REI · Waterproof Outdoor Gear Storage
Humangear Stax
Lower concern. Polypropylene stacking containers lack PFAS triggers.
Humangear Stax are modular polypropylene food containers with no documented nonstick, waterproof, or stain-resistant treatments. No known PFAS concerns for this basic plastic food storage product.
We flunk more products than we pass. This one earned its grade. How we grade
Material
polypropylene plastic
Brand disclosure
Brand is silent on PFAS
Lab data
No public lab test
Why this grade
Safe base material
Made from a material with no inherent PFAS use (ceramic, mineral, or natural fiber).
Category baseline
other is a category where PFAS exposure is more common.
The full breakdown
What it's made of and why it matters
Humangear Stax containers are injection-molded polypropylene (PP #5), a thermoplastic chosen for durability, lightweight design, and food-contact approval in most jurisdictions. Polypropylene is chemically inert at typical use temperatures and does not require the chemical additives (like BPA or phthalates) that concern regulators in other plastics. The stacking geometry is functional design, not a material concern.
The brand's record and disclosure
REI Co-op does not publish dedicated material safety data sheets for Humangear Stax. No recalls, safety complaints, or certifications (organic, non-toxic) are established in public records for this product line. REI maintains standard consumer return and safety policies but does not voluntarily disclose testing for contaminants or chemical additives beyond regulatory minimum.
How it compares in its category
Polypropylene food containers are the industry standard for reusable food storage and rank among the safest plastic food-contact materials by regulatory assessment. Stax competes with Rubbermaid, Sistema, and Tupperware products in the same material class. No material or design difference distinguishes Stax as higher or lower risk than equivalent PP containers from major brands.
If you buy it
Avoid heating contents directly in the containers; polypropylene's safe limit is around 100-120°C (212-248°F), below boiling water. Hand-wash or use cool/warm dishwasher cycles to extend coating life and reduce stress on plastic. Replace if lids crack, hinge breaks, or container becomes cloudy and brittle (sign of polymer degradation), typically after 3-5 years of regular use. Store away from direct sunlight to slow oxidative aging.
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.”
Microplastic release from mechanical wear
Polypropylene containers shed microscopic particles when repeatedly stacked, scratched, or heated. Risk is low under normal room-temperature storage but increases with dishwasher cycles and abrasion. No specific data on Stax; inherent to PP material class.
Thermal degradation and chemical leaching at elevated temperatures
Polypropylene begins to soften and may release oligomers (short polymer chains) above 120°C. Using Stax for hot foods or hot-fill scenarios (e.g., pouring boiling water) exceeds safe temperature margins and increases leaching risk.
Colorants and pigment stability
No documented safety issues, heavy metal contamination, or pigment failure reported for Humangear Stax. Coloring additives in polypropylene are generally non-regulated under FDA food-contact rules if suppliers are compliant, but manufacturer testing data is not public.
Mold and bacterial growth in crevices
Stacking interlocking rims and hinges create hard-to-clean crevices where moisture and food residue can harbor mold or bacteria if containers are not fully dried after washing. Standard risk for any sealed food container; mitigation is thorough drying and occasional hot-water rinse.
Lid hinge brittleness and small-part ingestion risk
Hinged polypropylene lids are prone to cracking and potentially releasing small fragments after repeated opening or low-temperature stress. Not a documented recall issue for Stax, but inherent durability concern in stacking container design, especially if used by children.
What we don’t know
This grade is a model-based estimate from public materials, coatings, and brand disclosure at 72% 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 waterproof outdoor gear storage 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.