Above: Base Image © Chombosan, iStock photo

What kind of advice do people give you about your future? Do they talk about your future career, money, or love? In the late 1990s, a Chicago Tribune columnist suggested this advice for graduates: “Wear sunscreen. If I could offer you only one tip for the future, sunscreen would be it.” Sound like good advice? Some people thought so - the advice was even turned into a popular song!

Chances are, someone in your life has given you similar advice. Or someone might have told you that sunscreen is loaded with chemicals and potentially unsafe. Scientists are still debating that second point. What they do know is that the sun’s rays are unsafe - and that sunscreen can protect you from the dangerous effects of the sun.

What makes the sun so damaging to your skin?

The light released by the sun is a form of electromagnetic radiation. When you think of sunlight, you might think of light you can see - the sun’s rays beaming down on a nice day, for example. But the sun also emits light you can’t see, like infrared (IR) rays and ultraviolet (UV) rays.

UV rays are very damaging. You may have seen (or even experienced) one of their temporary effects: a red sunburn. But over time, they can lead to skin cancer.

There are different types of UV radiation: UVA, UVB and UVC. UVA makes up 95% of the UV radiation reaching Earth. Its rays can penetrate the skin more deeply than other UV rays and can lead to skin cancer, as well as to skin damage and aging.

Meanwhile, UVB makes up the remaining 5%. That’s because most UVB rays are filtered out by ozone, water vapour and oxygen and carbon dioxide gases.

Did you know? The Earth’s ozone layer prevents the sun’s UV-C radiation from reaching Earth.

How does sunscreen work?

Sunscreen is made up of ingredients that stop the sun’s UV light from reaching your skin. The specific ingredients vary from one brand of sunscreen to another. Inorganic chemicals like zinc oxide and titanium oxide protect your skin by absorbing and scattering the UV light. Organic chemicals like avobenzone and oxybenzone protect your skin by absorbing UV radiation.

Did you know? Organic chemicals contain the element carbon. All other chemicals are called inorganic chemicals.

How safe is sunscreen?

The chemical names of the sunscreen ingredients might sound scary. Are they safe? Well, one thing that scientists know for sure is that the sun’s UV rays are carcinogenic (they cause cancer). Meanwhile, scientists haven't found any clear evidence that the chemicals, as they’re used in sunscreen, are harmful. However, researchers continue to study possible issues with ingredients like benzophenone-3.

What does that number on my bottle of sunscreen mean?

Sunscreen is a good way to limit your exposure to UV rays. When you’re shopping for sunscreen, pay attention to the SPF (sun protection factor) number.

The SPF number lets you know how much extra time it will take for your skin to burn if you’re wearing that particular sunscreen. Have you ever noticed how long it takes your skin to burn when it’s unprotected? If so, just take that time and multiply it by the SPF number. That’ll tell you how many minutes your sunscreen will protect you for.

Let’s say it takes you 20 minutes to get a sunburn when you're not wearing sunscreen. Your sunscreen has an SPF of 15. Multiply your usual sunburn time (20 minutes) by the SPF (15), and you’ll see that this particular sunscreen will give you about 300 minutes' (5 hours) worth of protection. Don’t forget to reapply that sunscreen if you get wet!

Did you know? Clouds won’t block out all UV radiation. If the weather forecast says UV levels are high, wear sunscreen even on a cloudy day!

How do I choose my sunscreen?

Look for an SPF of at least 15, though the Canadian Cancer Society recommends an SPF of at least 30. Look also for the words broad spectrum written on the bottle or tube. This means that the sunscreen will protect you from both UVA and UVB radiation.

Now you know why that columnist, that song, and probably many people in your own life consider “wear sunscreen” such important advice. Protect yourself, and enjoy the great outdoors!

Learn more!

About how sunscreen works

Are Sunscreens Safe?
Scientific American

Chemicals in Suncreen
Canadian Cancer Society

Kelly Resmer

Kelly is a chemistry undergraduate laboratory instructor in Halifax.  She loves working with students in the lab, watching chemistry happen! She has a PhD in chemistry and is very interested in studying and learning about bacteria, the good and the bad ones!