(a) General. Subpart B of this part and §158.2201 describe how to use the table in paragraph (g) of this section to determine the toxicology data requirements for an antimicrobial pesticide product. Notes that apply to an individual test, including specific conditions, qualifications, or exceptions are listed in paragraph (h) of this section.

(b) Uses. The applicant for registration must first determine whether the use is likely to result in pesticide residues in food or water and therefore consult the “Food Use” columns of the table in paragraph (g) of this section. Generally, if the residues of the antimicrobial result from an application to a surface or if incorporated into a material that may come into contact with food or feed, and residues may be expected to transfer to such food or feed, then the “Indirect Food Uses” columns is to be consulted.

(c) Tiering of data requirements. Applicants for registration of antimicrobials may perform tests in a tiered fashion. After the initially required tests are conducted, additional testing may be required if results of the initial tests trigger the need for additional data. Conditions that trigger the need for additional data are given in the test notes in paragraph (h) of this section.

(d) 200 parts per billion (ppb). The 200 ppb level was originally used by the Food and Drug Administration with respect to the concentration of residues in or on food for tiering of data requirements for indirect food use biocides. The Agency has also adopted this same residue level for determining toxicology data requirements for indirect food uses of antimicrobial pesticides. The 200 ppb level is the concentration of antimicrobial residues in the total estimated daily dietary intake.

(e) Use of OSHA standards. If EPA determines that industrial standards, such as the workplace standards set by the Occupational Safety and Health Administration (OSHA standards), provide adequate protection for a particular pesticide or a particular use pattern, additional toxicity data may not be required for that pesticide or the use pattern.

(f) Key. R = Required; CR = Conditionally required; NR = Not required; MP = Manufacturing-use product; EP = End-use product; TGAI = Technical grade of the active ingredient; TEP = Typical end-use product; PAI = Pure active ingredient; PAIRA = Pure active ingredient, radiolabeled; Choice = choice of several test substances depending on studies required.

(g) Antimicrobial toxicology data requirements table. The following table shows the data requirements for toxicology. The test notes applicable to the data requirements in this table appear in paragraph (h) of this section.

(h) Test notes. The following test notes apply to the data requirements in the table to paragraph (g) of this section:

1. Not required if test material is a gas or highly volatile liquid.

2. The six end-use product (EP) acute toxicity studies are required using the product as formulated for sale and distribution. In addition, if the EP label has directions for diluting the product, then, the applicant may also need to conduct certain of the acute toxicity studies using the highest concentration labeled for dilution (i.e., the least diluted product). The end-use dilution testing is in addition to the testing conducted on the EP.

3. Not required if test material is corrosive to skin or has pH less than 2 or greater than 11.5.

4. Data are required when the product consists of, or under conditions of use will result in, a respirable material (e.g., gas, vapor, aerosol or particulates).

5. Data are required if repeated dermal exposure is likely to occur under conditions of use.

6. For indirect food uses ≤200 ppb, and all other nonfood uses, data are required if the neurotoxicity screen in the 90-day oral rodent study or other data indicate neurotoxicity.

7. The 90-day dermal toxicity study and/or 90-day inhalation toxicity study are required if the Agency determines that dermal and/or inhalation exposure is the primary route of exposure.

8. All 90-day subchronic studies in the rodent can be designed to simultaneously fulfill the requirements of the 90-day neurotoxicity and/or immunotoxicity studies by adding separate groups of animals for testing of neurotoxicity and/or immunotoxicity parameters.

9. The 90-day study is required in the rodent for hazard characterization (possibly endpoint selection) and dose-setting for the chronic/carcinogenicity study. It is not required in the mouse, but the Agency would encourage the applicant to conduct a 90-day range finding study for the purposes of dose selection for the mouse carcinogenicity study to achieve adequate dosing and an acceptable study.

10. A 1-year non-rodent study (i.e., 1-year dog study) may be required if the Agency finds that a pesticide chemical is highly bioaccumulative and slowly eliminated. EPA may also require the appropriate metabolism and pharmacokinetic studies to evaluate more precisely bioavailability, half life, and steady state to determine if a longer duration dog toxicity study is needed.

11. Although the subchronic toxicity testing guidelines include measurement of neurological endpoints, such screens do not meet the requirement of the 90-day neurotoxicity study. For nonfood uses, if the 90-day study does not include a neurotoxicity screen, then the acute neurotoxicity study will be required.

12. Data are required if all of the following criteria are met:

i. The intended use of the antimicrobial pesticide product is expected to result in repeated dermal human exposure to the product.

ii. Data from a 90-day dermal toxicity study are not available.

iii. The 90-day dermal toxicity study has not been triggered.

13. EP testing is required if the product or any component of the product may increase dermal absorption of the active ingredient(s) or increases its toxic or pharmacologic effects, as determined by testing using the TGAI or based on available information about the toxic effects of the product or its components.

14. Data are required if the active ingredient in the product is known or expected to be metabolized differently by the dermal route of exposure than by the oral route, and a metabolite of the active ingredient is the toxic moiety.

15. A 90-day oral toxicity test is not required for heating, ventilation, air conditioning, and refrigeration systems (collectively referred to as HVAC&R). Instead, two 90-day toxicity tests, one by the dermal route and one by the inhalation route are required.

16. Data are required if there is the likelihood of significant repeated inhalation exposure to the pesticide as a gas, vapor, or aerosol.

17. Based on estimates of the magnitude and duration of human exposure, studies of shorter duration, e.g., 21- or 28-days, may be sufficient to satisfy this requirement. The prime consideration in determining the appropriateness of a shorter duration study is the likely period of time for which humans will be exposed.

18. Based on the positive results of the acute or 90-day neurotoxicity studies, or on other data indicating neurotoxicity, a chronic neurotoxicity study (i.e., a chronic study with additional neurotoxicity evaluations) may be required to provide information about potential neurotoxic effects from long-term exposures.

19. Studies which are designed to simultaneously fulfill the requirements of both the chronic oral and carcinogenicity studies (i.e., a combined study) may be conducted.

20. For indirect food uses ≤200 ppb, and all other nonfood uses, data are required if either of the following criteria are met:

i. The use of the pesticide is likely to result in repeated human exposure over a considerable portion of the human lifespan; or

ii. The use requires that a tolerance, tolerance exemption, or food additive regulation or clearance be established.

21. For indirect food uses ≤200 ppb, and all other nonfood uses, data are required if any of the following criteria, are met:

i. The use of the pesticide is likely to result in significant human exposure over a considerable portion of the human life span which is significant in terms of frequency, time, duration, and/or magnitude of exposure.

ii. The use requires that a tolerance, tolerance exemption, or food additive regulation or clearance be established.

iii. The active ingredient, metabolite, degradate, or impurity:

A. Is structurally related to a recognized carcinogen;

B. Causes mutagenic effects as demonstrated by in vitro or in vivo testing; or

C. Produces a morphologic effect in any organ (e.g., hyperplasia, metaplasia) in subchronic studies that may lead to a neoplastic change.

22. If the requirement for a carcinogenicity study in any species is modified or waived for any reason, then a subchronic 90-day oral study in the same species may be required.

23. Testing in two species is required for all uses.

24. The oral route, by oral intubation, is preferred, unless the chemical or physical properties of the test substance, or the pattern of human exposure, suggest a more appropriate route of exposure.

25. Additional testing by other routes of exposure may be required if the pesticide is determined to be a prenatal developmental toxicant after oral dosing.

26. The developmental toxicity study in rodents may be combined with the two-generation reproduction study in rodents by using a second mating of the parental animals in either generation. Protocols must be approved by the Agency prior to the initiation of the study.

27. A two-generation reproduction study is required.

28. An information-based approach to testing is preferred, which utilizes the best available knowledge on the chemical (hazard, pharmacokinetic, or mechanistic data) to determine whether a standard guideline study, an enhanced guideline study, or an alternative study should be conducted to assess potential hazard to the developing animal. Applicants must submit any alternative proposed testing protocols and supporting scientific rationale to the Agency. Protocols must be approved by the Agency prior to the initiation of the study.

29. The use of a combined two-generation reproduction/developmental neurotoxicity study that utilizes the two-generation reproduction study in rodents as a basic protocol for the addition of other endpoints or functional assessments in the immature animal is encouraged.

30. A DNT study is required using a weight-of-evidence approach when:

i. The pesticide causes treatment-related neurological effects in adult animal studies (i.e., clinical signs of neurotoxicity, neuropathology, functional or behavioral effects).

ii. The pesticide causes treatment-related neurological effects in developing animals, following pre- or post-natal exposure (i.e., nervous system malformations or neuropathy, brain weight changes in offspring, functional or behavioral changes in the offspring).

iii. The pesticide elicits a causative association between exposures and adverse neurological effects in human epidemiological studies.

iv. The pesticide evokes a mechanism that is associated with adverse effects on the development of the nervous system (i.e., structure-activity-relationship (SAR) to known neurotoxicants, altered neuroreceptor or neurotransmitter responses).

31. To facilitate the weight-of-evidence determination for the pesticide's mutagenicity, in addition to those specifically listed in this table, the Agency requires submission of other mutagenicity test results that may have been performed. A reference list of all studies and papers known to the applicant concerning the mutagenicity of the test chemical must be submitted with the required studies.

32. Due to the nature of antimicrobials, if testing with bacterial strains has not been conducted, then testing using a mammalian cell assay such as the mouse lymphoma TK ±assay is preferred. If reverse mutation assay testing with bacterial strains has already been conducted, and the testing was conducted at levels that did not cause toxicity to the bacterial strains tested, then the applicant may submit the study to fulfill this data requirement.

33. For the in vitro mammalian gene mutation study, there is a choice of assays using either mouse lymphoma L5178Y cell thymidine kinase (tk) gene locus, maximizing assay conditions for small colony expression and detection; Chinese hamster ovary (CHO) or Chinese hamster lung fibroblast (v79) cells, hypoxanthine-guanine phosphoribosyl transferase (hgprt) gene locus, accompanied by an appropriate in vitro test for clastogenicity; or CHO cells strains AS52, xanthine-guanine phosphoribosyl transferase (xprt) gene locus.

34. There is a choice of assays, but the micronucleus rodent bone marrow assay is preferred; the rodent bone marrow assays using metaphase analysis (aberrations) are acceptable.

35. Data are required when chronic toxicity or carcinogenicity studies are also required.

36. Data is required if the product label directs that it be applied to domestic animals, such as cats, dogs, cattle, pigs, and horses.

37. In the absence of dermal absorption data or a repeated dose dermal toxicity study, the assumption of 100 percent dermal absorption would be used in a risk assessment to determine if a dermal penetration study is required, and to identify the doses and duration of exposure for which dermal absorption is to be quantified.

38. Required for nonfood uses, if oral exposure could occur.

39. Data may be required if significant adverse effects are seen in available toxicology studies and these effects can be further elucidated by metabolism and pharmacokinetics studies.

[78 FR 26978, May 8, 2013, as amended at 84 FR 18996, May 3, 2019]