Bisphenol A (BPA) is an industrial chemical used primarily since the 1950s. It serves two main functions in manufacturing: creating polycarbonate plastics and acting as a component in epoxy resins. Polycarbonate is a hard, durable plastic used in reusable food and drink containers. Epoxy resins use BPA to create protective liners for metal products, most notably food and beverage cans. Small amounts of BPA can migrate from the plastic or resin into the food or liquid it contains, which is the source of public concern.
Plastics Associated with BPA Content
The primary plastic containing Bisphenol A is polycarbonate, often identified by the Resin Identification Code (RIC) #7. This code, labeled inside the chasing arrows symbol, stands for “Other” and is a catch-all category for plastics not covered by codes 1 through 6. Polycarbonate plastics include hard, clear items such as reusable water bottles, older baby bottles, and certain tableware. Since the #7 code is broad, it also includes many modern BPA-free alternatives and bioplastics.
A less common exposure pathway exists through plastics marked with code #3, or Polyvinyl Chloride (PVC). While BPA is not a primary building block of PVC, it can be added as an antioxidant to protect the material from degradation during processing. This use has been documented in certain flexible PVC products, such as some plastic food wraps and vinyl gloves. However, the most significant non-plastic source of exposure comes from the interior coatings of metal cans.
BPA is a component used in the manufacturing of epoxy resins that line the inside of most metal food and beverage cans. This resin lining prevents the metal from corroding or reacting with the contents, preserving the food’s quality. Canned foods and liquids are often cited as a main source of dietary BPA exposure because residual amounts can leach into the preserved food.
Factors Affecting BPA Release
The amount of Bisphenol A that migrates from the plastic into food or liquid is significantly influenced by environmental factors. The primary factor is the application of heat, which dramatically increases the rate of chemical breakdown and release. Heating polycarbonate containers—through microwaving, pouring in hot liquids, or high-temperature dishwashing—accelerates the leaching process. Exposing new and used polycarbonate bottles to boiling water can increase the rate of BPA release by as much as 55 times.
The surface condition and age of the plastic also play a role in migration rates. Over time, physical wear, such as scratches and repeated cleaning, causes the polymer bonds to break down. This wear increases the surface area from which BPA can leach. Older or frequently used polycarbonate containers are more likely to release higher concentrations of the chemical than new containers.
The composition of the stored food or liquid can also affect the rate of release. Both acidic and fatty contents accelerate the migration of BPA from the container or can lining. For example, highly acidic foods like tomato products or citrus juices, and fatty foods such as fish or coconut cream, are more likely to draw BPA out of the epoxy resin linings of cans.
Choosing BPA-Free Alternatives
Consumers seeking to reduce their exposure to Bisphenol A can prioritize non-plastic options for food and liquid storage. Materials like glass are chemically inert and do not leach chemicals, making them a safe choice for food containers and baby bottles. Stainless steel provides another excellent, durable alternative for items like water bottles and lunch containers, offering a non-plastic surface for food contact.
When plastic use is unavoidable, certain Resin Identification Codes are considered safer for food contact materials. These include polyethylene terephthalate #1 (PET), high-density polyethylene #2 (HDPE), and polypropylene #5 (PP). These plastics are not manufactured with BPA and are commonly used for disposable water bottles, milk jugs, and yogurt containers. Choosing containers made from these plastics minimizes the risk associated with BPA-containing materials.
Products labeled “BPA-Free” should be approached with caution, as this label only means the specific chemical Bisphenol A was not used. Manufacturers often replace BPA with structurally similar bisphenols, such as Bisphenol S (BPS) or Bisphenol F (BPF). Research suggests that BPS and BPF can act as endocrine disruptors, meaning they may not offer a significant safety improvement. Prioritizing glass and stainless steel remains the most definitive strategy for the lowest possible exposure.