CIESIN Thematic Guides

Suppression of the Immune System from Increased Ultraviolet-B Exposure due to Ozone Depletion

Excessive ultraviolet-B radiation (UV-B) exposure interferes with the normal functioning of immune systems in animals and human beings. Relatively low doses of UV-B compromise the immunological defenses of the skin, thus limiting the skin's allergic response to local attacks. Higher doses of UV-B can lower an individual's overall immunological response. Damage to the immune system has several implications for an individual's health: increased risk of the incidence and severity of infectious disease, increased risk of malignant melanoma, and diminished efficacy of vaccinations. Longstreth et al. (1991) present evidence indicating skin pigmentation does not serve a protective role for the immune system, as it does in the prevention of skin cancer. Vermeer et al. (1991) also reach this conclusion. Ilyas (1986) and Jeevan and Kripke (1993) emphasize that damage to the immune system due to UV-B could have far-reaching effects for the health of populations.

Several sources include good descriptions of immunosuppression as one of the health effects from increased UV-B radiation. In the chapter "Human Health" of the Environmental Effects Panel Report (UNEP 1989), van der Leun, Takizawa, and Longstreth summarize what is known about the effects of UV-B exposure and damage to the immune system. Longstreth et al. provide an update in the chapter "Human Health" of UNEP's 1991 report Environmental Effects of Ozone Depletion. In "Loss of Stratospheric Ozone and Health Effects of Increased Ultraviolet Radiation," Leaf's 1993 contribution to Critical Condition, the author provides a detailed review of the effects of UV-B exposure on the immune system. Van der Leun and de Gruijl (1993) also examine the complex relationship between exposure to increased UV-B irradiance and immunosuppression in the chapter "Influences of Ozone Depletion on Human and Animal Health" of UV-B Radiation and Ozone Depletion. Noonan and De Fabo (1992) explain the process by which exposure to UV-B radiation initiates systemic immunosuppression of delayed-type hypersensitivity responses in "Immunosuppression by Ultraviolet B Radiation."

Many of the papers that discuss the effects of UV-B exposure on the immune system are also concerned with the increasing incidence of skin cancer. These include Kripke's 1988 article "Impact of Ozone Depletion on Skin Cancers"; Bridges' 1990 review "Sunlight, DNA Damage and Skin Cancer"; Baadsgaard's 1991 study "In Vivo Ultraviolet Irradiation of Human Skin Results in Profound Perturbation of the Immune System"; and Urbach's 1991 paper "Potential Health Effects of Climatic Change." In "Sunscreens Do Not Abrogate UV-Induced Suppression of Contact Hypersensitivity," Fisher et al. (1986) indicate that sunscreen does not prevent the immunologic suppression of contact hypersensitivity by UV radiation in mice. In "Effects of Ultraviolet B Light on Cutaneous Immune Responses of Humans with Deeply Pigmented Skin," Vermeer et al. (1991) present findings that black- and white-skinned individuals were equally susceptible to the adverse effects of acute, low-dose exposure of UVB on their immune systems.

Giannini (1986) addresses the question of how UV-B radiation compromises a person's ability to fight infections entering via the skin in "Effects of UVB on Infectious Diseases." In the 1990 paper "Effects of UVB on Infectious Diseases," Giannini explores the possible effects of immunosuppression on the incidence and severity of several infectious diseases. In both papers, she points out that populations residing in the tropics are subjected to high UV-B flux, experiencing very high effective doses within a few hours of exposure to midday sun. These people are already at high risk for serious infectious diseases. The weakening of these individuals' immunological responses could dramatically increase morbidity and mortality rates for entire populations. Ilyas (1986) also considers the effects for populations residing in the tropics in "Ozone Modification: Importance for Developing Countries in the Tropical/Equatorial Region."

Two more articles presented here focus exclusively on the effects of UV-B exposure on the immune system: Daynes' 1990 paper "Immune System and Ultraviolet Light" and Jeevan's and Kripke's 1993 contribution to the Lancet series on health effects from global change, "Ozone Depletion and the Immune System." Together they highlight the urgent need for more research on this potentially devastating effect.