UV radiation: What it is and the different types

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UV radiation is a form of electromagnetic energy emitted primarily by the sun and specific artificial sources. It falls just beyond the violet end of the visible light spectrum, making it invisible to the human eye.

UV radiation is divided into three main categories based on wavelength:

• ultraviolet A (UVA)
• ultraviolet B (UVB)
• ultraviolet C (UVC)

As sunlight passes through Earth’s atmosphere, ozone, water vapor, oxygen, and carbon dioxide absorb all UVC, most UVB, and some UVA. Therefore, the types of UV radiation have varying energy levels and different effects on living organisms and materials.

UV radiation plays a crucial role in vitamin D synthesis, a vitamin essential to health that helps the body absorb calcium and phosphorus from food. Therefore, experts recommend 5–15 minutes of sun exposure 2–3 times a week.

However, excessive exposure also poses health risks, including:

• sunburn
• premature aging
• skin cancer
• potentially blinding eye conditions

UVA rays have the longest wavelengths among the three categories at 315–399 nanometers (nm) and make up most of the UV radiation received on Earth. About 95% of UV rays that reach the ground are UVA rays.

UVA is present in sunlight throughout the day, even in overcast conditions. Therefore, it is important for people to wear sun protection all year, even in fall and winter.

These rays can penetrate the skin more deeply than UVB rays, reaching the dermis, the skin’s second layer.

While UVA rays are less likely to cause sunburn, they can damage the collagen and elastin in the skin, contributing to premature skin aging or wrinkles.

It’s easy to remember that UVA rays “age” the skin. UVA exposure also contributes to free radical production that can damage cells and potentially lead to skin cancer.

Tanning beds often use UVA rays, increasing the risk of skin damage and cancer.

UVB rays have shorter wavelengths than UVA rays, at 280–314 nm, and are responsible for causing sunburn. These rays significantly affect the outer layer of the skin, the epidermis. UVB rays “burn” the skin.

Like UVA rays, UVB rays are also essential for vitamin D synthesis. But they can also increase the risk of skin damage, including burning, aging, and skin cancer.

A small amount of UVB — around 5% — reaches Earth from the sun. Tanning beds are another source of this radiation.

UVC radiation spans a wavelength of 100–279 nm. While it originates from the sun, it never reaches the Earth’s surface because the ozone layer absorbs it efficiently.

As a result, exposure to UVC radiation occurs exclusively through artificial sources, such as specialized lamps or lasers. These devices emit UVC rays for specific applications, leveraging their high energy to target and neutralize microorganisms effectively.

Heavy duty protective gear is required for anyone exposed to UVC rays.

Moderate UV radiation is essential for life, but excessive exposure can harm health. The primary risks include:

Sunburn

Overexposure to UVB, and to a lesser extent UVA, can cause sunburn, leading to the following symptoms:

• redness
• pain
• skin peeling

Sunburn is a visible sign of skin damage linked to an increased risk of skin cancer.

Skin aging

Both UVA and UVB rays can accelerate the aging process of the skin, causing the following:

• wrinkles
• fine lines
• age spots

This premature aging — known as photoaging — results from the skin’s breakdown of collagen and elastin fibers.

Eye damage

UV radiation can harm the eyes, contributing to the development of cataracts and other eye conditions. For example, skiers not wearing protective goggles at altitude risk painful UV burns to the surface of the corneas.

Prolonged UV exposure to the eyes can also increase the risk of macular degeneration, a leading cause of vision loss in older adults.

Skin cancer

The most concerning risk of excessive UV exposure is the increased likelihood of developing skin cancers, including:

• melanoma
• squamous cell carcinoma
• basal cell carcinoma

UV radiation damages the DNA within skin cells, potentially triggering mutations that lead to cancerous growths.

Below are some commonly asked questions about UV radiation:

Which type of UV radiation is most harmful?

UVC is the most damaging type of UV radiation, but as none reaches Earth, it poses no real risk.

Medium-wavelength UVB significantly promotes skin cancer development. Therefore, it could be considered the most harmful. However, more recently, experts have found that UVA also contributes to skin cancers, so people must protect themselves from UVB and UVA radiation.

Are there any health benefits of UV radiation exposure?

Despite the risks of excessive UV exposure, there are also some health benefits of moderate UV exposure, including:

• Vitamin D synthesis: UV rays help the skin synthesize vitamin D, which is crucial for maintaining healthy bones, supporting the immune system, and regulating cell growth.
• Mood enhancement: Sunlight, including UV radiation, can have a positive impact on mood by stimulating the release of serotonin, a neurotransmitter associated with feelings of well-being.
• Skin conditions: Controlled exposure to UV radiation is sometimes used in medical settings to treat certain skin conditions, such as psoriasis.

UV radiation comes primarily from the sun and is made up of UVA, UVB, and UVC rays. UVC rays do not reach Earth, but both UVA and UVB rays pose health risks.

While UVB rays are the primary culprits behind immediate skin damage and sunburn, the deeper-reaching UVA rays also contribute to long-term skin aging. Both types of radiation can contribute to skin cancer development.

However, UV radiation is also essential for well-being because it helps the body synthesize vitamin D. Therefore, people should aim for moderate sun exposure while limiting damage by using protective measures, such as sunscreen.