UV Rays and Sun Exposure: Benefits, Risks, and More

Fact checked by Olga Sadouskaya, MD
Clinical Pharmacologist, Chief Medical Officer

Warm summer days mean more time spent outdoors, and with that comes more exposure to UV light. Although you may protect yourself from the sun on summer hikes and when going to the beach, these are not the only times you’re exposed to the sun’s ultraviolet rays — UV radiation can also reach you on cloudy days, and even when you’re at home!

Continue reading to learn about different types and sources of UV radiation, the health benefits and risks of sun exposure, and ways to protect yourself against UV rays and make the most of sunny summer days.

Types of UV rays and sun radiation

We need the sun. It gives us light and heat, without which we wouldn’t be able to survive. But it also sends three kinds of UV radiation our way:

  • UVA. This type of solar radiation gives you a tan in summer, but it’s also the most dangerous for you. UVA rays have longer wavelengths, so they are able to penetrate deep layers of your skin and cause genetic damage to your cells, contributing to premature aging and playing a role in skin cancer formation. Always ensure that your chosen sunscreen is as effective at blocking UVA as UVB.
  • UVB. Most of these rays are blocked by the Earth’s atmosphere and can even be filtered by glass. They have a shorter wavelength, so they affect only the top layer of your skin. UVB rays cause sunburns and play the greatest role in causing skin cancers.
  • UVC. The highest energy portion of the UV radiation spectrum, this type of UV radiation is completely absorbed by the Earth’s atmosphere, so you don’t have to worry about it. You can only get exposed to the UVC rays from artificial sources like lasers.

So the UV light from the sun that reaches the Earth’s surface is mostly UVA and UVB rays. UV radiation is the strongest and most harmful from late morning to early afternoon, so it’s best to avoid spending a lot of time in direct sunlight during this time.

But what if the sun isn’t shining? Can its UV radiation affect you when it’s overcast? The answer is yes! UV rays can easily pass through the clouds, so it’s just as important to protect yourself on gray, gloomy days.

Sun loungers with a beach umbrella to protect from UV rays

UV light and sun exposure: What are the benefits?

Do you notice that your mood improves when the sun is shining? Well, there’s a reason for that. When you’re exposed to sunlight, your brain releases the mood-boosting hormone serotonin, which helps you feel calm and focused during the day. Spending time in the sun can also help to regulate your circadian rhythms, contributing to more restful sleep, more energy during the day, and a better mood.

Sunlight also helps you get a healthy dose of vitamin D — it’s called a sunshine vitamin for a reason!

UV light boosts vitamin D production in your body; how much of it you can get from sun exposure depends on many factors, such as your skin color and how strong the sunlight is. People with darker skin produce more natural pigments called melanin which prevents their skin from absorbing as much UV radiation. Studies show that darker skin doesn’t produce as much vitamin D, so fair-skinned people may need to spend less time in the sun to get their daily dose of vitamin D.

Getting enough vitamin D has several health benefits. It helps to keep your bones and teeth healthy, supports your immune system, and — again — helps to regulate your mood and lower your risk of depression. So sunshine can really make you happier, you just need to be careful with it.

Although exposure to UV rays is the best way to get enough vitamin D naturally, you can also get it from your diet and supplements — this is often a more reliable way to get the right amount for you, plus it doesn’t increase your risk of skin damage.

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Can UV radiation kill coronavirus?

Going through a global pandemic, many people started wondering if UV radiation could kill viruses, particularly coronavirus. Well, it can… at least certain UV rays.

UVC radiation has been used as a disinfectant for air, water, and nonporous surfaces and has been known to effectively stop the spread of bacteria for decades. And far-UVC lamps have been found to successfully deactivate the airborne coronavirus.

Unfortunately for us though, UVC radiation doesn’t occur naturally, so we can’t benefit from its disinfecting properties every time the sun’s out. UVB and UVA rays that reach the Earth’s surface are less effective at killing viruses. Otherwise, we’d see a significant drop in Covid-19 cases in summer or in areas with a high UV index, which isn’t the case.

However, lamps with UVC radiation are commonly used in air ducts to disinfect the air.

But of course, there are certain limitations to how effective they can be: the virus needs to be directly exposed to UVC radiation to be affected by it. Also, many germicidal or UVC lamps for home use offer low-dose radiation, so it may take longer for them to effectively kill bacteria or viruses.

Not just the sun: Other sources of UV radiation

The sun is the main source of UV radiation, but there’re other sneaky ways you can get exposed to ultraviolet light from man-made sources:

  • Tanning beds. This is an obvious one. Most of them emit UVA rays, with a small amount of UVB. How much UV radiation you are exposed to when using a tanning bed depends on the lamps in the bed, the time you spend in it, and how often you use it, but they’re the second biggest source of UV damage.
  • Nail lamps. UV lamps or as they’re sometimes called LED lamps that are used to set a gel manicure emit UV radiation, mostly UVA. They don’t pose a serious risk, but it’s best to avoid them if you can or apply sunscreen to your hands 20 minutes before using them.
  • Mercury-vapor lamps. They are usually used in large public areas like gyms and sports arenas. They are made up of two bulbs — one that gives off light and UV rays, and the outer bulb that blocks that UV radiation. These lamps are completely safe when working properly, the UV exposure only happens when the outer bulb is broken. Some of them are designed to turn themselves off in this case, so your risk of getting UV exposure from mercury-vapor lamps is pretty low.
  • Black-light lamps. They give off little visible light, hence the name, and emit mostly UVA radiation. These lamps have a purple glow and are used for artistic effects, to view fluorescence, to attract insects, and to cure plastics, so they are easily avoidable.
  • High-pressure xenon and xenon-mercury arc lamps. They are used for curing inks and coatings, disinfection, and simulating sunlight — to test solar panels, for example. So you are unlikely to come across them unknowingly, and they are mainly a concern for those who work with these types of lamps.

Risks of UV radiation

Without a doubt, sunlight in moderation has its benefits, but spending too much time in the sun can cause certain health problems, such as:

  • Sunburn
  • Premature skin aging
  • Eye problems like photokeratitis
  • Skin cancer

How much damage UV rays can do depends on their intensity and how long you’ve been exposed to them without sun protection. Location is also an important factor — the UV index can tell you how strong UV radiation is where you are. If you live in an area with a high UV index year-round, your risk of sun-induced conditions is higher.

A woman sunbathing on the beach exposed to the UV rays

Everyone is susceptible to the effects of UV radiation, but you may be more sensitive to them if you:

  • Spend a lot of time in the sun, especially around noon
  • Have been sunburned
  • Have light skin, hair, and eyes
  • Have a family history of cancer, particularly skin cancer
  • Take certain medications that may increase your sensitivity to UV rays
  • Are over 50 years of age

Of course, protecting yourself from UV radiation is important for everyone, but it’s particularly crucial for children — most of our UV exposure to the sun happens before the age of 18. Too much sun exposure or frequent sunburns during your early years can increase your risk of skin cancer later in life.

The two most common types of skin cancer — basal cell and squamous cell cancers — form on the parts of the body that are most exposed to UV rays, such as the face, neck, hands, and arms. The risk of melanoma, a more serious type of skin cancer, is also linked to sun exposure and sun damage. Man-made sources of UV radiation like tanning beds also contribute to the risk of skin cancer.

How to protect yourself against UV rays

  • Limit your time in the sun around noon. The sun is strongest between 10 a.m. and 4 p.m., so it’s best to stay indoors during these hours if possible, even during winter. Alternatively, try to limit your time in direct sunlight to a maximum of 30 minutes.
  • Use a broad-spectrum sunscreen with an SPF 30 or higher. Apply it on the exposed skin 20 minutes before going outside and reapply every two hours, or more regularly if you’re swimming or sweating a lot.
  • Stay in the shade. It’s a good way to limit your sun exposure, but keep in mind that it doesn’t offer complete protection from the UV rays, so it’s still best to wear sunscreen — you can’t be too careful!
  • Use extra protection near water, snow, and sand. They reflect the damaging UV rays from the sun back at you, increasing your exposure and chance of sunburn. Sunglasses with 99 to 100% UVA and UVB protection can significantly reduce eye damage from bright sunlight. If you’re on a snowy mountaintop, you have to be particularly vigilant — the sun's rays are more powerful at higher altitudes.
  • Wear protective clothing. Long-sleeved tops made from tightly woven, dark fabrics can absorb UV radiation and prevent sunburn and skin damage. And a wide-brimmed hat can help protect your eyes, ears, face, and neck.
  • Keep track of the UV Index. WeatherWell app tells you when the UV Index is safe, so you can plan your outdoor activities accordingly.
  • Avoid tanning beds. UV light from tanning beds can also cause skin aging and cancer.
  • If you’re taking any medications, carefully read the information leaflets and check the side effects. Certain medications like antibiotics, antifungal, and blood pressure medications can make you more sensitive to the sun.

Note: UVB rays that cause sunburn are mostly blocked by the glass, but UVA radiation that causes premature aging can still get to you. So if you often sit near a window when you’re at home, remember to apply sunscreen.

Even if you limit your sun exposure and take steps to protect your skin against UV radiation, it’s still important to have regular check-ups with a dermatologist to look for any skin abnormalities. You can conduct self-checks too — look for moles that have changed size, shape, or color, and bumps that don't seem to heal. Remember that most cases of skin cancer can be successfully treated when caught early.

November 7, 2022