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Radioactivity
Exposure of the Population to All Sources of
Radiation: 2003
1
Average annual dose
(microSieverts)
Natural sources | µSv | Artificial sources | µSv |
|---|
Radon | 1,040 | Medical | 410 |
|---|
Gamma rays | 390 | Occupational | 6 |
|---|
Cosmic | 330 | Fallout | 6 |
|---|
Internal (from diet) | 250 | Disposals | 0.9 |
|---|
Consumer products | 0.1 |
|---|
The average annual dose of radiation to someone living
in Scotland is 2,400 microSieverts, 82% of which comes from
natural sources. The main source of natural radiation
exposure is radon, a radioactive gas that is emitted from
tiny amounts of uranium naturally present in materials such
as rocks, soils, bricks and concrete. Radon decays and
emits short-lived products that can increase the risk of
lung cancer. The action level for radon in the home is
200Bq/m
3, above which, measures should be taken to
reduce concentrations. Other important natural sources of
radiation are cosmic rays, terrestrial gamma rays and
long-lived radionuclides that enter the body through food
and drink.
The greatest artificial source of exposure to radiation
comes from medical x-rays. Nuclear waste disposals and
fall-out account for less than 0.3% of exposure. The
Chernobyl reactor incident in 1986 caused average annual
doses from fall-out to increase by about five times that
year.
SOURCE:
HPA, RADIATION PROTECTION DIVISION
Activity Concentrations in Milk:
1966-2003
4
Activity concentrations in milk
| 1966 | 1975 | 1987 | 2001 | 2002 | 2003 |
|---|
Caesium 137 (Bq/litre) | 1.90 | 0.30 | 11.00 | <0.073 | <0.058 | <0.074 |
|---|
Strontium 90 (Bq/gram of
calcium) | 0.60 | 0.13 | 0.06 | <0.083 | <0.083 | <0.083 |
|---|
Exposure to high levels of ionising radiation from
radioactive substances can lead to radiation sickness and
is associated with genetic damage that can cause
cancer.
To monitor exposure to radionuclides through the diet,
activity concentrations in cows' milk are valuable
indicators. Between 1966 and 1980, there were gradual falls
in the concentrations of caesium-137 (137Cs) and
strontium-90 (90Sr). This reflects a decline in atmospheric
radioactive fall-out, following the ban on above-ground
nuclear weapons testing under the 1963 Partial Test Ban
Treaty between the
UK,
USA and former
USSR.
Activity levels of 137Cs in milk peaked following the
Chernobyl reactor incident in 1986, with 1987 levels 220
times greater than in 1985.
5 Concentrations then fell rapidly in 1988, and are now
below pre-Chernobyl levels.
Community Food Intervention Levels (
EC/686/95) set post-accident activity
levels for food at which intervention should occur. In
milk, these are 1000 Bq/kg (1030 Bq/l) for 137Cs and 125
Bq/kg (1.01 Bq/g of calcium) for 90Sr. Peak concentrations
in milk are now well below the
EC intervention levels, which were
derived to ensure public protection.
SOURCE:
HPA - RADIATION PROTECTION DIVISION
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