They soak up the water, and they soak up air directly through the skin rather than through the lungs. They also soak up whatever chemicals and toxins are present in the soil, water, and air. Trace amounts of toxic compounds carried by the wind might deal fatal blows to animals that tend to breathe through skins that are permeable to airborne gasses. Acid rain, acid snow, and acid soil have very negative effects on amphibians, which are in such close contact with their surroundings. Species such as the spotted salamander have been reported to try to relocate to different habitats as a result of acid snow, which melts in the spring and runs off into ponds and lakes.
Amphibians absorb and concentrate toxins in their fatty tissues.
This is the same form of ultraviolet radiation that has been shown to cause skin cancer in humans. Amphibian eggs lack protective shells and are laid in shallow water, so their risk of exposure to ultraviolet radiation is quite high. Ultraviolet radiation interferes with early cell division in amphibians and often damages their eggs. Juvenile amphibians spend large amounts of time basking in the sun, so their thin skin is highly exposed to ultraviolet radiation. Western toads and cascade frogs are in decline reportedly due to increased ultraviolet radiation.