Key Scottish Environment Statistics 2014

Radioactivity

Exposure of the Population to All Sources of Radiation: 2010^[1]

Average annual dose in Scotland, 2,300 microsieverts^[2]

In 2010, the average annual dose of radiation to someone living in Scotland was 2,300 microsieverts, this has fallen from 2,400 microsieverts in 2003. At 81%, the majority of the annual dose comes from natural sources.

The greatest 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 200 Bq/m³, above which measures should be taken to reduce concentrations. Other important natural sources of radiation are terrestrial gamma rays, cosmic rays, and long-lived radionuclides that enter the body through food and drink (classed as internal in the above chart).

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: Health Protection Agency - Radiation Protection Division / Metadata

Activity Concentrations in Milk: 1966-2013^[3]

Exposure to ionising radiation from radioactive substances can have an impact on human health. For this reason a number of foodstuffs are monitored each year to assess that the public has been adequately protected from ionising radiation.

Cows' milk is measured because air-borne radioactive particles falling on pasture are taken up by grazing animals and passed onto their milk. This concentrates radioactive materials from the grazing range of the animals, effectively giving a very large surveillance area. Samples of milk are bulked from a number of farms to give the final activity concentration for Scotland.

From 1966 until 1980, there were gradual falls in the concentrations of Caesium-137 (¹³⁷Cs) and Strontium-90 (⁹⁰Sr) until the concentration was so low it was difficult to detect. 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.

Following the Chernobyl reactor incident in 1986, concentrations of¹³⁷Cs in milk peaked in 1987 and then began to fall again and are now below pre-Chernobyl levels.^[4] In 2013, the concentration of ¹³⁷Cs was <0.052 Bq/litre and ⁹⁰Sr was <0.083 Bq/gram of calcium. However, even at its peak, the ¹³⁷Cs concentration in milk following the Chernobyl accident was around 100 times lower than the Community Food Intervention Levels, defined by Euratom Regulations EC/3954/87 and EC/2218/89, which were derived to ensure the protection of the public.

Source: Scottish Environment Protection Agency / Metadata