Micro- and Macrobiological Damage, Biological Degradation

While the destruction of plastics by microorganisms is a process based mainly on the chemical effects of metabolites, higher organisms typically cause mechanical destruction. These different damage types have to be taken into consideration, because they can be the reasons for the failure of individual products or entire 

The resistance of plastic materials to attack by microorganisms (mold, fungi, and bacteria) depends not only on the chemical composition of the plastic, but also on the composition and amount of filler and additives as well as on relative ambient humidity. Additives serve as food for microorganisms, thus enabling attack on plastics that are inherently resistant. 

Right washed (etching pits generated under fungal hyphae) 

The majority of animals that attack plastics are insects and rodents. Other than microorganisms, they generally cause mechanical damage. Rodents chew up any plastics products in their way - out of pure impulse or to utilize the attacked material for nest building [29]. 

The physical properties of plastic materials are also responsible for the proneness to mechanical attack. High hardness and smooth, planar surfaces hamper attack, while soft materials and unevenness as well as grooves and joints encourage intense gnawing [29]. 

---