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2. Health Effects of UV Exposure | Ultraviolet Radiation in the Workplace

  • ISBN: 978-1-4249-9714-5
  • Issued: August 1994
  • Revised: March 2009
  • Content last reviewed: June 2009
  • See also: Heat and Radiation Hazards

Although exposure to small amounts of UV radiation can have beneficial effects, such as vitamin D synthesis in the skin, overexposure can cause serious acute (short-term) and chronic (long-term) health effects.

Acute Effects

Sunburn

(medical name: erythema)
This is a reddening of the skin, with blistering and peeling in severe cases. Of the three UV bands, UV-B is most effective in causing sunburn. To protect itself against UV radiation, the skin "tans": that is, the pigment that gives the skin its colour becomes darker and more of it is produced. Prolonged exposure to UV radiation causes a thickening of the skin's outer layer. Since people with lighter skin, hair and eyes have less pigment, they are more sensitive to UV exposure.

Damage to the skin accumulates over the day, and the injury does not become obvious until a few hours later. Given time, sunburned skin repairs itself.

Welders' flash, also known as arc-eye and snow-blindness

(medical name: photokeratoconjunctivitis)
This is a painful irritation of the cornea and the conjunctiva (the membrane connecting the eyeball with the inner eyelid). There is a feeling of "sand in the eye" and sensitivity to light. UV-B is most effective in causing this "sunburn of the eye". The eye is more sensitive than the skin to UV radiation because it lacks the skin's horny outer layer and protective pigment.

Symptoms appear from six to 24 hours after exposure and usually disappear within the following 48 hours. No permanent damage to the eye results unless a severe exposure has occurred.

Retinal injury, possibly resulting in loss of sight, may be caused by UV radiation in people who have had the lens of an eye (the crystalline) removed, for example due to cataracts. This can be prevented with UV-absorbing lens implants or eyeglasses. In the normal eye, the retina is protected from UV injury because the crystalline filters out UV.

Recent research indicates that exposure to UV radiation can adversely affect the immune system.

Note: Hypersensitivity to UV radiation may result from the use of certain prescription drugs, such as tetracycline (a common antibiotic), or from exposure to some industrial chemicals, such as coal-tar distillates. Workers who may be exposed to UV radiation should ask their physicians about the possibility of sensitization when given any new prescriptions.

Chronic Effects

Skin Cancer

Excessive exposure to UV radiation over many years has been shown to increase a person's risk of developing skin cancer. The most common types of skin cancer, basal cell carcinoma and squamous cell carcinoma, are not usually life-threatening if treated early. Malignant melanoma is a rarer but much more dangerous form of skin cancer.

A person's chance of getting skin cancer increases with the lifetime UV dose, that is, the total UV radiation he or she has received. The risk of getting malignant melanoma also increases with the number of blistering sunburns experienced during childhood. An alarming increase in skin cancer rates in Canada over the last few years has been attributed to the excessive sun-tanning habits that became popular in the 1950s.

Lighter-complexioned people are more likely to develop UV-related skin cancers than darker-complexioned people, so they should be particularly careful to minimize their UV exposure.

Photoaging

This is the premature aging of the skin caused by chronic exposure to UV radiation. The resulting changes in the skin include excessive wrinkling, dark spots, loss of elasticity and a leathery appearance.

Senile Cataracts

A senile cataract is a clouding of the lens of the eye in older people, often impairing vision and eventually requiring surgery. Long-term UV exposure has been shown to be an important factor in the development of this disease.

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