Inert Ingredients in Pesticides
What are inert ingredients in pesticides?
Inert ingredients are everything in a pesticide product that is not the active ingredient. US federal law defines an "inert ingredient" as "an ingredient which is not active" (FIFRA §2(m), 7 U.S.C. 136(m)) [1]. "Inert" says nothing about safety. Some of these ingredients can be more toxic than the active ingredient, so EPA reviews them before they can be used.
Approach: I searched FIFRA (7 U.S.C. ch. 6), EPA Pesticide Registration Notices, 40 CFR Parts 158/152 and 180, and Regulation (EC) No 1107/2009 for the EU equivalent. I did not search other jurisdictions such as Canada.
What they are (US)
- EPA describes an active ingredient as one that "prevents, destroys, repels or mitigates a pest." An inert ingredient "is simply any ingredient in the product that is not pesticidally active" [2].
- The word refers to what the ingredient does, not how hazardous it is. EPA states that "Neither FIFRA nor the regulations define the term 'inert ingredient' on the basis of toxicity, hazard or risk." It also says that inerts in some products "may be more toxic or pose greater risks than the active ingredient" [2].
How they are regulated (US)
- Label: the ingredient statement must give the name and percentage of each active ingredient, and only the total percentage of all inert ingredients [1]. An inert ingredient does not have to be named on the label unless it is found to be highly toxic.
- Since PRN 97-6, registrants "may" use the heading "Other ingredients" instead of "Inert ingredients", and EPA encourages it. Changing the heading does not change the ingredient's legal status under FIFRA §2(m) [2].
- Inerts of toxicological concern: under the 1987 and 1989 policy statements, products containing these inerts must carry a label statement naming the ingredient [3][4].
- Confidentiality: FIFRA §10 protects information that discloses "the identity or percentage quantity of any deliberately added inert ingredient" [5].
- Food use: inerts in food-use products need a tolerance or a tolerance exemption under 40 CFR Part 180 Subpart D. Each section covers a different use:
| Section | What it covers |
|---|---|
| § 180.910 | Pre- and post-harvest use [6] |
| § 180.920 | Pre-harvest only [7] |
| § 180.930 | Applied to animals [8] |
| § 180.940 | Food-contact surface sanitizers [9] |
| § 180.950 | Minimal-risk active and inert ingredients [10] |
| § 180.960 | Polymers [11] |
- Data: EPA may waive the acute toxicity studies for a product when the applicant shows "the combination of inert ingredients is not likely to pose any significant human health risks" [12].
EU equivalent: co-formulants EU plant protection law uses the term "co-formulant" instead. Under Article 27 of Regulation (EC) No 1107/2009, a co-formulant "shall not be accepted" in a plant protection product where it has been established that its residues or its use have a harmful effect on human or animal health or groundwater, or an unacceptable effect on plants, plant products or the environment. Rejected co-formulants "shall be included in Annex III" [13].
An Annex III co-formulant can still be present as an unintentional impurity in another, acceptable co-formulant. It is treated as an acceptable impurity if its concentration in the finished product is below 0.1 % w/w, or below a lower CMR-specific limit set in CLP Annex VI [14].
How do I check which ones EPA allows?
You can check whether EPA allows an inert ingredient by searching EPA's inert ingredient databases by chemical name or CAS number. Which one you use depends on when the approval was made. You then need to confirm the approval covers your use: food use, nonfood use, fragrance or minimum-risk products.
Approach: I searched EPA's Individual Inert Ingredient Database, the 40 CFR Part 180 Subpart D tolerance exemptions, the 40 CFR 152.25(f) minimum-risk ingredient tables and EPA Pesticide Registration Notices. I also opened EPA's official database and guidance pages.
1. Search the right EPA database
- Approvals from February 1, 2024 onwards: use the Individual Inert Ingredient Database. EPA says these approvals "can be found in the table below. Historical approvals prior to this date can be found on InertFinder."
- Approvals before February 1, 2024: use InertFinder. EPA says it "allows users to search for historical individual inert ingredient approvals by chemical name and CAS Reg. No." (EPA guidance page).
- Trade-name products (proprietary mixtures): use EPA's separate trade name database.
A name or CAS that isn't in the newer table may still have an older approval in InertFinder, so search both.
2. Read the approval columns EPA explains the columns on the database page:
- Food: the 40 CFR 180 section(s) the approval falls under (910 to 960).
- NF: nonfood pesticide uses.
- Fr: fragrance use under the Fragrance Notification Program.
- Co: commodity uses.
- Data Comp/Rights: data compensation periods and exclusive-use agreements.
For example, the colorant/dye with CAS 123944-63-8 is listed as follows [15]:
- Food approval under §§ 180.910, 930 and 940.
- Nonfood: "Yes".
- Limitation: "no more than 0.5% for uses under 40 CFR 180.910 and 180.930 and no more than 300 ppm for uses under 40 CFR 180.940(a)".
Some entries also carry data-compensation or exclusive-use dates. For example, one entry reads "Data Compensation for BASF expires on 1/18/2032, Exclusive Use until 6/5/2028." [15]. These terms affect whether you can rely on an approval without compensating the data owner.
3. For food-use products, check the 40 CFR Part 180 entry EPA says food-use inerts must have "tolerances or tolerance exemptions in the Code of Federal Regulations (CFR), 40 CFR part 180" (EPA guidance page). Read the Subpart D entry itself, because many entries carry use and percentage limits. For example, under § 180.910, "Resin acids, esters with glycerol (CAS Reg. No. 8050-31-5)" is exempt as a surfactant at a "Maximum of 50% in pesticide formulation" [16].
4. Nonfood-only approvals EPA says nonfood-only inerts are "permitted solely for use in pesticide products applied to nonfood use sites, such as ornamental plants, highway right-of-ways, rodent control, etc." (EPA guidance page).
5. Minimum-risk (FIFRA 25(b)) products use a separate, closed list These products may only use the inerts in Table 2 of 40 CFR 152.25(f). For example, Glycerin (1,2,3-Propanetriol, CAS 56-81-5) is on it [17]. An inert approved for registered products is not automatically allowed in a 25(b) product.
6. If the inert isn't approved for your use EPA publishes guidance documents for inert ingredients. They cover petitions for new or amended food-use tolerances, low-risk polymer submissions, new nonfood-use requests and adding trade product names.
If you send me specific inert names or CAS numbers, I can look up their approval status, Part 180 limits and 25(b) status.