Bisphenol A (BPA) is a synthetic industrial chemical primarily used to make polycarbonate plastics and epoxy resins. Polycarbonate plastic is rigid and transparent, commonly found in reusable water bottles, food storage containers, and tableware. Epoxy resins containing BPA line the inside of metal products, such as food cans, to prevent corrosion. The public concern centers on the fact that this chemical can migrate from the packaging materials into the food or beverage it holds. This raises the question of whether washing can effectively remove or prevent this contamination source.
Understanding BPA Leaching
BPA is not a surface coating that can be easily rinsed away; it is a fundamental molecular building block of the plastic itself. During manufacturing, BPA molecules are linked together to form a stable, long-chain polymer structure. This polymer gives polycarbonate plastic its strength, clarity, and shatter-resistant properties. However, the polymerization process is rarely complete, leaving small amounts of unreacted BPA molecules, known as monomers, trapped within the plastic matrix.
These unbound BPA molecules are the source of contamination, capable of slowly migrating out of the plastic into the surrounding contents. This process is known as leaching or migration, and it is an inherent characteristic of the material. Leaching occurs because the chemical bonds holding the polymer together are not entirely stable, allowing the unattached BPA to escape. The migration rate depends on external and internal factors, not the cleanliness of the surface.
The Effectiveness of Standard Cleaning
Washing does not solve the problem of leaching. While washing a plastic container may remove trace amounts of BPA that have already migrated to the surface, standard handwashing cannot address the reservoir of unreacted BPA embedded deep within the plastic’s chemical structure.
Washing methods, even with gentle soap and cool water, do little to stop the internal migration process. Aggressive cleaning or the use of certain detergents can actually worsen the situation by damaging the plastic’s surface. Since the plastic itself is the source of contamination, washing cannot chemically alter the material to prevent future migration. Cleaning only removes the surface-level symptom, not the underlying cause.
Environmental Factors That Increase BPA Release
The most significant factor accelerating BPA migration is heat. High temperatures cause the polymer matrix to expand and chemical bonds to vibrate, dramatically increasing the speed at which unreacted BPA molecules escape. Studies show that exposing polycarbonate bottles to boiling water can increase the rate of BPA release by as much as 55 times compared to room temperature water. This thermal acceleration means microwaving food in plastic containers or running them through a dishwasher on a hot cycle poses a substantial risk.
Mechanical stress is another major contributor to increased leaching. Physical wear and tear, such as scratching from abrasive cleaners or repeated scrubbing, degrades the plastic’s surface integrity. This damage creates new pathways for the trapped BPA to escape into the contents.
The chemical nature of the stored food or cleaning agents also influences the migration rate. Both highly acidic substances, like tomato products or citrus juices, and alkaline substances, such as certain dishwashing detergents, can degrade the plastic’s chemical structure. This chemical attack on the polymer bonds facilitates the release of BPA. The combination of heat and harsh alkaline detergents in a dishwasher is particularly problematic.
Practical Steps for Minimizing Exposure
Since cleaning cannot stop the continuous leaching of BPA, minimizing exposure requires focusing on prevention and substitution. The most direct approach is to avoid using plastics known to contain BPA, often marked with the recycling code “7.” Consumers should look for alternatives made from materials that do not rely on bisphenols.
Choosing Safer Alternatives
Safer choices for food and beverage storage include containers made of glass, stainless steel, or ceramics, as these materials do not contain BPA. When purchasing canned goods, look for products labeled “BPA-free” or opt for fresh and frozen alternatives. If using canned food, transfer the contents to a non-plastic container before heating, as the epoxy lining is a major source of contamination.
It is also advisable to avoid heating any plastic food container, even those labeled “microwave-safe,” as heat accelerates the leaching process. While many manufacturers offer “BPA-free” plastics, substitutes like Bisphenol S (BPS) or Bisphenol F (BPF) are structurally similar to BPA and may also exhibit endocrine-disrupting properties. Choosing non-plastic alternatives remains the most reliable strategy.