Subscribe to the OSS Weekly Newsletter!

Are Summer Clothes Protecting Your Skin from Sunburns?

Much like sunscreen gets an SPF rating, some specialty clothes are rated for their UV protection factor. Is this a meaningful rating?

How much protection does your white T-shirt offer you in the summer when you’re out in the sun? Would you say it’s impossible to get a sunburn underneath that garment?

It’s an important question to ask ourselves. Sun exposure is a major risk factor for skin cancer and, in Canada, about one third of all new cases of cancer are skin cancers. We are seeing more and more instances of it over the years, and while many are treatable, a type like melanoma is particularly insidious and dangerous. (Melanoma will affect 1 in 73 Canadian women over their lifetime, and 1 in 59 Canadian men.)

We hear about sunscreen a lot in the media, but a protective layer that doesn’t get as much coverage, pun intended, is clothing.

Summer clothes are not a suit of armour

I was recently given a New Yorker cartoon that depicts a medieval knight standing on a beach, with the caption “S.P.F. 1,000”. The truth is, no one in their right mind would wear armour plating to protect their skin while making sandcastles, but your average summer getup is not as protective as you might think.

You can read online that a white T-shirt usually lets about 20% of the UV radiation through. While it may not sound dramatic, over a period of an hour or two, that’s a lot of ultraviolet light hitting your skin. Part of the reason is that the cotton fibres are not woven tightly enough. Under a microscope, we can easily see the holes.

Regular summer clothing, by and large, is not a replacement for sunscreen. But there is a type of apparel that is (sort of).

Sun protective clothing

Sunscreens receive a “sun protection factor” rating or SPF; some clothes have an equivalent rating called UPF or “ultraviolet protection factor”. Many sun protective clothes available for purchase display a rating of UPF 50+. It means that less than one out of every 50 UV rays that hit the material will actually pass through. Thus, over 98% of UV radiation is blocked by the fabric. By comparison, our white T-shirt from earlier would be rated UPF 5 for letting through one out of five (or 20% of) UV rays.

The technology used to create sun protective clothing is manifold. Some manufacturers will blend in bamboo and viscose, materials that are naturally better at blocking UV rays. Many will also treat their fabric with zinc oxide or titanium dioxide, the same minerals used in sunscreens. And to add to this barrier, sun protective clothing tends to have thicker fibres woven very tightly to create a dense material that can’t easily be penetrated by ultraviolet light.

So how do we know it works? In the early 1990s, the FDA was regulating the industry in the United States, but they subsequently passed the torch to the Federal Trade Commission (FTC). Manufacturers use a set of international standards developed by the American Society for Testing and Materials, and the FTC can come after companies for making false claims. In Canada, it’s the Consumer Product Safety Program at Health Canada that oversees such claims. The testing required to meet the standards involves simulated launderings, exposure to simulated sunlight and, in the case of clothes meant for swimming, to chlorinated water. In the end, this is a self-regulating industry, which means it is possible for less reputable companies to cut corners until they get caught.

Summer clothes, revisited

If sun protective clothing is too expensive, can you safely rely on regular summer clothing? Many years ago, an NPR journalist spoke to a textile scientist who tested her family’s old T-shirts in the lab to find out that most of them yielded a UPF of 50 and above, comparable to most sun protective garments available for sale and much higher than what has traditionally been reported. But how reliable were her results?

It turns out that many factors positively and negatively impact an item of clothing’s UV protection.

Let’s imagine a typical T-shirt. Every decision that would make the T-shirt more protective for our skin would also make it less convenient for a summer outing. (For an in-depth look, this review paper has you covered.)

Thicker is better, but less comfortable. Darker colours absorb more UV light, which is good, but they also absorb infrared heat and feel stuffier. Linen breathes well, but is not woven tightly enough to offer much UV protection. Polyester is much better to shield your skin, but it’s not exactly cooling in the summer (though it can be combined with lighter fabrics to improve its comfort yet maintain a certain amount of sun protection).

What is cooling, though? Water! But be careful: a wet cotton T-shirt may only be half as good at protecting you than a dry T-shirt.

The reason why the textile scientist’s old T-shirts had such a high protection rating might have something to do with how they were laundered. While bleaching cotton and rayon will make UV pass through more easily, many laundry detergents contain optical brightening agents which do the opposite. These molecules absorb UV light and reemit its energy in the visible range. This makes your clothes look spiffier while also adding a layer of UV protection. There are even specific products, like SunGuard (which contains Tinosorb), marketed as laundry additives that will increase your clothes’ UV protection factor for up to 20 wash cycles. And finally, anyone who’s washed a garment inappropriately will know that it shrinks. Washing clothes shrinks them, which results in a tighter fabric that lets fewer ultraviolet rays through. Hence the older the article of clothing, the better the shielding it theoretically provides against the sun.

UPF-rated sun protective clothing isn’t necessary for many people, but it can be useful for those of us with fair skin, for children, for people who exercise outside or who live at high elevations where the UV exposure is greater, and for anyone taking drugs that increase the sensitivity of their skin to sun damage.

But even while wearing clothing with a high UPF rating, there will be exposed areas, and they should be protected with a broad-spectrum (UVA and UVB) sunscreen with an SPF of at least 30. Long sleeves help, as does a wide-brimmed hat. And sunglasses can be bought really cheaply and still offer sufficient protection for your eyes.

In the end, the best protection against the sun remains the shade. As with abstinence-only sex education, though, I suspect the message is a tad unrealistic. If you’re going to enjoy the sun, wear protection.

Take-home message:
- Regular summer clothes do not offer a strong protection against UV light, though repeat laundering (especially with brightening agents) will make them better at protecting your skin.
- Sun protective clothing is available for sale. It is based on strict standards but keep in mind that the industry regulates itself


@CrackedScience

Want to comment on this article? View it here on our Facebook page!