We’re all aware of the long-term damage UV light can cause to our skin, but we don’t always think about the damage it can cause to our eyes. Workers can usually feel the heat and see the glare the sun exposes them to on the jobsite, but what workers can't see is the ultraviolet exposure reaching their eyes throughout the day.

If the eyewear says it has UV protection, that’s enough... right? In this case, what you can’t see can hurt you. For outdoor and mixed-light work environments, understanding what UV400 protection means can help safety managers choose eyewear that supports visibility, comfort, and compliance for their crew – without leaving UV protection up to interpretation.

What is UV light?

UV light, or ultraviolet light, is a form of electromagnetic radiation emitted by the sun. Unlike visible light, UV light can’t be seen by the human eye – which is part of what makes it easy to overlook on the jobsite.

There are electromagnetic waves your eyes can detect - called visible light - and our brain interprets these various wavelengths of light as different colors, form red to violet. If you’ve ever seen sunlight pass through a prism and create a rainbow, you’ve seen how different wavelengths of visible light separate into different colors.

UV light sits just beyond violet on the light spectrum. It travels in shorter wavelengths than visible light and is typically measured in nanometers, or nm. Because UV light is invisible, workers won’t see it the way they see glare or brightness – but that doesn’t mean it isn’t reaching their eyes.

To understand when UV exposure becomes a concern, it helps to look at the three types of UV light: UVA, UVB, and UVC.

What are UVA, UVB, and UVC rays?

UV light is broken into three main categories: UVA, UVB, and UVC. Each one falls within a different wavelength range, which affects how far it can travel and how much exposure risk it creates.

UVA rays (315-400nm): UVA rays have the longest wavelength and can reach the Earth’s surface. Because UVA rays are part of everyday sunlight exposure, they’re one of the biggest reasons UV protection matters for workers spending long hours outdoors.

UVB rays (280-315nm): UVB rays have a shorter wavelength than UVA rays. Most UVB rays are absorbed by the atmosphere, but some still reach the surface. These rays are often associated with sunburn, which is why they’re usually talked about when people think about skin protection.

UVC rays (100-280nm): UVC rays have the shortest wavelength and are mostly absorbed by the Earth’s atmosphere before they reach outdoor workers. That means when we’re talking about sun exposure on the jobsite, the biggest focus is usually UVA and UVB protection.

In terms of safety eyewear, that distinction matters. UV protection needs to cover the rays workers are actually exposed to throughout the day – and to understand why, it helps to look at when UV exposure becomes harmful.

When does UV light become harmful?

UV light doesn’t become harmful at one single moment. The risk depends on UV intensity, length of exposure, time of day, surrounding surfaces, and whether workers are wearing eyewear designed to block the full UV range.

A practical way to think about exposure is the UV Index. When the UV Index reaches 3 or higher, sun protection becomes important. For workers spending long hours outdoors, that should include safety eyewear with UV protection – especially during peak daylight hours or around reflective surfaces such as pavement, metal, sand, water, concrete, or snow (which can double a person's UV exposure).

Cloudy days can also be misleading. Light or thin clouds may have little effect on UV levels, and UV rays can still reach workers even when the sun doesn’t feel strong. Even in open shade, like between buildings or under partial cover, workers can still be exposed to UV radiation when UV levels are high.

Short-term, too much UV exposure can lead to photokeratitis, often called “sunburn of the eye.” Long-term, repeated UV exposure can contribute to more serious eye concerns over time. And because UV light is invisible, workers may not realize they’re being exposed until irritation or discomfort shows up later.

This is where UV400 protection matters. According to The Vision Council, most harmful UV radiation comes through at higher frequencies, and the 380–400nm range lets through as much as 40% of the most harmful UV rays. While some eyewear may only account for UV protection up to 380nm, UVA radiation still extends all the way to 400nm. That final 20nm range may sound small, but it makes up a significant portion of the solar UV radiation that reaches the Earth’s surface – and it’s exactly why UV400 protection is recommended.

For safety managers, the takeaway is simple: don’t stop at a general “UV protection” claim. Look for safety eyewear that clearly states 100% UV protection or UV400 protection, meaning the lens is designed to help block UV rays up to 400nm.

Right next to UV light and partway through visible light is another potentially harmful light from 400-450nm - blue light. Most people associate blue light exposure with screens or indoor fluorescent lighting; however, the biggest source of blue light is actually the sun.

Learn more about blue light and the need for protection in the workplace.

How do you protect eyes against UV light?

The most important step is choosing safety eyewear that clearly states 100% UV protection or UV400 protection. This means the lens is designed to help block UV rays up to 400nm, covering the UVA and UVB range workers are exposed to outdoors.

It’s also important not to confuse UV protection with lens darkness, especially when lens tint, glare reduction, and polarization are part of the conversation. A clear safety lens can still offer UV400 protection, while a tinted lens without the right UV filtering may still leave workers exposed.

Here's the difference:

• Lens tint helps reduce brightness from visible light, making it easier for workers to see comfortably in bright outdoor conditions.
• Polarized lenses help reduce glare from reflective surfaces like water, pavement, metal, or snow.
• UV protection helps block ultraviolet rays, which are invisible. A lens can be tinted or polarized, but that does not automatically mean it offers full UV protection.

Those features can work together, but they should not be used interchangeably. For outdoor work, safety managers should look for the right combination of UV protection, lens tint, glare reduction, and jobsite hazard protection.

HexArmor® safety eyewear can help

All HexArmor® safety eyewear lenses provide 100% UV protection up to 400nm – and that starts with the lens itself.

Most safety eyewear lenses are made with polycarbonate, a material that naturally helps filter some UV light. But “some” UV protection isn’t the same as full UV400 protection. Without coverage up to 400nm, workers may still be exposed to part of the UVA range.

Because we manufacture our own polycarbonate lenses, we’re able to build UV-blocking protection directly into the lens during the manufacturing process – helping ensure every HexArmor® safety eyewear lens delivers the full UV400 protection workers need outdoors.

See our full lineup of Z87+ approved eyewear or explore our safety eyewear technology.

Need help finding the right eyewear for your crew? Our Solution Specialists are ready to work with you. Call 1-877-MY ARMOR or send us a message.

[Blog originally published May 5, 2018]

Browse all HexArmor® eye protection