The term inert implies that a substance is non-toxic, but all inerts are toxic to some degree. The inert ingredients used in pesticide products must be tested to determine their toxicity. Only inert ingredients approved by EPA are allowed to be used in pesticide products. In addition, EPA encourages pesticide registrants to use the least toxic inerts in their products. In addition to testing the toxicity of the active ingredient, the toxicity of pesticide products, including the inert ingredients, must be determined.
Pesticide formulation is as much an art as a science.
What is public knowledge is the list of EPA approved substances that can be used in pesticide products. For certain pesticide products commonly used in forest applications, the criteria for determining whether the composition of inert ingredients qualifies as confidential business information was challenged in court. The court ruled that for these products only the composition of inert ingredients did not qualify and ordered EPA to release the information to the petitioners. Inert ingredients are used in many consumer products, such as cosmetics, cleaners, soaps, and perfumes. Many of these inert ingredients are the same as those used in pesticide products.