The safety of bottled water depends on its source, processing, and container material. Consumers recognize that bottled water quality varies significantly and is not inherently superior to tap water. Determining the safest choice requires examining these factors, as differences in treatment and packaging directly influence the final purity and potential for chemical exposure.
Understanding Bottled Water Sources and Processing
Bottled water is categorized as either natural source water or processed water. Natural source water, including spring and mineral water, is collected from protected underground formations. Spring water is collected from a natural emergence or borehole and may undergo minimal treatment, such as filtration, but must retain its original source properties.
Mineral water must also come from a protected underground source and is defined by regulation as containing at least 250 parts per million (ppm) of total dissolved solids (TDS). These minerals, such as magnesium, calcium, and potassium, must be naturally occurring. Since mineral content varies by source, the levels of dissolved solids are often inconsistent across different brands.
Purified water, sometimes labeled distilled or reverse osmosis (RO) water, can originate from any source, including tap water. This water is defined by the rigorous treatment it undergoes to remove chemicals and contaminants. Purification methods like RO force water through a membrane, stripping out up to 99% of dissolved solids, heavy metals, and pathogens. Distillation involves boiling the water into vapor and condensing it back into a liquid, leaving minerals and metals behind. This extensive processing results in exceptionally pure water, regardless of its initial quality.
The Impact of Packaging on Water Safety
The container introduces safety concerns related to chemical migration and microplastics. Most bottled water uses polyethylene terephthalate (PET) plastic, which degrades under environmental conditions, especially heat and prolonged storage.
Chemical leaching occurs when compounds migrate from the plastic into the water. Exposure to warmer temperatures significantly accelerates the leaching of chemicals like antimony, used in PET production. Endocrine-disrupting compounds, such as Bisphenol A (BPA) and its substitutes (BPS), can also migrate from certain plastic types. Improper storage in a hot warehouse or sun-exposed vehicle can introduce contaminants, even if the water was pure at bottling.
Microplastics are tiny plastic fragments present in nearly all brands of bottled water, often at higher concentrations than in tap water. The bottle and cap contribute to this contamination. While the long-term health effects of ingesting these particles are still under review, their presence makes the container a significant factor in water safety.
Choosing non-plastic containers, such as glass or certain boxed options, is a safer alternative. Glass bottles are chemically inert and do not leach plasticizers or microplastics, eliminating primary packaging risks. If plastic is necessary, select bottles labeled as BPA-free or BPS-free, and avoid containers stored in hot environments to minimize exposure.
Regulatory Oversight and Quality Assurance
The safety of bottled water in the United States is regulated by the Food and Drug Administration (FDA) as a packaged food product. This framework is distinct from the Environmental Protection Agency (EPA), which regulates public tap water systems.
Federal law requires FDA standards for bottled water to be at least as protective as EPA standards for tap water, often mirroring the EPA’s maximum contaminant levels for over 90 substances. A key difference is public disclosure: municipal systems must publish annual consumer confidence reports, but bottled water companies are not federally mandated to disclose their test results.
Due to this difference in public oversight, third-party certification is an important indicator of quality assurance beyond minimum federal requirements. Independent organizations like NSF International and the International Bottled Water Association (IBWA) offer voluntary certification programs. These programs involve unannounced annual plant inspections and testing to verify that the bottler meets or exceeds FDA requirements. Products displaying these seals demonstrate a commitment to safety and quality that surpasses baseline regulatory standards.
Criteria for Selecting the Safest Brands
The safest choice prioritizes water that has undergone comprehensive treatment and is stored in inert packaging. The purification method is the most reliable predictor of purity, regardless of the source. Water purified using reverse osmosis (RO) is generally preferred because it removes the widest spectrum of contaminants, including dissolved solids, chemicals, and pathogens.
Consumers should look for packaging that minimizes chemical migration and microplastic exposure. Glass containers are the safest option, as they eliminate the risk of plasticizer leaching. If purchasing plastic, ensure the bottle is labeled as BPA-free and BPS-free, and avoid the more concerning polycarbonate plastic.
Additionally, avoid purchasing water stored in direct sunlight or exposed to high heat, such as near a store window. Finally, look for brands that voluntarily participate in third-party quality assurance programs. Seals from organizations like NSF International indicate adherence to standards that include regular, independent testing and plant audits, providing extra confidence in the product’s safety.