What is the difference between UVA and UVB rays?

What you need to know about UV radiation

As much as we love to bask in it, sunlight contains ultraviolet (UV) radiation. UV radiation is a form of electromagnetic energy which primarily comes from the sun.

However, UV rays also appear in smaller amounts from artificial sources such as lasers, black lights, and tanning beds.

UV rays are classified according to their wavelength with UVA being the longest wavelengths and UVB being the medium wavelengths.

UVC rays are the shortest kind of wavelength and are completely filtered out by the ozone layer. These types of rays never even reach the ground so are not a cause for concern for people.

What can UVA radiation do?

• UVA rays have higher wavelengths, but lower energy levels than other UV rays.
• Penetrate deeper than UVB rays affecting cells deeper in the skin.
• Indirectly damage DNA.
• Overexposure leads to visible effects such as wrinkles. Associated with some skin cancers.
• UVA rays are not absorbed by the ozone layer, unlike UVB rays.
• Effects of UVA rays appear right away (tanning, sunburning).
• UVA rays are the main type of light used in tanning beds.
• UVA rays penetrate windows and clouds.

What can UVB radiation do?

• UVB rays cause most forms of skin cancers and can contribute to premature skin-ageing.
• UVB rays have shorter wavelengths than UVA rays and higher energy levels.
• UVB rays damage the outermost layers of the skin and directly damage DNA.
• Overexposure to UVB rays leads to sunburn.
• Most tanning beds use a combination of UVA and UVB rays. UVB-only tanning beds are advertised as safe, but can still cause skin damage. No tanning beds are safe to use.
• UVB rays don’t penetrate windows, and are more likely to be filtered by clouds.

What can you do to stay safe?

Here are some simple things you can do to keep yourself protected.

Sunscreen - You should always choose a sunscreen that offers broad-spectrum protection (meaning it protects against both UVA and UVB rays).

Cover up - Clothes can provide protection from UV rays, particularly tightly-woven dry fabrics. Outdoor companies are now making clothes that provide increased UV protection.

Wear a hat - Wearing a wide-brimmed hat can provide additional protection for exposed neck and ears.

Stay in the shade - A simple but effective one. If you can limit your exposure to direct sunlight by staying in the shade. Particularly, between 10am and 4pm the UV rays are strongest.

Wear sunglasses - If possible choose sunglasses that have UV protection which can prevent damage to your eyes and surrounding, sensitive skin.

Both UVA and UVB rays are capable of irreparably damaging your skin so it’s important to maintain a broad spectrum protection that fights both. While only 5% of UVB rays reach the earth’s surface, the damage they cause can be significant. 95% of UVA rays reach the earth’s surface so it’s possible you’re more familiar with them but combined they are dangerous and can lead to skin cancer.

As a general rule of thumb, you should choose a sunscreen that protects against both UVA and UVB rays and never go below SPF 15.