To get a new active ingredient product approved, there are a significant number of studies a company must complete first. These scientific studies are extremely expensive, many of them costing over $150,000 — and some of them even costing millions of dollars! It is extremely important these studies are conducted to affirm the safety and efficacy of any product seeking approval.
The EPA will review the ingredients of the pesticide, the particular site or crop where it is to be used, the amount, frequency, and timing of its use, along with storage and disposal practices.
…
The application from the company will give the EPA details on the data collected from the research studies conducted, this data is then subject to an extensive scientific peer review to ensure it is correct. The EPA is especially concerned with potential harm to humans, wildlife, fish, and plants, or the contamination of surface/ground water. These risks include short-term toxicity issues, long-term effects like cancer or reproductive disorders, and of course the risk of death.
Development, research, and approval of a pesticide can take years, and in some cases, even more than a decade.