Zojirushi · Insulated Drink Tumblers
Zojirushi 34 oz. Stainless Mug with Lid Handle
Lower concern; stainless steel and silicone lack inherent PFAS.
Zojirushi's stainless steel mug is a bare metal product with no reported nonstick or water-resistant coatings. No brand PFAS disclosure exists, but material composition poses lower risk.
We flunk more products than we pass. This one earned its grade. How we grade
Material
stainless steel with silicone lid gasket
Lab data
No public lab test
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What Zojirushi 34 oz. Stainless Mug Lid Handle is made of, ingredients and materials
This mug uses 18/8 stainless steel (304 grade) as the primary material, which is corrosion-resistant and does not leach metals under normal use conditions. The lid contains a silicone gasket, an inert elastomer that resists degradation from hot liquids and repeated cleaning. Silicone lacks the thermal instability of some plastics and does not off-gas volatile compounds at typical beverage temperatures. Stainless steel is a metal food-contact material not linked to PFAS concerns in typical use.
What’s concerning
Category baseline
The starting point for this type of product, before anything specific to this product is counted.
No PFAS disclosure
No public statement from the brand about PFAS in this product.
Silicone gasket degradation and off-gassing
Silicone gaskets can degrade over years of thermal cycling and exposure to hot liquids, potentially releasing oligomers (small silicone compounds) at very low levels. This is not documented as a health risk at trace exposures, but replacement of visibly degraded gaskets is prudent to avoid mold colonization in cracks.
Microbial growth (mold, bacteria) in gasket seams
Silicone gaskets in tumbler lids are moisture traps if not dried thoroughly. Inadequate cleaning or storage while wet can promote mold. This is a maintenance issue, not a material defect, and is preventable with proper care.
Lid latch or handle durability
Over time, the silicone lid seal and handle attachment points can wear or crack from repeated use and drops. This is a mechanical failure, not a chemical hazard, but affects product lifespan and usability.
What’s reassuring
Bare uncoated material
Recorded as a bare, uncoated material with no surface coating or treatment.
Stainless steel leaching (chromium, nickel)
18/8 stainless steel is passive and stable under normal beverage use. Leaching is not reported in food-contact applications unless the steel is severely damaged, corroded, or exposed to extreme pH for prolonged periods. This mug has no known issues.
How is this PFAS grade calculated?
The brand's record and disclosure
Zojirushi is a Japanese brand with a decades-long reputation in thermal drinkware and kitchen appliances, with no major product safety recalls or widespread contamination reports on record for their stainless steel tumblers. The company does not publicly disclose detailed material sourcing or third-party certifications (such as NSF or FDA testing reports) on their website, which is typical for mid-market drinkware manufacturers but limits transparency. No established controversies or regulatory actions against Zojirushi exist in publicly available safety databases. Their silence on PFAS is consistent with the fact that stainless steel and silicone are not typical sources of intentional PFAS addition.
How it compares in its category
Stainless steel tumblers are among reusable drinkware options with lower concern for PFAS, alongside glass and ceramic. This product sits above plastic-lined or coated metal alternatives, which carry leaching risks from polymer coatings or silicone-based sealants under stress. Compared to aluminum tumblers (which can leach if uncoated or acidic beverages are stored long-term), stainless steel avoids that concern. The silicone gasket is more durable and inert than rubber or foam gaskets found in lower-cost competitors.
If you buy it
Hand wash the silicone gasket separately after each use to prevent mold or bacterial growth in tight seams; do not leave wet gaskets sitting in the lid for extended periods. Avoid prolonged contact with highly acidic beverages (lemon juice, vinegar) stored overnight, as stainless steel can pit under extreme conditions, though this is rare with 304-grade steel. Check the gasket annually for cracking, discoloration, or odor; replace if compromised (Zojirushi sells replacement gaskets). The mug itself is dishwasher-safe and will not degrade with repeated cleaning.
What is not known about PFAS in this product?
- Basis
- Model estimate, 85% confidence, not a lab result
- Lab test
- None on record for this exact product
- Brand statement
- Zojirushi has made a specific claim
Formulations change between production runs, so check the current label. How we grade.
What are the PFAS-free alternatives to Zojirushi 34 oz. Stainless Mug with Lid Handle?
- Stainless steel bottle, stainless steel cap
- The brand calls it PFAS-free, which we have not verified
- Powder-coat cap degradation over time
3 hazards checked on this product, all on its full breakdown.
- Stainless steel body, powder-coat finish
- The brand calls it PFAS-free, which we have not verified
- Powder-coat finish degradation
3 hazards checked on this product, all on its full breakdown.
- Stainless steel bottle, plastic cap and silicone gasket
- The brand calls it PFAS-free, which we have not verified
- Silicone gasket degradation and leaching
3 hazards checked on this product, all on its full breakdown.
More insulated drink tumblers 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.