Sea to Summit · Waterproof Outdoor Bags
Ultra-Sil Daypack - Atoll Blue
Silicone daypack; PFAS risk unclear without material disclosure.
Sea to Summit's Ultra-Sil line uses silicone-coated nylon. Brand provides no PFAS disclosure. Silicone itself is lower concern, but water-repellent treatment details remain unstated.
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Material
Silicone-coated fabric (likely water-repellent coating treatment)
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 Ultra-Sil Daypack uses silicone-coated nylon or polyester fabric, which provides water resistance without relying on traditional fluorocarbon-based water-repellent coating (water-repellent coating) treatments. Silicone itself is generally considered chemically inert and does not off-gas volatile compounds at normal temperatures. However, Sea to Summit has not publicly disclosed whether the water-repellent coating treatment on this specific product contains PFAS, what alternative chemistry is used, or whether the silicone coating contains any additives (such as antimony catalysts in polyester) that could migrate under stress or abrasion.
The brand's record and disclosure
Sea to Summit does not maintain a public PFAS disclosure policy or sustainability statement specifically addressing water-repellent coating chemistry in their daypack line. The brand has not voluntarily committed to PFAS-free manufacturing or published third-party testing results for water-resistant coatings. This silence is notable given that outdoor apparel companies like Patagonia and Arc'teryx have made explicit PFAS commitments; the absence of such disclosure suggests either use of PFAS-based treatments or simply lack of transparency rather than proven safety.
How it compares in its category
Most lightweight daypacks in this price range use either traditional fluorocarbon water-repellent coating (Teflon-based, persistent PFAS) or silicone coatings. Silicone-coated alternatives from competing brands (e.g., Zpacks, some Hyperlite models) face the same disclosure gap. Sea to Summit's approach is neither better nor worse than category norms, but it sits in the middle tier of transparency, not as transparent as brands with explicit PFAS policies, and not as cheap as fully uncoated options that require rewaxing or sealing.
If you buy it
The daypack is safe for normal use (hiking, commuting, travel); silicone coatings do not off-gas significantly and do not leach under dry conditions. Avoid machine washing, which can accelerate any coating degradation; hand wash with mild soap and air dry. Inspect the seams and coating annually for cracking or peeling; once the waterproof layer fails substantially, consider replacement rather than repair, as recoating is difficult and may not restore performance. Store in a cool, dry place to minimize UV and thermal stress on the silicone layer.
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.”
PFAS in water-repellent coating treatment (water-repellent coating)
Sea to Summit has not disclosed whether the water-repellent coating applied to this daypack's silicone-coated fabric contains PFAS. Silicone coating itself does not inherently require PFAS, but water-repellent coating finishes commonly do unless explicitly formulated otherwise. Without material testing or brand confirmation, PFAS presence cannot be ruled out.
Coating degradation and microplastic release
Silicone coatings can crack, peel, or degrade over 3-5 years of heavy use, particularly at stress points (seams, folds, straps). Fragments shed during washing or wear could theoretically enter waterways, though the quantity from a single daypack is negligible. Normal hand washing minimizes this risk.
Antimony in polyester substrate
If the base fabric is polyester (likely), it may contain antimony as a polymerization catalyst. Antimony leaching from fabric is not established as a hazard at skin contact, and no recalls or reports specific to Sea to Summit daypacks exist. This is a category-level concern with no brand-specific evidence.
Formaldehyde-based fabric finishes (sizing or anti-wrinkle)
Lightweight nylon and polyester fabrics occasionally use formaldehyde-containing sizing or finishing agents. No specific testing or complaints have been reported for Ultra-Sil products, and silicone coating may encapsulate such residues. First wash recommended to reduce any residual finish.
Fragrance or dye allergens
Atoll Blue colorant and any applied water-resistant treatments are unlikely to trigger contact dermatitis in typical use, but no material safety data sheet is publicly available for this specific product. Individuals with sensitive skin should test with a patch of fabric before extended wear.
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.
Safer alternatives in Waterproof Outdoor Bags
Granite Gear
Wrought Iron Food Pack
nylon fabric pack, likely uncoated or minimally treated
Food pack likely lower concern; confirm no water-repellent coating with brand.
⚠Risky category by default
More waterproof outdoor bags 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.