Zojirushi · Insulated Drink Tumblers
Zojirushi Stainless Mug
Low risk. Stainless steel mug, no treatment claimed.
Zojirushi stainless mugs typically have bare metal with no special coatings or water-repellent finishes, lowering PFAS risk. The brand doesn't claim PFAS-free status.
We flunk more products than we pass. This one earned its grade. How we grade
Material
stainless steel, no coating specified
Lab data
No public lab test
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What Zojirushi Stainless Mug is made of, ingredients and materials
Zojirushi stainless steel mugs are constructed from food-grade stainless steel (typically 18/8 or 18/10 composition, 18% chromium, 8-10% nickel, remainder iron). This alloy is passivated during manufacturing, creating a stable oxide layer that prevents metal leaching into beverages. Unlike ceramic mugs with glazes or plastic tumblers with interior coatings, bare stainless steel has no polymeric or ceramic layer to degrade, chip, or migrate compounds into liquid.
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.
Nickel leaching (from stainless steel alloy)
Stainless steel 18/8 contains 8% nickel. Leaching is minimal under normal conditions (cold to warm beverages, neutral pH), but individuals with nickel sensitivity may experience contact dermatitis on the lip if the mug's rim is not smooth. No documented incidents in Zojirushi products, but sensitive users should test tolerance.
Bacterial growth in trapped water (between walls)
If the seal between inner and outer walls fails, water trapped in the cavity can harbor mold or bacteria. This is a hygiene concern, not a direct chemical hazard, but indicates the mug should be discarded. Regular inspection and hand-washing reduce this risk.
Thermal stress from extreme temperature swings
Filling a cold mug with boiling liquid (or vice versa) can stress welds and the seal between walls. Over time, repeated thermal cycling may compromise structural integrity, though this is mechanical rather than chemical. Zojirushi mugs are rated for hot and cold beverages; gradual temperature transitions minimize risk.
What’s reassuring
Bare uncoated material
Recorded as a bare, uncoated material with no surface coating or treatment.
Epoxy or silicone seal degradation in double-wall cavity
The internal adhesive bonding the walls is set and does not contact liquid. No recalls or field reports of seal adhesive leaching into contents in Zojirushi mugs. Seals can fail mechanically (water ingress) after years of thermal cycling, but this does not pose chemical hazard.
Lead
Zojirushi uses food-safe inks for branding on stainless steel mugs; no testing data is publicly available, but the brand's manufacturing standards and lack of recalls suggest compliance with FDA ink regulations. Exterior graphics do not contact beverages.
Source, ATSDR ↗How is this PFAS grade calculated?
The brand's record and disclosure
Zojirushi is a Japanese manufacturer with a long history in food and beverage containers; the brand maintains ISO 9001 quality certification and has not faced documented recalls for chemical leaching or coating hazards in drinkware. The company does not publicly disclose PFAS treatment of its products, but stainless steel mugs typically require no water-repellent coating. No third-party certifications (e.g., BPA-free claims) are typically marketed because stainless steel itself contains no BPA or phthalates by composition.
How it compares in its category
Stainless steel mugs occupy a lower-hazard tier compared to plastic tumblers (which may leach BPA or phthalates if damaged or heated) and ceramic mugs with uncertain glaze composition (lead/cadmium risk in some imports). Double-wall insulated construction in Zojirushi models involves an air gap sealed with epoxy or silicone adhesive at seams; these adhesives are set and do not contact liquid directly. This design has lower concern than single-wall plastic liners or polymer-coated paper cups.
If you buy it
Hand-wash rather than dishwasher to avoid prolonged exposure to harsh detergents and heat cycling, which can theoretically stress seals over decades. Do not fill with extremely acidic beverages (pH < 3, e.g., vinegar solutions) for extended periods, as acid can slowly etch stainless steel and mobilize trace nickel, though this is rare at typical use levels. Inspect the seal between inner and outer walls annually; if the mug begins to leak or feels heavy (indicating water ingress), discontinue use. Stainless steel mugs are durable and typically outlast 5-10 years with normal care.
What is not known about PFAS in this product?
- Basis
- Model estimate, 82% 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 Stainless Mug?
- 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.