Analysis of the natural radioactivity content of bottled waters

The Food Standards Agency has completed a survey to determine the levels of natural radioactivity and uranium in 100 brands of either natural mineral water, spring water or bottled drinking water sold in the UK.

None of the 175 samples analysed breached any legal limits.

The samples which give rise to the highest doses of radioactivity would not add significantly to the average annual background dose received by people living in the UK.

No samples contained soluble uranium at levels which would cause consumers to exceed safe levels of intake.

The results provide no evidence that consumers should change their dietary habits on health grounds.

This survey of natural radioactivity levels in bottled water repeats an earlier survey conducted by the Ministry of Agriculture Fisheries and Food in 1991. Food naturally contains low levels of radioactivity which is increased by man's activities such as authorised discharges to the environment. The Agency decided to conduct this study due to the steady increase in the consumption of bottled waters in the past decade.

The survey was commissioned in 2001 and samples were collected between October and December 2001. The survey was carried out in three separate stages. The results from the initial screening of the samples for gross alpha and beta activities were received in 2002. 51 samples were chosen from the original samples for individual radionuclide analysis to provide estimates of doses of radioactivity. The late delivery of the data on radionuclide levels severely delayed the final reporting of all results and some of the waters sampled in this survey may no longer be available. However, natural mineral waters are required by legislation to have a stable composition and therefore the results of this survey are still relevant. Spring water and other bottled waters may have a more variable composition but the results are still indicative of the levels of radioactivity and uranium present in these products.

The activity of a radionuclide describes the rate at which disintegrations occur within it. The unit is the Becquerel (symbol Bq), with 1 Bq equal to 1 disintegration per second. Each disintegration will release radiation which has an associated amount of energy. It is this energy which can damage the body and so is detrimental to health.

The effective dose (simplified to dose in this paper) is calculated by multiplying the measured activity for each radionuclide by its dose coefficient which takes into account how the energy will interact with the body. The dose is measured in Sieverts (Sv) and gives a broad indication of any detriment to health from the exposure to radiation regardless of the energy or type of radiation.

The average dose from all sources of natural radioactivity in the UK ranges from 2.2 to 7.8 milli Sieverts per year (mSv/yr), depending on location, of which about 0.3 mSv comes from natural radioactivity in food. The radiation dose received from drinking bottled water is part of this natural dose total. However, most of the annual dose comes from radon and cosmic rays. In addition, the population also receives an average dose of 0.4 mSv/yr from medical practices.

Current World Health Organization (WHO) guidelines recommend that any water which could lead to an annual exposure to radiation of more than 0.1 mSv per year should be investigated further. This is known as the reference dose level. Two samples from this survey could lead to this level of exposure. However, this would only be if people drank 2 litres of these particular waters every day all year. This consumption pattern is unlikely. In addition, this amount would only add slightly to the average dose of radiation people are exposed to in the UK from all sources (average 2.2 mSv/yr up to 7.7 mSv/yr). Consequently the Agency does not believe that these waters add any significant risk to consumers.

The WHO also recommends a maximum consumption of 0.5 micrograms per kilogram of bodyweight per day for soluble uranium. This limit is concerned with the toxicity of uranium as a heavy metal rather than its radioactivity. Although the primary concern of this survey is in radiation protection, total uranium levels were also checked during this study and compared with levels found in the Agency's recent total diet survey. The results from the total diet survey for uranium-238 in food indicate that bottled waters could contain up to 14 micrograms per litre of soluble uranium without causing any food safety concerns.

The Natural Mineral Water, Spring Water and Bottled Drinking Water Regulations 1999 (as amended), lay down the maximum levels of radioactivity in spring water and bottled drinking water in the UK. There is no similar limit for natural mineral waters. An amendment to this legislation, which came into force after this survey was started, imposes a maximum Total Indicative Dose (TID) of 0.1 mSv/yr per person. The TID is a legally defined dose that is not identical to the committed effective dose in the WHO guidelines. The TID does not include the contribution from potassium-40, radon and radon decay products, and tritium. The legislation also sets a maximum level for tritium of 100 Bq/l. The results of this survey for natural mineral waters were therefore compared with the WHO reference level while the results for other bottled waters were compared with these regulations.