What is bisphenol A?
Bisphenol A (BPA) is a phenolic compound (C15H16O2, CAS No. 80-05-7), also referred to as 2,2-bis(4-hydroxyphenyl)propane. It was first synthesized over a hundred years ago and is an important industrial chemical used in manufacturing processes. BPA is a major component of rigid polycarbonate plastics and epoxy-resin coatings.
Polycarbonate is commonly used in the food industry for water and soft-drink bottles, and epoxy resins are used as protective linings for metal food cans, wine storage vats and other liquid containers, and as coatings on metal lids used for glass bottles and jars. In addition, polycarbonate plastic containers and tableware are widely used by consumers and the material is also used to manufacture infant feeding bottles.
Although materials containing BPA have been used in packaging and storage vessels for food and beverages for over 50 years, some scientific studies have shown that under certain conditions BPA can migrate into food products. This is of concern because BPA is known to cause adverse health effects in animals at high levels. Canada has recently placed bisphenol A on its list of toxic substances and the US Environmental Protection Agency has identified BPA as a chemical of concern.
What foods can be contaminated?
Detection of BPA has been reported in various canned food and drink products including canned fruit, vegetables, coffee, tea, infant formula concentrate and sake.
A survey of 62 canned food and drink products by the UK Food Standards Agency (FSA) published in 2001 found detectable levels of BPA in fruits and vegetable products, stout, fish, soups, dairy products, meat products and pasta in tomato sauce. However, the Independent Committee on Toxicology of Chemicals in Food, Consumer Products and the Environment (COT) concluded that the levels of BPA found during the FSA survey were unlikely to be a concern for human health.
More recently Canadian surveys published between 2009 – 2010 detected low levels of BPA in bottled and canned beer and soft drinks, canned tuna, soups, vegetables, and pasta products, baby foods in glass jars with metal lids and canned liquid infant formula products.
Estimates of dietary exposure to BPA vary widely and can be based on different methods of calculation.
Using migration figures from food contact materials, levels of BPA found in foods and the amount of food consumed, a recent conservative estimate published in 2006 by the European Food Safety Authority (EFSA) Scientific Panel of Food Additives, Flavourings, Processing Aids and Materials in Contact with Food, gives values ranging from 0.2µg/kg bodyweight (bw)/day for a breast-fed 3 month infant to 13µg/kg bw/day for a 6 month infant fed formula from a polycarbonate bottle and consuming commercial foods and beverages. This highest value falls to 1.5µg/kg bw/day for an adult consuming commercial foods and beverages.
How does it affect human health?
Based on studies in mice and rats, it is widely accepted that exposure to BPA (from the environment as well as from food) at high levels is potentially detrimental to human health. It is an endocrine disruptor and may have an effect on fertility. It has weak oestrogenic activity and has been shown to reduce sperm count and sperm activity. Studies indicate that it could affect development, and there are concerns that BPA can affect the brain, prostate gland and behaviour in foetuses, infants, and young children. Some research suggests that BPA may be carcinogenic, possibly leading to the precursors of breast cancer. Other reports also indicate that it has liver toxicity and may even be linked to obesity by triggering fat-cell activity.
The effect of low level exposure to BPA on human health is far less clear. Some researchers believe that there is evidence in the literature demonstrating that animals exposed to very low doses of BPA suffer adverse affects. However, expert panels asked to review the data generally consider that there is not enough evidence from animal studies to suggest that low levels of BPA adversely affect humans.
It is generally agreed that the overall no-observed-adverse-effect level (NOAEL) for BPA is 5 mg/kg bw/day. Government agencies add in an uncertainly factor to calculations to arrive at what is known as either a tolerable daily intake (TDI), or the maximum acceptable or oral reference dose (RfD). Currently the European Food Safety Authority’s TDI (established November 2006), and the Japanese TDI, as well as the US Environmental Protection Agency’s RfD (established in 1993) for BPA is 0.05 mg/kg bw/day. This value is considerably greater than the highest estimates of dietary intake.
Where does it come from?
BPA can be present in foods as a result of migration from the epoxy-resin coatings used to line metallic food cans and on metal closures for glass jars and bottles. The other main source is the polycarbonate plastic bottles and containers used to package a wide range of products, such as water, soft drinks and milk. BPA in food may also originate from epoxy coatings and polycarbonate plastic used in tanks and containers in the processing environment
Another potential source of BPA in food is polycarbonate tableware used to store foods in the domestic environment. BPA may migrate from tableware to foodstuffs, either from residual BPA in the material, or because various extreme conditions, including repeated cleaning, exposure to heat and contact with acid foods, results in the polycarbonate breaking down to produce BPA, which subsequently migrates into the food.
BPA is also found in a wide variety of non-food sources, such as drinking water storage tanks and water pipes, electrical equipment and various household appliances.
Is it stable in foods?
BPA appears to be readily biodegradable and after a short period of adaptation (3-8 days), levels in natural water environments rapidly decrease (100 % removal in 2 – 17 days). Levels of BPA are also reduced rapidly during wastewater treatment.
BPA is very heat stable. It has a melting point of 155 – 157 °C and polycarbonate plastics can be used up to temperatures of around 145 °C.
How can it be controlled?
It is generally agreed that the levels of ingested BPA should be as low as possible because of the uncertainties that exist about its potential adverse effects on human health. Health Canada has recommended that a general principle of ALARA (as low as reasonably achievable) be applied to limiting exposure of newborns and infants to BPA.
For food processors
The food industry is being encouraged to implement techniques and procedures to reduce the migration of BPA into foodstuffs and to source can and container coatings that contain lower levels of BPA, or are BPA-free. In the USA, the Food and Drug Administration (FDA) is working with manufacturers to develop safe alternatives to BPA for the linings of infant formula cans, and ensuring that these reach the market as soon as possible.
It is important to note that for canned food products, alternatives should not permit bacterial or metallic contamination of the contents, and should not give rise to other safety concerns. The use of alternatives may also reduce the final shelf life of a canned product, if the resistance of the alternative is lower than that of an epoxy-resin-based lining.
Alternatives to BPA-containing plastics can be used for feeding infants and for storing and serving food. The US FDA and Health Canada are actively supporting reasonable efforts to reduce levels of BPA in the food supply, especially for infants and young children.
The FDA is encouraging industry to stop producing new BPA-containing baby bottles and infant feeding cups destined for the US market, and elsewhere some countries have introduced legislation banning the use of BPA in the manufacture of infant feeding bottles.
Are there rules and regulations?
There are no restrictions, at present, on the amount of BPA that can be present in most final plastic products, but the tendency of BPA to migrate from food contact materials has been acknowledged in European Union food law. In 2002, EU legislation was introduced setting a Specific Migration Limit (SML) of 3 mg BPA per kg food. This was amended in 2004 to set a SML(T) of 0.6 mg BPA per kg food. The migration limit in Japan allows a maximum of 2.5 ppm. There is no SML in the USA at present.
Some countries have recently considered banning, or have banned, the use of BPA in plastics used for baby feeding bottles. Following national bans in Denmark and France, the EU banned the manufacture, marketing or importation of BPA-containing polycarbonate infant feeding bottles in 2011 and the Canadian Government is reported to be considering similar restrictions.