Harmful Effects of Ultraviolet Lamps - UVA, UVB, UVC

Years ago, we published an article on the harmful effects of ultraviolet light from the sun. This article is a follow-up discussing the harmful effects of ultraviolet radiation from artificial sources like light bulbs.

Ultraviolet light is naturally-occurring, and most of it reaching earth originates from sunlight. While it can be dangerous, simply getting out of direct sunlight can remove almost all the risk of exposure.

Man-made light bulbs can also emit radiation in the ultraviolet part of the electromagnetic spectrum and pose the same risks as sunlight. In the case of UVC, the earth's ozone layer and atmosphere absorbs it completely before it can reach the surface.

Overexposure to any type of ultraviolet light bulbs can pose serious health risks, depending on the wavelength, intensity, and duration of exposure.

This article is a breakdown of the dangers and approximate exposure times for each type before skin or eye damage can occur.

UVA (315-400 nm)

Dangers

Because UVA light can break down collagen in skin, premature aging or wrinkles are one possible side effect. With repeated, prolonged exposure, the risk of skin cancer also increases. UVA contributes to melanoma risk.

Although not as painfully damaging as UVB or UVC, eye damage can also occur with long or high-intensity exposure. Cataracts and retinal damage may result, because UVA penetrates deeper into the eye.

Finally, suppression of immune system is a potential danger of overexposure to UVA radiation.

Time to Danger

UVA is the least risky of the types of UV radiation. It can take minutes to hours of exposure to begin to cause damage, depending on the intensity of the bulbs.

Tanning beds use lamps high in UVA, which can cause damage in 10-15 minutes.

Lower-intensity bulbs like blacklights for special effects may take hours for noticeable harm. This is one reason clubs and concert halls may use UVA bulbs during an event, despite long exposure times for the participants.

UVB (280-315 nm)

Dangers

The main danger of UVB exposure is sunburn, as these wavelengths are strongly absorbed by skin.

The risk of skin cancer is also increased by exposure to UVB radiation, as it can cause direct DNA damage and increased melanoma risk.

Eye damage is also a danger of UVB exposure. Snow blindness (photokeratitis) is caused by UV rays reflecting off of snow-covered surfaces and can cause pain or a shift in color perception.

The risk of cataracts is also increased, but UVA is linked to this more than UVB.

Finally, as with UVA overexposure, general immune suppression can result from UVB lighting.

Time to Danger

Depending on the intensity of the UVB light source, it can take seconds to minutes to start producing skin or eye damage. Under strong UVB sources like welding arcs or UV sterilization lamps, seconds matter.

Tanning bed lamps often use a combination of phosphors to emit UVA and UVB radiation, which is why 10-15 minutes per session is typically the recommended limit for tanning.

Depending on skin type, closer to 5 minutes might be safest. UVB from the sun can burn fair skin in 10-30 minutes, but high-intensity tanning lamps may cause damage faster.

Artificial UVB bulbs like reptile lamps or phototherapy lamps can cause burns in minutes if too close. Compared to broadband UVB, narrowband UVB bulbs are safer, according to more recent research.

UVC (100-280 nm)

Dangers

UVC light poses the greatest danger for human skin and eyes. While it is present in the radiation emitted by the sun, the earth's ozone layer and atmosphere absorb all of it, making light bulbs the only source of danger on earth.

Severe skin burns can result very quickly and are similar to a radiation burn. In addition, eye damage is a danger, with painful photokeratitis or corneal burns occurring rapidly.

With repeated exposure, there is an increased risk of skin cancer.

Most germicidal UVC bulbs are low-pressure mercury lamps, which emit peak UVC radiation at 253.7 nm. LED UVCs can be tuned, although most are available between 255-280 nm. All of these wavelengths pose danger to living creatures on earth.

Recent research on far UVC 222 nm excimer lamps show that they are less damaging to human skin and eyes, as this wavelength does not penetrate as deeply. However, these lamps make up a tiny percentage of the UVC light sources currently in use for air or surface disinfection.

Time to Danger

Depending on the intensity of the lamps, distance, and time, it can take a few seconds to a few minutes for UVC light to cause harm. Some lamps are so powerful that they are extremely dangerous even in small doses.

Direct exposure to a germicidal UVC lamp can cause skin or eye damage in seconds, which is why UVC equipment is usually provided with safety/danger signs to warn people of the risks.

General Safety Guidelines

Skin protection should always be used with UVC and considered when using UVA/UVB. Wearing long sleeves, gloves, and sunscreen (for UVA/UVB) is recommended. Products like UVC dosimeters or SmartSun UV wristbands can be worn to indicate when exposure limits have been reached.

UV-blocking goggles or face shields should also be considered, especially for UVC. Eye protection is also recommended when using any ultraviolet curing equipment, due to the high intensity of the light sources.

Distance and shielding can also be used to reduce UV intensity or block it completely. Simply staying out of a room is one way to eliminate exposure to UV bulbs. Stay away from UV sources and use enclosures.

Finally, exposure limits are published by several organizations. Employers should be familiar with OSHA/NIOSH guidelines for occupational exposure. The ACGIH also publishes Threshold Limit Values (TLVs) for UV radiation by wavelength.