The Invisible Layer: Why Cans Need a Liner
For many years, consumers have turned to aluminum cans as a seemingly more sustainable alternative to plastic bottles. However, most people are unaware of the hidden plastic lining that is a near-universal feature of modern cans. This liner is typically made from an epoxy resin, historically containing Bisphenol A (BPA), although many manufacturers have now moved to 'BPA-free' alternatives like BPS and BPF. The primary purpose of this coating is to prevent the acidic nature of beverages, particularly sodas, from corroding the aluminum and giving the drink a metallic taste. Without this barrier, the beverage would be unsafe to consume and have a significantly shorter shelf life. While beneficial for the product's integrity, this plastic barrier is the root cause of microplastic contamination from cans.
How Microplastics Get from Liner to Drink
Over time, several factors can cause the protective plastic lining inside a soda can to degrade, leading to the release of microplastics into the liquid. The highly acidic nature of many soft drinks is a primary culprit, as it can slowly break down the polymer coating. Furthermore, environmental factors such as heat during storage, transportation, and pasteurization can significantly increase the rate at which chemicals and microplastics migrate from the liner into the beverage. While a soda can's shelf life is relatively short, cumulative stress on the lining can cause a gradual release of these microscopic particles, which are then consumed along with the drink. A study found that an average person might ingest tens of thousands of microplastic particles from various sources annually, with can liners being one such pathway.
Beyond BPA: The Problem with Alternatives
When public awareness of BPA's potential health risks grew, many companies began marketing their products as "BPA-free." However, this doesn't mean the product is free of all harmful chemicals or plastics. Manufacturers often substituted BPA with similar bisphenol compounds, such as BPS or BPF, which may have comparable hormone-disrupting effects. Other chemical additives in can linings, including acrylics, polyesters, and PVC compounds, also carry their own environmental and health concerns, with some being toxic to aquatic life or considered possible carcinogens. The lack of comprehensive long-term safety data for these alternatives means that switching to a BPA-free can doesn't eliminate the risk of microplastic and chemical exposure.
The Environmental Conundrum of Lined Cans
While aluminum is infinitely recyclable, the addition of a plastic liner complicates the entire recycling process. During the recycling process, cans are melted down at high temperatures. The plastic liner burns off, a process that requires more energy and releases pollutants into the atmosphere. The liner can also compromise the purity of the recycled aluminum, potentially reducing its overall value and usefulness. For a product marketed as a sustainable choice, the presence of this hidden plastic introduces significant inefficiencies and environmental costs.
A Comparison of Beverage Packaging
| Packaging Material | Microplastic Risk from Container | Potential Chemical Leaching | Recyclability | Other Considerations |
|---|---|---|---|---|
| Aluminum Can | Low-to-moderate, primarily from internal plastic liner. | Potential for bisphenol (BPA, BPS, BPF) and other plastic chemical leaching. | High, but complicated by plastic liner. | Lightweight, portable, and opaque. High energy use in manufacturing. |
| Glass Bottle | High, potentially from cap seals and friction during recycling. | Very low, inert material. | Excellent, can be recycled indefinitely. | Heavier, more fragile, and requires more energy for transport. |
| Plastic Bottle (PET) | Low-to-moderate, especially with repeat openings. | BPA not typically used, but other chemicals may leach, especially with heat. | Moderate, though often downcycled into lower-quality products. | Lightweight, transparent, and prone to degradation. |
| Cardboard Carton | Low-to-moderate, from polyethylene linings. | Chemicals can migrate from plastic lining. | Variable, depends on recycling infrastructure for multi-material cartons. | Often lined with multiple materials, complicating recycling. |
Mitigating Your Exposure to Can-Based Microplastics
For conscious consumers, reducing exposure to microplastics from soda cans involves a shift in purchasing and consumption habits. Opting for beverages packaged in glass bottles or using reusable stainless-steel containers can significantly reduce your contact with can linings. Choosing filtered water over bottled water is another step, as some filters are designed to capture microplastics. Minimizing consumption of canned foods and drinks and supporting brands that are transparent about their packaging materials is also effective. While completely avoiding microplastics is nearly impossible due to their prevalence in the environment, making these intentional changes helps reduce your overall intake. For more information on reducing overall plastic exposure, you can review this guide from Consumer Reports: The Plastic Chemicals Hiding in Your Food.
Conclusion
Contrary to popular belief, soda cans do have microplastics, which originate from the internal epoxy resin lining necessary to protect the aluminum from the corrosive beverage. As this lining degrades over time, it can leach microplastics and other potentially harmful chemicals, like bisphenols, into your drink. This practice has environmental consequences, as the liner complicates the otherwise efficient aluminum recycling process. While many manufacturers have moved away from BPA, the safety of the substitute chemicals used is not yet fully understood, leaving consumers with limited transparency. Ultimately, a proactive approach involves re-evaluating your beverage choices and considering plastic-free alternatives to reduce personal exposure and encourage more sustainable packaging solutions across the industry.
