S'well · Insulated Travel Mugs
S'well Vacuum Insulated Travel Mug with Handle
Low concern, though S'well discloses no PFAS information.
The insulated walls are stainless steel, a material that avoids PFAS-prone treatments. S'well says nothing about PFAS testing, and the plastic handle and cap remain unidentified.
We flunk more products than we pass. This one earned its grade. How we grade
Material
Stainless steel body, plastic handle and cap
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.
Plastic cap/handle thermal migration
Polypropylene handles and caps may release trace amounts of oligomers or processing residues if exposed to sustained temperatures above 70-80°C. Risk is low under normal use (filling with fresh hot beverages and drinking within minutes) but increases if boiling water is poured directly into an unsecured cap or if the mug is left filled with hot liquid for hours.
Undisclosed polymer type and additives in handle/cap
S'well does not publicly specify whether the plastic handle is virgin or recycled polypropylene, or what UV stabilizers, release agents, or colorants are used. Without material transparency, potential presence of legacy additives (e.g., heavy metals in pigments or unknown phthalate alternatives) cannot be ruled out, though food-contact regulations make this unlikely.
Vacuum seal degradation and mold growth
If the cap gasket or seal is damaged, moisture can enter the vacuum cavity, leading to condensation and potential microbial growth (mold, bacteria) in the insulation layer. This is a maintenance issue rather than a manufacturing hazard but can occur if the mug is not hand-dried after washing or if the seal is compromised by repeated impact or drops.
PFAS
S'well has made no public commitment to PFAS testing, BPA-free certification, or heavy metal screening for either the stainless steel or plastic components. While stainless steel is inherently low-risk, the plastic handle's undisclosed manufacturing provenance creates an information gap, though no specific hazard has been reported in product testing or complaints.
Source: ATSDR ↗What’s reassuring
Safe base material
Made from ceramic, mineral, or natural fiber with no PFAS risk.
Stainless steel body integrity and welding seams
No recalls or documented issues with corrosion, leaching, or defects in S'well's 18/8 stainless steel bodies. This grade is resistant to rust and metal ion leaching under all normal beverage use conditions, including acidic drinks like citrus juice or coffee.
The full breakdown
What it's made of and why it matters
S'well travel mugs use 18/8 stainless steel for the main body, which is highly resistant to corrosion and does not leach metals into beverages under normal use. The plastic handle and cap are typically polypropylene or similar commodity polymers, which are food-contact approved but can release small amounts of monomers or additives if exposed to sustained heat well above normal hot-beverage temperatures (above 70°C for extended periods). The interior vacuum seal eliminates direct plastic-to-liquid contact for the beverage itself, limiting exposure routes.
The brand's record and disclosure
S'well does not publicly disclose PFAS test results, manufacturing certifications (BPA-free, heavy-metal tested), or third-party safety audits on their website or product labels. The brand has no documented product recalls related to chemical leaching or safety hazards on the FDA or CPSC databases. They market products as suitable for hot and cold beverages but provide no technical guidance on temperature limits or polymer composition details, which limits independent verification of safety claims.
How it compares in its category
Stainless steel vacuum travel mugs are among the safest beverage vessels because the material itself does not leach; S'well is mid-to-premium priced ($30-50 range) and competes on design rather than safety differentiation. Compared to ceramic-lined or non-insulated plastic bottles, this design eliminates ceramic glaze unknowns and plastic-beverage contact, making it objectively lower-risk. However, competing brands like Hydro Flask and Contigo similarly lack public PFAS or toxicology disclosure, so S'well is not exceptional in transparency.
If you buy it
Hand-wash the lid and handle rather than running through a dishwasher to minimize plastic thermal stress and preserve coatings. Do not fill with water above 80°C or leave hot liquids in the mug overnight, as prolonged heat exposure to the cap seal is the highest-risk scenario for plastic additive migration. Replace the lid if it shows visible cracks, discoloration, or odor, as these indicate polymer breakdown. Store dry and away from direct sunlight to prevent UV degradation of the plastic handle over years of use.
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.