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 PFAS disclosure available, but material composition poses lower risk.
Shop Zojirushi on Amazon →Material
stainless steel with silicone lid gasket
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
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 one of the safest food-contact metals for long-term use.
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 the safest reusable drinkware options, 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.
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.”
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.
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 we don’t know
This grade is a model-based estimate from public materials, coatings, and brand disclosure at 85% 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.
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.