Ultraviolet Radiation

Exposure Pathway

Exposure to ultraviolet (UV) radiation occurs via a dermal pathway. UV radiation has low penetrating properties of less than 1 mm in human tissues, and therefore, the observable biological effects of UV radiation exposure are limited in man to the skin and eyes (1).

UV exposure to the skin and eyes varies by the same factors that affect UV levels in the atmosphere including stratospheric ozone, time of day, time of year, latitude, altitude, clouds, and reflection by ground surfaces (2).See fate and transport page.

In addition, the amount of UV radiation a person is exposed to also depends on his/her precautionary behavior including use of sunscreen, sunglasses, and protective clothing (tightly woven cotton fabrics and brimmed or billed hats). (2)

Finally, given that a person’s skin is uncovered or not protected via sunscreen, UV radiation exposure varies by anatomical site. In general, the horizontal surfaces on an upright person, including the shoulders, receive up to 75% of ambient UV radiation, while vertical surfaces receive approximately 50% (1). Below is a table comparing the mean fraction of ambient UV radiation received at anatomical sites on a rotating manikin and also in living subjects.

The health effects from exposure to UV radiation can be classified as acute or chronic. The acute effects of UVA and UVB exposure are both short-lived and reversible. These effects include mainly sunburn (or erythema) and tanning (or pigment darkening). The chronic effects of UV exposure can be much more serious, even life threatening, and include premature aging of the skin, suppression of the immune system, and skin cancer. In addition, UV rays can also damage the eyes as more than 99% of UV radiation is absorbed by the front of the eyes. Corneal damage, cataracts, and macular degeneration are all possible chronic effects from UV exposure and can ultimately lead to blindness. Melanoma, a type of skin cancer, can also develop within the eye (3).

References

1. Diffey BL. Solar ultraviolet radiation effects on biological system. Phys Med Biol. 1991; 36(3): 299-328.

2. CIESIN Thematic Guides. Health Effects from Increased Exposure to Ultraviolet-B (UV-B) Radiation due to Stratospheric Ozone Depletion. http://www.ciesin.org/TG/HH/ozhlthhm.html

3. Kane AB, Kumar V. (1999). Environmental and Nutritional Pathology. In Cotran RS, Kumar V, Collins T. (Eds.), Robbins Pathologic Basis of Disease- Sixth Edition (pp. 403-458). Philadelphia, PA: W.B. Saunders Company.