When we eat food, it is digested by various enzymes present in our body. However, these enzymes cannot digest everything. This is why we cannot eat stone, plastic, or other such material. Similarly, micro-organisms make use of enzymes to digest the wastes (organic matter). However, these micro-organisms cannot digest certain substances, which we classify as non-biodegradable substances. These non-biodegradable substances get accumulated in the environment and cause pollution. further, these substances are responsible for the harmful effects on the environment.