Plastic water bottles are a convenient way to stay hydrated, but concerns exist regarding the chemicals they may introduce into drinking water. The safety of a plastic container depends entirely on the type of plastic resin used, how it is manufactured, and how the bottle is used and stored. Understanding these differences helps consumers make informed choices. This guide will demystify the identification codes on plastic products and outline the safest options for long-term use.
How to Read Plastic Identification Codes
The standardized system used to classify plastic materials is the Resin Identification Code (RIC). This code is a triangular symbol with a number inside, typically embossed on the bottom of a container. The RIC identifies the specific polymer used, primarily to aid in recycling sorting.
The numbers range from 1 to 7, with each digit corresponding to a different type of plastic resin. Code 1 indicates Polyethylene Terephthalate (PET), commonly used for single-use beverage bottles. Code 2 represents High-Density Polyethylene (HDPE), and Code 5 indicates Polypropylene (PP). Code 7 is a catch-all category for “Other” plastics, including polycarbonate, bioplastics, and materials not covered by codes 1 through 6.
Chemical Leaching and Potential Health Concerns
Safety concerns arise from chemical leaching, which is the migration of additives or monomers from the plastic into the stored water. This migration is accelerated by factors like heat, prolonged storage, and repeated use.
The compounds of concern mimic or interfere with the body’s hormones, leading to endocrine disruption. These include Bisphenol A (BPA) and phthalates (PAEs). BPA is used to harden certain plastics, while phthalates are added as plasticizers to increase flexibility. Exposure to these chemicals is associated with health issues, including altered reproductive development and metabolic disruption.
The Safest Plastics for Reusable Water Bottles
The appropriate materials for reusable water bottles exhibit high chemical stability, heat resistance, and inertness.
High-Density Polyethylene (HDPE), code 2, is a durable plastic. It is considered a safe, non-leaching option for long-term use.
Polypropylene (PP), code 5, is highly recommended because it possesses the highest heat resistance among common food-grade plastics. This makes PP safe for sterilization and dishwasher cleaning.
Low-Density Polyethylene (LDPE), code 4, is also safe and is often used for flexible, squeezable bottles, though it is less durable than PP.
An increasingly popular choice under the Code 7 “Other” category is Tritan copolyester. Tritan is engineered to be free of bisphenol compounds, including BPA and BPS, and maintains clarity and durability. When selecting a Code 7 plastic, look for explicit labeling confirming it is BPA-free or made of Tritan.
Specific Safety Concerns for Single-Use Plastics
Single-use plastic bottles are typically made from Polyethylene Terephthalate (PET), designated by code 1. PET is safe for its intended single use, but its safety profile changes significantly when exposed to environmental stresses.
When PET bottles are exposed to heat, such as being left in a hot car, antimony trioxide can leach into the water. Antimony is a toxic heavy metal used as a catalyst during PET production, and its leaching rate increases sharply above 45°C. Studies show that at temperatures around 65°C, antimony levels can exceed the maximum contaminant level in drinking water.
Repeated use, scratching, or harsh cleaning of single-use PET bottles can accelerate the release of chemicals and create micro-abrasions that harbor bacteria.
Certain other plastics should also be avoided for drinking water storage. Polyvinyl Chloride (PVC), code 3, is known to contain phthalates which can leach into the contents. Traditional Polycarbonate (PC), often included in the Code 7 category, is made with BPA and releases the compound into liquids, particularly when heated.