It makes the plants grow.

It keeps me warm.

Helps me make Vitamin D. And - incessantly bombards me with dangerous UV radiation.

That’s right.

The sun is both our friend, and our enemy.

Our big, burning frenemy.

Don’t go out there without protection.

Sunglasses.

Long sleeves, big hat - and sunscreen.

You know the Sun makes visible light - it lights up everything we see!

Even the moon.

But today, we’re talking about the light we CAN’T see.

There’s infrared - that makes up about half of the Sun’s energy that hits the earth.

Although it’s invisible, infrared radiation keeps us nice and cozy.

But that’s not what’s going to give you a sunburn or make you have wrinkles, or cause

skin cancer.

I’m talking about UV.

Ultraviolet Radiation.

About 8 percent of the Sun’s radiation is in this part of the spectrum.

UV light has a shorter wavelength than visible light.

MOST of the Sun’s radiation gets filtered out by our atmosphere, thank goodness.

This is one of the challenges of space travel, by the way - you want to be an astronaut,

you’re going to have to protect yourself against UV radiation - no more Earth’s cushy

atmosphere protecting you.

Our ozone layer catches a good portion of UV.

But some of it still reaches us down here on the ground.

How much UV are we exposed to?

That depends.

Where are you on Earth?

Are you on the top of a mountain?

How far are you from the equator?

What season is it?

What time of day?

The peak hours for UV radiation are 10AM to 4PM.

Is it cloudy?

Around 20% of UV radiation can be blocked on an overcast day.

Is there anything reflective near you?

Water/snow/sand?

Those rays are going to reflect right back at you.

Double whammy.

All these factors will affect how much UV radiation reaches you.

Do you know your UVI?

The Ultraviolet Index is a rating scale, with numbers from 1 to 11.

The higher the UVI number, the more intense the UV rays you will be exposed to.The “daily

UVI” forecasts the amount of UV reaching your area at noon - when the sun typically

reaches its highest point in the sky.

If you want to get into specifics, there are websites you can visit and apps you can download

to let you know what is your UV exposure on any given day, at your specific location.

For example, in the United States, The Environmental Protection Agency (EPA) offers UVI forecasts

by ZIP code on their UV Index page.You can even buy a little meter so you can make the

measurements yourself.

We’ll include links in the description below.

This is all to say - you need to take steps to protect yourself from UV radiation.

You can wear protective clothing - like this shirt I’m wearing was advertised as sun

protection.

The tighter the weave, the more protection your clothes will offer you.

Now keep in mind, the protection generally goes down when it gets wet.

Still, it’s not like I go around bundled up all the time.

I don’t know about you, but when it’s burning hot out, and I start shedding layers,

I want to slap on some sunscreen.

Let’s talk SPF.

The effectiveness of sunscreen is measured in terms of FACTORS.

That’s what SPF stands for: sun protection FACTOR.

This depends on YOU.

Your baseline determines how well the sunscreen will work for you, personally.

It’s not going to work exactly the same for you and all your friends, unless you just

randomly happen to have exactly the same amount of sun tolerance.

So let’s say you, PERSONALLY, can stay out in the sun for 15 minutes before you start

burning.

And you put on some sunscreen that is SPF 20.

Think of multiplying your personal tolerance by a FACTOR of 20.

15 minutes x 20 = 300 minutes, or 5 hours.

So this kind of sunscreen should, theoretically, protect you for up to 5 hours before you start

burning.

Hey, great, you’re thinking.

That means I can put on sunscreen and go out for 5 hours without thinking about it!

NO, no good, stop it, no wonder you’re a lobster!

Sunscreens aren’t magic.

They wear off, they rub off, they sweat off.

Most dermatologists recommend reapplying sunscreen every 2 hours.

But you should re-apply even sooner if you noticed you rubbed off on a towel, or washed

your hands, or whatever.

And just how much did you put on?

Most people don’t put on nearly enough sunscreen.

In fact, one study showed that it was best if you told people to put sunscreen on TWICE

- because then, they *might* put on enough sunscreen.

The general recommendation is 1 oz - about a shot glass full.

That’s a LOT of sunscreen.

Have you been putting on enough?

Don’t forget your ears, and the tops of your feet.

A lot of people skip those spots.

This is what you should be aiming for.

This man put sunscreen on one half of his face.

Then a photo was taken with UV light, so you can see just how much of the UV is absorbed

in the areas where he put on sunscreen.

Everywhere UV is absorbed, his face is dark.

Nice work, pal.

Now let’s take a closer look at the enemy.

UV can be broken down into 3 subclasses of radiation - UVA, UVB, and UVC.

UVC has the shortest wavelength - 100-290 nm.

It’s completely caught by our ozone layer.

So, let’s cross that off our list of things to worry about today.

UVB is the next longest wavelength - 290 to 320 nm.

UVB is partly blocked by the ozone layer.

Also, if you’re working in an office or driving in your car, no worries.

UVB can’t travel through glass.

This is the UV radiation that gives us a sunburn.

Ouch.

UVA is the longest wavelength - 320 to 400 nm.

This kind of UV radiation penetrates the ozone layer, glass, and goes into the deeper layers

of our skin.

This is the kind of UV radiation that causes wrinkling and those unpredictable age spots.

According to the American Cancer Society, most skin cancers are a direct result of exposure

to the UV rays in sunlight.

Skin cancer has also been linked to exposure to artificial sources of UV rays, like tanning

beds.

So - other than the obvious - avoiding the sun and artificial UV, how do you protect

yourself?

Look for a sunscreen that says “broad spectrum” on it - and it should spell out, in the fine

print, that it protects against UVA *AND* UVB radiation.

You have a choice when it comes to sunscreens.

Physical, or chemical?

Physical sunscreens are a literal PHYSICAL barrier to UV radiation.

These are inorganic compounds, like zinc oxide or titanium dioxide.

In the early days of sunscreen, these looked a lot like white paint.

Now with more advanced manufacturing, we can make nanoparticles of these materials, so

they practically look transparent.

But those particles are still in there, physically reflecting and scattering the UV rays.

There’s a wider variety of CHEMICAL sunscreens to choose from.

These are organic compounds that actually ABSORB UV rays and TRANSFORM the energy of

the radiation into a different form.

It’s released as heat - and so it can no longer harm you.

Some common chemical sunscreens include Para Amino Benzoic Acid (PABA); oxybenzone, avobenzone,

octyl salicylate - many sunscreens contain a mixture of ingredients, with each chemical

playing a different role.

Some are better at dealing with UVA, some handle UVB.

Most UV protection works better when it works in concert.

One concern is that using some chemical sunscreens gives rise to problems in the environment.

For example, several sunscreen ingredients were shown to kill or bleach coral, even at

extremely low concentrations, including oxybenzone, butylparaben, and octyl methoxycinnamate.

So do your research - many sunscreen bottles let you know if they are reef safe.

Now go out there and enjoy some time with our dangerous friend!

But let’s be safe out there!

Where are my sunglasses?

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