In mid-February 2006 the US Food and Drug Administration (FDA) reported the results of tests showing that some soft drinks were contaminated with the chemical benzene at levels above the World Health Organisation limit for drinking water of 10 parts per billion (ppb). The problem had originally been identified in the early 1990s, when it was demonstrated in laboratory trials that benzene could be produced in soft drinks containing sodium benzoate (E211) and ascorbic acid (Vitamin C) (E300) through interaction of these two permitted food additives. The benzoates are preservatives and can occur naturally for instance, in cranberries. Benzoates are used in beverages to inhibit the growth of bacteria, yeasts and moulds. A maximum amount of 150 mg/L benzoates may be added to non-alcoholic flavoured beverages (except milk based beverages). Ascorbic acid can also occur naturally in many berries and fruit but can also be added as an antioxidant in order to maintain colour and other quality characteristics. No maximum limits for ascorbic acid are laid down in legislation. However, in accordance with good manufacturing practice, the amount of ascorbic acid used should be as low as possible to achieve the desired technological effect (" quantum satis "). The presence of these two food additives in food products must be declared in the ingredients list on the food packaging or label, in accordance with the legislation on food additives.

The formation of benzene in soft drinks is often exacerbated when the beverages are stored for extended periods at elevated temperatures. Light can also promote benzene formation. Evidence indicates that nutritive sweeteners (sugar, high fructose corn or starch syrup) can delay the reaction as the phenomenon seems most noticeable in diet beverages, however the longer the shelf-life of a product, the greater potential for benzene formation if its precursors are present. There is also some evidence to suggest that ethylene diamine tetraacetic acid (EDTA) which is used as a sequestrant may mitigate the reaction by complexing metal ions that may act as catalysts. EDTA is an approved additive in the EU but it is only permitted in a small number of products and so far it is not approved for use in soft drinks.

This FDA report attracted widespread media attention, because exposure of humans to benzene has been associated with leukaemia and other blood disorders. Benzene is a solvent that was widely used in the past and is still used in industry and in a variety of applications. These applications include its use as an additive in unleaded petrol. It is found in air, particularly in urban areas, as a result of emissions from motor vehicle exhaust , service stations and industrial emissions. Benzene also occurs naturally at a low level in some foodstuffs of plant origin. People are therefore exposed routinely to benzene via their environment. It has been estimated by the UK Department of Health that people in an urban environment may be exposed to approximately 400 ppb of benzene per day just by breathing traffic fumes. This results in an exposure level which is equivalent to drinking about 40 litres of water containing approximately 10 ppb benzene per litre. Cigarettes have also been found to release between 50 and 150 ppb of benzene per cigarette, making smoking and second-hand smoke sources of benzene exposure. The European Beverages Association (UNESDA) has estimated that the average population exposure to benzene via air is 220 ppb per day. Like all carcinogenic substances for which no toxicological threshold value can be indicated, benzene intake should be minimised and/or avoided as far as possible in line with preventive consumer protection.

The European soft drinks industry represented by UNESDA have been working with regulatory authorities to reduce and where possible to completely eliminate the formation of benzene, whilst still ensuring the microbiological stability and quality of soft drinks. Industry have produced a guidance document to mitigate the formation of benzene in soft drinks and this was presented at the EC Standing Committee on Food Chain and Animal Health, Toxicological Safety held in Brussels at the end of March, 2006. Industry reported that levels in soft drinks are typically found at the analytical limit of detection (1-5 ppb) and always below 10 ppb. There are currently no legal limits for benzene that apply directly to finished soft drinks. There are several regulatory guidelines and limits set for drinking water and bottled water ranging from the World Health Organisation limit of 10 ppb to the U.S. EPA/FDA level of 5 ppb and the EU level of 1 ppb. As a result of discussions at a recent EC Standing Committee meeting, a consensus among the Member States was that a general approach should be taken and a limit for control and enforcement purposes should be set for benzene. The majority of Member States favoured setting the action limit at 10 ppb.

A number of surveys have been carried out by food safety agencies and industry across the EU. These included a survey by UK industry on benzene in 230 soft drinks available on the UK market. The results of this survey showed that where benzene levels were detected they were very low and are not a concern for the public. Since then further testing of 150 products has been carried out by the Food Standards Agency (FSA) in the UK and the results showed that benzene was not detectable or between 1 and 10 ppb in the majority of products (146 out of 150). There were however, four products which exceeded 10 ppb and these were withdrawn from the market. Testing is also ongoing in other EU Member States.

During March 2006 the FSAI conducted a survey in conjunction with the Galway Public Analysts Laboratory in order to establish the levels of benzene present in 76 samples of soft drinks, squashes and flavoured waters available on the Irish market