1. solar radiation (ultraviolet radiation, visible light and X-rays);
2. microorganisms – bacteria, fungi, mold;
3. high humidity;
4. ozone and oxygen;
5. a pair of water, moisture in liquid and solid form;
6. heat;
7. industrial pollution, chemical emissions.

The combined impact of these factors can have a much stronger effect than each of them by itself, repeatedly speeding up the process of degradation. Many of the test results do not account for this synergistic effect, which almost always present in real life.