Questions About What is in Pesticides - Inert Ingredients

Haven't you ever wondered what is in a pesticide?


A pesticide product has two main components: the active ingredient(s) and the inert (other) ingredient(s). The active ingredient is the technical grade of the pure pesticide. A pesticide is rarely applied in its pure form. It is usually formulated by adding inert ingredients that improve storage, handling, application, effectiveness, or safety. The percent active ingredient(s) and inerts ingredient(s) is given on the label.


An inert ingredient is any substance in a pesticide product having no pesticidal action.


A common pesticide formulation is called an emusifiable concentrate (EC). The primary inert ingredients in a pesticide product formulated as an EC are an emulsifier and a petroleum solvent, such as kerosene. The emulsifier is a detergentlike substance that makes it possible for the pesticide dissolved in the solvent to mix with water. Other common formulations include: wettable powders, containing a clay dust which adsorbs the pesticide, and a wetting agent to facilitate mixing with water; water soluble powders in which the technical grade pesticide is finely ground and a wetting agent is added to aid in mixing with water; flowable and sprayable suspensions are similar to emulsifiable concentrates, but use different concentrations of both emulsifier and solvent; granular pesticide products contain small pellets of clay (similar to kitty litter), or other materials such as corn grits, impregnated with the pesticide; aerosols contain the pesticide dissolved under pressure in CFC substitutes, such as dimethylether, hydrocarbons, or nitrogen.


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. For each pesticide product, the recipe developed by formulation chemists to meet all the requirements of storage, handling, application, effectiveness, and safety is considered a trade secret, and is protected by federal statute as "confidential business information". 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.


Once in the environment, the fate of inert ingredients is determined by their physical and chemical properties. Solvents with high vapor pressures will be lost to the atmosphere and degraded by sunlight. Clays will become an extremely minor soil or sediment component. Emulsifiers used in pesticide formulations do not generally last long in the environment, however there is little data published in the open literature which reports on persistence of inerts in the environment.

Here are some very informative external links that pertain to pesticide inert ingredients:

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Extoxnet Pesticides

This Page prepared by the EXTOXNET FAQ Team. , January 1998