Feb 23, 2026 Ana Bohr

The Science of Swimwear That Protects You: UV Radiation, Chlorine Chemistry, and the Fabrics Engineered to Fight Both

Why Your Swimwear Is a Health Decision

Most people think about swimwear in terms of style, fit, and price. Those matter. But there’s a conversation the swimwear industry rarely has: the material your swimsuit is made from directly affects your health, your wallet, and the environment.

Two invisible forces are working against you every time you step outside in a swimsuit: ultraviolet radiation from the sun and chlorine in pool water. UV radiation causes DNA damage that leads to skin cancer—the most commonly diagnosed cancer in the United States, with more than 5.4 million cases of nonmelanoma skin cancer treated annually. Chlorine, the chemical that keeps pools sanitary, systematically destroys conventional swimwear fabrics through oxidative degradation.

The right fabric can protect you from both. The wrong fabric leaves you exposed to one and is destroyed by the other. This article explains the science behind UV-protective and chlorine-resistant swimwear—what it is, how it works, and why it matters—backed by peer-reviewed research and data from leading dermatological and textile science organizations.

Part 1: Ultraviolet Radiation and Your Skin

1.1 What UV Radiation Does to Skin

The sun emits ultraviolet radiation in three wavelength bands: UVA (315–400 nm), UVB (280–315 nm), and UVC (100–280 nm). UVC is absorbed by the ozone layer and doesn’t reach Earth’s surface. UVA and UVB both reach your skin, but they cause damage through different mechanisms.

UVB radiation is absorbed by the epidermis and directly damages DNA by creating cyclobutane pyrimidine dimers—structural distortions in the DNA molecule. This is what causes sunburn. The body’s repair mechanisms can fix most of this damage, but accumulated errors over time lead to mutations that may develop into skin cancer.

UVA radiation penetrates deeper into the dermis and generates reactive oxygen species (free radicals) that indirectly damage DNA, collagen, and elastin. UVA is the primary driver of photoaging—wrinkles, loss of elasticity, and hyperpigmentation. Critically, UVA intensity remains relatively consistent throughout the year and throughout the day, passes through clouds, and penetrates glass.

Source: D’Orazio J, Jarrett S, Amaro-Ortiz A, Scott T. UV Radiation and the Skin. Int J Mol Sci. 2013;14(6):12222–12248.

1.2 The Scale of the Problem

Skin cancer is not a rare disease. It is a public health crisis that the U.S. Surgeon General has formally designated a “major public health problem.” The numbers:

Nearly one in five Americans will develop skin cancer in their lifetime.
Approximately 5.4 million cases of nonmelanoma skin cancer (basal cell carcinoma and squamous cell carcinoma) are treated in 3.3 million Americans annually.
About 90% of nonmelanoma skin cancers are associated with UV radiation exposure.
An estimated 112,000 new cases of invasive melanoma will be diagnosed in the U.S. in 2026, along with 122,680 noninvasive cases.
The annual cost of treating skin cancers in the U.S. is estimated at $8.1 billion.
Sun damage is cumulative: only about 23% of lifetime UV exposure occurs before age 18.

Sources: Skin Cancer Foundation, skincancer.org/skin-cancer-facts (2026); American Cancer Society, Cancer Facts & Figures 2026; AAD, aad.org/media/stats-skin-cancer; U.S. Surgeon General’s Call to Action to Prevent Skin Cancer, 2014.

That last statistic is critical for active adults. The majority of your UV exposure happens in your 20s, 30s, 40s, and beyond—the years you’re most likely to be exercising outdoors, swimming, traveling, and spending extended time in the sun.

1.3 How Fabric Blocks UV Radiation

Fabric provides UV protection through three mechanisms: absorption, reflection, and scattering of UV photons. Effectiveness depends on four measurable fabric properties:

Fiber composition. Synthetic fibers like polyamide (nylon) and polyester absorb UV radiation more effectively than natural fibers like cotton or linen. Polyamide contains chromophores—chemical groups that absorb specific wavelengths of light—that are particularly effective at capturing UV photons. Research published in the Journal of the Textile Institute found that polyamide fabrics consistently outperformed cotton in UV protection testing, with untreated polyamide achieving UPF ratings 2–3 times higher than equivalent-weight cotton.

Source: Gambichler T, Altmeyer P, Hoffmann K. Role of clothes in sun protection. Recent Results Cancer Res. 2002;160:15–25.

Weave density. Tighter weaves leave fewer gaps for UV photons. The “cover factor” of a fabric—the ratio of area covered by yarn to total fabric area—directly correlates with UV protection. High-density knits used in performance swimwear achieve cover factors above 95%.

Fabric weight. Heavier fabrics (grams per square meter, or GSM) provide more material between UV radiation and skin. A 220 GSM fabric offers meaningfully more protection than a 120 GSM fabric of the same fiber type.

Color and dye. Darker colors absorb more UV radiation. However, certain dyes also absorb UV independently. Modern UV-protective fabrics achieve high UPF even in lighter colorways through fiber type, weave density, and UV-absorbing dye combinations.

1.4 UPF: How It’s Measured

UPF (Ultraviolet Protection Factor) is tested using spectrophotometry—a lab method measuring UV radiation transmitted through fabric across the full UVA and UVB spectrum (290–400 nm). Test protocols include AATCC Test Method 183 (U.S.), AS/NZS 4399 (Australia/NZ), and EN 13758 (Europe).

UPF Rating	UV Through	UV Blocked	Category	SCF Seal
UPF 15	6.7%	93.3%	Good	No
UPF 25	4.0%	96.0%	Very Good	No
UPF 30	3.3%	96.7%	Very Good	No*
UPF 40	2.5%	97.5%	Excellent	No
UPF 50+	<2%	98%+	Excellent	Yes

*The Skin Cancer Foundation raised its Seal of Recommendation minimum to UPF 50 as of 2025, up from UPF 30 previously.

A key nuance: UPF measures performance under laboratory conditions on new, dry, unstretched fabric. In real-world use, stretching, wetting, and wear can reduce protection. High-quality performance fabrics are engineered to maintain their rated UPF under these conditions; cheap fabrics often cannot.

1.5 The Wet Fabric Problem

This is one of the most overlooked aspects of sun protection. When conventional fabric gets wet, the fibers swell and separate, creating larger gaps for UV penetration. A standard white cotton t-shirt—already providing only UPF 5–7 dry—can drop to UPF 3 when wet, offering almost no meaningful protection.

For swimwear, this is a fundamental design failure. Your suit is wet by definition. If the fabric loses UV protection when wet, it’s protecting you least when you need it most—in direct sun, near reflective water surfaces (which amplify UV exposure by 10–25%), with no shade.

Performance polyamide and polyester fabrics maintain their UPF rating when wet because the UV-blocking is a property of the fiber itself, not a function of the dry-fabric geometry. The chromophores in synthetic fibers continue absorbing UV photons regardless of whether the fiber is wet or dry.

Source: Skin Cancer Foundation, skincancer.org/sun-protective-clothing; Gies HP, Roy CR, Toomey S, McLennan A. Protection against solar ultraviolet radiation. Mutation Research. 1998;422(1):15–22.

Part 2: Chlorine and Swimwear Degradation

2.1 What Chlorine Does to Fabric

Pool water contains hypochlorous acid (HOCl), an oxidizing agent used to kill bacteria and maintain water hygiene. Typical pool chlorine concentrations range from 1–3 parts per million (ppm), with some commercial and competitive pools running higher.

Hypochlorous acid attacks the polymer chains in elastane (also marketed as spandex or Lycra)—the fiber responsible for stretch and recovery in most swimwear. The mechanism is oxidative degradation: chlorine breaks the urethane and urea bonds in the elastane polymer backbone, causing irreversible chain scission (the polymer chain literally breaks apart).

This degradation is cumulative, progressive, and irreversible. Each exposure adds to the total damage. There is no way to “restore” chlorine-damaged elastane—once the polymer bonds are broken, the stretch and recovery properties are permanently lost.

Source: Caze C, Devaux E, Crespy A, Marchand JP. A study of the effect of chlorinated water on the ageing of elastane. Textile Research Journal. 2001;71(12):1070–1076.

2.2 The Timeline of Destruction

For a standard elastane-based swimsuit used 3–4 times per week in chlorinated water:

Weeks 1–2: Molecular damage accumulates but isn’t visible. Fabric feels normal.
Weeks 3–4: Colors fade. Fabric texture roughens. Elastic recovery begins declining—the suit doesn’t snap back as firmly.
Months 2–3: Significant sagging at seat and straps. Fabric thins in high-friction areas. Pilling appears.
Months 4+: Suit is functionally destroyed. Transparency in spots. All compression and support lost.

For regular swimmers, a standard swimsuit provides approximately 24–48 usable sessions before requiring replacement.

2.3 How Chlorine-Resistant Fibers Work

Chlorine-resistant swimwear replaces elastane with alternative stretch systems—typically polyester-based or polyamide-based fibers that achieve stretch through fiber engineering rather than through the chemical bonds that chlorine attacks.

Polyamide (nylon) fibers resist chlorine oxidation far more effectively than elastane because their polymer backbone uses different chemical bonds (amide bonds) that are more stable against hypochlorous acid attack. The amide bonds in polyamide have a bond dissociation energy significantly higher than the urethane bonds in elastane, making them inherently more resistant to oxidative chain scission.

The result: a chlorine-resistant polyamide swimsuit maintains its shape, compression, and color for 200+ pool sessions versus 24–48 for a standard elastane suit. That’s roughly 5–10 times the usable lifespan.

Source: Caze C et al. Textile Research Journal. 2001;71(12):1070–1076; Textile Research Centre, University of Leeds, polymer degradation studies.

2.4 The Cost-Per-Wear Equation

Let’s quantify the difference:

Metric	Standard Suit ($25)	Chlorine-Resistant ($48.50)
Usable sessions	~36	200+
Cost per wear	$0.69	$0.24
Suits needed per year (3x/wk)	4–5 suits	1 suit
Annual cost	$100–$125	$48.50
Fit quality at session 100	Replaced twice already	Like new

Chlorine-resistant swimwear costs more upfront but saves $50–$75 annually while providing superior fit and performance throughout its lifespan. For competitive swimmers, coaches, lifeguards, and anyone who swims regularly, the economics are clear.

Part 3: The Intersection — Fabrics That Do Both

3.1 Why Most Swimwear Fails at One or Both

Most swimwear brands optimize for one performance attribute at the expense of others. Fashion-forward brands prioritize aesthetics and softness, using elastane-heavy blends that feel luxurious but degrade rapidly in chlorinated water and offer minimal UV protection. Athletic brands prioritize chlorine resistance but often produce utilitarian-looking suits with limited style appeal.

Very few brands engineer fabrics that simultaneously deliver UV protection, chlorine resistance, compression support, quick-dry performance, and an aesthetic that works beyond the pool deck. The technical challenge is real: each property requires specific fiber characteristics, and these requirements sometimes conflict.

3.2 The Engineering of Multi-Performance Fabric

Achieving UV protection, chlorine resistance, and athletic performance in a single fabric requires careful engineering across multiple variables:

Fiber selection: Recycled polyamide provides the UV-absorbing chromophores for sun protection and the chemical bond stability for chlorine resistance simultaneously. The recycling process (depolymerization and repolymerization of post-consumer nylon waste) does not compromise these performance properties.
Knit construction: A dense knit achieves high cover factor (>95%) for UV blocking while maintaining the two-way stretch needed for athletic movement. The 220 GSM weight provides sufficient material density for UV protection without becoming rigid or uncomfortable.
Fiber-level UV integration: UV protection built into the fiber’s molecular structure (through chromophores inherent to the polyamide) maintains its effectiveness wash after wash, unlike surface-applied UV treatments that gradually wash off.
Quick-dry engineering: The hydrophobic (water-repelling) properties of polyamide mean the fiber absorbs minimal water, allowing the fabric to dry rapidly after swimming—typically within minutes rather than hours.

Source: Textile Research Journal; Kan CW, Yuen CWM. Evaluation of the performance of UV-absorbers on cotton fabric. Textile Research Journal. 2012;82(8):756–764.

3.3 Recycled vs. Virgin Polyamide: Performance Comparison

A common concern with recycled fibers is whether the recycling process compromises performance. For polyamide, the answer is no. The chemical recycling process used by leading fiber manufacturers (including Aquafil’s ECONYL and similar programs) involves complete depolymerization of post-consumer nylon waste back to its monomer (caprolactam), followed by repolymerization into virgin-quality fiber.

Because the polymer is rebuilt from the ground up, recycled polyamide has identical molecular structure and mechanical properties to virgin polyamide. UV absorption, chlorine resistance, tensile strength, and stretch recovery are all maintained at equivalent levels. The environmental benefit—diverting nylon waste from landfills and reducing dependence on petroleum-derived raw materials—comes without any performance trade-off.

Source: Aquafil sustainability reports; Hawley JM. Textile recycling options. Textiles and Clothing Sustainability. Springer, 2015.

Part 4: Putting It Into Practice

4.1 How to Evaluate Swimwear Fabric Claims

Not all “UV-protective” and “chlorine-resistant” marketing claims are equal. Here’s how to evaluate them:

Look for a stated UPF rating. Vague claims like “sun-protective” or “built for the sun” are meaningless without a tested UPF number. Legitimate UV protection requires standardized testing (AATCC 183 or equivalent). UPF 50+ is the Skin Cancer Foundation’s minimum for its Seal of Recommendation.
Check the fiber composition. Polyamide and polyester resist chlorine. Elastane does not. If a swimsuit’s composition label lists a high percentage of elastane or spandex (above 15–20%), it will degrade quickly in chlorinated water regardless of marketing claims.
Consider the fabric weight. Lightweight fabrics (under 150 GSM) generally provide less UV protection than heavier-weight fabrics (200+ GSM). If a brand doesn’t disclose fabric weight, it may be using a lighter, less protective material.
Understand fiber-level vs. topical UV protection. UV protection that’s inherent to the fiber (as in polyamide) is permanent. UV protection applied as a surface finish will wash off over time, potentially dropping below effective levels after 20–30 washes.
Test the stretch. Stretch the fabric and hold it up to light. If you can see through it when stretched, it will transmit UV radiation when worn tightly against your body—even if the UPF was tested on unstretched fabric.

4.2 Swimwear Care for Maximum Lifespan

Even chlorine-resistant swimwear benefits from proper care:

Rinse immediately. Cold fresh water within 10 minutes of leaving the pool removes residual chlorine before it can accumulate.
Hand wash gently. Use mild detergent. Avoid machine washing—the agitation and heat accelerate fiber degradation.
Never wring. Press excess water out by rolling in a towel. Wringing stretches and distorts fibers.
Dry flat in shade. Heat and UV from direct sunlight can degrade fabric over time. Air dry on a flat surface away from direct sun.
Rotate suits. If swimming daily, alternate between two suits. This gives each suit time to fully dry and recover, extending both lifespans.

4.3 The Complete Active Protection System

The most effective approach to skin protection and swimwear longevity combines multiple strategies:

UV-protective swimwear (UPF 50+) for consistent, passive protection of covered skin areas.
Broad-spectrum sunscreen (SPF 30+) on all exposed skin, reapplied every 2 hours and after water exposure.
Wide-brim hat and UV sunglasses for face, scalp, and eye protection.
Shade-seeking behavior during peak UV hours (10 AM–4 PM).
Proper swimwear care to maintain fabric performance over time.

Part 5: How PLAY Swimwear Is Engineered

PLAY swimwear is designed at the intersection of every principle discussed in this article. Each material and construction decision is driven by performance science:

Fabric: 220 GSM recycled Shiny polyamide by Hung Yen. High GSM for UV protection. Polyamide base for both UV absorption and chlorine resistance. Recycled content for environmental responsibility without performance compromise.
UV protection: Built into the fiber’s molecular structure through the polyamide’s natural chromophores. Does not wash off, does not fade, does not degrade with use. Maintains protection when wet and when stretched.
Chlorine resistance: Polyamide’s amide bonds resist oxidative degradation from hypochlorous acid. Maintains shape, compression, and color through 200+ pool sessions.
Quick-dry performance: Polyamide’s hydrophobic properties minimize water absorption, allowing the fabric to dry within minutes of leaving the water.
Two-way stretch: Engineered into the knit construction to provide athletic compression and freedom of movement for Pilates, swimming, gym workouts, and everyday wear.
Made in LA: Local manufacturing in Los Angeles enables quality control oversight, shorter supply chains, faster restocking, and support for local jobs and fair labor practices.
Recycled content: Post-consumer polyamide waste diverted from landfills and reprocessed into virgin-quality fiber, reducing petroleum dependence and environmental impact.

Conclusion: Fabric Is Not a Fashion Detail — It’s a Health Decision

The swimwear industry has conditioned consumers to choose based on cut, color, and price. Those considerations have their place. But the science is unambiguous: the fabric your swimsuit is made from determines how much UV radiation reaches your skin, how long your suit lasts in chlorinated water, and whether you’re paying $48 once or $125 every year for the same amount of swimming.

UV radiation is the leading modifiable risk factor for skin cancer. Chlorine degrades conventional swimwear fabrics. Both problems are solved by the same engineering: high-density, UV-absorbing, chlorine-resistant polyamide fabric built at a weight and construction that provides real protection under real-world conditions.

At PLAY, we believe your swimwear should work as hard as you do—protecting your skin, surviving your pool, and performing through your workout. Not because we say so, but because the material science demands it.

Full references cited throughout. Primary sources: Skin Cancer Foundation (skincancer.org), American Academy of Dermatology (aad.org), American Cancer Society (cancer.org), World Health Organization (who.int), U.S. Surgeon General’s Call to Action 2014, Textile Research Journal, International Journal of Molecular Sciences, Journal of the Textile Institute, PMC/National Library of Medicine.