments, and by a variety of other natural and medical causes.

Radiation exposure is measured by the rem, which is calculated so that values from different kinds of radiation can be compared. A rem is equivalent to one rad applied uniformly to the whole body; one rad equals the deposition of one erg of energy per gram of matter.

The highest dose of radiation received by any of the subjects was 330 millirem. The equivalent increase in the lifetime risk of fatal cancer it caused is 1 in 2,000. The normal lifetime risk of contracting fatal cancer is 1 in 5, and the lifetime risk of contracting some cancer, fatal or otherwise, is 1 in 3.