Reusable plastic water bottles (R-PWBs) are popular for convenience, cost savings, and reducing single-use plastic waste. While designed for repeated use, their widespread adoption has led to questions concerning their safety, primarily revolving around chemical exposure from the plastic and the potential for microbial growth. Addressing these concerns involves examining the specific materials used and the required hygiene practices.
Understanding the Chemical Concerns in Plastic Bottles
The primary safety concern involves the leaching of chemical compounds from the plastic into the stored water. Plastic is not inert, and chemical additives used during manufacturing can migrate out of the polymer structure over time. Bisphenol A (BPA) is the most recognized of these compounds, traditionally used to make hard, clear polycarbonate plastic.
BPA is an endocrine-disrupting chemical (EDC) that can interfere with the body’s hormonal system, linked to issues like fertility problems and obesity. In response to public concern, manufacturers began labeling products as “BPA-free,” often replacing BPA with chemically similar substitutes. These alternatives, such as Bisphenol S (BPS) and Bisphenol F (BPF), are also coming under scrutiny.
Initial studies indicate that BPS and BPF exhibit endocrine-disrupting properties similar to BPA. The rate at which these and other plastic additives leach increases significantly when the bottle is exposed to certain conditions. High temperatures, such as those found inside a hot car or from repeated cycles in a dishwasher, accelerate this migration of chemicals.
Physical damage to the plastic, like deep scratches on the interior surface, provides a pathway for chemical release. The aging of the plastic material over years of use can cause the polymer to break down, increasing the risk of chemical migration. One study observed that dishwashing a reusable plastic bottle increased the release of compounds, identifying hundreds of different chemicals migrating into the water.
How Different Plastic Materials Affect Safety
Understanding the Resin Identification Code (RIC) helps consumers determine the relative safety of a plastic bottle. These codes classify the type of plastic resin used, with numbers 2 and 5 generally considered the safest for reusable water bottles. High-Density Polyethylene (#2 HDPE) is a sturdy material that shows high durability and is less likely to leach chemicals.
Polypropylene (#5 PP) is another popular option for reusable containers due to its resistance to chemical leaching and higher tolerance for heat. These materials are robust and are preferred choices for manufacturers aiming for a safer product. In contrast, Polyethylene Terephthalate (#1 PET), commonly used for single-use bottles, is not designed for repeated use, and its safety decreases as chemical leaching risk increases over time.
The catch-all category, Resin Identification Code #7 “Other,” requires careful attention from consumers. This code includes a wide variety of plastics, prominently polycarbonate, which traditionally contained BPA. The safest approach is to avoid this code entirely unless the product is specifically labeled as being made from an alternative material like Tritan copolyester.
Tritan is a type of plastic widely used in “BPA-free” products and is considered a safer alternative to polycarbonate. Studies show that Tritan does not leach detectable levels of BPA, contributing to its popularity. When selecting a bottle, looking for materials explicitly labeled as #2 HDPE, #5 PP, or a trusted alternative like Tritan offers a path to reducing chemical exposure risk.
Preventing Microbial Risk Through Proper Hygiene
Beyond chemical concerns, the most common safety issue is the buildup of microbes, including bacteria, mold, and fungi. The combination of a moist interior environment, oral bacteria introduced through backwash, and the warmth of a carried bottle creates an ideal breeding ground for these organisms. Studies have found high concentrations of bacteria, including skin and oral microbes like Staphylococcus and Streptococcus.
Bacteria tend to multiply in difficult-to-clean areas, such as the lid threads, spouts, and straws. To mitigate this risk, experts recommend washing the bottle daily with warm water and detergent. If daily washing is not feasible, the bottle should be cleaned at least a few times per week to prevent the accumulation of microbial films. A bottle brush should be used to thoroughly scrub the interior surfaces and lid components to ensure all crevices are reached.
For deeper sanitization, the bottle can be cleaned with a solution of half white vinegar and half water, or placed in a dishwasher if the plastic is rated as safe. After cleaning, allow the bottle to air-dry completely, as sealing a damp bottle promotes mold growth.