On Running · Running & Athletic Shoes
Men's On Cloud 5
Running shoe with likely water-repellent coating treatment; On Running does not disclose PFAS status.
On Cloud 5 uses standard athletic shoe materials with waterproof coating, typical of the category. On Running has not publicly disclosed PFAS policies or testing for this shoe.
Still want this one anyway? Check the price on Amazon. We’d swap it.
Material
Knit textile upper with foam/rubber midsole; waterproof treatment likely applied
Brand disclosure
Brand is silent on PFAS
Lab data
No public lab test
What’s concerning
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.
Formaldehyde / VOCs
Knit textiles may contain formaldehyde-based wrinkle-resist or antimicrobial finishes applied during manufacturing. On Running does not disclose finishing chemistry, so presence cannot be ruled out. Off-gassing is typically mild in athletic footwear compared to apparel worn against skin for hours.
Source: ATSDR ↗Azo dyes in knit upper
Synthetic knit textiles are commonly dyed with azo dyes, some of which are restricted (AZO-banned amines) but many are not. No specific testing of the Cloud 5's colorants is on record. The shoe is worn on the foot, not close to the mouth, limiting dermal absorption risk compared to close-fitting garments.
Microplastic shedding from foam midsole degradation
EVA and polyurethane midsoles break down over time and shed microparticles, especially with age and heat exposure. This is not product-specific to Cloud 5 but is a known class issue across foam athletic shoes. Shedding increases after 300+ miles of use or storage in warm environments.
Glue and solvent residues in midsole-upper bonding
Polyurethane or polyester-based adhesives used to attach the upper to the midsole may off-gas volatile organic compounds (VOCs) during the first few weeks after purchase. Airing the shoe in a well-ventilated space before first wear can reduce this. No specific adhesive composition is disclosed by On Running.
What’s reassuring
Antimony in polyester components
Polyester knit uppers may theoretically contain antimony as a catalyst residue; however, this is typically bound in the polymer matrix and does not leach under normal wear conditions. No recalls or contamination reports specific to On Cloud 5 or On Running polyester components.
The full breakdown
What it's made of and why it matters
The Cloud 5 upper is a knit textile blend (typically polyester/nylon mix) with a foam midsole and rubber outsole. The waterproof treatment applied to the upper is the primary chemical concern; On Running does not specify the water-repellent coating (water-repellent coating) chemistry, but industry standard for performance running shoes is PFAS-based fluorocarbon coatings. Knit textiles themselves carry lower chemical risk than woven or treated leather, but the finishing process is where hazards concentrate. The foam midsole is generally ethylene-vinyl acetate (EVA) or polyurethane, both of which off-gas minimally after curing.
The brand's record and disclosure
On Running has not published a PFAS elimination roadmap, ingredients transparency statement, or third-party chemical certifications (such as OEKO-TEX or bluesign) as of available records. The brand markets sustainability via recycled materials and carbon offsetting but does not address PFAS "forever chemicals" in their supply chain communications. This silence is common in the running shoe industry but represents a transparency gap for consumers seeking to avoid PFAS exposure.
How it compares in its category
Most mainstream running shoes in the premium segment ($120-$180) use similar PFAS-based water repellent treatments without disclosure. Brands like Nike and Adidas similarly do not specify water-repellent coating chemistry on consumer-facing materials. Some specialty outdoor brands (Salomon, ASICS partnerships with certain certifications) offer PFAS-free or disclosed alternatives, though at comparable or higher price points. The Cloud 5 is typical of its market tier in chemical transparency, neither better nor worse than direct competitors.
If you buy it
Wash the shoe in cool water (below 40°C/104°F) to avoid accelerating foam breakdown and shedding microfibers; hot water can degrade adhesives between upper and sole. Air dry away from direct heat and sunlight, as UV and high temperatures weaken the waterproof coating and foam structure. Expect the water-repellent coating treatment to lose effectiveness after 50-100 washes; reapplication products exist but introduce additional chemical contact. Replace the shoe when the midsole compresses visibly (typically 300-500 miles) or cushioning feels flattened, as worn foam poses no specific toxicity but is a safety/injury risk.
What we don’t know
- Basis
- Model estimate, 55% confidence, not a lab result
- Lab test
- None on record for this exact product
- Brand statement
- On Running has made none
Formulations change between production runs, so check the current label. How we grade.
Safer alternatives in Running & Athletic Shoes
New Balance
Women's Fresh Foam Arishi v4 Shoes
Mesh upper, Fresh Foam midsole, rubber outsole
Azo dyes and color-based toxins
Limited concern
Antimony in polyester
Limited concern
Standard athletic shoe with no known PFAS triggers, but no brand disclosure.
⚠Risky category by default
Diadora
Atomo V7000-2
Textile fabric, likely polyester or nylon blend
Azo dyes and synthetic dyes
Limited concern
Formaldehyde / VOCs
Limited concern
Antimony in polyester fibers
Limited concern
Adhesive and rubber off-gassing
Limited concern
No public PFAS disclosure; lower concern but unverified.
⚠Risky category by default
More running & athletic shoes 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.