S'well · Insulated Travel Mugs
S'ip by S'well Takeaway Mug
Low concern. Stainless steel design with no reported coatings.
This tumbler uses bare stainless steel without water-repellent or grease-resistant coatings. The brand doesn't address PFAS, but the material type poses minimal risk.
We flunk more products than we pass. This one earned its grade. How we grade
Material
Stainless steel exterior, insulated
Brand disclosure
Brand is silent on PFAS
Lab data
No public lab test
What’s concerning
Category baseline
PFAS exposure happens more often with clothing products.
No PFAS disclosure
The company has not publicly discussed PFAS in this product.
BPA & bisphenols
S'well states products are BPA-free, but independent lab confirmation of all interior components is not publicly available. Risk is low for cold beverages but increases with hot-liquid prolonged contact.
Source: FDA ↗Bacterial growth in lid seals
Silicone or rubber gaskets can harbor Listeria, E. coli, or mold if moisture is trapped and drying is incomplete. This is a use-maintenance issue, not a manufacturing defect.
Thermal shock or seal failure from temperature cycling
Repeated exposure to boiling water followed by cold storage can stress the bond between stainless and insulation, and degrade interior elastomer seals, potentially releasing volatile compounds or allowing metal-to-plastic contact.
What’s reassuring
Safe base material
Made from ceramic, mineral, or natural fiber with no PFAS risk.
Phthalates
No documented cases or recalls; stainless and food-grade silicone alternatives to vinyl are now standard in this price category, making phthalate exposure unlikely.
Source: ATSDR ↗Heavy metals
Stainless steel 18/8 alloy contains nickel (8-11%) and chromium, both present as stable oxides that do not leach under normal beverage pH. Nickel sensitivity can occur in individuals with contact dermatitis, but ingestion risk is negligible.
Source: FDA ↗The full breakdown
What it's made of and why it matters
The S'ip by S'well uses a food-grade stainless steel exterior (typically 18/8 or similar austenitic alloy) bonded to an insulating layer, with a plastic or silicone interior liner and lid components. Stainless steel itself is chemically inert and does not leach heavy metals like lead or cadmium under normal use. The critical safety variable is the interior lining material: if it is a durable elastomer (silicone) or polypropylene, it poses minimal risk; if it contains older plastic formulations, there is a small window for BPA or phthalate exposure, particularly if subjected to high heat or prolonged hot beverage contact.
The brand's record and disclosure
S'well (owned by Caldera Brands) has not published detailed third-party safety certifications or material disclosures in public domain, and does not maintain an explicit PFAS-free statement. The brand has no major recalls or documented safety incidents on record for the S'ip line. S'well markets products as BPA-free, though independent verification of all interior components is limited. The company's general silence on manufacturing standards and material sourcing is typical of the sector but leaves some opacity regarding interior sealants and adhesives.
How it compares in its category
Stainless steel insulated tumblers are among the safest reusable drinkware options available because they avoid the coating-degradation and ceramic-glaze risks of thermal-shock vessels. S'well's price point and design place it in the premium segment; competitors like Hydro Flask and YETI use similar stainless construction. Unlike ceramic or coated metal alternatives, this category carries virtually no risk of lead, cadmium, or Teflon-type coating fume exposure. The main differentiator is lid and interior gasket durability, which varies by brand maintenance and material quality.
If you buy it
Use only with beverages under 80C (176F) to avoid stressing interior seals; repeated boiling-water contact can degrade elastomer liners over years. Hand-wash the lid assembly thoroughly, as crevices can harbor bacterial biofilm if stored damp. Inspect the interior seal annually for discoloration, odor, or visible degradation; replace if compromised. Store dry and avoid prolonged contact with acidic beverages (citrus, vinegar) in the lid, which can corrode stainless steel over extended periods, though the tumbler itself is corrosion-resistant.
What we don’t know
- Basis
- Model estimate, 72% confidence, not a lab result
- Lab test
- None on record for this exact product
- Brand statement
- S'well has made none
Formulations change between production runs, so check the current label. How we grade.
Safer alternatives in Insulated Travel Mugs
Thermos
Stainless Steel King Travel Mug
Stainless steel interior and exterior, plastic lid
Plastic lid polymer degradation
Limited concern
Gasket/seal material composition
Limited concern
Thermal shock stress on seals
Limited concern
Lower concern; bare stainless steel has minimal PFAS risk.
✓Bare metal or glass, no coating at all
Thermos
Icon 16 oz Stainless Steel Mug
stainless steel, no stated interior coating
Seal degradation and bacterial growth
Limited concern
Lid or cup material (not specified)
Limited concern
Lower concern; bare stainless steel has minimal PFAS risk.
✓Bare metal or glass, no coating at all
Thermos
18 oz. Icon Vacuum Insulated Stainless Steel Mug
stainless steel exterior, vacuum insulation, stainless steel interior
Nickel leaching from stainless steel
Limited concern
Chromium leaching from stainless steel
Limited concern
Thermal shock and seal degradation
Moderate concern
Lower concern; stainless steel mug has no water-repellent coating.
✓Bare metal or glass, no coating at all
More insulated travel mugs grades
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.