Background radiation levels, health effects

For comparison, we have calculated the health effects for typical residential properties (4 occupants each) based on 1) the naturally occurring background radiation levels and radionuclide concentrations in four cities across the U.S. (see Table V) and 2) the EPA (CFR, 1981) guideline values (20 yR/h, 0.02 WL, 5 pCi Ra-226/g of soil) for cleanup at inactive uranium processing sites (see Table VI). 

Table V. Lifetime Health Effects Estimates at Background Radiation Levels for a Typical Residential Property in Several U.S. Cities...

For comparison, the health effects calculated from exposure to natural background radiation levels for typical residential properties were all about 0.01 per property, with radon daughters accounting for more than 50% of the total health effects estimated. 

The National Coimcil for Radiation Protection (NCRP) has identified a negligible individual risk level (NIRL) as a level of annual excess risk of health effects attributable to irradiation below which further effort to reduce radiation to the individual is unwarranted. The NCRP emphasized that this level should not be confused with an acceptable risk level, a level of significance or a standard. The NCRP recommended a level around half the natural background radiation level the final recommended NIRL level is 1 mrem this level is now called negligible individual dose (NID) level (Harley, 2001, 2008). 

The human body is equipped to deal with nominal levels of radiation doses. Background (natural) radiation from radon gas, cosmic sources, soil, and water produces an average dose of about 0.3 rem (0.003 Sv) per year.4 However, large doses of radiation generated after a terrorist attack can overwhelm the body s ability to repair damage, leading to stochastic or acute health effects. 

How is the actual incidence of cancer caused by radiation exposure actually related to the total incidence of cancer, and can it be reduced One study (235) showed that of the total number of cancer fatalities in the United States in 1975 resulting from radiation, only 2.7 percent of the ongoing exposures would result in low-level radiation-induced cancer fatalities. Most arise from natural background radiation or medical exposures. The only significant change that could be made to alter this number is to attempt to modify the incidence of medical exposure. Since most exposures to medical radiation are undertaken to benefit the individual, and presumably other adverse health effects would result as a consequence of withholding the exposure, limiting medical exposures would probably not reduce the total overall mortality. 

The creation of our world occurred in intense radiation Helds and, consequently, we have inherited an Earth drenched in radiation from cosmic sources and the minerals in the groimd (Ch. S, 10 and 17). Though the intensity of these radiation sources is much smaller than produced by human techniques, no human can avoid these natural sources. Therefore, the effects of the natural radiation background has become an important health issue, particularly radon levels in houses. Closely related to this problem is the effects of man-made sources of similarly low levels, such as the storage of nuclear waste. Much research is presently devoted to the effects of low-level radiation. 

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