S'well · Insulated Travel Mugs
S'well 40 oz Stainless Steel Traveler
Lower concern. Bare stainless steel vessel, check lid material separately.
S'well bottles are primarily 18/8 stainless steel, which is inherently PFAS-free. Plastic lids and seals are the uncertain component; brand does not disclose treatment details.
Shop S'well on Amazon →Material
18/8 stainless steel interior and exterior, plastic lid components
Brand disclosure
Brand is silent on PFAS
Lab data
No public lab test
Why this grade
Uncoated safe material
Bare, uncoated material (cast iron, stainless, carbon steel, or glass) with no surface treatment to contain PFAS.
Category baseline
other is a category where PFAS exposure is more common.
No PFAS disclosure
No public statement about PFAS in this product.
The full breakdown
What it's made of and why it matters
The S'well 40 oz uses 18/8 (304) stainless steel for the vessel interior and exterior, which is food-grade and highly resistant to corrosion and leaching. The lid contains plastic components (material composition not clearly disclosed by brand) that will have direct contact with liquids and lips. 18/8 stainless steel is considered chemically inert under normal use; the main variability is in the plastic lid's durability and what polymers or additives it contains.
The brand's record and disclosure
S'well does not publicly disclose detailed material specifications for plastic lid components or provide third-party certifications (BPA-free labeling, FDA compliance statements, etc.), which is uncommon transparency for a premium hydration brand. The company has no widely documented recalls or safety controversies tied to the stainless steel vessel itself. The silence on PFAS and plastic additive composition reflects a broader industry pattern rather than a specific red flag, but limits independent verification.
How it compares in its category
This product sits in the premium stainless steel drinkware segment alongside brands like Hydro Flask and YETI, which similarly use 18/8 stainless steel vessels and face the same plastic-lid transparency gaps. Unlike some lower-cost alternatives, S'well does not use aluminum or bare copper linings that carry leaching risks. The 40 oz size and sealed design reduce exposure to external contamination compared to open-mouth bottles, though the lid remains a potential weak point.
If you buy it
Hand-wash the lid regularly and inspect it for cracks or discoloration, as plastic degradation accelerates with repeated hot-water dishwashing and extended sunlight exposure. Avoid prolonged storage of acidic beverages (citrus, vinegar-based drinks) in contact with the plastic lid, as acidic conditions can leach additives. Replace the lid every 1-2 years if you use the bottle daily, as plastic does degrade; S'well sells replacement lids. The stainless steel vessel itself is durable and does not require replacement under normal use.
Beyond PFAS: other things we checked
Established hazard classes for this product type, assessed from public information. These never change the PFAS grade; a Likely flag caps the Verdict at “Buy with care.”
Plastic lid additive leaching (BPA/BPS/phthalates)
S'well does not disclose the specific plastic resin or additive chemistry of the lid. While many modern lids use BPA-free polymers, the brand's silence on this makes it impossible to rule out secondary plasticizers or manufacturing additives. Risk increases with hot liquid contact and age.
Plastic lid degradation over time
All plastic lids degrade through repeated thermal cycling, UV exposure, and contact with oils/acids. Visible signs include cloudiness, brittleness, or odor changes. Microplastic shedding is theoretically possible but not documented for this specific product.
Stainless steel corrosion or pitting
18/8 stainless steel is highly corrosion-resistant under normal beverage use. Pitting is extremely rare in food-grade applications and no reported cases exist for S'well vessels. Risk only escalates in extreme chloride environments (salt water) or if the bottle is damaged.
Heavy metals in vessel coating or interior finish
S'well uses bare stainless steel without enamels, glazes, or colored coatings on the interior, eliminating lead, cadmium, and chromium leaching risks common in lower-quality cookware or drinkware.
Lid seal integrity loss
The seal gasket (typically silicone or rubber) can deteriorate, crack, or harden over 12-24 months of regular use. Loss of seal does not pose a direct safety hazard but compromises the product's core function and may allow bacterial growth in the gasket itself if moisture is trapped.
What we don’t know
This grade is a model-based estimate from public materials, coatings, and brand disclosure at 78% confidence. It is not a lab result.
No independent PFAS lab test is on record for this exact product. A lab test could move the score in either direction.
The brand has not made a specific, verifiable PFAS-free statement, so part of this score reflects that missing disclosure rather than a confirmed material.
Formulations and coatings change between production runs. Always check the current label before buying.
Safer alternatives in Insulated Travel Mugs
Corkcicle
Coffee Mug
Stainless steel interior, insulated walls with cork/polymer exterior
Lower concern. Stainless steel interior poses minimal PFAS risk.
✓Naturally PFAS-free material
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How we score: every product runs through the same public 0–100 rubric based on materials, coatings, brand disclosure, lab findings, and recalls. See the full methodology → Spotted a mistake? Report an error.