For more than 100
years, research has been conducted in an attempt to understand the
effects of radiation to humans and the environment.
Much of this research was done using standard
epidemiological and toxicological approaches to characterize the
response of populations and individuals to high radiation doses.
From this, a good understanding of risks associated with
high radiation doses was achieved.
At low exposures to radiation, however, healing of cells
does occur so the risks from these levels are less known.
This problem is compounded because scientists are searching
for effects from exposure to low levels of radiation in the midst
of exposures to much larger amounts of natural radiation.
The only measurable increased cancer incidence has occurred
following high radiation doses and mathematical models have been
used to predict risks from low radiation doses.
dose limits are set well below levels where measurable
health effects have been observed.
The total radiation dose limit for individual
members of the public as defined by the Code of Federal
Regulations (10 CFR 20.1301) is 1 mSv/y (100 mrem/y),
not including the dose contribution from background
on emissions of radionuclides to the air from DOE
facilities are set such that they will not result in a
dose greater than 0.1 mSv/y (10 mrem/y) to any member of
the public (40 CFR 61.92).
DOE drinking water criterion have set limits of
0.04 mSv/y (4 mrem/y) for the ingestion of drinking
water (DOE Order 5400.5, ), and EPA limits on drinking
water supplies specify low allowable limits for
radioactive constituents (40 CFR Parts 9, 141, and 142).
DOE Order 5400.5 lists Derived Concentration
Guide (DCG) values which are the concentrations in air
and water that a person exposed to continuously
(ingested and inhaled given certain assumptions) will
result in the dose limit.
DCG values are used as a reference to ensure
observed concentrations are lower than concentrations
that would result in a dose near the limit.
ESER Program laboratories analyze for
radionuclides at levels ranging from 10 to over one
million times lower than those that would result in a
dose near the limits.