Understanding UVA Protection and the PA Indicator: What Science (and EWG) Says About True Sunscreen Effectiveness

When it comes to sun protection, most people know about SPF, the number on sunscreen bottles that supposedly tells you how well a product protects your skin. But here’s the key point: SPF only measures protection against UVB rays, which cause sunburn. It doesn't directly measure how well a product protects you from UVA rays, the deeper-penetrating radiation responsible for premature ageing, immune system suppression, and an increased risk of skin cancer.

That’s why understanding UVA protection, how it’s measured, and why sunscreen labels sometimes include a PA rating is essential for truly effective sun care.

Why UVA Protection Matters

UVA rays differ from UVB rays in several important ways:

1. UVA Rays Penetrate More Deeply

UVA radiation can penetrate deep into the skin, affecting cells and connective tissue long below the surface. This type of radiation:

• contributes significantly to photoaging (wrinkles and sagging)

• accelerates pigmentation and dark spots

• influences DNA damage deep inside skin cells

• is linked with higher risks of melanoma and other skin cancers

2. UVA Rays Are More Abundant

UVA makes up the bulk of ultraviolet radiation reaching the Earth’s surface, and unlike UVB, UVA remains strong even on cloudy days and during winter months.

3. SPF Misleads Many Consumers

SPF testing focuses on UVB protection, the level of protection from burning. But research by the Environmental Working Group (EWG) shows that many sunscreens with high SPF provide far less UVA protection than people expect. In one study, the average UVA protection was only about a quarter of what the SPF number might imply.

This disparity matters because even if you don’t burn, your skin can still be accumulating UVA-related damage.

What Is “Broad Spectrum” and Why It’s Not Enough

In the U.S., sunscreen products labelled “broad spectrum” must meet a minimum requirement for UVA coverage, but this standard is relatively weak. It doesn’t distinguish between mediocre protection and strong, effective protection. It simply marks a product that blocks some UVA.

That’s why consumers often see products with very high SPF but due to unbalanced UVA coverage they still aren’t protecting the deeper layers of the skin where UVA does its most insidious damage.

PA Ratings: What They Are and Why They Matter

The PA system originated in Japan and is widely used in Asian sunscreens to provide a more transparent measure of UVA protection. PA stands for Protection grade of UVA, and the number of “+” signs indicates the strength of UVA defense:

Unlike SPF, which specifically measures how much longer a person can stay in the sun without burning, PA ratings estimate how well a sunscreen blocks UVA rays.

Many Asian and some European products include this PA rating because it gives a clearer sense of UVA performance. It’s particularly useful since SPF alone doesn’t describe how well a sunscreen defends against deeper UVA penetration.

How PA Relates to Scientific UVA Measures

In technical research and testing, UVA protection is often measured by Persistent Pigment Darkening (PPD) or UVA-PF (UVA Protection Factor). These metrics are more precise but less commonly shown on packaging.

The PA system roughly correlates with PPD values:

• PA+ ≈ PPD 2–4

• PA++ ≈ PPD 4–8

• PA+++ ≈ PPD 8–16

• PA++++ ≈ PPD ≥ 16

The higher the PPD or PA level, the longer it takes for UVA to induce pigmentation or ageing effects compared to unprotected skin, meaning stronger UVA defence.

How UVA/UVB Balance Is Evaluated in Science 

EWG’s scientific methodology evaluates sunscreens by not only looking at SPF but also by modelling how effectively a product absorbs UVA across a range of wavelengths. This gives a realistic picture of how well a sunscreen defends against deep-penetrating UVA rays.

EWG also scores sunscreens for UVA/UVB balance, the degree to which a product’s UVA protection corresponds to its labelled SPF. Many products with high SPF fail to provide proportionate UVA defence, which leaves users vulnerable to long-term harm despite strong sunburn prevention.

How to Choose Better UVA Protection

Here are evidence-based tips for stronger UVA protection:

Look for Explicit UVA Indicators

If a product shows:

• PA+++ or PA++++ — this indicates increasingly strong UVA shielding

• OR a UVA circle logo (in EU products), which means UVA protection ≥ ⅓ of SPF

These give more detail than SPF alone.

Prefer Mineral Filters for Reliable UVA Defence

Mineral filters like zinc oxide and titanium dioxide provide consistent UVA and UVB coverage without degrading under sunlight — and are among the top recommended ingredients in EWG’s Guide to Sunscreens.

Use Broad Spectrum and Reapply

Even products labelled broad spectrum vary widely in actual UVA defence, so checking for PA or similar indicators is key. Reapply every 2 hours (or sooner if you’re sweating or swimming).

Balance With Other Sun Safety Measures

Clothing, shade, sunglasses, and timing outdoor exposure (avoid 10am – 4pm peak intensity) all help reduce the total UVA dose your skin receives.

Why This Matters for Daily Skin Health

Consistent UVA exposure contributes to:

• Premature aging

• Suppressed skin immune response

• Pigmentation changes

• Elevated cancer risk

Even on cloudy days or indoors near windows, UVA rays penetrate deeper and persist, and SPF alone won’t tell you how well a sunscreen guards against these effects.

Understanding the role of UVA and paying attention to protective indicators like PA ratings gives you a clearer and more scientifically grounded way to choose sunscreens that truly defend your skin.