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SILENT SPRING: WHAT CAN MAKE A PESTICIDE DANGEROUS?

Some pesticides in current use, when applied as recommended, have little known impact on the environment and can achieve great benefits in controlling pests in agriculture and human health. Other pesticides, including many now banned in the US, had—and can still have— serious negative impacts on animals and plants that were not the intended targets.

Several aspects of pesticides influence how much danger they pose to the environment and human health, including:

  • How toxic is the pesticide to a variety of organisms?
  • How readily does the pesticide accumulate in living organisms?
  • How persistent is the pesticide in the environment?
  • How does the pesticide distribute in the environment?

Pesticides that kill or harm a wide range of organisms can pose greater risks than those that target a narrower range of pests.

Accumulation of a chemical in living organisms is called bioaccumulation.

This can result in concentration of the chemical up the food chain, a process called biomagnification, resulting in higher order feeders (like large fish or birds of prey) being more affected by the chemical.

Persistence is the tendency of a chemical to remain stable in the environment.

Some pesticides break down quickly, while others can be active for many months or years.

Some pesticides can evaporate and be transported long distances in the air. Others are soluble in water and can readily move along rivers or through ground water.