Bisphenol A (BPA) is a chemical compound classified as an endocrine disruptor because it can interfere with the body’s hormonal systems. Consumers often question whether BPA is present in everyday items like plastic bags. The direct answer is that common, flexible plastic bags made from polyethylene and polypropylene generally do not contain BPA. This chemical is not a necessary ingredient in the production of the polymers used for the vast majority of single-use and reusable grocery bags.
The Core Components of Plastic Bags
The primary materials used in the manufacture of most plastic bags are High-Density Polyethylene (HDPE) and Low-Density Polyethylene (LDPE), both of which are polymers of ethylene. HDPE is the material used for the thin, crinkly grocery bags and is characterized by long, straight molecular chains with minimal branching, which gives the material its strength and relative opacity. LDPE is used for sandwich bags, trash bags, and other flexible films, and its molecular structure features significant branching, resulting in a softer, clearer, and less dense material.
The polymerization process for creating both HDPE and LDPE involves linking together thousands of ethylene monomers. This process does not require the use of BPA as a building block or an additive. Polypropylene (PP), sometimes used for thicker, reusable shopping bags, is also a distinct polymer that does not utilize BPA in its synthesis. The absence of BPA in these polyethylene and polypropylene materials confirms that plastic bags are considered BPA-free.
What BPA Is and Where It Is Found
BPA is a synthetic organic compound formed from the reaction of two primary chemicals: phenol and acetone. Its primary commercial application is as a monomer, a building block chemical, in the creation of specific types of plastics and resins. The most common use is in the production of polycarbonate plastic, which is a hard, clear plastic often marked with the recycling code 7. Examples of polycarbonate products include durable water bottles, some food storage containers, and eyeglass lenses.
BPA is also a component of epoxy resins, which are used as a protective lining inside metal food and beverage cans to prevent corrosion. The Food and Drug Administration (FDA) has regulated BPA in food contact materials, and regulations no longer allow its use in baby bottles, sippy cups, and infant formula packaging.
Alternative Chemicals in Flexible Plastics
While common plastic bags are not made with BPA, the conversation about the safety of flexible plastics often turns to other chemical additives. The family of chemicals known as phthalates are sometimes used as plasticizers to increase the flexibility and durability of certain plastics, particularly polyvinyl chloride (PVC) or vinyl. Phthalates are not typically added to polyethylene or polypropylene plastic bags, but they are found in other flexible food contact materials like some types of cling wrap, tubing, and gaskets.
These plasticizers are generally not chemically bound to the polymer, meaning they can migrate out of the material and into food, especially when the food is fatty or heated. Phthalate exposure is a concern because some are also classified as endocrine-disrupting chemicals. Regulatory bodies have been reviewing and revoking authorizations for the food contact uses of many phthalates, leading the industry to replace them with alternative plasticizers.