Polyethylene Terephthalate (PET) plastic is a lightweight, clear, and durable material that is the primary choice for packaging single-serving bottled water and other beverages globally. This material, also known as PETE, is a polyester resin that is chemically stable and resistant to micro-organisms, making it highly suitable for food and drink contact. Its widespread adoption is due to its excellent barrier properties, shatter-resistance, and efficiency in transport. The safety of PET plastic for drinking water has been a frequent subject of public debate and scientific scrutiny, requiring an objective assessment of chemical migration and the conditions under which it might occur.
Composition and Global Safety Approval
Polyethylene terephthalate is chemically formed by combining ethylene glycol and terephthalic acid, which link together to create long polymer chains. This plastic is easily identified by the recycling symbol #1, typically molded onto the container. A key characteristic of PET is its chemical inertness, meaning it is not prone to reacting with its contents, which is a major factor in its approval for food contact applications. Major international health and regulatory organizations have consistently determined that PET is safe for single-use food and beverage packaging. Agencies like the U.S. Food and Drug Administration (FDA) and the European Food Safety Authority (EFSA) have approved PET based on extensive testing. This consensus confirms that PET bottles are safe for storing water under normal conditions, rooted in the material’s inherent stability and the fact that it does not contain chemicals like Bisphenol A (BPA) or phthalates.
Key Chemicals and Leaching Studies
Despite broad regulatory approval, scientific studies examine the potential for trace amounts of manufacturing byproducts to migrate into the water. The two primary substances of concern are antimony and acetaldehyde. Antimony, a metalloid element, is used as a catalyst in PET production and remains trapped within the plastic matrix. Acetaldehyde is a volatile organic compound and a degradation byproduct of PET, sometimes forming during manufacturing or over time. Leaching studies confirm that small amounts of both antimony and acetaldehyde can migrate into the bottled water, but concentrations are generally extremely low, often in the parts-per-billion range. Regulatory bodies have set strict safety thresholds for these chemicals. The typical levels of antimony found in bottled water are far below these limits, such as the 5 to 6 micrograms per liter limit set by European and U.S. regulations. The World Health Organization (WHO) has stated that antimony concentrations found in bottled water represent a negligible health risk, amounting to only about 1% of the tolerable daily intake. This context suggests that while migration occurs, the resulting chemical exposure poses a low risk when bottles are used as intended.
How Temperature and Time Influence Leaching
The safety profile of PET plastic changes significantly when bottled water is subjected to external factors like heat and extended storage. Temperature is the most influential variable, as it increases kinetic energy within the plastic, accelerating the release of chemicals like antimony. Research shows that a sharp increase in leaching occurs when PET bottles are exposed to temperatures above 45–50°C (113–122°F). Storing water at 80°C (176°F) for 48 hours can increase antimony concentrations to levels that exceed established drinking water limits. Leaving a PET bottle in a hot car or direct sunlight can easily reach or surpass these critical temperature thresholds.
Prolonged storage time also contributes to increased chemical migration, as the contact time between the water and the plastic matrix is extended, allowing for a gradual accumulation of leached substances. Repeated reuse of a PET bottle can compromise its integrity, further increasing the potential for chemical release. Physical wear, such as scratches, cracks, and the stress from repeated washing, can degrade the polymer structure. Washing bottles with hot water or strong detergents accelerates the breakdown of the plastic, which is designed for single-use. Therefore, the combination of high heat, long storage, and physical damage represents the highest risk scenarios for increased chemical leaching.
Responsible Use and Disposal
To ensure the safety of bottled water, consumers must manage the conditions under which PET bottles are stored and used. The fundamental guidance is to keep bottled water in a cool, dark location, away from direct sunlight or sources of high heat. Consumers should avoid leaving bottles in places like a car trunk, a garage, or a windowsill, especially in warmer climates, as this minimizes the thermal acceleration of chemical leaching. Because PET bottles are designed for single use, repeated refilling should be approached with caution.
Reusing a bottle can introduce bacteria from the environment and the user, and the physical act of washing and refilling can damage the plastic. If a bottle must be reused for a short time, it should only be gently hand-washed with mild soap and cold water. Any bottle showing signs of physical damage, cloudiness, or wear should be immediately discarded. Following these practical steps helps maintain the low-risk profile of PET packaging.