Onia Two-Tone Swimsuit
No PFAS disclosure; typical swimwear water-repellent coating treatment raises concern, request material details.
Onia doesn't publicly disclose PFAS use or absence. Most performance swimwear uses PFAS-based water-repellent coating finishes, though some brands now use PFAS-free alternatives. Risk cannot be ruled out.
The better-graded swap
Patagonia
Patagonia Women's Bottom Turn Racerback Bikini Top
90/100 safety
Same rubric that flunked this product. The swap earned Excellent.
Still want this one anyway? Check the price on Amazon. We’d swap it.
Material
Nylon/polyester blend with water-resistant treatment
Brand disclosure
Brand is silent on PFAS
Lab data
No public lab test
What Onia Two-Tone Swimsuit is made of, ingredients and materials
This swimsuit is a nylon and polyester blend, both synthetic plastics that are chemically stable in normal use but vulnerable to breakdown when exposed to high heat, chlorine, and UV light. The 'water-resistant treatment' applied to the fabric is the critical unknown, most mass-market swimwear water-repellent coating (water-repellent coating) finishes historically rely on PFAS-based chemistry to persist through washing. Onia has not publicly disclosed the type of water-resistant treatment used, leaving uncertainty about PFAS presence. Nylon and polyester themselves do not inherently leach hazardous chemicals into skin or water under normal wear, but degraded fibers and unknown finishing chemicals are the real concern.
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.
Waterproof / stain-resistant treatment
Water-repellent coating treatments have historically used PFAS.
PFAS
Undisclosed water-resistant treatment is consistent with historical PFAS-based water-repellent coating chemistry in mass-market swimwear; Onia provides no testing or alternative-finish verification. PFAS accumulates in body and environment, making transparency critical for this product class.
Source, ATSDR ↗Microplastic fiber shedding
Nylon and polyester swimwear shed microfibers during washing and wear, especially as elastic and seams degrade. Two-tone construction may involve multiple dyeing or coating steps, potentially increasing fiber fragmentation risk; no data specific to Onia product durability.
Fabric degradation from chlorine, salt, and UV
All nylon/polyester swimwear degrades over time in harsh conditions; breakdown of fibers and finish chemicals accelerates with use frequency. This product has no marketed UV or chlorine resistance enhancement, so lifespan and chemical release profile follow standard swimwear aging patterns.
What’s reassuring
Heavy metals
No recalls or testing results reported for Onia swimwear. Contemporary dyeing for nylon/polyester typically avoids restricted azo dyes due to industry standards, but absence of OEKO-TEX or similar certification means no third-party verification of this product's colorant chemistry.
Source, FDA ↗Formaldehyde / VOCs
Formaldehyde-based resins are used in some synthetic fabric finishes and elastic components for crease resistance and elasticity retention. No public data exists for this specific Onia product; industry trend favors reduced-formaldehyde options but remains unregulated in swimwear.
Source, ATSDR ↗The full breakdown
The brand's record and disclosure
Onia is a contemporary swimwear and resort-wear brand with no publicly available PFAS disclosure, testing data, or certification statements (such as bluesign or GOTS). No major recalls or chemical controversies are on record for this brand. The silence on water-resistant treatment chemistry is notable given industry-wide awareness of PFAS in water-repellent coating finishes since the mid-2010s, suggesting either legacy formulations or a lack of transparency rather than a deliberate commitment to lower concern alternatives. Absence of evidence is not evidence of safety.
How it compares in its category
Mass-market swimwear typically uses nylon or polyester with undisclosed water-repellent coating treatments; premium brands like Patagonia (recycled nylon, PFAS-free finishes) and certified alternatives (bluesign, OEKO-TEX) are exceptions. Onia positions itself as mid-to-upper-market but does not match the transparency or certification rigor of category leaders on chemical content. The two-tone styling adds no chemical risk but does not offset the opacity on finishing agents. For a product worn against skin and in chlorinated/salt water, lack of water-repellent coating chemistry disclosure is a material gap.
If you buy it
Rinse thoroughly with fresh water after each use, especially in chlorinated pools, to minimize fiber degradation and finish breakdown. Wash in cool water, air dry, and avoid high-heat drying or direct sunlight exposure for extended periods, as heat can accelerate release of finish chemicals and polymer breakdown. Replace after visible pilling, color loss, or elastic degradation, typically 1-2 seasons of regular use. Consider requesting Onia's water-resistant treatment specifications before purchase if PFAS minimization is a priority.
What we don’t know
- Basis
- Model estimate, 42% confidence, not a lab result
- Lab test
- None on record for this exact product
- Brand statement
- Onia has made none
Formulations change between production runs, so check the current label. How we grade.
Better-graded alternatives in Swimwear
Patagonia
Women's Bottom Turn Racerback Bikini Top
- Nylon/polyester blend with elastane (standard swimwear)
- The brand calls it PFAS-free, which we have not verified
- Elastane (spandex) degradation under heat or chlorine
Solid & Striped
Taylor One Piece Seersucker Plaid
- Cotton/cotton-blend seersucker plaid
- We found no PFAS statement from the brand
- Azo dyes and colorfast stability
2 hazards checked on this product. See all of them.
Adidas
Women's Mexicana Florals Tie-Back Swimsuit
- Polyester/nylon swimsuit fabric, likely uncoated or standard finish
- Azo dyes and synthetic colorants
4 hazards checked on this product. See all of them.
More swimwear 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.