ARCHIVE: e-Digest Statistics about: Radioactivity

Artificial Sources of Radiation


Average concentrations of strontium-90 and caesium-137 in milk

Up to 1985, the main source of the exposure to fallout was the nuclear weapons testing that took place between the late 1940s and early 1960s. The average annual dose from this source reached a peak of 0.14 mSv in the early 1960s, and then, as a result of the implementation of the Partial Nuclear Test Ban Treaty of 1963, fell steadily to 0.006 mSv in 1985. The important radionuclides from this source are strontium-90 (90Sr), caesium-137 (137Cs) and carbon-14 (14C), all of which persist in the environment.

The table and figure 'Annual doses from fallout' shows the trend in average annual dose from fallout between 1986 and 1995. In recent years activity concentrations have decreased almost to the level of detection and NRPB have ceased their programme of surveillance measurements. The Chernobyl reactor incident in 1986 caused a near fivefold increase in average annual doses from fallout in that year, most notably for radio-caesium (a mixture of 134Cs and 137Cs) and iodine-131 (131I). The worst affected areas in the UK were Southern Scotland, Northern Ireland, North Wales and Cumbria (see also table and figure 'Average concentrations of strontium-90 and caesium-137 in milk' which give trends in concentrations of 90Sr and 137Cs in milk, mainly from world-wide fallout). By 1992, the fallout from the Chernobyl incident only accounted for about 20 per cent and weapons testing about 80 per cent of the overall average dose from fallout. Fallout currently accounts for a small proportion (0.2 per cent) of total exposure and about 1 per cent of all internal exposure from radionuclides in the body [17]. The average annual dose in 1997 was 0.004 mSv [1].

In Detail:

Radioactive Incident Monitoring Network (RIMNET)

Further Information:
Key Facts:
Artificial sources:
Occupational radiation
Direct shine
Data Tables:
No Title Download
file type
4 Annual doses from fallout: 1986-1995
5 Average concentrations of strontium-90 and caesium-137 in milk from world-wide fallout: 1962-1995
References, further reading and links to other resources:
[1] Hughes, J S, National Radiological Protection Board (1999). Ionising Radiation Exposure of the UK Population: 1999 Review, NRPB-R311. TSO.
[17] Department for Environment, Food & Rural Affairs - Monitoring of Radioactivity in Air and Rainwater in the UK Annual Results Report 1999 DETR/RAS/00.008. Defra.

Your questions and comments about information presented on this page are welcome. Contact information and Email . Copyright of data and/or information presented or attached in this document may not reside solely with this Department. Please see guidance on Copyright.

Page last modified: 16 September 2003
Page published: 10 September 2003