In the United Kingdom all sites where ionising radiation is used (e.g. hospitals, universities, nuclear establishments) have a statutory responsibility to monitor their environment and keep records of any disposals. The means of monitoring are diverse and often complex radiological protection instrumentation capable of measuring specific isotopes or kinds of radiation are deployed. For example specific measuring systems dedicated to the monitoring of plutonium isotopes and Iodine-131 exist around and within nuclear sites.

Public concern following the Chernobyl incident stimulated many local authorities to engage in some kind of local radiological assessment. In some cases the authorities do monitoring themselves although generally an independent third party is used (university, hospital, commercial laboratories). To date over 300 local authorities are involved in some kind of independent radiation monitoring. This involvement has followed advice from the Institute of Environmental Health Officers (now CIEHO).

The responsibility for authorising discharges of radioactive material into the environment from establishments rests with the Environment Agency (EA) and the Scottish Environment Protection Agency (SEPA). These agencies have responsibility for check monitoring of discharges and the environment around these establishments. MAFF or a delegated laboratory conducts the monitoring of these discharges, particularly around nuclear sites. Additionally, individual sites are required by the environment agencies to monitor their local environment e.g. UKAEA Winfrith reports. In recent times, following Chernobyl, a more wide ranging assessment of other areas has also been undertaken (eg Radioactivity in Food and the Environment 1995 RIFE, MAFF, HMSO). The levels permitted are determined from a detailed consideration of the likely pathways of the radionuclides, their physical lifetime and the possible radiation doses that might affect the critical group. This is the group of people who are likely to receive the highest radiation exposure as a result of the discharges. The critical group is usually identified after a careful survey of the eating habits of the local population has been undertaken. The nuclear establishment and the government department that issue the authorisations are strongly of the opinion that radiation doses to the public are well below internationally agreed limits in all UK sites. Indeed, the National Radiological Protection Board (NRPB), on the basis of comprehensive monitoring around British Nuclear Fuels Limited sites believes that exposure to the general public from effluent discharges is within their guidance level of 0.5 milli-Sieverts/year.


Radiation dose limits are those that should not be exceeded in order that the normal member of society is not exposed to an unacceptable risk. These dose limits are determined from a wide range of criteria such as epidemiological studies (especially from Japanese bomb survivors) and are set in the first instance by the ICRP (International Commission for Radiological Protection). In radiological practice the dose limit is considered to be a precautionary limit and not a danger limit. That is, if the limit is exceeded a situation should not arise that was irremediable. Thus, the risk associated with an increase in dose by several times the dose limit may only cause a very slight increase in the real risk of, for example, death from cancer. Another radiological principle recommended by the ICRP and accepted by the UK establishment is that doses should be as low as reasonably achievable, the ALARA principle. This means that it is not sufficient to merely ensure that dose limits are complied with but that all efforts should be made to minimise them to the lowest practicable levels.

The principal limit for radiation exposure is now an effective dose equivalent of 1 mSv committed effective dose equivalent per year. The limit to be used in Waste Discharge Agreements with the DOE is 0.5 mSv/year. This is based on the annual risk being less than the risk correspon-ding to an annual effective dose equivalent of 0.5 mSv/year i.e. a mortality risk of 5x10-6 per annum, based on 1977 ICRP values.

The inference to be drawn from this proposal is that there are no sites in the UK that constitute any appreciable radiological hazard to members of the public. To place these dose limits into perspective the average annual dose, from all sources is 2.6 mSv (i.e. natural and made-made sources).


The primary dose limit for members of the public is set at 1 mSv per year for artificial sources of radiation. This does not include medical exposure but does include any possible incorporation, via ingestion or inhalation, of radioactive substances. In the latter case where incorporation may take place over some time it is difficult to make any direct measurement of the dose received. In order to comply with the limits, therefore, the ICRP has calculated secondary limits (known as the CEDE - committed effective dose equivalent) which enables the dose taken into the body to be estimated. In order to do this the Commission has calculated dose factors for the whole body and for each organ or tissue, which expresses the total dose received per unit of activity intake. These factors can then be used to calculate the total activity of a particular radionuclide taken into the body. These calculations take into consideration the physical, chemical and metabolic properties (assimilation, organ concerned, retention period in the organ etc) of the nuclide in question.


Annual limits of intake of radioactive substances (an ICRP concept) should be used with caution. For example, with the isotope 137Caesium, it is possible to calculate the mass concentration that should be tolerated in foods liable to be consumed on a daily basis by the population. The figure calculated represents the acceptable concentration for the consumption of the contaminated food, day after day, year after year throughout the lifetime of the individual critical group member in order to comply with the ICRP dose limit. In reality, however, consumption is rarely continuous and therefore concentrations may be found to be much in excess of the calculated figure. Thus, although a particular isotope may be found having an elevated level in a particular foodstuff, its long-term radiological significance may be less serious than is evident at first seen if measures are taken to counteract the observed levels. As with all radiological data, caution should be exercised in their interpretation and an understanding of their limitations should be borne in mind.


Generalised derived limits (GDLs) and derived limited (DLs) are values expressed as an activity per unit weight or unit volume. The GDL is a generally applicable value based on detailed habit surveys. DLs may have a more restricted significance but are based on similar considerations. They are secondary standards set and used to ensure virtual certainty that a critical group will not be exposed to a radiation dose in excess of the recommended limit, at present 1mSv per annum. They are calculated generally only for those environmental materials which are considered important to a particular critical group. GDLs and DLs are calculated using data published by the ICRP, presented as the committed effective dose equivalent CEDE. From these data the Annual Limits of Intake ALIs are calculated (which may be quoted for three main age groups, viz infants, children or adults). From this information a GDL or DL may be determined by dividing the ALI by the mass of food consumed, volume of air inhaled etc. The following scheme shows the sequence involved in their calculation.

  •   Obtain CEDE from tabulations e.g. NRPB-GS7 HMSO 1987,
  •   Calculate ALI by dividing 1 mSv by the CEDE,
  •   Calculate GDL or DL by dividing ALI by the consumption factor.

    N.B.  In all calculations the units should be consistent.

In Southern England the effluent discharges from UKAEA Winfrith are the current main source of environmentally significant radioisotopes although since closure of the reactor discharge levels have decreased. In all cases no levels of these nuclides have been measured which either exceed or even approach closely the GDLs or DLs.

** Note that the NRPB has revised many of these data in line with international guidelines (January 1996)


The NRPB maintains surveillance on levels of radiation affecting the general public, and others, in the UK and publishes reports. The data used to construct the graphs in Figure 9 are extracted from a review conducted during 1993 (NRPB R263 - Radiation Exposure of the UK Population 1993 Review). The dose to the average person in the UK is from all sources but there can be wide variations based on geographical location. These are fully described in R263.


World Health Organisation (WHO) Guidelines for drinking water

Guideline values recommended by the WHO propose a total alpha activity level of 100Bq/m3. These guideline values 'are specified assuming that only the most toxic radionuclides are present in significant quantities', and the recommendations conclude with the statement 'A value in excess of the guideline figure does not in itself imply that the water is unsuitable for consumption'.

Soil and other solids

The level of activity in unspecified soil, or other solid materials, below which no special precautions need to be considered in the disposal of that material is given as 400 Bq/kg (0.4 kBq/kg) in 'A review of Cmnd 884 : The Control of Radioactive wastes'. Certain elements have been exempted - see Statutory Instrument 1002 (June 1986)

Radiation Exposure

The principal limit for radiation exposure is now an effective dose equivalent of 1 mSv committed effective dose equivalent per year. The limit to be used in Waste Discharge Agreements with the DOE is 0.5 mSv/year. This is based on the annual risk being less than the risk correspon-ding to an annual effective dose equivalent of 0.5 mSv/year i.e. a mortality risk of 5x10-6 per annum, based on 1977 ICRP values.