Harmful chemicals such as pesticides get accumulated in the soil and the water gets polluted and this, in turn, is consumed by the plants to take up nutrients. Those chemicals get accumulated in the plants and go to the next trophic level. This process is also known as biomagnifications. For example, when pesticides are sprayed they enter the food chain through producers while they are absorbing nutrients from the soil. Since herbivores eat many types of plants, therefore their body will accumulate more amounts of pesticides. Similarly, carnivores will feed on more than one herbivore; hence it will have much more amount of pesticide in it.
