Canned water is drinking water sealed in aluminum beverage cans, gaining popularity as an alternative to plastic bottles. This shift prompts questions regarding the safety and purity of the water, particularly concerning potential chemical transfer from the metal and its linings. Understanding the material science and regulatory oversight helps clarify the health implications of this packaging option.
How Aluminum Packaging Affects Water Safety
The aluminum shell poses a minimal health risk because aluminum naturally forms a stable, protective layer of aluminum oxide when exposed to air and water. This oxide layer acts as a barrier, preventing the metal from reacting with the contents and stopping aluminum leaching. The can’s interior is coated with a thin, protective polymer lining, typically an epoxy resin, which serves as a second barrier. This liner prevents the water from corroding the aluminum, which could otherwise create a metallic taste.
Concerns surrounding the can lining center on chemicals such as bisphenol A (BPA) or its common replacements, bisphenol S (BPS) and bisphenol F (BPF), used in the epoxy resin. These bisphenols are classified as endocrine-disrupting chemicals because they can interfere with hormonal systems. Trace amounts of BPA can leach from the lining into the contents. Leaching levels are much lower in water than in acidic or fatty foods, which are more corrosive to the lining.
Regulatory bodies maintain that the current low levels of chemical transfer from these linings are within safe exposure limits. Manufacturers are moving toward BPA-free linings using BPS, BPF, or acrylic and polyester alternatives, though these replacements also carry chemical concerns. A compromised liner, such as one caused by a deep dent, could increase the potential for both chemical and aluminum leaching. The risk of aluminum leaching is low because the water’s near-neutral pH does not readily dissolve the metal’s protective oxide layer or the lining.
Purity Standards for Packaged Water
The quality of the water inside the aluminum can is governed by the same regulatory standards that apply to all packaged water. In the United States, the Food and Drug Administration (FDA) regulates packaged water under stringent standards. These regulations establish a standard of quality that sets maximum allowable levels for contaminants, including chemical, physical, microbial, and radiological types. The FDA requires that packaged water be produced using Current Good Manufacturing Practice (CGMP) regulations to ensure safety and sanitation.
The water destined for canning undergoes multiple purification steps before being sealed. Common purification techniques include distillation, reverse osmosis, and deionization, which are effective at removing impurities and dissolved solids. This processing ensures the finished product meets high criteria for purity, often matching or exceeding the quality standards of municipal tap water. Bottlers must regularly test their source water and finished products to confirm compliance with regulatory limits.
Strict regulatory oversight ensures the water in an aluminum can is held to a consistent and high level of quality, regardless of the container type. Concerns about heavy metals or microbiological contaminants are mitigated by required purification processes and testing protocols. The container is considered a packaging material, and its use does not alter the fundamental purity requirements of the liquid it holds.
Canned Water Versus Plastic Bottles
Comparing canned water to polyethylene terephthalate (PET) plastic bottles helps contextualize the health risks associated with the packaging material. Both containers carry a risk of chemical leaching, but the specific compounds and the nature of the risk differ. Aluminum cans are primarily scrutinized for bisphenols from the liner, while PET plastic bottles are associated with the leaching of antimony and phthalates.
Antimony, a compound used as a catalyst in PET plastic production, can migrate into the water, especially when the bottle is exposed to higher temperatures or prolonged storage. Phthalates, often used as plasticizers, are also endocrine disruptors that can leach from PET containers. While the levels of both antimony and phthalates are low and remain below regulatory thresholds, their presence is a consideration for consumers seeking to minimize exposure.
A primary comparative factor is the potential for microplastic contamination. Microplastics are tiny plastic particles that can be shed by the plastic container itself. Aluminum cans present a near-zero risk of microplastic contamination because the water only touches the polymer liner. In contrast, PET plastic bottles can release microplastics into the water, making the aluminum can a preferable option.
Environmental and Practical Storage Factors
Aluminum cans offer an environmental advantage over plastic bottles due to aluminum’s superior recyclability. Aluminum is considered a permanent material, meaning it can be recycled repeatedly without loss in quality. The recycling process for aluminum is energy efficient, requiring approximately 95% less energy than producing new aluminum from raw materials. This results in a high closed-loop circularity rate where the recycled material returns to the same product.
In contrast, PET plastic is often downcycled, and its recycling rates are substantially lower than those of aluminum. Beyond the environmental profile, aluminum cans also provide practical benefits for product longevity and storage. Because the aluminum fully blocks light and oxygen, it helps maintain the water’s freshness and prevents the growth of algae or other microorganisms.
The physical structure of the can introduces specific storage considerations. A deep dent can compromise the integrity of the internal epoxy liner, which exposes the water to the bare aluminum and increases the potential for leaching. Furthermore, freezing canned water will cause the contents to expand, which will rupture the can. Consumers should be mindful of physical damage and temperature extremes to ensure the can’s protective barriers remain intact.