What is the primary type of pesticide that leads to fish kills due to water pollution?

Insecticides are often the primary type of pesticide that leads to fish kills due to water pollution. This occurs because many insecticides contain chemical compounds that are toxic to aquatic organisms, including fish. When these substances enter water bodies — whether through agricultural runoff, improper disposal, or other means — they can disrupt aquatic ecosystems, leading to diminished oxygen levels and harming or killing fish.

Moreover, the components in some insecticides can bioaccumulate in fish, causing harm not only to the fish populations but also to the larger food web, including birds and mammals that feed on fish. The toxicity levels can vary based on the formulation of the insecticide, its persistence in the environment, and the specific fish species exposed to it.

While herbicides, fungicides, and rodenticides can also pollute waterways and affect aquatic life, they are less frequently the primary culprits in fish kills compared to insecticides, which are designed to target insects but often have broader ecological effects.