Regulatory Limits

 

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.  

 

Regulatory 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 radiation.  Limits 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.