Thermos Review, Is Thermos Non-Toxic?
PFAS Authority is a scoring system, not a laboratory. We do not test products ourselves. Grades are model-based, built from published ingredients, materials, certifications, brand disclosures and third-party lab results where they exist. See the rubric.
Across 8 graded products, Thermos averages Excellent (94/100). On disclosure, the brand says nothing publicly about PFAS. 8 of its products grade Good or better. Grades are model-based estimates, not lab results.
Does Thermos have PFAS, by category
Worth buying from Thermos Good or better, safest first
Thermos
Stainless Steel King Travel Mug
Stainless steel interior and exterior, plastic lid
Plastic lid polymer degradation
Repeated dishwasher cycles or exposure to very hot liquids can degrade the polypropylene…
Gasket/seal material composition
The rubber or silicone gasket in the lid lid is not disclosed by Thermos. Standard…
Thermal shock stress on seals
Rapid temperature changes (hot liquid immediately sealed, then placed in freezer) can…
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
The rubber gasket or silicone seal can degrade after 3-5 years of repeated thermal cycles…
Lid or cup material (not specified)
Thermos Icon lids typically use plastic (polypropylene or similar) or silicone. If…
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
18/8 stainless steel does contain nickel (up to 8%). Under normal use with neutral pH…
Chromium leaching from stainless steel
Chromium in the passive oxide layer is typically hexavalent and immobilized; measurable…
Thermal shock and seal degradation
Long-term vacuum integrity loss has been documented in user reviews and product…
Lower concern; stainless steel mug has no water-repellent coating.
✓Bare metal or glass, no coating at all
Thermos
16oz Stainless King Coffee Mug
stainless steel interior, plastic exterior
Plastic exterior degradation and leachates
The exterior plastic shell contacts only air and hands, not beverages, limiting exposure.…
Rubber gasket degradation
The silicone or rubber lid gasket can degrade over time with repeated heat and washing…
Lead
If the inner and outer walls separate due to manufacturing defect or pressure damage, the…
Lower PFAS concern; stainless steel contact surface unlikely PFAS source.
✓Bare metal or glass, no coating at all
Thermos
Icon 16 oz Stainless Steel Tumbler
Stainless steel interior, BPA-free plastic exterior
Plastic exterior degradation and microplastic shedding
The outer plastic shell can crack, peel, or degrade with impact or prolonged UV exposure…
Silicone gasket bacterial or mold growth
The silicone seal on the lid can harbor bacteria or mold if not dried thoroughly after…
Lower concern; stainless steel tumbler has no known PFAS risk.
✓Bare metal or glass, no coating at all
Thermos
Guardian Stainless Steel Mug
Stainless steel (uncoated)
Bacterial growth in storage
If stored wet or with residual liquid for extended periods, stainless steel can harbor…
Lower concern; bare stainless steel mug has no known PFAS risk.
✓Bare metal or glass, no coating at all
Thermos
Stainless Steel Mug
stainless steel, no stated coating
Seam or lid leachables
The lid may contain polymer components (silicone gaskets, plastic valve mechanisms) that…
Bacterial growth in valve/seal areas
Insulated mugs with lids and drink valves can harbor bacteria if not cleaned thoroughly…
Lower concern; bare stainless steel unlikely to contain PFAS.
✓Bare metal or glass, no coating at all
Thermos
Foam Insulated Travel Mug GS1500TRI6
Stainless steel interior, foam insulation outer shell
Foam insulation degradation
Polyurethane and polystyrene foams can break down over years of use, especially if…
Flame retardants
Polyurethane foam may contain isocyanate-based adhesives or flame retardant additives…
Bacterial colonization in crevices
The seal between the foam layer and stainless steel interior can trap moisture and harbor…
Lower concern; stainless steel interior, typical foam shell unlikely PFAS.
⚠Brand says nothing about PFAS
Every grade uses the same public rubric. How grades work →