Photodegradation is when energy from the sun destroys the chemical composition of substances. When pigments go through photodegradation, they are bleached.
Photons are particles of light. When they are absorbed in the wavelength range of 290-700 (at surface of the earth, they change the structure of molecules. Specifically, the energy the photon has is given to the electrons inside the molecules of pigments. This excess energy brings the molecule from a ground state to an excited state. At the excited state, the molecule is not stable. Due to the instability of the molecule, it is subject to decompose in the presence of water (hydrolize) or oxygen (oxidize). In addition, molecules can decompose into high energy fragments that react with molecules around them (photolysis).
In pigments, photodegradation is bad because the pigments lose their color. But in other situations photodegradation can be important because it can deactivate and remove pollutants from the environment. Ways to prevent photodegredation of pigments is to limit oxygen’s access to the dye (think: antioxidants).
Photodegradation also is important when it comes to NSAIDs in the environment. NSAIDs such as ibuprofen and naproxen have been found in surface waters and some view this as a potential environmental crisis. In sunlight, the chemicals of NSAIDs decompose in the water. But the effects of this decomposition are not really known.
The environmental impact of NSAIDs can be limited in the following ways:
“California Sate Board of Pharmacy recommends that medication be properly disposed of by following these five steps: 1. Keep medicine in its original child-resistant container. 2. Place some water into the solid medication, such as pills or capsules. Add a nontoxic absorbent such as saw dust, kitty litter, charcoal, or powdered spices. 3. Close and seal the container lids tightly with tape. 4. Place medicine containers in durable packaging that does not show what’s inside. 5. Place in trash close to garbage pickup time.”