Why do food cans have liners?
The hard plastic coating on the insides of metal food cans acts as a barrier between the metal and the food, creating a seal that keeps the food safe from bacterial contamination. The lining prevents food from corroding the metal can as well as preventing metal from leaching into the food and altering its taste.
Some light-colored fruits are packaged in cans with no lining in the can body. These cans are steel with a tinplate interior surface. The tin reduces oxidation and discoloration of the fruit. The can lid (and the bottom end) are, however, coated to protect the welded side seams from corrosion.
Doesn't the FDA approve food can linings?
Yes, but the regulatory systems governing chemicals used in food packaging fall far short of ensuring that these chemicals are safe for consumption. For example, hazardous chemicals such as phthalates, several of which have been banned in children’s products, are approved for use in food packaging. We know from many research studies that chemicals present in food packaging routinely leach into food and enter people’s bodies.
How do the chemicals in the can liners get into the food?
All can linings start with a mix of ingredients, including chemical building blocks called monomers. For example, BPA is a monomer for BPA-based epoxy. Other chemicals are also added. The monomers and other chemicals react with one another, binding together to make up the final coating. The resulting polymer can be incomplete, leaving BPA (or other monomers) not bound to the can lining. As a result, can linings can contain unreacted, free BPA, which migrates from the liner into food.
Some research suggests that much of the BPA present in canned foods gets there during the sterilization step, in which the filled can is heated. Heat greatly increases migration rates. Other research suggests that the type of food may influence BPA migration rate.
Our study identified a major research gap regarding residual chemicals in food can linings: Dozens of different chemicals other than BPA are used in the various alternative coatings, as well as in BPA-based epoxy. Research is lacking on safety of these chemicals and the extent to which they may migrate into food.
What lining is preferable?
Thus far, we do not see any replacements in use with sufficient data on their safety or capacity to migrate. We know the canned food and can lining industry is actively exploring replacements, and we encourage transparency about the chemistry and safety data regarding those alternatives to both food companies and consumers.
What is BPA? / What is the problem with BPA?
BPA is a synthetic chemical that is recognized as endocrine-disrupting because of its effects on hormones, including estrogen.
The scientific evidence linking BPA exposure to harm in humans is growing: Hundreds of animal and human studies have linked BPA exposure, often in extremely small amounts measured in parts per billion and parts per trillion, to a number of health problems, including breast and prostate cancer, asthma, obesity, behavioral changes including attention deficit disorder, altered development of the brain and immune system, low birth weight and lowered sperm counts.
Should I buy canned food labeled "BPA-free"?
Yes, it is a good idea to avoid BPA. However, our investigation questions the safety of BPA-free coatings as well. Due to lack of safety assessments, retailers and brands could be replacing BPA-based epoxy with regrettable substitutes. The data from FDA’s review and approval of packaging additives are extremely limited when it comes to BPA-free can coatings. We also have found very little data in the published scientific literature regarding the health effects of BPA epoxy replacements.
We suggest 1) avoiding cans with BPA epoxy and 2) minimizing consumption of canned foods in general.
How do I avoid BPA in food cans?
Until we see strengthened federal regulation of food packaging and voluntary market-based solutions that provide people with the information they need to make safe and informed purchases of canned food, we recommend consumers do the following:
Why would a company knowingly use something that's potentially harmful?
Food manufacturers purchase cans, coated and ready for filling, from can suppliers, who purchase the can coating mixtures from resin suppliers. Our research revealed that the resin and can suppliers are not always providing their customers--the food manufacturers—with full disclosure regarding the chemical identity or safety data for the can linings they’re buying. The national brands and retailers thus find it impossible to be fully transparent with the public about the safety of their food cans.
Why aren't cans labeled to inform consumers of the lining material in the can?
Even though most national brands — and a number of private-label retail brands — now claim to be manufacturing BPA-free canned foods, few are labeling their products BPA-free, with the notable exception of Amy’s Kitchen and Eden Foods.
We are calling on manufacturers to label food cans with the identity of their can linings, but it is not required by law that they do so.
Did you find other bisphenols being used in place of BPA in can linings?
No, we did not see evidence of other bisphenols. Other bisphenols would have different infrared (IR) spectra than BPA. All the can linings identified as BPA-based epoxy in our study match the spectral pattern of BPA.
How did you choose which stores and products to test?
192 cans were purchased from 22 retail stores. The cans included 68 brands from 44 food manufacturing companies. Cans were chosen to include samples representing the following categories:
For each selected retailer, the study included at least one can each of 1) plain beans (pinto, black, garbanzo, etc.) and 2) tomatoes or tomato sauce. This allowed us to compare two commonly purchased food types, each with different requirements for can coatings due to their different properties, across multiple retailers and brands.
How is this report different than recent reports published on BPA in cans?
Our report is the first to include extensive product testing to determine the types of linings currently being used. We went beyond the usual focus on BPA-based coatings by identifying the lining types in nearly 200 cans, including the alternatives being used in place of BPA-based epoxy. We found widespread use of PVC (25% of tested cans) and polystyrene-acrylic resins (39%)--two potentially poor substitutes.
Also, our survey of food manufacturers and retailers achieved a relatively high response rate.
Why this report?
This report is meant to serve as a wake-up call for national brands and retailers who may be jumping from the frying pan into the fire by eliminating BPA in favor of regrettable substitutions. Consumers want BPA-free food cans that are truly safer, not food cans lined with alternative chemicals that are toxic or that have unknown safety.
What recommendations do you have for the national brands, retailers, dollar stores and suppliers?
National brands, grocery stores, big box retailers, and dollar stores, should take these steps:
Can lining suppliers can be part of the solution by publicly disclosing the chemical composition of their can linings and ensuring that the final materials have been rigorously assessed for their impacts on environmental and human health.
What can I do?
Reinforce and strengthen the call for safer food cans in the following ways: