standardsIn practice, radiation protection is based on the understanding that small increases over natural levels of exposure are not likely to be harmful but should be kept to a minimum. To put this into practice, the International Commission for Radiological Protection (ICRP) has established recommended standards of protection (both for members of the public and radiation workers) based on three basic principles:
Justification. No practice involving exposure to radiation should be adopted unless it produces a net benefit to those exposed or to society generally.
Optimisation. Radiation doses and risks should be kept as low as reasonably achievable (ALARA), economic and social factors being taken into account.
Limitation. The exposure of individuals should be subject to dose or risk limits above which the radiation risk would be deemed unacceptable.
These principles apply to the potential for accidental exposures as well as predictable normal exposures.Underlying these is the application of the 'linear hypothesis' based on the idea that any level of radiation dose, no matter how low, involves the possibility of risk to human health. This assumption enables 'risk factors' derived from studies of high radiation dose to populations (e.g. from Japanese atomic bomb survivors) to be used in determining the risk to an individual from low doses (ICRP Publication 60). However the weight of scientific evidence does not indicate any cancer risk or immediate effects at doses below about 50 millisieverts (mSv) per year.Based on these conservative principles, the ICRP recommends that the additional dose above natural background and excluding medical exposure should be limited to prescribed levels. These are: 1 mSv/yr for members of the public, and 20 mSv/yr averaged over five years for radiation workers, who are required to work under closely-monitored conditions.Early uranium mining, for example in Soviet-occupied East Germany between 1946 and 1953, had a poor safety record. Lack of appropriate protection exposed German miners to a variety of health hazards including high levels of radiation, toxic chemicals (such as arsenic), crystalline silica and dust. The mining operation, known as Wismut, took place on a very large scale, and occupational exposure is thought to be attributable to thousands of cases of lung cancer and other health impairments. It is estimated that in some East German mines, mean radiation exposures were 750 mSv/yr, well above the modern-day regulated limit of 20 mSv/yr.The modern uranium mining industry is regulated and has a good safety record. Radiation dose records compiled by major mining companies under the scrutiny of regulatory authorities have shown that company employees are not exposed to radiation doses in excess of defined limits during normal operations. The maximum dose received is normally about half of the 20 mSv/yr limit and the average is considerably less. Low-level radiation doses for employees are achieved through a variety of protective measures (see below).Aside from radiation, the occupational health and safety hazards of modern uranium mining are no greater than, nor distinct from, other comparable mining operations.