Research has shown that aerial applications of pesticides can be inaccurate and thus ineffective in eradicating the target organism while posing a threat to other living things in the area, particularly salmon. Pesticides that are applied aerially drift transported by the air from the intended area into other areas nearby, including rivers and streams. The US Congress Office of Technology Assessment estimates that 40% of an aerial pesticide application leaves the target area and that only one percent actually reaches the target pest. Additionally, a 1994 report from the EPA Ecological Effects Branch states that during an aerial application, "a predictable percentage of spray will transport potentially as far as two or more miles from the treatment site."

A January 2004 court decision in Washington regarding salmon and pesticides led to a ban of the use of pesticides near salmon bearing rivers and streams in the Northwest. This decision is in response to the mounting evidence that shows that even small amounts of pesticides can cause harm. For example, certain pesticides at non-lethal levels can still disrupt basic functions in fish by deadening their ability to smell. In salmon the sense of smell is critical to many important life functions, including avoiding predators, finding their birth streams, and triggering spawning. The ruling, which covers Washington, Oregon, and California, will also require "retail stores in urban areas to post warnings about the most commonly used and potentially dangerous chemicals." The warnings will read "Salmon Hazard."