Those pollutants which are not degraded by microbial actions over time are called non-biodegradable pollutants. These pollutants cannot be broken down in simpler and harmless substances in nature. They are responsible for long term pollution. Examples of non-biodegradable pollutants are DDT, plastics, polythene, bags, insecticides, pesticides, mercury, lead, arsenic, metal objects like aluminium cans, synthetic fibers, glass objects, etc.