Nike · Hiking Shoes & Trail Runners
Nike Terrex Ax4 Mid Gore Tex Hiking Shoes - US9
Gore-Tex likely contains PFAS; Nike discloses nothing publicly.
Gore-Tex waterproof technology historically relies on PFAS chemistry. Nike makes no public PFAS claims for this shoe. Third-party testing would clarify actual fluorochemical content.
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Material
Gore-Tex waterproof membrane with synthetic uppers and rubber sole
Brand disclosure
Brand is silent on PFAS
Lab data
No public lab test
Why this grade
Waterproof / stain-resistant treatment
water-repellent coating treatments have historically used PFAS.
Category baseline
clothing 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
The Terrex Ax4 uses Gore-Tex membrane bonded to synthetic textile uppers (likely polyester/nylon blend) with a rubber outsole. Gore-Tex provides waterproofing via microscopic pores but historically relies on fluorinated compounds (PFAS) to maintain water-repellency; Nike has never publicly disclosed whether their Gore-Tex layers contain legacy PFOA or newer PFAS alternatives. The synthetic uppers are not inherently hazardous, but any applied dyes, finishes, or adhesives used in construction carry low but non-zero risk of formaldehyde-releasing resins or azo dyes, which are unconfirmed for this specific model.
The brand's record and disclosure
Nike has not published detailed PFAS ingredient sourcing or testing data for footwear, despite being named in multiple environmental reports linking apparel brands to PFAS-contaminated water. The company signed the AFIRM (Apparel and Footwear International RSL Management) Group charter but does not mandate supplier PFAS phase-out timelines publicly. No recalls or safety notices specific to Terrex Ax4 chemistry have been reported. Nike's silence on Gore-Tex sourcing leaves PFAS content unverified.
How it compares in its category
Most mid-range hiking boots use Gore-Tex or similar fluorinated waterproof membranes; Gore-Tex remains the industry standard despite PFAS concerns. Brands like Salomon and Merrell face identical PFAS exposure through their Gore-Tex models. Non-fluorinated waterproof alternatives (waxed leather, hydrophobic synthetic coatings) exist but are less common and often require more frequent maintenance. Nike Terrex Ax4 is typical for its price tier and performance class, not an outlier.
If you buy it
Keep shoes dry when not in use and air-dry after wet conditions (do not machine wash or heat dry, which can degrade Gore-Tex bonding and release microplastics). Inspect the sole and upper seams annually for separation or cracking; replace boots once the outsole tread flattens significantly or waterproofing visibly fails (typically 300-500 miles). Avoid prolonged submersion. Do not apply fluorinated water-repellent resprays, which add additional PFAS exposure.
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.”
Formaldehyde-releasing resins in textile finishes
No specific test data or recalls for formaldehyde in Terrex Ax4 uppers are on record. Standard polyester/nylon used in hiking boots may be treated with finishing agents, but Nike does not disclose finish chemistry. Risk is typical for the category and low at normal wear.
Azo dyes in synthetic textile uppers
Nike adheres to OEKO-TEX and similar dye standards for many products, but no third-party certification is publicly listed for this specific model. Azo dye hazard is not documented but cannot be ruled out without supplier testing data that Nike does not publish.
Microplastic shedding from synthetic upper and rubber sole
All synthetic hiking shoes shed microplastics during wear and laundering. Gore-Tex membrane itself does not shed; risk comes from polyester/nylon and rubber degradation. Extent and toxicity of inhaled or ingested microplastics remain under study; this is not unique to Nike Terrex.
Adhesive toxicity from sole-to-upper bonding
Modern athletic shoe adhesives are typically solvent-based polyurethane, which off-gas volatile organic compounds (VOCs) during the first weeks of use. Nike does not publish adhesive specifications. Ventilation and air-drying shoes indoors away from living areas minimizes exposure.
Gore-Tex membrane delamination and microplastic/PFAS release
Industry reports document Gore-Tex layer separation after 2-3 years of intensive use in hiking boots. Delamination may release particulates and potential PFAS leachate into sweat or soil. Replacement or repair is the only mitigation once onset begins.
What we don’t know
This grade is a model-based estimate from public materials, coatings, and brand disclosure at 45% 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 hiking shoes & trail runners 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.