Inert Ingredient Intel A Recipe For Pest Control Success

How well do you know what is in the pesticides used in your integrated pest management programs? Let’s review some basic terminology. The mixture of active and inert ingredients that comes from your grower supply company is called a pesticide formulation.
Diluents — most often water — are mixed by the applicator with the formulated products in spray tanks. We expect that specific active ingredients — the toxic compounds — will help keep pests below manageable levels. But there’s more to the mix than just the recommended ingredients. Many applicators refer to the other chemicals in the purchased product as inert ingredients. These unseen additives may include wetting agents, spreaders, stickers, or extenders. In some cases, they are far from being harmless.

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The terms “active ingredient” and “inert ingredient” are defined by the Federal Insecticide, Fungicide, and Rodenticide Act [FIFRA]. An active ingredient “prevents, destroys, repels, or mitigates a pest, or is a plant regulator, defoliant, desiccant or nitrogen stabilizer”. By law, the active ingredient must be identified by name on the pesticide product’s label together with its percentage by weight.
All other ingredients in a pesticide product are called inert ingredients: “any substance (or group of similar substances) other than an active ingredient that is intentionally included in a pesticide product.”

Why Are Inert Ingredients Added To Pesticides?

Pesticide products often contain more than one inert ingredient, and each plays a key role in the effectiveness of the pesticides. They can make the product easier to use, safer for the applicator or environment, and can even extend the pesticide’s shelf life. Here are some examples of what different kinds of inert ingredients might do:

  • Aerosol – carriers that are propellant gasses that expand when pressure is released.
  • Carriers – liquids or solid chemicals that are added to a pesticide product to aid in the delivery of the active ingredient.
  • Buffer – prevents a rapid change in pH when acids or bases are added to the solution.
  • Defoamer – prevents the buildup of bubbles in the formulation.
  • Dispersing agents or emulsifiers – aids in mixing products that would otherwise not mix, or can prevent caking or foaming.
  • Fragrances and dyes – added to aid the applicator in identifying product dangers or assessing spray coverage.
  • Peservative or stabilizer – extend product shelf-life.
  • Sequestrant – improves the quality and stability of the products, often forming complexes (chelates) and can act like a kind of preservative.
  • Solvents – liquids that dissolve the active ingredient.
  • Synergist – enhances the potency of certain pesticides.
  • Surfactant- can help make the pesticide stick to or spread out on the application surface.
  • Thickener – reduces drift.
  • Wetting agents – allow pesticides to penetrate plant surfaces.

Are Inert Ingredients Toxic?

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A few years back, EPA’s Consumer Labeling Initiative (CLI) included a consumer survey on the use of household pesticides. Responses indicated that many consumers felt the term “inert ingredient” meant “harmless.” Many comments from the public and consumer interviews prompted EPA to discontinue the use of the term “inert.” In September 1997, EPA issued a memo (Pesticide Regulation Notice 97-6) which encouraged manufacturers of pesticide products to voluntarily use the term “other ingredients” instead of “inert” on the label.

Federal law and other pesticide regulations do not define the term “inert” on the basis of toxicity, hazard or risk to humans, non-target species, or the environment. So, it should not be assumed that all inert ingredients are non-toxic.

The Food Quality Protection Act (FQPA) required the EPA to look at pesticide formulations that were applied to food crops. Both inert ingredient tolerances and tolerance exemptions were evaluated. In 1987, approximately 1,200 inert ingredients found in pesticides were placed into four toxicity categories:
1. Inerts of toxicological concern (“List 1”) – about 50 inert ingredients were identified as being of known toxicological concern (e.g., benzene). FIFRA rules required pesticide formulators to adding statements to the label saying “This product contains the toxic inert ingredient (e.g.) benzene.
2. Potentially toxic inerts/high priority for testing (“List 2”) – EPA identified about 60 inert substances that were evaluated to see if additional warnings were needed.
3. Inerts of unknown toxicity (“List 3”) – approximately 800 inert ingredients were placed on this list if there was no basis for listing it on the other three lists.
4. Inerts of minimal concern (List 4) – there were approximately 300 inert ingredients that were generally regarded as innocuous. These included inert ingredients such as cookie crumbs, corn cobs, and other substances “generally recognized as safe” (GRAS) by the FDA. List 4, representing inerts generally recorded as safe, has now become List 4A. A newer list [4B] has since been created to identify inerts for which EPA feels that current use in pesticides will not adversely affect public health and the environment.

Will Inert Ingredients Affect My Pesticide Choices?

These lists (above) helped EPA to evaluate of the toxicity of inert chemicals. Pesticide labeling now reflects how EPA evaluates the toxicity of inert ingredients. The resulting labels may restrict a product to a non-food uses. Because the reassessment of these other materials under the FQPA is now complete, inert ingredients are no longer classified as List 1, 2, or 3.

Today, no “List 1” ingredients are permitted in food use pesticides because they do not meet the stringent safety standards of the Federal Food, Drug, and Cosmetic Act. The “4A” category is still being used for the purposes of FIFRA’s definition of “Minimum Risk Pesticides.” And, USDA is still utilizing “List 4” to identify allowable substances that are regulated under the National Organic Program.

For non-food pesticides, the 1987 lists of inert ingredients remains pertinent (including labeling) for those identified as “List 1” ingredients – those with toxicological concerns. Although the lists are no longer updated by EPA, the information is still available.

Where Can I Find Out More About Inert Ingredients?

Two sources of information about the other ingredients may be easily found – the pesticide label and the Material Safety Data Sheet (MSDS). Labels rarely include direct information about inert materials, but a user could infer hazards that would result from the addition of certain ingredients. For example, a formulation that uses a highly flammable or toxic solvent would include label statements on the special handling requirements.
By looking at section 3 of a pesticide’s MSDS, the ingredients that affect the safe use of the product are listed. Chemicals on a MSDS are also given a unique Chemical Abstracts Service (CAS) Number. There is a considerable body of knowledge available about any chemical available by this identification system. Lists of inert ingredients compiled by EPA and many other governmental agencies use CAS numbers.
However, pesticide registrants may sometimes not be able to provide information about the other ingredients because of confidential business information (CBI). For example, a pesticide registrant may elect to add a certain inert ingredient that is purchased from another supplier, and that supplier may choose not to disclose those ingredients directly to the registrant. When the registrant applies for EPA product registration, the secondary supplier must provide a list of the actual ingredients. EPA does not currently identify inert/other ingredients on pesticide labels to registrants and is obligated to protect the supplier’s CBI except when medical professionals require it to treat persons exposed to a pesticide.

EPA is encouraging pesticide manufacturers to voluntarily list the other ingredients in their pesticide formulations. The InertFinder website, http://www.epa.gov/pesticides/inertfinder, allows users to search for inert ingredients by chemical name and CAS numbers to find inert ingredients permitted for use in three categories:

  • Food and Nonfood Use – when used on food products, inert ingredients may have use limitations and restrictions. Note that all food use inert ingredients are also permitted for nonfood use.
  • Nonfood Use Only – these other ingredients are permitted solely for use in pesticide products applied to nonfood use sites, such as ornamental plants, highway right-of-ways, rodent control, etc. Food use is not permitted.
  • Fragrance Ingredient List (FIL) – Ingredients on the FIL are a nonfood use only, but are subject to additional limitations and requirements.

A trade named inert/other ingredient may be a single component, or more commonly a mixture of components. For a trade-named inert ingredient to be listed as such on a label, the full and complete composition of the trade name ingredients must be submitted to the EPA. The public listing does not include any information related to the composition of the inert ingredients which is claimed as confidential business information (CBI).

There are ongoing efforts by EPA to provide a greater level of disclosure of inert ingredients to consumers. Consumers want to be aware of all potentially toxic chemicals, both the active and inert/other ingredients, found in pesticide products. Disclosure will assist the public in making more informed decisions.

EPA suggests that pesticide manufacturers who currently use more toxic inert ingredients in their pesticide products will replace them with less toxic ingredients in order to meet consumer preferences. In 1987, EPA required that several inerts of “toxicological concern” (“List 1”) had to be listed as such on pesticide labels. In most cases, these manufacturers replaced toxic chemicals with less toxic ingredients.

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