The layer of ozone in the stratosphere, which is between 10 and 50 km above the Earth, protects life on the planet from harmful ultraviolet solar radiation. Discoveries in the mid-1970s revealed that some human-made chemicals react with and destroy stratospheric ozone molecules. The main ozone depleting substances (ODS) include chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), which are used as refrigerants; halons, used as fire suppressants; carbon tetrachloride, which is used as a cleaning agent; and methyl bromide, an ozone-depleting pesticide. The depletion of the ozone layer, as it has come to be called, leads to an increase in ultraviolet radiation at the Earth’s surface. In consequence, there are a number of adverse impacts on human and animal health, and to terrestrial and aquatic ecosystems. First, increased ultraviolet radiation increases the risk of eye diseases due to cornea and lens damage, skin cancer and infectious diseases (Morrisette 1989). The immune system of humans and animals could also be weakened by ultraviolet radiation, and light-skinned human populations are more likely to develop non-melanoma skin cancer. Second, ultraviolet radiation affects the physiological and developmental processes of plants (Anderson et al. 1977). Increased radiation could change species composition (mutation), leading to altered biodiversity in different ecosystems. It could also affect plant competitive balance, plant pathogens and bio-geochemical cycles (Sivasakthivel and Reddy 2011). Third, increased ultraviolet exposure in the tropics and subtropics can have adverse impacts on the distribution of phytoplankton (the foundation of aquatic food webs; see Smith et al. 1992). Finally, fish, shrimp, crab, amphibians and other animals could be affected by ultraviolet radiation, leading to a decrease in reproductive capacity and impaired larval development (Sivasakthivel and Reddy 2011).
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