Why are ODS harmful?

• A. They thin the ozone layer → increased UV exposure
• B. They cause acid rain
• C. They are greenhouse gases more powerful than CO2
• D. They corrode metals

Answer: (A)

ODS harm mainly because they release chlorine and bromine in the stratosphere, which catalytically destroy ozone molecules. When the ozone layer is thinned, less ultraviolet B radiation is absorbed, so more UV-B reaches Earth's surface. That increased UV exposure raises risks of skin cancer, cataracts, immune suppression, and can disrupt ecosystems. The other options describe related environmental issues (acid rain from sulfur/nitrogen oxides, very powerful greenhouse gas effects, or metal corrosion) but they are not the direct mechanism by which ozone-depleting substances cause harm.