WHAT IS ACCEPTABLE LEVEL OF RISK ?

The health risk considered here is the fatal cancer, the ultimate end effect of exposure to carcinogens, which is also used as the basis for establishing the radiation dose limits for workers and the public. It is often said that “Nothing is poison but the dose makes it so”. Many substances (such as chemicals) which are toxic at high doses are beneficial to health in small doses, as medicines, to cure diseases. There is no credible scientific evidence that low-dose radiation is harmful. It is also widely reported that low-dose ionizing radiation is harmless and often beneficial to health.

Life is evolved, over millions of years in an environment of ionizing radiation. Even today, there are many radioactive elements existing in the nature. The variation in the background radiation exposures due to these radioactive isotopes is in the range of about 2 to 6 milli-Sievert and more per year in various countries and areas. No adverse health effects are found amongst people living in High Background Radiation Areas (HBRAs).

Public perception of acceptability of risk is based on the benefits that can be derived by taking or accepting the risk. For example, the risk of radiation exposure to much higher levels is accepted by the people in diagnostic and therapeutic radiological procedures. Whereas, the general exposure levels of occupational radiation workers fall in the same range of variation of natural background radiation doses.

For the purpose of regulation of public exposures, a numerical value for the acceptable risk is arrived at in accordance with the principle of protection optimization. In line with the US-Nuclear Regulatory Commission, one can accept a risk of fatality from cancer of one in a million per year, corresponding to the annual public exposure of 0.01 mSv (exposure which can be considered as of below regulatory concern) may be adopted. In case of annual exposures of 1 mSv (dose limit to the public) of small population (like critical group), one can accept a conservative lifetime (75 years) risks to individuals as high as five cancer fatalities in a thousand exposed.

Radiation exposures of the individual members of the public which result in risks below these limits are considered to be safe and acceptable.