Polyethylene Terephthalate, or PET, is a thermoplastic resin that has become the most widely used plastic for packaging beverages and many foods. This polymer is recognizable as the clear, lightweight material in soft drink bottles, water bottles, and various food containers. Although its ubiquity has led to frequent public concern, the current scientific consensus is that PET is safe for human consumption under normal conditions of use. Global health and safety organizations have repeatedly reviewed the data and approved its use for food and beverage contact.
The Chemistry of PET and Its Stability
The inherent safety of PET stems from its unique molecular architecture as a long-chain polyester. This polymer is synthesized through a polycondensation reaction between two primary building blocks: purified terephthalic acid and ethylene glycol. The resulting chemical structure consists of long, complex molecular chains linked by stable ester bonds.
The sheer size of these long polymer chains makes the base material non-toxic, as they are far too large to be absorbed into the human body. PET is chemically inert, meaning it does not readily react with the substances it contains, preserving the flavor and quality of the food or drink. Furthermore, its mechanical properties offer excellent strength, impact resistance, and low permeability to gases like oxygen and carbon dioxide, which helps extend the shelf life of packaged contents.
Addressing Specific Compound Leaching Concerns
Despite the material’s inherent stability, the manufacturing process and subsequent storage can lead to the presence of trace compounds that have fueled concerns about leaching. Scientific investigations have focused on the migration of these substances from the plastic matrix into the packaged food or liquid. These studies reveal that while migration can occur, the concentrations are extremely low and depend heavily on environmental conditions.
Antimony Trioxide
Antimony trioxide is a metallic compound commonly used as a catalyst during PET production. Studies confirm that antimony can leach from the bottle wall into the contents, with the rate of migration increasing significantly when the plastic is exposed to elevated temperatures. Storing water in PET bottles at 50 degrees Celsius or higher, such as during transport or in a hot car, increases antimony concentrations. While these elevated concentrations may occasionally exceed the most stringent regulatory guidelines, the levels remain many times lower than those considered an immediate health risk.
Acetaldehyde
Acetaldehyde is another compound of interest, forming as a volatile byproduct during the high-heat manufacturing process of PET bottles. This compound is not considered a health risk at typical concentrations, but it can create a noticeable sensory effect. In sensitive products like still water, acetaldehyde can migrate and impart a faint, sweet, or fruity off-taste, which is considered a quality defect rather than a safety hazard. Manufacturers often employ methods like using scavengers or specialized barrier layers to minimize its presence and prevent this undesirable flavor change.
Confusion often relates to plasticizers, specifically phthalates, which are used to soften certain other types of plastic. PET does not require phthalates for flexibility and is not manufactured with them. Although the chemical name, polyethylene terephthalate, is a source of misunderstanding, the polymer is chemically distinct from phthalate plasticizers. Trace amounts of phthalates detected in some studies are often attributed to environmental contamination, such as from bottle caps, labels, or the recycling process, rather than being an intentional component of the PET polymer itself.
Regulatory Findings and Public Misconceptions
Major regulatory organizations around the world have extensively evaluated PET and consistently affirm its safety for food contact. The U.S. Food and Drug Administration (FDA), for example, has approved PET resins for use in food packaging under its specific regulation, 21 CFR 177.1630. Similarly, the European Food Safety Authority (EFSA) has concluded that PET is safe for its intended use, with migration levels of its constituent substances falling well within acceptable limits.
A significant public misconception involves confusing PET with other types of plastic, particularly polycarbonate. Polycarbonate plastics sometimes contain Bisphenol A (BPA), an industrial chemical that has raised health concerns. PET is made from completely different monomers—terephthalic acid and ethylene glycol—and does not contain BPA. This chemical difference means PET is inherently BPA-free.
Another common rumor is that freezing or reusing PET bottles significantly increases the migration of harmful chemicals. Scientific data does not support this claim, as migration rates remain well below safety thresholds under normal storage and use, including freezing. The primary concern with reusing PET bottles is not chemical leaching, but rather the potential for bacterial contamination from improper washing and repeated use, which is a concern for any reusable container.