Kasugamycin Human Health Risk Assessment DP Barcode 0376608 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, DC 20460 

OFFICE OF 

CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

MEMORANDUM 

DATE: 13 July 2012 

SUBJECT: Kasugamycin. Human Health Risk Assessment for the Proposed Use of the 

Fungicide on Fruiting Vegetables, Po me Fruits, and Walnuts. 

PC Code: 230001 

Decision Number: 427886 

Petition Number: OF7689 

Risk Assessment Type: Single Chemical Aggregate 

TXR Number: NA 

MRID Numbers: NA 

FROM: 

THROUGH: 

To: Shaunta Hill, RM Team 21 

Cynthia Giles-Parker, Chief 

Fungicide Branch (FB) 

Registration Division (RD), 7505P 

DP Barcode: 0376608 

Registration Number: 66330-404 

Regulatory Action: Section 3 Registration 

Case Number: 7045 

CAS Number: 6980-18-3 

40CFR: §180.614 

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Table of Contents

2.0 HED Recommendations ................................................................................................... 5

2.2 Tolerance Considerations .............................................................................................. 6

2.2.1 Enforcement Analytical Method ............................................................................... 6

2.2.2 International Harmonization..................................................................................... 6

2.2.3 Recommended Tolerances ......................................................................................... 7

2.2.4 Revisions to Petitioned-for Tolerances ..................................................................... 8

2.3 Label Recommendations................................................................................................ 8

2.3.1 Recommendations from Residue Chemistry Reviews ............................................. 8

3.5 Consideration of Environmental Justice .................................................................... 12

4.0 Hazard Characterization and Dose-Response Assessment ......................................... 12

4.1 Toxicology Studies Available for Analysis ................................................................. 13

4.2 Absorption, Distribution, Metabolism, & Elimination (ADME) ............................. 13

4.2.1 Dermal Absorption ................................................................................................... 14

4.3 Toxicological Effects .................................................................................................... 14

4.4 Safety Factor for Infants and Children (FQPA Safety Factor) ............................... 16

4.4.1 Completeness of the Toxicology Database .............................................................. 17

4.4.2 Evidence of Neurotoxicity ........................................................................................ 17

4.4.3 Evidence of Sensitivity/Susceptibility in the Developing or Young Animal ........ 17

4.4.4 Residual Uncertainty in the Exposure Database ................................................... 17

4.5 Toxicity Endpoint and Point of Departure Selections .............................................. 17

4.5.1 Dose-Response Assessment ...................................................................................... 17

4.5.2 Recommendation for Combining Routes of Exposures for Risk Assessment ..... 19

4.5.3 Cancer Classification and Risk Assessment Recommendation ............................ 19

4.5.4 Summary of Points of Departure and Toxicity Endpoints Used in Human Risk 

Assessment ............................................................................................................................... 19

A.3 Hazard Identification and Endpoint Selection .......................................................... 43

A.4 Executive Summaries (Studies Submitted since Previous Assessments) ................. 45
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1.0 Executive Summary

Arysta LifeScience North America LLC, as an agent for Hokko Chemical Industry Company 

Limited (Japan), has proposed the establishment of permanent tolerances for residues of the 

aminoglycoside fungicide kasugamycin (3-O-[2-amino-4-[(carboxyimino-methyl)amino]-

2,3,4,6-tetradeoxy-α-D-arabino-hexopyranosyl]-D-chiro-inositol, CAS #6980-18-3) in or on 

fruiting vegetables, pome fruits, and walnuts. The proposal is associated with the first US 

registration for this active ingredient (ai). 

Kasugamycin is a low-use-rate, wide-spectrum aminoglycoside antibiotic fungicide produced 

from Streptomyces kasugaensis. Kasugamycin formulations are applied as foliar sprays in 

agriculture and horticulture. Kasugamycin has preventative, curative and systemic activity at 

low application rates. The compound controls a range of phytopathogenic organisms in the 

proposed crops. Kasugamycin is currently used in over 20 countries on different crops including 

tomato, paprika, eggplant, rice and potato. HED previously recommended in favor of a tolerance 

for residues of kasugamycin in imported fruiting vegetables and a time-limited tolerance for 

residues in apples. 

Kasugamycin is a member of the aminoglycoside family of antibiotics, which also includes 

streptomycin and gentamicin. These agents inhibit bacterial protein synthesis by binding to the 

30S subunit of the bacterial ribosome. Their penetration through the cell membrane of the 

bacterium depends partly on oxygen-dependent active transport by a polyamine carrier system 

that seems to be absent in mammalian systems. This risk assessment document does not address 

the potential impact of the pesticidal use of kasugamycin on antibiotic resistance. Tolerance 

levels as recommended within this document are presented excluding antibiotic resistance 

impacts/concerns. 

The toxicology database is complete for kasugamycin, and the available guideline toxicity data 

are considered adequate for risk assessment purposes. Kasugamycin exhibits low acute toxicity. 

The major effects observed across species in multiple-dose studies were decreased body weights 

and body weight gains. Testicular atrophy was also observed in the rat reproductive and mouse 

subchronic toxicity studies, but only at doses significantly higher than the lowest-observedadverse-effect level (LOAEL) in the rat study, or above the limit dose in the mouse. There was 

no evidence that exposure to kasugamycin results in neurotoxicity, and a developmental 

neurotoxicity (DNT) study is not required. A 28-day rat inhalation toxicity study has not been 

submitted. However, HED’s Hazard and Science Policy Council (HASPOC) has determined that 

a repeated exposure inhalation study is not required, based on the available hazard and exposure 

information, including the following considerations: selection of irritation as the endpoint of 

concern for inhalation exposure, based on irritation seen following oral exposures in multiple 

studies; the use of an oral no-observed-adverse-effect level (NOAEL) which results in 

occupational handler margins of exposure (MOEs) ranging from 58,000 to 2,500,000 for risk via 

the inhalation route; the physicochemical properties, and low volatility, of kasugamycin; the low 
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acute inhalation toxicity (Toxicity Category IV); and the low potential for inhalation exposure, 

based on the proposed use pattern (TXR #0052461). 

Because of kasugamycin’s toxicological profile, low application rates, low vapor pressure, lack 

of residential uses, lack of persistence in the environment, and inhalation MOEs all ≥58,000, a 

10X UFDB is not required for the lack of the inhalation study. 

The database is complete with respect to pre- and post-natal toxicity, and shows no evidence of 

increased qualitative or quantitative susceptibility in the offspring, or in the developing fetus. 

Based on the hazard and exposure data, HED has recommended that the required Food Quality 

Protection Act (FQPA) 10X safety factor be reduced to 1X. Therefore, uncertainty factors used 

in the assessment consist of a 10X factor for interspecies extrapolation, and a 10X factor for 

intraspecies variability. There was no evidence of carcinogenicity in male and female mice, nor 

in male and female rats at doses that were adequate to assess the carcinogenic potential of 

kasugamycin. There was no evidence of mutagenicity. Based on the overall weight of the 

evidence, kasugamycin is classified as "not likely to be carcinogenic to humans”. 

There were no toxic effects associated with a single dose of kasugamycin; therefore, an acute 

dietary endpoint and dose were not selected for the general US population, or any population 

subgroup. The dose and endpoint from the rat combined chronic toxicity/carcinogenicity study 

were selected for chronic dietary exposure and risk assessment. The NOAEL of 11.3 mg/kg/day 

was based on testicular softening and atrophy at the LOAEL of 116 mg/kg/day. Testicular 

atrophy is consistent with findings of other studies. 

There was no systemic toxicity associated with dermal exposure in an acceptable dermal toxicity 

study in the rat, and therefore a dermal endpoint and dose were not selected. For inhalation 

exposure (short- and intermediate-term), the dog subchronic and rabbit developmental toxicity 

studies were selected as co-critical studies. The endpoint of concern is irritation since 

kasugamycin appears to be irritating to the oral and gastrointestinal tract mucosa following oral 

exposures. In the subchronic study with dogs, irritation of the oral cavity was characterized as 

tongue lesions, swollen mouth, excessive salivation, and thickening of the skin at the 

commissures of the mouth. The NOAEL was 11 mg/kg/day, and the LOAEL was 106 

mg/kg/day. The developmental rabbit study was selected as the co-critical study since the 

maternal NOAEL (10 mg/kg/day) was comparable to the NOAEL in the dog study, and the 

maternal toxicity may have manifested due to the irritation potential of the compound. The use of 

the oral NOAEL results in MOEs ranging from 58,000 to 2,500,000 for risk from occupational 

exposure via the inhalation route. 

The nature of kasugamycin residues in plants and livestock (ruminants) is adequately 

understood. The residue of concern for tolerance enforcement and risk assessment is the parent 

compound, although no tolerances are needed in livestock commodities based on the proposed 

uses. The parent kasugamycin and 2 degradates with similar mobility were recommended for 
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inclusion in the drinking water modeling. Adequate residue data were submitted to support the 

proposed uses on fruiting vegetables, pome fruits, and walnuts. HED has used conservative 

assumptions to assess the risk from chronic dietary exposure to kasugamycin through food and 

drinking water. These include the use of recommended tolerance-level residues, modeled 

drinking water estimates, and the assumption that all requested commodities are treated, or 100% 

crop treated (CT). Chronic dietary risk estimates for kasugamycin are below HED’s level of 

concern (LOC) of 100% of the chronic population adjusted dose (cPAD) for all population 

subgroups. The most highly exposed population subgroup, children 1-2 years old, had a risk 

estimate of 1.7% cPAD. 

There are no existing or proposed residential uses of kasugamycin. Therefore, the only 

aggregate scenario assessed was chronic aggregate risk, equivalent to chronic dietary risk, which 

is not of concern. 

Occupational handler exposures to kasugamycin were estimated assuming the maximum 

application rate, and label-recommended equipment and methods, and standard assumptions with 

respect to the area treated. In the absence of chemical-specific data to assess handlers’ exposure 

and risk, HED relied on surrogate unit exposure data to estimate exposure and risk. HED 

assumed a single layer of clothing (baseline), without additional personal protective equipment 

(PPE). The resulting handler risk estimates, or MOEs, are all above 100, and are thus below 

HED’s LOC. Depending on the scenario, MOEs ranged from 58,000 to 2,500,000. 

Although a quantitative occupational post-application inhalation exposure assessment was not 

performed, an inhalation exposure assessment was performed for occupational handlers. This 

assessment resulted in risk estimates that did not exceed HED’s LOC at baseline inhalation PPE. 

Handler exposure resulting from application of pesticides outdoors is likely to result in higher 

exposure than post-application exposure. Therefore, it is expected that these handler inhalation 

exposure estimates would be protective of occupational post-application inhalation exposure 

scenarios. 

Review of human research: This risk assessment relies in part on data from studies in which 

adult human subjects were intentionally exposed to a pesticide or other chemical. These studies 

(listed in Appendix D) have been determined to require a review of their ethical conduct, have 

received that review, and have been determined to be ethically conducted. 

2.0 HED Recommendations 

HED recommends in favor of registration and establishment of tolerances for the use of 

kasugamycin on fruiting vegetables, pome fruits, and walnuts, as described below. 
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2.1 Data Deficiencies

None. 

2.2 Tolerance Considerations 

2.2.1 Enforcement Analytical Method 

Adequate analytical methods are available for the purpose of tolerance enforcement. 

In conjunction with the establishment of tolerances without US registration (PP#3E6579), the 

petitioner proposed a reverse phase, ion pairing method utilizing high-performance liquid 

chromatography with ultraviolet detection (HPLC/UV) for the enforcement of tolerances for 

residues of kasugamycin in plant commodities. The method is entitled Determination of 

Kasugamycin in Tomatoes, Potatoes, and Peppers (Morse Laboratories Method #Meth-146). 

The enforcement method for kasugamycin residues, as originally proposed, was forwarded to the 

Biological and Economic Analysis Division’s (BEAD’s) Analytical Chemistry Branch (ACB) 

for a petition method validation (PMV) trial. The method was subsequently modified as 

recommended by ACB, and was then deemed acceptable as an enforcement method. 

The HPLC/UV enforcement method (Meth-146, Revision #4) was used to determine residues of 

kasugamycin in the studies associated with the proposed uses. Samples were analyzed for 

residues of kasugamycin using laboratory working methods (FEQL Project #0407 for apple 

commodities, and FEQL Project #0706 for pears) which were adapted from Method #Meth-146, 

Revision #4, and included minor modifications to improve the performance of the methods. The 

methods were adequately validated both prior to, and in conjunction with, the analysis of the 

field trial and processing study samples. The lowest level of method validation (LLMV) was 

0.040 ppm in each matrix tested. 

2.2.2 International Harmonization 

There are no established or proposed Codex or Canadian maximum residue limits (MRLs) for 

kasugamycin in any food or feed crops. Tolerances were established in 40CFR §180.614 at 0.04 

ppm to cover residues in/on imported tomatoes and peppers from Mexico. There are no issues 

regarding compatibility of the proposed tolerances because Mexico adopts US tolerances, and/or 

Codex MRLs, for its export purposes. The currently proposed uses are also under review in 

Canada’s Pest Management Regulatory Agency (PMRA); both EPA and PMRA have agreed to 

harmonize recommended tolerances, based on the use of the OECD tolerance calculation 

procedure. 
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2.2.3 Recommended Tolerances 

The tolerance expression should be revised to reflect specific coverage and compliance 

statements for the tolerances to be properly enforced in accordance with the Federal Food, Drug 

and Cosmetic Act (FFDCA). Therefore, the tolerance expression for kasugamycin cited in 

40CFR §180.614[a] should be revised to state: 

Tolerances are established for residues of kasugamycin, including its 

metabolites and degradates, in or on the commodities listed in the table 

below. Compliance with the tolerance levels specified below is to be 

determined by measuring only kasugamycin (3-O-[2-amino-4-

[(carboxyimino-methyl)amino]-2,3,4,6-tetradeoxy-α-D-arabinohexopyranosyl]-D-chiro-inositol) in or on the commodity. 

HED is now recommending the revocation of the established tolerance in imported fruiting 

vegetables at 0.04 ppm, concomitant with the establishment of a domestic crop group tolerance 

in fruiting vegetables, group 8-10, at 0.15 ppm. 

HED has reviewed the available toxicological and residue chemistry studies for kasugamycin, 

and is recommending that the requested uses be registered, and that permanent tolerances be 

established in/on the commodities in Table 2.3.3, at the specified recommended levels.
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TABLE 2.3.3 Tolerance Summary for Kasugamycin.‡ 

Commodity Proposed 

Tolerance (ppm) 

Recommended 

Tolerance (ppm) 

Correct Commodity Definition 

Comments 

Vegetable, fruiting, Group 8 0.15 0.15 Vegetable, fruiting, group 8-10 

Pome Fruit, Group 11 0.25 None Fruit, pome, group 11-10

Additional data are required for apples.* 

Walnut 0.04 0.07 

Apple None 0.08 Provided the label is amended to replace 

“Pome Fruit” with “Pear” and “All Pome 

Fruits Other than Pear”, and to specify a 

30-day PHI for pear, and a 90-day PHI 

for all pome fruits other than pear. 

Azarole None 0.08 

Loquat None 0.08 

Crabapple None 0.08 

Mayhaw None 0.08 

Medlar None 0.08 

Pear, Asian None 0.08 

Quince None 0.08 

Quince, Chinese None 0.08 

Quince, Japanese None 0.08 

Tejocote None 0.08 

Pear None 0.30 

* In lieu of establishing a crop group tolerance in pome fruits, adequate field trial data are available to support 

individual tolerances in the various pome fruit commodities. 

‡Tolerance levels as recommended within this document are presented excluding antibiotic resistance 

impacts/concerns. 

2.2.4 Revisions to Petitioned-for Tolerances 

All recommended tolerances were determined via the OECD tolerance calculation procedures. 

Other than the tolerance in fruiting vegetables, all recommended tolerances differed from those 

proposed by the petitioner, due to use of the OECD tolerance calculation procedures. 

Although a pome fruit crop group tolerance (fruit, pome, group 11-10) was requested, HED is 

recommending for the establishment of individual tolerances in the commodities included in the 

crop group, since the residue data for apple, one of the representative commodities of crop group 

11-10 reflected a different use pattern than for other members of the crop group. Specifically, 

the pre-harvest interval (PHI) used in the apple field trials was significantly greater than the 

proposed label PHI (90 days instead of the proposed 30). If a pome fruit crop group tolerance is 

still desired, additional apple field trials reflecting the 30-day PHI are required. 

2.3 Label Recommendations 

2.3.1 Recommendations from Residue Chemistry Reviews 

The product label for Kasumin 2L (EPA File Symbol 66330-UNU) should be amended as 

stipulated below and revised petition Sections B and F should be submitted. 
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General use directions: The label should specify that adjuvants may not be added to spray 

mixtures for crops other than pome fruits and walnuts. 

Rotational crop statement: No rotational crop restrictions are specified on the proposed label. 

The label should be revised to specify a 30-day plant-back interval (PBI) for all crops except 

those which are on the label as directly treated crops (which may be planted at any time). 

Pome fruits: Since the submitted residue data for apple and pear, the representative commodities 

of pome fruits, group 11-10, are not adequate to fulfill data requirements for a crop group 

tolerance at this time, “Pome Fruit” should be removed from the label and replaced with “Pear” 

and “All Pome Fruits Other than Pear”. 

PHI: For all pome fruits other than pears, the product label should be amended to specify a 

minimum PHI of 90 days. For pears, the proposed PHI of 30 days is appropriate. 

3.0 Introduction 

3.1 Chemical Identity 

The chemical structure and nomenclature of kasugamycin are presented in Table 3.1 (below). 

TABLE 3.1 Kasugamycin Nomenclature. 

Chemical Structure 

 [·HCl ·H2O] 

Empirical Formula C14H25N3O9 [C14H25N3O9•HCl•H2O] 

Common Name Kasugamycin [Kasugamycin hydrochloride hydrate] 

Company Experimental Name TM-416 

IUPAC Name (Kasugamycin) 1L-1,3,4/2,5,6-1-deoxy-2,3,4,5,6-pentahydroxycyclohexyl-2-amino-2,3,4,6-

tetradeoxy-4-(α-iminoglycino)-α-D-arabino-hexopyranoside 

or 

[5-amino-2-methyl-6-(2,3,4,5,6-pentahydroxycyclohexyloxy)tetrahydropyran-3-

yl]amino-α-iminoacetic acid 

CAS Name (Kasugamycin) 3-O-[2-amino-4-[(carboxyiminomethyl)amino]-2,3,4,6-tetradeoxy-α-D-arabinohexopyranosyl]-D-chiro-inositol 

O

O

OH

OH

OH

OH

HO

H C3

N

H

NH

HO

O

NH2
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TABLE 3.1 Kasugamycin Nomenclature. 

CAS Registry Number 6980-18-3 [19408-46-9] 

End-Use Product Kasumin 2L 

Chemical Class Aminoglycoside antibiotic fungicide 

Known Impurities of Concern None 

3.2 Physical/Chemical Properties

Kasugamycin is an aminoglycoside antibiotic that has high stability and water solubility. It has a 

low vapor pressure (0.013 mPa). Its major routes of degradation in the environment are aqueous 

photolysis, aerobic biodegradation, and hydrolysis. Kasugamycin and its degradates are likely to 

be mobile in soils, but are not persistent. Based on the available information, there is no 

indication that kasugamcyin is likely to bioaccumulate. A detailed description of the 

physicochemical properties of kasugamycin is provided in Table C (see Appendix C). 

3.3 Pesticide Use Pattern 

A liquid (L) formulation end-use product (EP) containing 2% kasugamycin (by weight) is being 

proposed by Arysta for use as a foliar broadcast spray on fruiting vegetables, pome fruits, and 

walnuts. The product will be marketed under the trade name Kasumin 2L, and is formulated 

with kasugamycin hydrochloride hydrate at 2.3% (by weight), which is equivalent to 2% 

kasugamycin (0.1667 lb ai/gal), the free base. Table 3.3 (below) summarizes the proposed use 

patterns. 

The PPE requirements proposed on the Kasumin 2L Agricultural Antibiotic label state that 

applicators and other handlers must wear a long-sleeved shirt, long pants, socks plus shoes, 

and chemical-resistant gloves. 
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TABLE 3.3 Summary of Proposed Use Directions for Kasugamycin. 

Application Timing; 

Type; and 

Equipment

EP 1 

[EPA File 

Symbol] 

Use Rate 

(lb ai/A) 

Maximum # 

of Uses Per 

Season 

Maximum 

Seasonal Use 

Rate (lb ai/A) 

PHI 2

(Days) 

Use Directions and Limitat

Fruiting Vegetables (Group 8-10) 

Disease development conditions; foliar directed or broadcast; ground. 

0.1667 lb ai/gal L 

[66330-UNU] 

0.021 3 0.063 1 Minimum spray volume of 50 GPA 

by ground. The addition of a wettor spreader/sticker may enhance ethe product. The minimum retreatinterval (RTI) is 7 days. 

Pome Fruits (Group 11-10)

Disease development conditions (during bloom); foliar directed or broadcast; ground. 

0.1667 lb ai/gal L 

[66330-UNU] 

0.083 4 0.333 30 Application after petal fall is proh

not use alternate tree-row applicatmethod. Spray volume of 100 GPground. Reduced spray volumes mutilized for small trees where comcoverage can be obtained with <10The addition of a wetting agent or spreader/sticker may enhance efficproduct. The minimum RTI is 3 d

Walnuts

Disease development conditions; foliar directed or broadcast; ground. 

0.1667 lb ai/gal L 

[66330-UNU] 

0.042-

0.083 

4 0.333 100 Do not use alternate tree-row appl

method. Spray volume of 100 GPground. Reduced spray volumes mutilized for small trees where comcoverage can be obtained with <10The addition of a wetting agent or spreader/sticker may enhance efficproduct. The minimum RTI is 14 

1. EP = End-use Product. 2. PHI = Pre-Harvest Interval. 3. No rotational crop restrictions were specified. 4. GPA = Gallons per Acre. 
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3.4 Anticipated Exposure Pathways 

RD has requested that HED perform an assessment of human health risk to support Arysta’s 

request for kasugamycin uses on fruiting vegetables, pome fruit and walnuts. Humans may be 

exposed to kasugamycin through consumption of food and drinking water containing 

kasugamycin residues. In addition, occupational handlers may be exposed via the dermal and 

inhalation routes when they mix/load and apply the pesticide to growing crops. Finally, workers 

re-entering treated areas to conduct crop-related activities may be exposed via the dermal route. 

The current risk assessment considers these potential exposure pathways, in conjunction with the 

hazard database, and the endpoints and doses selected for risk assessment. 

3.5 Consideration of Environmental Justice

Potential areas of environmental justice concerns, to the extent possible, were considered for this 

human health risk assessment, in accordance with US Executive Order 12898, Federal Actions to 

Address Environmental Justice in Minority Populations and Low-Income Populations

(http://www.epa.gov/compliance/resources/policies/ej/exec_order_12898.pdf). 

As a part of every pesticide risk assessment, the Office of Pesticide Programs (OPP) considers a 

large variety of consumer subgroups according to well-established procedures. In line with OPP 

policy, HED estimates risks to population subgroups from pesticide exposures that are based on 

patterns of that subgroup’s food and water consumption, and activities in and around the home 

that involve pesticide use in a residential setting. Extensive data on food consumption patterns 

are compiled by USDA under the Continuing Survey of Food Intakes by Individuals (CSFII), 

and are used in pesticide risk assessments for all registered food uses of a pesticide. These data 

are analyzed and categorized by subgroups based on age, season of the year, ethnic group, and 

region of the country. Additionally, OPP is able to assess dietary exposure to smaller, 

specialized subgroups, and exposure assessments are performed when conditions or 

circumstances warrant. Whenever appropriate, non-dietary exposures based on home use of 

pesticide products, and the associated risk estimates for adult applicators, and for toddlers, 

youths, and adults entering or playing on treated areas post-application are evaluated. Further 

considerations are currently in development, as OPP has committed resources and expertise to 

the development of specialized software and models that consider exposure to bystanders and 

farm workers, as well as lifestyle and traditional dietary patterns among specific subgroups. 

4.0 Hazard Characterization and Dose-Response Assessment

This hazard characterization updates the previous risk assessments for kasugamycin, conducted 

in 2005 (D301735; W.T. Drew; 17 August 2005) and 2009 (D356204; W.T. Drew; 29 April 

2009). Additional toxicology data have been submitted since the most recent review (see 

below). 
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4.1 Toxicology Studies Available for Analysis 

Studies considered for this assessment include acute lethality (oral, dermal and inhalation 

routes), primary eye and dermal irritation, dermal sensitization, subchronic oral toxicity (rat, 

mouse and dog), rat 21-day dermal toxicity, dog chronic toxicity, rat combined chronic 

toxicity/carcinogenicity, mouse carcinogenicity, developmental toxicity (rat and rabbit), rat twogeneration reproductive toxicity, genotoxicity, rat metabolism, rat acute and subchronic 

neurotoxicity, and mouse immunotoxicity. Additional data submitted since the previous 

assessment were the acute and subchronic neurotoxicity studies, mouse immunotoxicity study, 

rat 21-day dermal toxicity study, bacterial reverse gene mutation assay, and in vitro mammalian 

cell clastogenicity assay. The oral and dermal studies are of appropriate routes for potential 

exposure scenarios. Study executive summaries for the most recently submitted data and for 

updated DERs are provided in Appendix A.4; refer to the previous risk assessments (2005 and 

2009) for all other executive summaries. 

A 28-day inhalation toxicity study in the rat is not available; however, HED’s HASPOC 

concluded that an inhalation study is not required for kasugamycin, based on the toxicological 

profile, low application rates, low vapor pressure, and lack of residential uses (TXR #0052461). 

Furthermore, MOEs for inhalation exposure, calculated using a conservative NOAEL and 

endpoint from an oral study, were all ≥58,000. This approach is, therefore, considered protective 

of potential effects from occupational inhalation exposure; a 10X UFDB is not required for the 

lack of this study. 

4.2 Absorption, Distribution, Metabolism, & Elimination (ADME) 

Kasugamycin was poorly absorbed and metabolized (<5% of the administered radioactive dose, 

or AD) in the rat following oral exposure to 100 or 1000 mg/kg/day. Absorption at low dosing 

levels (such as 1 or 10 mg/kg) was not examined. The maximum plasma concentration occurred 

about one hour after the administration of a single low or high dose, with a t1/2 of 1.17-1.55 

hours. Bioavailability, as indicated by the area under the curve (AUC) was proportional to the 

dose. At 168 hours post-dosing, the majority of the AD was excreted in the feces (81.9 to 93.9% 

AD), with only small amounts in the urine (1.26-3.07% AD). Most of the excreted radioactivity 

was recovered within 48 hours. Biliary excretion was not observed; the fecal radioactivity 

therefore represented unabsorbed kasugamycin. By 168 hours, tissue radioactivity was nondetectable except for low levels in the kidneys, and at the high dose, the intestinal tract and 

stomach. Most of the excreted radioactivity in the urine and feces was the un-metabolized parent 

compound, and metabolism was not affected by dose, duration of dose, or sex. Minor amounts 

(less than 1% AD) of the metabolite kasuganobiosamine were identified in the urine, liver, 

kidney and plasma, but none was detected in the feces. 
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4.2.1 Dermal Absorption 

A dermal absorption study is not available for kasugamycin. However, a dermal study was 

available to assess toxicity via the dermal route. No systemic effects were observed at doses 

causing dermal irritation at the application site. Females were more sensitive than males; the 

high dose of 500 mg/kg/day was reduced to 200 mg/kg/day in females after one week due to 

significant irritation. 

4.3 Toxicological Effects 

Kasugamycin is an aminoglycoside antibiotic pesticide with limited activity against some plant 

bacterial and fungal pathogens. It does not have human or veterinary therapeutic applications 

due to low efficacy, but at one time was used clinically in Japan to treat Pseudomonas kidney 

infections in humans (Shuwirth et al (2006) Nat. Struct. Mol. Biol. 13(10):879-886). The mode 

of action is distinct from other aminoglycosides such as streptomycin, which also has pesticidal 

uses. Kasugamycin inhibits the formation of the 30S ribosomal subunit at initiation of protein 

synthesis by perturbing the mRNA-tRNA codon/anticodon interaction. Other aminoglycoside 

antibiotics bind to the 30S ribosomal subunit, but disrupt translation of mRNA at later stages of 

initiation. 

Evaluation of metabolism in the rat indicates that, although peak plasma concentrations occur 

rapidly, absorption is poor. Kasugamycin is rapidly excreted, largely as un-metabolized and 

unabsorbed parent compound, in the feces. Kasugamycin is not retained at significant levels in 

tissues. Metabolism is described in detail in Section 4.2 (above). 

The primary target organs identified for kasugamycin were the testes and kidney in the rat and 

mouse. However, these effects were only seen at higher dose levels, generally at the highest 

dose tested (HDT). In the combined chronic toxicity/carcinogenicity study in rats, the basis for 

the LOAEL was an increased incidence and severity of testicular tubular atrophy, observed 

during the histopathologic examinations at the end of the two-year dosing period, as well as at 6 

months, and one year. Testicular degeneration and atrophy were observed in adult F1 males in 

the rat reproductive toxicity study at the highest dose. Testicular tubular dilatation and 

degeneration were observed in the mouse subchronic study, but at a dose that exceeded the limit 

dose; the mouse carcinogenicity study tested at much lower doses, and these effects were not 

observed. In the dog chronic toxicity study, testicular inflammation was reported at the high 

dose, but was not accompanied by atrophic or degenerative changes, and was not considered a 

treatment-related adverse effect. 

Kidney toxicity is often associated with exposure to aminoglycoside antibiotics, and the 

metabolism study indicated higher levels of radioactivity in the kidneys than other tissues. In 

male F1 rats in the reproductive toxicity study, dilatation of the kidney, and an increased 

incidence of chronic progressive nephropathy were observed. In the subchronic rat study, an 
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increased incidence of eosinophilic bodies (graded slight for severity) in the renal proximal 

tubular cells was reported in males at several dose levels. These effects were considered 

treatment-related, but not adverse due to their low severity grade, and lack of associated findings. 

However, in female rats, increased epithelial cells in the urinary sediment, along with decreased 

urine pH (decreased pH was also seen in males), were observed at the high dose, and considered 

evidence of possible kidney toxicity. Lipofuscin deposition (slight) was observed in the rat 

combined chronic toxicity/carcinogenicity study, but was not considered adverse due to the lack 

of other related findings; this study tested up to the NOAEL of the subchronic study. In the 

mouse, following subchronic exposure, minimal to severe basophilia/hyperplasia in the renal 

pars recta in females was observed. No renal effects were reported in the mouse carcinogenicity 

study at lower doses, or in the dog subchronic or chronic studies. 

Kasugamycin caused decreased body weight and/or weight gain in the subchronic studies in the 

rat, mouse and dog (including the neurotoxicity screening study in the rat). The chronic studies, 

which tested at lower doses, did not show body weight effects. Decreased body weight was also 

observed in developmental and reproductive studies in the rat, and in the range-finding study for 

the rabbit developmental study. Body weight effects in the mouse immunotoxicity study were 

observed only at a dose significantly exceeding the limit dose. 

Kasugamycin appears to be irritating to the oral and gastrointestinal tract mucosa. Anal lesions 

and perianal/perigenital staining were observed in the subchronic mouse study. Red and swollen 

skin around the anal opening, and inflammation and ulceration of the rectum, were noted in rats 

of both sexes in both generations in the two-generation reproduction study. In the rat 

developmental toxicity study, distention of the large intestine with stool in the cecum, and an 

increased incidence of loose stool were reported. Similar findings were seen in the rabbit 

developmental range-finding study among females that died or were sacrificed in extremis. 

These effects may be related to the acidity (or other irritant property) of the active ingredient, 

which is primarily excreted unabsorbed and un-metabolized in the feces. Similar findings were 

not seen in the dog, although tongue and mouth lesions were reported at the highest dose tested 

in the dog subchronic toxicity study (but not the chronic dog study, which tested at a lower 

dose). 

The available studies, which include acute and subchronic neurobehavioral screening studies in 

the rat, did not show evidence of neurotoxicity. A 28-day mouse immunotoxicity study did not 

show evidence of immune system effects. 

 

Although kasugamycin did not show dermal irritation following an acute exposure, it was 

irritating to the skin following repeated dermal dosing. Systemic effects were not observed in 

the rat 21-day dermal study, in which dosing was not conducted up to the limit dose, due to 

significant dermal irritation at the application site following repeated dose applications. 
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There was no evidence of increased quantitative or qualitative susceptibility in rat or rabbit 

developmental toxicity studies, or in the rat reproductive study. No developmental effects were 

seen in the rat developmental study, whereas maternal toxicity (decreased body weight gain, 

food consumption, and feed efficiency) was observed at the highest dose. Although no maternal 

or developmental toxicity was observed in the main rabbit developmental toxicity study, in the 

dose range-finding study, maternal weight loss, reduced food consumption during dosing, and 

abortions (occurring at GD 18 or later) were observed at higher doses. Fetal weight was 

decreased at the maternally toxic dose but, due to abortions or maternal death, was not evaluated 

at the higher doses. In the rat reproductive toxicity study, parental toxicity included decreased 

parental body weight/weight gain at the mid and high doses. No offspring toxicity was observed. 

Reproductive toxicity was observed only at the highest dose tested (above the parental LOAEL), 

with testicular atrophy, decreased fertility and fecundity in the F1 parents for both litters, and an 

increased pre-coital interval during the mating period for the F2b litter. 

Kasugamycin is classified as “not likely to be carcinogenic to humans”, based on lack of 

evidence of carcinogenicity in rat and mouse carcinogenicity studies, and lack of evidence of 

genotoxic potential in gene mutation, chromosomal aberration, and unscheduled DNA synthesis 

assays. 

The acute toxicity of kasugamycin is low by all routes (Category III-IV). It is a mild dermal and 

ocular irritant (Category III), and does not show potential for dermal sensitization. 

 

4.4 Safety Factor for Infants and Children (FQPA Safety Factor) 

HED recommends that the 10X FQPA safety factor for infants and children be reduced to 1X for 

kasugamycin, for the following reasons: 

1. The toxicology database is complete, including rat acute and subchronic 

neurotoxicity screening studies, and a mouse immunotoxicity 

study. 

2. Based on the lack of observed neurotoxicity, a DNT study is not 

required. 

3. There is no evidence of increased quantitative or qualitative pre- and/or 

postnatal susceptibility observed in developmental toxicity studies 

in the rat and rabbit, or in a two-generation reproduction study in 

the rat. 

4. The exposure assessment for food and drinking water will not 

underestimate potential dietary exposure to kasugamycin, and there 

are no proposed or existing residential uses for kasugamycin. 
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4.4.1 Completeness of the Toxicology Database 

The database is considered adequate for purposes of assessing the susceptibility of infants and 

children to the effects of kasugamycin. Acceptable developmental toxicity studies in two species 

(rat and rabbit), a rat multigeneration reproductive toxicity study, rat acute and subchronic 

neurotoxicity studies, and a mouse immunotoxicity study are available. As previously discussed 

(Section 4.1), an inhalation exposure study is not required. 

4.4.2 Evidence of Neurotoxicity 

Kasugamycin did not show evidence of neurotoxicity in the available studies, which included rat 

acute and subchronic neurotoxicity studies. Additionally, no potential neurotoxic effects were 

noted in other toxicity studies, or in other species. A DNT study is not required. 

4.4.3 Evidence of Sensitivity/Susceptibility in the Developing or Young Animal 

There was no evidence of increased quantitative or qualitative pre- and/or postnatal susceptibility 

in developmental toxicity studies in two species, or the rat two-generation reproductive toxicity 

study. Abortions and a reduction in fetal body weight in the rabbit developmental toxicity rangefinding study were considered secondary to maternal toxicity (weight loss, and decreased food 

consumption). Decreased fertility and testicular effects in the F1 generation of the rat 

reproductive toxicity study were observed at the LOAEL for parental toxicity, but no toxicity to 

offspring was observed. 

4.4.4 Residual Uncertainty in the Exposure Database 

There is low concern, and no residual uncertainty, for susceptibility for the reasons discussed 

above. Underestimation of exposure is not anticipated because conservative assumptions 

(tolerance-level crop residues, and modeled drinking water estimates) were used to estimate risk 

from dietary exposure, and there are no existing or proposed residential uses. 

4.5 Toxicity Endpoint and Point of Departure Selections 

4.5.1 Dose-Response Assessment 

In the available studies, many of the effects observed following exposure to kasugamycin were 

only observed at the highest dose tested. Testicular atrophy was observed at the highest dose 

levels in the mouse subchronic study, and in the rat chronic and reproductive toxicity studies. 

Decreased body weight and/or weight gain was also usually observed only at the highest dose 

tested. Renal toxicity, observed in some studies in the rat and mouse, was also a high-dose 

effect. Neither the chronic dog, nor the mouse carcinogenicity study, showed any effects at the 

doses tested, which were lower than those tested in the subchronic studies. 
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For acute dietary exposure, a dose and endpoint were not selected because there were no findings 

attributable to a single dose. Abortions in the rabbit range-finding study at 30 and 100 

mg/kg/day (1 of 4 and 3 of 4, respectively) were only observed at or beyond 12 days of dosing 

and in females that died or were sacrificed in extremis occurred after multiple doses. Maternal 

body weight loss during dosing and decreased food consumption were also observed at this dose, 

but are not considered a single-dose effect, and decreased fetal weights were considered 

secondary to maternal toxicity. 

For chronic dietary exposure, the rat combined chronic toxicity/carcinogenicity study was 

selected. The NOAEL of 11.3 mg/kg/day was based on testicular softening and atrophy at the 

LOAEL of 116 mg/kg/day. Testicular atrophy is consistent with findings of other studies. It was 

also observed in the rat two-generation reproduction study, at 425.3 mg/kg/day (NOAEL = 70.3 

mg/kg/day) and in the mouse subchronic study above the limit dose. 

For dermal exposure (short- and intermediate-term), a dose and endpoint were not selected 

because no systemic toxicity was observed in the rat 21-day dermal study, which tested up to 

doses causing local dermal irritation. Endpoints of concern (body weight, renal and testicular 

toxicity, gastrointestinal and oral cavity effects) were evaluated in the dermal study. 

 For inhalation exposure (short- and intermediate-term), the subchronic study in the dog and the 

rabbit developmental toxicity studies were selected as co-critical. The endpoint of concern is 

irritation since kasugamycin appears to be irritating to the oral cavity and gastrointestinal tract 

mucosa following oral exposures. In the subchronic study with dogs, the NOAEL was 11 

mg/kg/day, and the LOAEL was 106 mg/kg/day, based on irritation of the oral cavity, 

characterized as tongue lesions, swollen mouth, excessive salivation, and thickening of the skin 

at the commissures of the mouth. The irritation potential of kasugamycin is further demonstrated 

with the presence of anal lesions, and perianal/perigenital staining seen in the subchronic mouse 

study; red/swollen skin around the anal opening, and inflammation/ulceration of the rectum in 

the offspring of both sexes in the two-generation reproduction study; and distention of the large 

intestine in the developmental rat study. The developmental rabbit study was selected as the cocritical study since the maternal NOAEL (10 mg/kg/day) was comparable to the NOAEL in the 

dog study, and the concern for the maternal toxicity seen in this species. In the range-finding 

study, maternal toxicity manifested as abortions and weight loss at 30 mg/kg/day (LOAEL). In 

the rabbit developmental toxicity studies (range-finder and definitive evaluated together), the 

incidence and severity of the maternal toxicity was increased at the high dose (100 mg/kg/day) 

where one doe died, abortions were seen in 3 of 4 litters, and the weight loss was more 

pronounced. Given kasugamycin’s apparent poor oral absorption (< 5% in the rat metabolism 

study), and the consistent evidence of irritation effects to mucous membranes seen across 

numerous species, it is reasonable to surmise that the bolus (gavage) dosing causes irritation to 

the gastrointestinal tract resulting in maternal toxicity. Additionally, the use of the oral NOAEL 
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results in MOEs ranging from 58,000 to 2,500,000 for risk from occupational exposure via the 

inhalation route. 

4.5.2 Recommendation for Combining Routes of Exposures for Risk Assessment 

For chronic dietary assessment, exposure from food and drinking water should be combined. 

There are no residential uses at this time, so it is not necessary to address the suitability of 

combining exposures from different routes (such as oral and inhalation). Only inhalation 

exposure was assessed for occupational workers, since there was no hazard associated with 

dermal exposure. 

4.5.3 Cancer Classification and Risk Assessment Recommendation 

In accordance with the Agency’s 2005 Guidelines for Carcinogen Risk Assessment, 

kasugamycin is classified as “not likely to be carcinogenic to humans”, based on lack of 

evidence of carcinogenicity in male and female mice, and in male and female rats, and the lack 

of evidence for mutagenicity both in both in vivo and in vitro assays. 

4.5.4 Summary of Points of Departure and Toxicity Endpoints Used in Human Risk 

Assessment 

 TABLE 4.5.4.1 Summary of Kasugamycin Toxicological Doses and Endpoints for Use in Dietary 

 Human Health Risk Assessments. 

Exposure Scenario Point of 

Departure 

Uncertainty 

and FQPA 

Safety Factors

RfD, PAD, LOC 

for Risk 

Assessment 

Study and Toxicological Effects 

Acute dietary (all 

populations) 

An appropriate dose and endpoint for this risk assessment scenario was not identified, based 

on a lack of single-dose effects in the database. 

Chronic dietary 

(all populations 

including infants 

and children, and 

females age 13 to 

49) 

NOAEL = 11 

mg/kg/day 

UFA = 10X 

UFH = 10X 

FQPA SF = 1X 

Chronic RfD = 

0.11 mg/kg/day 

cPAD = 0.11 

mg/kg/day 

Combined chronic 

toxicity/carcinogenicity study in the 

rat 

LOAEL = 116 mg/kg/day, based on 

testicular atrophy and softening. 

Cancer (oral, 

dermal, inhalation) 

Classification: “Not likely to be carcinogenic to humans.” 

Point of Departure (POD) = a data point or estimated point derived from observed dose-response data, which is used 

to mark the beginning of extrapolation to determine risk associated with lower environmentally relevant human 

exposures. HDT = Highest Dose Tested. UF = Uncertainty Factor. UFA = extrapolation from animal to human 

(interspecies). UFH = potential variation in sensitivity among members of the human population (intraspecies). 

FQPA SF = FQPA Safety Factor. NOAEL = No Observed Adverse Effect Level. LOAEL = Lowest Observed 

Adverse Effect Level. PAD = Population Adjusted Dose (a = acute, c = chronic). RfD = Reference Dose. LOC = 

Level of Concern. 
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TABLE 4.5.4.2 Summary of Kasugamycin Toxicological Doses and Endpoints for Use in 

 Occupational Human Health Risk Assessments. 

Exposure 

Scenario 

Point of 

Departure 

Uncertainty 

Factors 

RfD, PAD, 

LOC for Risk 

Assessment 

Study and Toxicological Effects 

Dermal, shortterm (1 to 30 

days) and 

intermediateterm (1 to 6 

months) 

An appropriate dose and endpoint for these scenarios was not identified. No toxicity was 

observed in the rat 21-day dermal toxicity study, which tested up to doses causing local dermal 

irritation. 

Dermal, longterm (>6 

months) 

Long-term dermal exposure is not anticipated from the proposed or existing uses. 

Inhalation, 

short-term (1 

to 30 days) and 

intermediateterm (1 to 6 

months) 

Oral NOAEL = 11 

mg/kg/day* 

UFA=10X 

UFH=10X 

Occupational 

LOC for MOE 

≤100 

Co-critical studies: 

1. Subchronic oral toxicity in the dog; 

LOAEL = 106 mg/kg/day 

2. Developmental toxicity study in rabbits. 

Maternal LOAEL = 30 mg/kg/day 

Endpoint of concern is irritation (see 

Section 4.5.1 for details). 

Inhalation longterm (>6 

months) 

Long-term inhalation exposure is not anticipated from the proposed or existing uses. 

Cancer (oral, 

dermal, 

inhalation) 

Classification: “Not likely to be carcinogenic to humans.” 

Point of Departure (POD) = A data point or an estimated point that is derived from observed dose-response data, 

which is used to mark the beginning of extrapolation to determine risk associated with lower environmentally 

relevant human exposures. UF = Uncertainty Factor. UFA = extrapolation from animal to human (interspecies). 

UFH = potential variation in sensitivity among members of the human population (intraspecies). NOAEL = No 

Observed Adverse Effect Level. LOAEL = Lowest Observed Adverse Effect Level. MOE = Margin of Exposure. 

LOC = Level of Concern. 

* Absorption via the inhalation route is equivalent to 100% oral absorption. 

5.0 Dietary Exposure/Risk Characterization 

5.1 Metabolite/Degradate Residue Profile

5.1.1 Summary of Plant and Animal Metabolism Studies 

The nature of kasugamycin residues in plants and rotational crops is considered adequately 

understood for the purpose of assessing the proposed uses, based on an acceptable tomato 

metabolism study and an acceptable confined rotational crop study. The residue of concern in 
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fruiting vegetables for both tolerance enforcement and risk assessment purposes is the parent 

kasugamycin only, and this conclusion applies to both walnuts and pome fruit. HED concluded 

that a metabolism study is not required for walnuts, since the maximum field trial residues were 

at the limit of quantitation (LOQ), 0.040 ppm, and are therefore unlikely to be present in 

quantities sufficient to allow characterization. For any future requested uses on leafy, root or 

grain crops (or other crops dissimilar to tree nuts, fruiting vegetables, or pome fruits), 

metabolism studies would be required in order to determine the nature of the residue in those 

commodities. No rotational crop tolerances are needed, based on the overall lack of residues in 

rotated crops. 

Based on the results of the goat metabolism study, kasugamycin residues orally ingested by a 

lactating goat were poorly absorbed from the gastro-intestinal (GI) tract of the goat, and the 

small fraction of the dose that was absorbed was rapidly excreted unchanged in the urine. 

Kasugamycin did not accumulate in the milk or edible tissues of the goat. The nature of the 

residue is adequately understood, and HED has recommended use of the parent compound only 

for purposes of tolerance enforcement and risk assessment. However, based on the proposed 

uses, there is no reasonable expectation of finite residues in livestock commodities (a category 

6[a][3] situation), so no tolerances are being recommended in livestock commodities at this time. 

 

5.1.2 Summary of Environmental Degradation 

EFED provided a fate summary and drinking water assessment (DWA) for the proposed uses 

(D376600; T. Dowen, J. Hetrick, Dana Spatz; 28 April 2011). The primary routes of dissipation 

for kasugamycin are aqueous photolysis, aerobic biodegradation, and hydrolysis, with half-lives 

of 17.4, 45, and 11.4 to 462 days (for pH 4 to 9), respectively. The aerobic soil metabolism halflife was 73 days in clay-loam soil. Since aerobic soil metabolism data are only available on one 

soil type, there is uncertainty regarding the variability of degradation in aerobic soils. The field 

dissipation half-lives ranged from 5.7 to 12.3 days. The degradate kasugamycinic acid was not 

detected above the LOQ at any sampling interval. No other degradates were looked for in this 

study. Based on the FAO Mobility classification, kasugamycin is classified as highly mobile (in 

sand) to moderately mobile (in clay loam soil). The mobility of kasugamycin acid and 

kasuganobiosamine is expected to be similar to, or greater than, the parent. Therefore, they will 

likely range from highly mobile to moderately mobile. All have the potential to be found in both 

surface water and groundwater sources of drinking water. 

5.1.3 Comparison of Metabolic Pathways 

In a rat metabolism study, kasugamycin was poorly absorbed following oral exposure, and 

excreted almost entirely in the feces as un-metabolized parent compound. Excretion in the urine 

accounted for ≤3% of the dose. The metabolite kasuganobiosamine was identified at low levels 

in urine, liver, kidney and plasma (<1% of dose). Little or no radioactivity was retained in 

tissues. 
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In the tomato metabolism study, the metabolite profile was similar for tomato fruit and foliage. 

Based on the results of the tomato metabolism study, the major metabolic pathway of 

kasugamycin in plants involves conjugation of the parent compound, conversion to 

kasugamycinic acid, and subsequent conjugation of kasugamycinic acid. Conversion of 

kasugamycin to 2-N-acetyl kasugamycin and kasuganobiosamine was thought to be a minor 

metabolic route. Parent compound (kasugamycin per se) was the major identified component in 

all samples from all harvest intervals. 

The submitted data shows that the major metabolic pathway of kasugamycin in tomato fruit and 

leaves consists of deamination and oxidation to produce kasugamycinic acid. Metabolism 

studies in rotational crops (lettuce, radish and wheat) show uptake of kasugamycin in all crops, 

while kasugamycinic acid was identified in only one commodity, wheat hay. The livestock 

metabolism study conducted in goat showed kasugamycin as the only residue identified in the 

liver and kidney. Similarly, parent compound was the major residue identified in the urine, 

feces, liver, kidney and plasma of rats. 

Compounds detected in the tomato, ruminant, rotational crop, and rat metabolism studies are 

presented in Tables B.1 and B.2 (see Appendix B). 

5.1.4 Residues of Concern Summary and Rationale 

Kasugamycin is susceptible to aqueous photolysis, aerobic biodegradation and hydrolysis. It is 

highly soluble in water, and does not appear to volatilize significantly. Adsorption-desorption 

studies indicate that kasugamycin is highly to moderately mobile in soil. Major identified 

degradates of kasugamycin include kasugamycinic acid and kasuganobiosamine. The soil 

mobility of these two metabolites is expected to be similar to, or greater than, the parent 

kasugamycin. Therefore, both of these degradates have the potential to be found in surface and 

ground sources of drinking water. 

Although kasugamycinic acid, 2-N-acetyl-kasugamycin and/or kasuganobiosamine were 

detected in primary crops, rotational crops, and/or water, these metabolites have similar 

structures to the parent, and thus can be reasonably expected to have similar toxicity. Moreover, 

a DEREK analysis was conducted for these three metabolites, and major differences in toxicity 

were not predicted relative to the parent. 

Water: The ROCKS committee recommended that parent kasugamycin, as well as its major 

degradation products kasugamycinic acid and kasuganobiosamine, be included in the risk 

assessment. 

Plants: Kasugamycin accounts for 55-94% of the total radioactive residue (TRR) in tomato 

fruit, and 52-84% of the TRR in tomato leaves for PHIs from 2 hours to 28-days. Therefore, the 
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parent compound can serve as an adequate measure of misuse for tolerance enforcement. 

Kasugamycinic acid accounted for 10% and 12% of the TRR in tomato fruit at 21-day and 28-

day PHIs, respectively, compared to only 2-7% of the TRR in tomato leaves at all PHIs. 

Kasugamycinic acid seems to be formed at long PHIs; the proposed PHI is 1-day for fruiting 

vegetables. In addition, crop field trials with walnut show kasugamycin residues below the 

LOQ. Although the PHIs for pears (30 days) and apples (90 days) will be longer than the 28 

days for tomatoes in the metabolism study, ROCKS concluded that use of only the parent in risk 

assessment is adequate for the proposed uses, based on the relatively low toxicity, and low 

residues of the parent. Moreover, no special concerns regarding the potential toxicity of 

kasugamycinic acid were noted. Based on this information, the ROCKS recommends that parent 

kasugamycin only be used for tolerance enforcement and risk assessment. However, for further 

petitions of new uses on fruiting-type crops with longer PHIs, the crop field trial data should 

include analysis for kasugamycinic acid. For future uses on other types of crops (such as leafy 

vegetables, or grains) a new metabolism study will be required which should quantitatively 

assess the formation of kasugamycinic acid. 

Rotational Crops: In the limited field rotational crop trials with lettuce, radish and wheat planted 

at 30, 120 and 365 days after soil treatment, uptake of kasugamycin was observed at levels below 

0.01 ppm. The only metabolite identified was kasugamycinic acid in wheat hay, but only at 

levels below 0.001 ppm. Based on this, the ROCKS committee recommended that parent 

kasugamycin only be included for risk assessment and tolerance enforcement purposes. 

Livestock: The only residue identified in a goat metabolism study was kasugamycin, accounting 

for 92.9% TRR in the liver and kidney, and 85.7% TRR in renal fat. Kasugamycin is not 

metabolized to a major extent. Based on this, the ROCKS committee recommended that parent 

kasugamycin only be included for risk assessment and tolerance enforcement purposes. 

TABLE 5.1.4 Summary of Metabolites and Degradates to be Included in Risk Assessments and the 

 Tolerance Expression. 

Matrix Residues Included in Risk 

Assessments 

Residues Included in the 

Tolerance Expression 

Plants Primary crop Parent kasugamycin only Parent kasugamycin only 

Rotational crop Parent kasugamycin only Parent kasugamycin only 

Livestock Ruminant Parent kasugamycin only Parent kasugamycin only 

Poultry NA* NA 

Drinking Water Kasugamycin, kasugamycinic acid, 

and kasuganobiosamine 

NA

* NA = Not Applicable. 
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5.2 Food Residue Profile

Analytical chemistry and residue data for kasugamycin were addressed in detail in the summary 

document associated with the current petition (D376563; W.T. Drew; 13 July 2012). All 

recommended tolerances were determined via the OECD tolerance calculation procedure. 

The submitted and available residue data for fruiting vegetables, group 8-10, and walnuts are 

adequate to fulfill data requirements. For pome fruit, the data are adequate to support individual 

crop tolerances, but not the crop group tolerance. If the petitioner wishes to pursue a crop group 

tolerance in pome fruits, group 11-10, residue data from 6 additional geographically diverse 

apple field trials (including adjuvant) are required at a 30-day PHI. The submitted data are 

adequate to support individual tolerances in pome fruit commodities, provided the label is 

amended to specify a 90-day PHI for all pome fruit crops other than pears. 

Adjuvants were not used in any of the fruiting vegetable or walnut field trials. However, in the 

case of walnuts, HED concludes that adjuvants will not have a significant impact on residues, 

given the long PHI, the low observed residues in the available trials, and the nutmeats being 

protected (by the walnut’s shell) from direct spray during application. Therefore, HED is 

recommending that the product label be amended to specify that adjuvants may not be added to 

spray mixtures for crops other than pome fruits and walnuts. 

 

Adequate processing studies were conducted with apples and tomatoes. The processing study in 

apples demonstrated that residues concentrated slightly (1.5X) in apple juice, but a separate 

tolerance for residues in juice is not needed. No processing factor could be calculated for wet 

pomace because residues were below the LOQ in pomace. No processing factors could be 

calculated for tomato processed commodities because there were no detectable residues in the 

RAC or the processed fractions. The Agency would have preferred the use of exaggerated rates 

in the conduct of the processing study to yield a RAC with quantifiable residues. However, in 

conjunction with the previous petition (PP#3E6579; D308573; W.T. Drew; 17 August 2005), the 

petitioner provided supporting information, and was granted a waiver from the requirement for 

another tomato processing study. Since the proposed use is nearly identical to the previous use 

directions for fruiting vegetables, HED continues to recommend for a waiver from the 

requirement for a new tomato processing study at exaggerated rates. 

A summary of the crop field trial residue data is presented in Table 5.2. 
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TABLE 5.2 Summary of Residue Data from Crop Field Trials with Kasugamycin. 

Commodity Total Use Rate 

(lb ai/A) 

PHI 

(Days)

Residue Levels (ppm) 1

n Min. Max. HAFT Median Mean Std. 

Dev. 

Fruiting Vegetables (proposed use = 0.063 lb ai/A total use rate, 1-day PHI, plus adjuvant) 

Data submitted in current petition (PP#0F7689) 

Pepper fruit 

(foliar broadcast) 

0.0619-0.0714 1 18 <0.04 0.107 0.0837 0.0400 0.0472 0.0167 

Tomato fruit 

(foliar 

directed/foliar 

broadcast) 

0.0623-0.0687 0-1 20 <0.04 0.0728 0.0727 0.04 0.0441 0.0105 

Tomato fruit 

(drench) 

0.0624 lb ai/ 

25 gal water 

0 2 <0.04 <0.04 <0.04 <0.04 <0.04 NA 2

Data available from the previous petition (PP#3E6579) 3

Pepper fruit 0.053-0.054 1 14 <0.04 <0.04 <0.04 <0.04 <0.04 NA 

Tomato fruit 0.052-0.054 1 16 <0.04 <0.04 <0.04 <0.04 <0.04 NA 

0.270 1 2 0.044 0.056 0.050 NR4 0.050 0.008 

Pome Fruit (proposed use = 0.333 lb ai/A total application rate, 30-day PHI, plus adjuvant) 

Data submitted in current petition (PP#0F7689) 

Kasumin 2L + Surfactant (All Trials) 

Apple fruit 0.261-0.341 90-100 40 <0.04 0.075 0.068 0.04 0.043 0.007 

Kasumin 2L + Surfactant (Canadian Side-by-SideTrials) 

Apple fruit 0.325-0.341 91-94 10 <0.04 <0.04 <0.04 <0.04 <0.04 NA 

Kasumin 2L Only (Canadian Side-by-Side Trials) 

Apple fruit 0.325-0.341 91-94 10 <0.04 <0.04 <0.04 <0.04 <0.04 NA 

Kasumin 2L + Surfactant (All Trials) 

Pear fruit 0.494-0.538 27-32 16 0.044 0.172 0.166 0.100 0.097 0.038 

Data associated with Section 18 emergency exemption for use on apples (PP#08MI10) 3 

Apple fruit 0.32 30 6 0.014 0.029 0.025 0.021 0.022 0.006 

Walnuts (proposed use = 0.333 lb ai/A total application rate, 100-day PHI, plus adjuvant) 

Walnut nutmeat 0.335-0.340 98-110 6 <0.04 0.04 0.04 0.04 0.04 0 

1. The LOQ is 0.040 ppm. 

2. NA = Not Applicable. 

3. D308573; W.T. Drew; 17 August 2005; PP#3E6579. 

4. NR = Not Reported. 

5. D356204; W.T. Drew; 29 April 2009; PP#08MI10. 

5.3 Water Residue Profile

The kasugamycin drinking water residues used in risk assessment were provided in the DWA by 

EFED (D376600; T. Dowen, J. Hetrick, Dana Spatz; 28 April 2011), and incorporated directly 

into the dietary exposure and risk assessment. Water residues were incorporated in the dietary 

assessment model using the food categories “water, direct, all sources” and “water, indirect, all 

sources”. 
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In general, estimated concentrations in drinking water sources are considered to be low, but 

surface water estimates were slightly higher than those for groundwater. Although EFED 

provided values for acute, chronic and cancer assessments, only the chronic surface water value 

was used quantitatively in the risk assessment. The EDWCs in surface water are 0.011562 ppm 

and 0.001178 ppm for acute and chronic scenarios, respectively. The EDWC in groundwater is 

0.000116 ppm for all durations (see Table 5.3.1). The chronic surface water EDWC (0.001178 

ppm) was used in the chronic dietary analysis because it is the higher of the chronic residues in 

water; use of this value in the dietary assessment is considered protective of potential exposure to 

residues in ground water sources of drinking water. 

The modeled surface water EDWCs were generated using the linked PRZM (Pesticide Root 

Zone Model) and EXAMS (EXposure Analysis Modeling System) models. These models and 

their descriptions are available at the EPA internet website via the web link, 

http://www.epa.gov/oppefed1/models/water/. No surface or groundwater monitoring data were 

available for kasugamycin. The PRZM/EXAMS modeling was based on application of 

kasugamycin to tomatoes in Florida. 

TABLE 5.3.1 EDWCs for Kasugamycin, Plus Degradates Kasugamycinic Acid and Kasuganobiosamine. 

Crop Acute Exposure (ppm) Chronic Exposure (ppm) Cancer Exposure (ppm) 

Surface Water (via PRZM/EXAMS) 

Tomato 0.011562 0.001178* 0.000602 

Ground Water (via SCI-GROW) 

Walnut 0.000116 0.000116 0.000116 

* EDWC used in the chronic dietary assessment. 

5.4 Dietary Risk Assessment

5.4.1 Description of Residue Data and Percent Crop Treated Used in Dietary Assessment 

An unrefined chronic aggregate dietary (food and drinking water) exposure and risk assessment 

was conducted for kasugamycin (D390458; W.T. Drew; 13 July 2012) using the Dietary 

Exposure Evaluation Model software with the Food Commodity Intake Database (DEEMFCIDTM), Version 2.03. This model uses food consumption data from the US Department of 

Agriculture’s (USDA’s) Continuing Surveys of Food Intakes by Individuals (CSFII), collected 

from 1994 to 1996, and 1998. The residue inputs into the dietary model were the recommended 

tolerance level residues; default processing factors were used, with the exception of the apple 

juice processing factor, for which the 1.5X data-derived factor was used. The dietary exposure 

assessment is based on the assumption of 100%CT for all crops with proposed uses on the 

kasugamycin label. 
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5.4.2 Chronic Dietary Risk Assessment 

Based on these highly conservative assumptions, chronic dietary risk estimates are less than or 

equal to 1.7% of the cPAD for all population subgroups. Children 1-2 years of age are the most 

highly-exposed subgroup, with a risk estimate of 1.7% of the cPAD, while the general US 

population had a risk estimate of <1% of the cPAD. Generally, HED is concerned when risk 

estimates exceed 100% of the PAD; therefore, all chronic dietary risk estimates are not of 

concern (see Table 5.4.3). 

5.4.3 Summary Table 

TABLE 5.4.3 Summary of Chronic Dietary Exposure and Risk Estimates for Kasugamycin. 

Population Subgroup* 

[Years of Age] 

cPAD (mg/kg/day) Dietary Exposure Estimate 

(mg/kg/day) 

% cPAD 

General US Population 0.11 0.000450 <1 

All Infants [< 1] 0.11 0.001215 1.1 

Children [1-2] 0.11 0.001839 1.7 

Children [3-5] 0.11 0.001281 1.2 

Children [6-12] 0.11 0.000647 <1 

Youth [13-19] 0.11 0.000373 <1 

Adults [20-49] 0.11 0.000310 <1 

Adults [50+] 0.11 0.000279 <1 

Females [13-49] 0.11 0.000307 <1 

* Values for the population subgroup with the highest risk are in bold type. 

6.0 Residential (Non-Occupational) Exposure/Risk Characterization

There are no proposed residential uses for kasugamycin associated with the subject petition, nor 

are there any currently registered residential uses. Kasugamycin is not intended for use in public 

or residential settings. Therefore, residential exposure is not expected, and residential risks are 

not of concern. 

6.1 Spray Drift

Spray drift is always a potential source of exposure to residents living in close proximity to 

spraying operations. This situation is particularly the case with aerial application. However, to a 

lesser extent, spray drift resulting from the ground application of kasugamycin could also be a 

potential source of exposure. The Agency has been working with the Spray Drift Task Force (a 

membership of US pesticide registrants), EPA Regional Offices, various state lead agencies for 

pesticide regulation, and other parties to develop the best spray drift management practices. On 

a chemical-by-chemical basis, the Agency is now requiring interim mitigation measures for 

aerial applications that must be placed on product labels. The Agency has completed its 
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evaluation of the new database submitted by the Spray Drift Task Force, and is developing a 

policy on how to apply appropriately the data and the AgDRIFT computer model to its risk 

assessments for pesticides applied by air, orchard airblast, and ground hydraulic methods. After 

the policy is in place, the Agency may impose further refinements in spray drift management 

practices to reduce off-target drift and risks associated with aerial (as well as other) pesticide 

application methods, where appropriate. 

7.0 Aggregate Exposure/Risk Characterization

In accordance with the FQPA, HED must consider and aggregate pesticide exposures and risk 

estimates from three major sources: Food, drinking water, and residential exposures. In an 

aggregate assessment, exposures from dietary and residential sources are added together. Since 

there are no residential sources of exposure for kasugamycin, the only aggregate risk scenario is 

chronic dietary (food and water), which is not of concern (see Table 5.4.3). 

8.0 Cumulative Exposure/Risk Characterization

Unlike other pesticides for which EPA has followed a cumulative risk approach based on a 

common mechanism of toxicity, EPA has not made a common mechanism of toxicity finding as 

to kasugamycin and any other substances, and kasugamycin does not appear to produce a toxic 

metabolite produced by other substances. For the purposes of this tolerance action, therefore, 

EPA has not assumed that kasugamycin has a common mechanism of toxicity with other 

substances. For information regarding EPA’s efforts to determine which chemicals have a 

common mechanism of toxicity, and to evaluate the cumulative effects of such chemicals, see the 

policy statements released by EPA’s OPP concerning common mechanism determinations and 

procedures for cumulating effects from substances found to have a common mechanism on 

EPA’s website at http://www.epa.gov/pesticides/cumulative/. 

9.0 Occupational Exposure/Risk Characterization

Based on the proposed use patterns, both short- and intermediate-term exposure and risk 

assessments were conducted for occupational handlers, or those who mix, load and apply 

pesticides. In addition, HED considered the potential for post-application exposure for those reentering treated sites (D376591; S.C. Wang and C. Swartz; 26 June 2012). 

9.1 Short- and Intermediate-Term Handler Exposure and Risk

No chemical-specific data were available to assess potential exposure of pesticide handlers to 

kasugamycin. In the absence of chemical-specific data, it is HED policy to use the best available 

data to assess handler exposure. Sources of generic handler data, used as surrogate data in the 

absence of chemical-specific data, include the Pesticide Handlers Exposure Database Version 1.1 

(PHED 1.1), and the Agricultural Handler Exposure Task Force (AHETF) database. Some of 
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these data are proprietary (such as the AHETF data), and subject to the data protection provisions 

of FIFRA. The standard values recommended for use in predicting handler exposure that are 

used in this assessment, known as “unit exposures”, are outlined in the Occupational Pesticide 

Handler Unit Exposure Surrogate Reference Table 

(http://www.epa.gov/opp00001/science/handler-exposure-table.pdf), which, along with 

additional information on HED policy for use of surrogate data, including descriptions of the 

various sources, can be found at: http://www.epa.gov/pesticides/science/handler-exposuredata.html. The average adult body weight (80 kg) was used because the dose and endpoint 

selected for inhalation risk assessment are not sex-specific. The proposed label was used to 

determine the maximum application rate. 

There are 5 handler scenarios that are expected to result in the highest exposure for the proposed 

uses: 

1. Mixing/loading liquids for air-blast application, 

2. mixing/loading liquids for ground-boom application, 

3. applying sprays using air-blast equipment, 

4. applying sprays using ground-boom equipment, and 

5. mixing/loading/applying sprays using a manually pressurized 

handwand. 

No data on the number of exposure days per year was provided. For this risk assessment, HED 

assumed that most handlers would be exposed for less than 6 months (short-term and 

intermediate-term exposure). However, since the short- and intermediate-term toxicological 

endpoints are the same, only short-term exposure was quantitatively assessed, and is considered 

protective of potential intermediate-term exposure. 

Based on HED’s Exposure Science Advisory Council (ExpoSAC) Policy #9.1, the following 

assumptions were used for acres treated per day: 

1. 40 acres/day for air blast applications, 

2. 80 acres/day for ground-boom applications, and 

3. 0.8 acres/day (assuming 40 gal/day for use of a manually pressurized 

handwand); the draft label proposes using a spray volume of 50 

GPA for fruiting vegetables. 

The handler exposure estimates in this assessment are based on a central tendency estimate of 

unit exposure, and an upper-percentile assumption for the application rate. The uncertainties 

associated with this assessment stem from the use of surrogate exposure data (such as differences 

in use scenario, and data confidence), and assumptions regarding the amount of chemical 

handled. The estimated exposures are believed to be reasonable high-end estimates, based on 

observations from field studies, and professional judgment. 
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All MOEs for handlers are greater than 100 (ranging from 58,000 to 2,500,000), and are not of 

concern. The exposure and risk estimates for occupational handlers using kasugamycin are 

presented in Table 9.1. 
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TABLE 9.1 Non-Cancer Occupational Handlers’ Exposure and Risk Estimates for Kasugamycin. 

Exposure Scenario 

[Scenario Number, Data 

Source] 

Mitigation 

Level1

Inhalation Unit 

Exposure 

(μg/lb ai) 

Crops Application Rate 

(lb ai/A or lb 

ai/gal) 

Amount Treated2

(A/day or gal 

used/day) 

Da

Inhal

Dose3 (mg

Mixer/Loader 

Liquids for Air Blast Application [1, AHETF] 

Baseline 0.219 Pome Fruit 

Walnuts 

0.08 40 0.0000

Liquids for Ground-Boom Application [2, AHETF] 

Baseline 0.219 Fruiting 

Vegetables 

0.02 80 0.0000

Applicator 

Sprays with Air Blast Equipment [3, AHETF] 

Baseline 4.71 Pome Fruit 

Walnuts 

0.08 40 0.0001

Sprays with GroundBoom Equipment [4, AHETF] 

Baseline 0.34 Fruiting 

Vegetables 

0.02 80 0.0000

Mixer/Loader/Applicator 

Sprays with ManuallyPressurized Handwand [5, PHED] 

Baseline 30 Fruiting 

Vegetables 0.0004 lb ai/gal 

40 gal 0.000

1. Baseline Inhalation Exposure represents no respiratory protection, open mixing/loading, and open cab tractors, as appropriate. 2. Daily acres treated values are from EPA estimates of acreage that could be treated or volume handled in a single day for each exposu

based on the application method and formulation/packaging type. 

3. Daily Inhalation Dose (mg/kg/day) = [unit exposure (μg/lb ai) * (1mg/1000 μg) conversion * application rate (lb ai/acre or lb ai/gal) 

used /day] / body weight (80 kg). 

4. Inhalation MOE = NOAEL (11 mg/kg/day) / Daily inhalation dose (mg/kg/day). 
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9.2 Short- and Intermediate-Term Post-Application Exposure and Risk

9.2.1 Dermal Post-Application Risk 

Dermal post-application exposure was not assessed due to the lack of toxicity via the dermal 

route. There is no dermal risk associated with post-application activities following application of 

kasugamcyin on the proposed crops. The Restricted Entry Interval (REI) is based on the acute 

toxicity of kasugamycin technical material, which is classified in acute Toxicity Categories III 

and IV. Acute Category III or IV chemicals require a 12-hour REI. Thus, the 12-hour REI that 

appears on the labels is adequate. 

9.2.2 Inhalation Post-Application Risk 

Based on the Agency's current practices, a quantitative post-application inhalation exposure 

assessment was not performed for kasugamycin at this time, primarily because it has a low vapor 

pressure (vapor pressure <0.013 mpa at 25oC), and it is applied at low application rates. 

However, volatilization of pesticides may be a potential source of post-application inhalation 

exposure to individuals nearby to pesticide applications. The Agency sought expert advice and 

input on issues related to volatilization of pesticides from its Federal Insecticide, Fungicide, and 

Rodenticide Act Scientific Advisory Panel (SAP) in December 2009. The Agency received the 

SAP’s final report on 2 March 2010 

(http://www.epa.gov/scipoly/SAP/meetings/2009/120109meeting.html). Although a quantitative 

occupational post-application inhalation exposure assessment was not performed, an inhalation 

exposure assessment was performed for occupational handlers. This assessment resulted in risk 

estimates that did not exceed HED’s LOC at baseline inhalation PPE. Handler exposure 

resulting from application of pesticides outdoors is likely to result in higher exposure than postapplication exposure. Therefore, it is expected that these handler inhalation exposure estimates 

would be protective of most occupational post-application inhalation exposure scenarios. 

10.0 References

Risk Assessment Memorandum

Kasugamycin. Human Health Risk Assessment for Proposed Food Uses of the Fungicide 

Kasugamycin on Imported Fruiting Vegetables (Group 8).; D301735; W.T. Drew; 17 August 

2005. 

Residue Chemistry Summary Document Memorandum 

Kasugamycin. Petition to Establish Permanent Tolerances for Residues of the Fungicide 

Resulting from Food Use on Fruiting Vegetables, Pome Fruit, and Walnuts (PP#0F7689). 

Summary of Analytical Chemistry and Residue Data.; D376563; W.T. Drew; 13 July 2012. 
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Occupational and Residential Exposure Assessment Memorandum 

Kasugamycin: Occupational and Residential Exposure/Risk Assessment for Section 3 

Registration on Pome Fruit, Walnuts, and on Fruiting Vegetables; D376591; S.C. Wang; 26 

June 2012. 

Dietary Exposure Memorandum

Kasugamycin. Chronic Aggregate Dietary (Food and Drinking Water) Exposure and Risk 

Assessment for the Section 3 Registration Action Associated with Food/Feed Use of the 

Fungicide on Fruiting Vegetables, Pome Fruit, and Walnuts (PP#0F7689).; D390458; W.T. 

Drew; 13 July 2012. 

Drinking Water Assessment Memorandum 

Drinking Water Assessment for Tolerance Petition for New Chemical Kasugamycin [EPA Est 

No. 075703-JPN-001]; D376600; T. Dowen, J. Hetrick, Dana Spatz; 28 April 2011. 

ROCKS Decision Memorandum 

Kasugamycin. Report of the Residues of Concern Knowledgebase Subcommittee (ROCKS).; 

D387527; I. Negrón-Encarnación; 4 May 2011. 
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APPENDIX A: Toxicology Profile and Executive Summaries 

A.1 Toxicology Data Requirements

The requirements (40CFR §158.340) for food use of kasugamycin are shown in Table A.1, 

below. Use of the new guideline numbers does not imply that the new (1998) guideline 

protocols were used. 

TABLE A.1 Toxicology Data Requirements for Kasugamycin, Technical. 

Test Required Satisfied

870.1100 Acute Oral Toxicity..................................................... 

870.1200 Acute Dermal Toxicity ................................................ 

870.1300 Acute Inhalation Toxicity ........................................... 

870.2400 Primary Eye Irritation ................................................. 

870.2500 Primary Dermal Irritation ............................................ 

870.2600 Dermal Sensitization ................................................... 

yes 

yes 

yes 

yes 

yes 

yes 

yes1

yes1

yes 

yes 

yes 

yes 

870.3100 Oral Subchronic (rodent) ............................................. 

870.3150 Oral Subchronic (nonrodent) ....................................... 

870.3200 21-Day Dermal ............................................................ 

870.3250 90-Day Dermal ............................................................ 

870.3465 28-Day Inhalation........................................................ 

yes 

yes 

yes 

no 

no2 

yes 

yes 

yes 

-- 

-- 

870.3700a Developmental Toxicity (rodent) ................................ 

870.3700b Developmental Toxicity (nonrodent) .......................... 

870.3800 Reproduction .............................................................. 

yes 

yes 

yes 

yes 

yes 

yes 

870.4100a Chronic Toxicity (rodent) ........................................... 

870.4100b Chronic Toxicity (nonrodent) ...................................... 

870.4200a Oncogenicity (rat) ....................................................... 

870.4200b Oncogenicity (mouse) ................................................. 

870.4300 Chronic/Oncogenicity ................................................. 

yes 

yes 

yes 

yes 

yes 

yes3

yes3

yes 

yes 

yes 

870.5100 Mutagenicity—Gene Mutation - bacterial .................. 

870.5300 Mutagenicity—Gene Mutation - mammalian ............. 

870.5375 Mutagenicity—Structural Chromosomal Aberrations. 

870.5550 Mutagenicity—Other Genotoxic Effects ..................... 

yes 

yes 

yes 

yes 

yes 

yes 

yes 

yes 

870.6100a Acute Delayed Neurotoxicity (hen) ............................ 

870.6100b 90-Day Neurotoxicity (hen) ........................................ 

870.6200a Acute Neurotoxicity Screening Battery (rat) ............... 

870.6200b 90-Day Neurotoxicity Screening Battery (rat) ............ 

870.6300 Develop. Neurotoxicity ............................................... 

no 

no 

yes 

yes 

no 

-- 

-- 

yes 

yes 

-- 

870.7485 General Metabolism .................................................... 

870.7600 Dermal Penetration ...................................................... 

yes 

no 

yes 

no 

870.7800 Immunotoxicity Series................................................... yes yes 
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TABLE A.1 Toxicology Data Requirements for Kasugamycin, Technical. 

Test Required Satisfied

Special Studies for Ocular Effects 

Acute Oral (rat) ........................................................... 

Subchronic Oral (rat) .................................................. 

Six-month Oral (dog) .................................................. 

 no 

 no 

 no 

-- 

-- 

-- 

1. Test material purity for the material used in these studies not provided in report, but was reported in a different 

study. 

2. Study waived by HED, based on low acute toxicity, exposure potential, and high MOEs (HASPOC memo, TXR 

#0052461). 

3. Satisfied by OCSPP Toxicity Test Guideline 870.4300. 

A.2 Toxicity Profiles for Kasugamycin

TABLE A.2.1 Acute Toxicity Profile for Kasugamycin Technical Product. 

Test Material1

[% ai] 

Guideline 

Number 

Study Type MRID 

Number 

Results Toxicity 

Category 

Technical 

product [81] 

870.1100 Acute oral - rat 45910012 LD50 (♂+♀) > 5000 mg/kg IV2

Technical 

product [81] 

870.1200 Acute dermal-rat 47945757 LD50 (♂+♀) > 2000 mg/kg III2

Technical 

product [84.8] 

870.1300 Acute inhalation - rat 47945758 LC50 (♂+♀) > 4.892 mg/L IV 

Technical 

product [84.8] 

870.2400 Acute eye irritation - 

rabbit 

47945759 Mild eye irritant (iritis at 1 

hour, resolving by 24 hours; 

conjunctivitis at 1 hour, 

resolving by 24 hours). 

III 

Technical 

product [84.8] 

870.2500 Acute dermal 

irritation - rabbit 

47945760 Not irritating to the skin. III 

Technical 

product [84.8] 

870.2600 Skin sensitization - 

guinea pig 

47945761 Not a sensitizer under the 

conditions of this study. 

Not 

applicable. 

1. Technical product Lot #KP-913 contains 81%, and Lot #KP-459 contains 84.8% kasugamycin hydrochloride 

hydrate. Not adjusted for the free acid. 

2. Studies considered “supplementary/upgradable” due to lack of information on purity and characterization of test 

material. However, a stated purity of 81% for kasugamycin technical product Lot #KP-913 was located in 

other studies. 
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TABLE A.2.2 Subchronic, Chronic and Other Toxicity Profile for Kasugamycin. 

Guideline 

Number 

Study Type/ 

Classification

MRID 

Number 

Doses Results 

870.3100 90-Day oral toxicity 

rodents - rat 

Acceptable/guideline

45910020 0, 300, 1000, 3000, 6000 

ppm 

M: 0, 17.5, 58.2, 176.7, 

354.8 mg/kg/day 

F: 0, 20.3, 69.2, 201.0, 

395.5 mg/kg/day 

NOAEL = 176.7/201.0 mg/kg/day 

(M/F) 

LOAEL = 354.8/395.5 mg/kg/day 

(M/F) based on decreased body 

weights and body weight gains and 

kidney effects in females (increased 

urinary pH and epithelial cells in 

urine). Slight lipofuscin deposition 

in the proximal tubule cells were 

observed at ≥1000 ppm in males but 

were not considered adverse). 

870.3100 90-Day oral toxicity 

rodents - mouse 

Acceptable/guideline

45910019 0, 300, 1000, 3000, 10000 

ppm 

M: 0, 41.2, 135.4, 408.5, 

1559 mg/kg/day 

F: 0, 58.0, 170.9, 565.6, 

1834 mg/kg/day 

NOAEL = 135.4/170.9 mg/kg/day 

(M/F) 

LOAEL = 408.5/565.6 mg/kg/day 

(M/F) based on increased mortality 

and anal lesions (M&F), and kidney 

lesions (F). 

At 1559/1834 mg/kg/day (M/F), 

decreased body weights and body 

weight gains (M&F), testicular 

tubular dilatation and degeneration, 

perianal/perigenital staining (F), and 

extramedullary hematopoiesis of the 

spleen (M) were seen. 

870.3150 90-Day oral toxicity 

in nonrodents - dog 

Acceptable/guideline

46030302 0, 300, 3000, 

6000/0/4500* ppm 

M: 0, 10.6, 106.0, 182 

mg/kg/day 

F: 0, 11.4, 107.9, 179 

mg/kg/day 

* The high-dose group 

was exposed to 6000 ppm 

on weeks 1-5, control diet 

on weeks 6-8, and 4500 

ppm on weeks 8-13. 

NOAEL = 10.6/11.4 mg/kg/day 

(M/F) 

LOAEL = 106.0/107.9 mg/kg/day 

(M/F) based on tongue lesions, few 

feces, swollen mouth, excessive 

salivation, and thickened skin at the 

commissure of the mouth. 

At 182/170 mg/kg/day (M/F), 

decreased body weights, body 

weight gains, and food consumption 

were seen. 
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TABLE A.2.2 Subchronic, Chronic and Other Toxicity Profile for Kasugamycin. 

Guideline 

Number 

Study Type/ 

Classification

MRID 

Number 

Doses Results 

870.3200 21-Day dermal 

toxicity – rat 

Acceptable/guideline

47945762 M: 0, 50, 250 or 500 

mg/kg/day 

F: 0, 50, 250/100 or 

500/200 mg/kg/day, 

applied to the shaved 

skin; highest two dose 

levels were decreased 

beginning on Day 8. 

Systemic 

NOAEL ≥ 500 mg/kg/day (M), ≥

500/200 mg/kg/day (F). 

 LOAEL - not determined. No 

effects observed at the highest dose 

tested. 

Dermal 

NOAEL = 250 mg/kg/day (M), 

250/100 mg/kg/day (F). 

 LOAEL = 500 mg/kg/day (M), 

500/200 mg/kg/day (F), based on 

erythema, edema, eschar, ulceration, 

scabbing; microscopic findings of 

acanthosis, inflammation, and 

ulceration. 

870.3250 90-Day dermal 

toxicity 

Not required. 

870.3465 90-Day inhalation 

toxicity 

Not required. 

870.3700 Pre-natal 

developmental in 

rodents - rat 

Acceptable/guideline

45910022 0, 40, 200, 1000 

mg/kg/day 

Maternal 

NOAEL = 200 mg/kg/day 

LOAEL = 1000 mg/kg/day 

based on decreased body weights, 

body weight gains, and food 

consumption; increased incidence of 

loose stool; distention of the large 

intestine with stool in the cecum. 

Developmental 

NOAEL = 1000 mg/kg/day 

LOAEL = >1000 mg/kg/day 
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TABLE A.2.2 Subchronic, Chronic and Other Toxicity Profile for Kasugamycin. 

Guideline 

Number 

Study Type/ 

Classification

MRID 

Number 

Doses Results 

870.3700 Pre-natal 

developmental in 

nonrodents - rabbit 

Acceptable/guideline

46030303 

(main 

study) 

46428701 

(rangefinding 

study) 

0, 1, 3, 10 mg/kg/day 

(Main study) 

Range finding study: 

0, 10, 30, 100 mg/kg/day 

Initial range finding study 

0, 250, 500, 1000 – all 

doses of kasugamycin 

resulted in severe 

maternal toxicity and 

euthanasia. 

Maternal 

NOAEL = 10 mg/kg/day 

LOAEL = 30 mg/kg/day, based on 

the range-finding study results of 

maternal weight loss and decreased 

food consumption during treatment , 

abortion (1/4) on GD 22. 

At 100 mg/kg/day – weight loss, 

abortions in 3 of 4 females, GD 18-

27. 

Developmental 

NOAEL = 10 mg/kg/day

LOAEL = 30 mg/kg/day (rangefinding study) based on decreased 

mean fetal body weight 

870.3800 Reproduction and 

fertility effects - rat 

Acceptable/guideline

45910023 0, 200, 1000, 6000 ppm 

M: 0, 13.7, 70.3, 425.3 

mg/kg/day 

F: 0, 16.2, 82.9, 503.4 

mg/kg/day 

Parental/Systemic 

NOAEL = 70.3/82.9 mg/kg/day 

(M/F) 

LOAEL = 425.3/503.4 mg/kg/day 

(M/F), based on decreased body 

weights and body weight gains in P 

males, and red and swollen skin 

around the anal opening (M&F) (P 

and F1 animals). 

Reproductive 

NOAEL = 70.3/82.9 mg/kg/day 

(M/F) 

LOAEL = 425.3/503.4 mg/kg/day 

(M/F) based on testicular 

atrophy/degeneration in F1 males, 

decreased fertility and fecundity in 

the F1 parents for both litters and 

increased pre-coital interval during 

the mating period for the F2 litter. 

Offspring 

NOAEL = 425.3/503.4 mg/kg/day 

(M/F) 

LOAEL = >425.3/503.4 mg/kg/day 

(M/F) 

870.4100 Chronic toxicity - 

rodents 

 See 870.4300. This study includes 

requirements of both 870.4100 and 

870.4200. 
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TABLE A.2.2 Subchronic, Chronic and Other Toxicity Profile for Kasugamycin. 

Guideline 

Number 

Study Type/ 

Classification

MRID 

Number 

Doses Results 

870.4100 Chronic toxicity - 

dog 

Acceptable/guideline

46185901 0, 300, 1000, 3000 ppm 

M: 0, 10.5, 30.5, 99.6 

mg/kg/day 

F: 0, 9.4, 33.4, 103.6 

mg/kg/day 

NOAEL = 99.6/103.6 mg/kg/day 

(M/F) 

LOAEL = >99.6/103.6 mg/kg/day 

(M/F) 

870.4200 Carcinogenicity - rat See 870.4300. This study includes requirements of both 870.4100 and 

870.4200. 

870.4200 Carcinogenicity - 

mouse 

Acceptable/guideline

46030304 0, 50, 300, 1500 ppm 

M: 0, 5.93, 34.94, 186.3 

mg/kg/day 

F: 0, 7.25, 42.29, 215.2 

mg/kg/day 

NOAEL = 186.3/215.2 mg/kg/day 

(M/F) 

LOAEL = >186.3/215.2 mg/kg/day 

(M/F)

No evidence of carcinogenicity

870.4300 Combined chronic 

toxicity/ 

carcinogenicity - rat 

Acceptable/guideline

45910024 0, 30, 300, 3000 ppm 

M: 0, 1.1, 11.3, 116 

mg/kg/day 

F: 0, 1.4, 13.4, 140 

 mg/kg/day 

NOAEL = 11.3/140 mg/kg/day 

(M/F) 

LOAEL = 116/>140 mg/kg/day 

(M/F) based on increased testicular 

softening and atrophy in males. 

No evidence of carcinogenicity

870.5100 Gene mutation - 

bacterial reverse 

mutation assay 

Unacceptable/ 

upgradable

45910028 0, 5, 10, 50, 100, 500 

μg/plate, with or without 

S9 activation for 

Salmonella typhimurium

strain G46 (his-

). 

0, 5, 10, 50, 100, 200 

μg/plate, with or without 

S9 activation for all other 

strains tested. 

No mutagenic activity in bacteria 

(Salmonella typhimurium and

Escherichia coli) under conditions of 

this assay. 

Not tested up to the limit dose, no 

indication of cytotoxicity, and no 

defined limit of solubility. 

870.5100 Gene mutation - 

bacterial reverse 

mutation assay 

Acceptable/guideline 

47945764 0, 1.5, 5.0, 15, 50, 150, 

500, 1500 or 5000 

μg/plate, in the presence 

or absence of S9 

activation for Salmonella 

typhimuriumstrains 

TA98, TA100, TA1535 

and TA1537, and for 

Escherichia coli strain 

WP2 uvrA. 

No mutagenic activity in bacteria 

(Salmonella typhimurium and

Escherichia coli) under conditions of 

this assay. 
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TABLE A.2.2 Subchronic, Chronic and Other Toxicity Profile for Kasugamycin. 

Guideline 

Number 

Study Type/ 

Classification

MRID 

Number 

Doses Results 

870.5300 Cytogenetics - in 

vitro mammalian cell 

gene mutation test 

(CHO Cells) 

Acceptable/guideline

45910026 0, 0.5, 1, 2, 4, 6, 8, 10 

mg/ml 

No increase in mutant frequency at 

the HGPRT locus, in the presence or 

absence of S9 activation. 

870.5375 Cytogenetics - in 

vitro mammalian cell 

chromosome 

aberration test (CHO 

Cells) 

Unacceptable/not 

upgradable

45910025 0, 1, 2, 3, 4, 5 mg/ml No increase in mutant frequency, in 

the presence or absence of S9 

activation. 

The time from treatment to cell 

harvest was insufficient. 

870.5375 Cytogenetics - in 

vitro mammalian cell 

chromosome 

aberration test (CHO 

cells) 

Acceptable/guideline

47945765 0, 1085, 2170 or 4340 

μg/ml, with or without S9 

activation. 

No increase in mutant frequency, in 

the presence or absence of S9 

activation. 

870.5395 Cytogenetics - 

mammalian 

erythrocyte 

micronucleus test, 

mice 

Acceptable/guideline

46030305 0, 200, 1000, 5000 

mg/kg, with or without S9 

activation. 

No evidence of induced 

chromosomal damage or other 

damage leading to micronucleus 

formation. 

870.5550 Other effects - 

unscheduled DNA 

synthesis in cultured 

mammalian cells, 

HeLa S3 cells 

Acceptable/guideline

45910027 First assay: 0-2.5 mg/ml 

Second assay: 0-10 

mg/ml 

Third assay: 0-10 mg/ml, 

both assays with or 

without S9 activation.

No evidence that unscheduled DNA 

synthesis was induced. 

870.6200a Acute neurotoxicity 

screening battery - 

rat 

(dose range-finding 

study) 

Acceptable 

/nonguideline (rangefinding study) 

47945766 0, 500, 1000 or 2000 

mg/kg by gavage 

NOAEL = 2000 mg/kg 

LOAEL not determined. No 

systemic or neurotoxic effects were 

observed at the highest dose tested. 
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TABLE A.2.2 Subchronic, Chronic and Other Toxicity Profile for Kasugamycin. 

Guideline 

Number 

Study Type/ 

Classification

MRID 

Number 

Doses Results 

870.6200a Acute neurotoxicity 

screening battery - 

rat 

Acceptable/guideline

47945767 0, 500, 1000 or 2000 

mg/kg by gavage 

NOAEL = 2000 mg/kg 

LOAEL not determined. No 

systemic or neurotoxic effects were 

observed at the highest dose tested. 

870.6200b 90-day neurotoxicity 

screening battery - 

rat 

Acceptable/guideline

47945768 0, 300, 3000 or 6000 ppm 

in the diet 

M: 0, 21, 210 or 439 

mg/kg/day, males; 

F: 0, 23, 238 or 486 

mg/kg/day, females 

Systemic 

NOAEL = 210/238 mg/kg/day 

(M/F) 

 LOAEL = 439/486 mg/kg/day 

(M/F), based on decreased body 

weight and body weight gain. 

Neurotoxicity 

NOAEL ≥ 439/486 mg/kg/day. 

LOAEL not determined. No 

neurotoxic effects were observed at 

the highest dose tested. 
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TABLE A.2.2 Subchronic, Chronic and Other Toxicity Profile for Kasugamycin. 

Guideline 

Number 

Study Type/ 

Classification

MRID 

Number 

Doses Results 

870.7485 Metabolism and 

pharmacokinetics - 

rat 

Acceptable/guideline

46030306 (1) 100 mg/kg 

radiolabeled, single dose 

by oral gavage. 

(2) 100 mg/kg unlabeled, 

14 days in the diet, PLUS 

100 mg/kg radiolabeled, 

single dose by oral 

gavage. 

(3) 1000 mg/kg 

radiolabeled, single dose 

by oral gavage. 

(4) 1000 mg/kg 

unlabeled, 14 days in the 

diet, PLUS 1000 mg/kg 

radiolabeled, single dose 

by oral gavage. 

The mean radioactivity recovery 168 

hours after exposure ranged between 

90.6-96.7%, with the majority of the 

dose recovered within 48 hours in 

the feces (81.9-93.9%) and urine 

(1.26-3.07%). The maximum 

concentration found in the plasma of 

both males and females occurred 

approximately one hour after the 

administration of a single low or 

high dose. Between one and six 

hours after a single low or high dose, 

more kasugamycin accumulated in 

the kidneys, urinary bladder, and 

lymph nodes than in the blood, but 

after 168 hours, little or no 

kasugamycin was found in these 

tissues. The absorption and 

metabolism of kasugamycin in rats 

was limited (<5% dose) and was not 

affected by sex, dose level, or 

duration of dosing. Parent 

compound was the major component 

identified in the urine, feces, liver, 

kidney, and plasma. Minor amounts 

(<1% dose) of the metabolite 

kasuganobiosamine were identified 

in urine, liver, kidney, and plasma, 

but none was detected in the feces. 

Elimination occurred primarily in the 

feces (87.7-94.5%); however, 

kasugamycin was not excreted in the 

bile (enterohepatic circulation did 

not occur). 
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TABLE A.2.2 Subchronic, Chronic and Other Toxicity Profile for Kasugamycin. 

Guideline 

Number 

Study Type/ 

Classification

MRID 

Number 

Doses Results 

870.7800 Immunotoxicity - 

female mice 

Acceptable/guideline

48132601 0, 300, 3000 or 

10,000/7000 ppm in the 

diet for 28 days 

AFC group: 0, 70, 755 

or 2468 mg/kg/day; 

NK group: 0, 68, 691 or 

2531 mg/kg/day (high 

dose reduced to 7000 

ppm on Day 16)

Systemic 

NOAEL = 755/691 mg/kg/day (AFC 

group/NK group) 

 LOAEL = 2468/2531 mg/kg/day 

(AFC group/NK group), based on 

clinical observations, decreased 

mean body weights and decreased 

hematological parameters. 

Immunotoxicity 

NOAEL ≥ 2468/2531 mg/kg/day 

(AFC group/NK group) 

LOAEL not determined. A 

significant decrease (p≤0.05) in Total 

Spleen Activity (AFC/spleen) was 

only observed at a dose causing 

excessive toxicity (HDT) and that 

exceeded the limit dose. 

A.3 Hazard Identification and Endpoint Selection

A.3.1 Acute Reference Dose (aRfD) - All Populations (Including Infants and Children, 

and Females Age 13-49)

An acute reference dose was not selected because an appropriate endpoint resulting from a single 

exposure was not identified. No maternal or developmental effects were observed in the rabbit 

developmental toxicity study up to 10 mg/kg/day. In the dose range-finding study for the rabbit 

developmental toxicity study, maternal weight loss was observed at 30 mg/kg/day during dosing, 

along with decreased food consumption, but is not considered an acute effect. An abortion in 

one female at 30 mg/kg/day occurred following the weight loss on GD 22, and was therefore not 

considered a single-dose effect. Abortions at 100 mg/kg/day occurred on GD 18 or later 

following weight loss. No effects were observed in the rat acute neurotoxicity screening study, 

which tested up to a limit dose of 2000 mg/kg. 

A.3.2 Chronic Reference Dose (cRfD) 

Study selected: Combined chronic toxicity/carcinogenicity in the rat (oral). 

MRID numbers: 45910024 

Dose and endpoint for risk assessment: NOAEL = 11.3 mg/kg/day, based on testicular atrophy 

and softening in male rats at the LOAEL of 116 mg/kg/day. 
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Chronic RfD = 11 mg/kg/day (NOAEL) = 0.11 mg/kg/day 

 100 (UF) 

Comments about study/endpoint/uncertainty factors: The rat chronic toxicity/carcinogenicity 

study was selected for the cRfD because it was of the appropriate route and duration and is 

protective of effects seen in other studies. Although the testicular findings were not statistically 

significant compared to controls, these effects were selected as the basis for the study LOAEL 

because the incidence and severity were increased, and similar degenerative testicular effects 

were seen across species. 

Selection of this endpoint is supported by the rat two-generation reproductive toxicity study, in 

which a comparable parental NOAEL of 13.7 mg/kg/day was observed. The parental LOAEL is 

70.3 mg/kg/day, based on statistically significant decreased body weights/weight gains in P 

generation males, but no offspring toxicity was observed. Testicular atrophy, along with reduced 

male and female fertility and fecundity indices and increased precoital interval for the mating to 

produce the F2b litter, were observed at 425.3/503.4 mg/kg/day (M/F). 

The selected endpoint is also protective of maternal and developmental toxicity (weight loss and 

decreased food consumption during dosing, abortion in one female, decreased fetal weight) that 

was seen in the rabbit developmental toxicity range-finding study. No developmental toxicity 

was seen in the rat and maternal toxicity was seen at 1000 mg/kg/day (200 mg/kg/day). 

A.3.3 Incidental Oral Exposure (Short- and Intermediate-Term) 

An endpoint for incidental oral exposure was not selected because there are no proposed or 

existing residential uses for kasugamycin. 

A.3.4 Dermal Exposure (Short- and Intermediate-Term) 

A short- and intermediate-term dermal exposure assessment is not required because an 

appropriate endpoint was not identified. No systemic toxicity was observed in the rat 21-day 

dermal toxicity study at doses that caused local dermal irritation by one week of exposure. The 

selected dose and endpoint are protective of other endpoints of concern (decreased body weight, 

testicular or renal toxicity, gastrointestinal or oral cavity effects) because they were evaluated in 

the dermal study and there are no concerns for developmental susceptibility. 

A.3.5 Dermal Exposure (Long-Term) 

A long-term dermal occupational risk assessment is not required because long-term dermal 

exposure is not anticipated from the proposed uses. 

A.3.6 Occupational Inhalation Exposure, Short-Term (1 to 30 Days) and Intermediate-
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Term (1 to 6 Months)

Studies selected: Co-critical subchronic toxicity study in dogs (oral) and developmental toxicity 

study in rabbits (oral) and its range-finding study. 

MRID numbers: 46060302, dog subchronic study (lead study); 46030303, main study, and 

46428701, range-finding study, rabbit developmental study. 

Dose and endpoint for risk assessment: NOAEL = 11 mg/kg/day from the dog subchronic 

toxicity study, based on swollen mouth, tongue lesions, excessive salivation, thickened skin at 

the commissures of the mouth and few feces. Supported by the maternal toxicity NOAEL of 10 

mg/kg/day (main study HDT) from the rabbit developmental toxicity study, based on maternal 

weight loss and decreased food consumption during dosing, abortion (GD 22) and decreased 

fetal weight at 30 mg/kg/day in the rabbit range-finding study. 

Comments about study/endpoint/uncertainty factors: Since an inhalation toxicity study was not 

available, oral toxicity studies were used to select a dose and endpoint. The selected doses and 

endpoints are the most sensitive identified for subchronic exposure to kasugamycin. The studies 

are of the appropriate duration for short- and intermediate-term exposure, and are protective of 

potential developmental toxicity. These studies were selected to be protective of potential effects 

to the respiratory tract as well as systemic toxicity, since kasugamycin shows evidence of 

irritation to the oral cavity and the gastrointestinal mucosa, as well as the skin (as seen in the rat 

21-day dermal study). In the subchronic dog study, lesions of the oral cavity and tongue were 

considered portal of entry irritation effects. In the developmental rat study and the 

developmental range-finding study in the rabbit, gas distension of the stomach, large intestine, or 

cecum were observed; rabbits were more sensitive than rats. Kasugamycin is poorly absorbed 

and metabolized, and is excreted primarily in the feces as unchanged parent compound: the GI 

tract findings in these studies may therefore reflect the presence of irritation by the unabsorbed 

test material. A 28- or 90-day inhalation toxicity study is not required, based on low use rate and 

anticipated inhalation exposure, low acute inhalation toxicity, low vapor pressure, and lack of 

persistence of kasugamycin in the environment: exposure via volatilization is expected to be low. 

An additional uncertainty factor for lack of inhalation toxicity data (UFDB) is therefore not 

needed. In the absence of inhalation data, inhalation toxicity is assumed to be equivalent to oral 

study for the purpose of route-to-route extrapolation. 

A.3.7 Inhalation Exposure (Long-Term)

A long-term inhalation occupational risk assessment is not required because long-term inhalation 

exposure is not anticipated from the proposed or existing uses. 

A.4 Executive Summaries (Studies Submitted since Previous Assessments) 

A.4.1 Subchronic Toxicity
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870.3100 90-Day Dietary Toxicity – Rat (updated summary)

In a 90-day oral toxicity study (MRID #45910020), kasugamycin hydrochloride hydrate (64.5% 

ai; Lot #KP-834) was administered to 12 Wistar rats/sex/dose in the diet at dose levels of 0, 300, 

1000, 3000, or 6000 ppm (equivalent to 0/0, 17.5/20.3, 58.2/69.2, 176.7/201.0, and 354.8/395.5 

mg/kg bw/day in males/females, respectively). It was assumed, based on dose formulation 

concentration analyses, that the doses were adjusted for compound purity; however, this was not 

stated explicitly. 

No treatment-related effects were observed on mortality, clinical signs, food consumption, food 

efficiency, water consumption, ophthalmoscopic examination, hematology, clinical chemistry, 

organ weights, or macroscopic pathology. 

There were indications of a slight systemic toxicity at 6000 ppm. At this dose, male body 

weights were significantly lower (4-9%) than controls (p0.05) each week starting on Week 2 

until sacrifice, resulting in an 11% decrease in overall (Weeks 0-13) body weight gain. In the 

6000 ppm females, body weights were significantly lower (5%) than controls (p0.05) only on 

Week 6; however, non-significant decreases in body weight gain were observed throughout the 

study, resulting in a decrease of 8% in overall body weight gain. Although not considered 

treatment-related, significant (p0.05) decreases in food consumption were seen in both sexes 

during the first week of dosing, indicating a possible palatability issue; average food 

consumption (Weeks 0-13) was non-significantly decreased by 4-6% in 6000 ppm males and 

females. An increased (p0.05) number of epithelial cells in the urinary sediment were observed 

in females. Urine pH was decreased in both sexes (p0.05) at 6000 ppm and also in females at 

3000 ppm; this is possibly due to the acidic properties of the test compound. The urinalysis 

findings in females at 6000 ppm were considered evidence of possible urinary tract toxicity. 

Microscopically, at 6000 ppm in males, increased (p0.01) incidences of eosinophilic bodies in 

the kidney proximal tubular cells (slight severity) were observed (11/12 treated vs. 0/12 controls, 

p0.01). These lesions were also found in the 1000 and 3000 ppm males (7/11 and 11/12, 

p0.01). Foam cell aggregation in lungs of females (all of slight severity except 1 treated of 

moderate severity, 10/12 treated vs. 3/12 controls, p0.01) were also reported. While related to 

treatment, the increased incidence of both of these effects was not considered biologically 

significant due to the low severity and lack of associated adverse findings. 

No adverse effects were observed at doses equal to or lower than 3000 ppm. Although an 

apparent decrease in water consumption was seen in the 3000 ppm males, mean water 

consumption data was based on individual cage values, and no baseline water consumption 

measurements were taken prior to dosing. Therefore, there is not enough information to make a 

definitive evaluation of a treatment-related effect on male water consumption. Decreases in 

hematocrit, hemoglobin, and erythrocyte counts at 3000 and 6000 ppm were minor and not 

considered biologically significant. The increased incidences of increased eosinophilic bodies 
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(of slight severity) in the kidneys in males at ≥1000 ppm and foam cell aggregation (slight) in the 

lungs in the females at ≥1000 ppm were considered treatment-related but not toxicologically 

significant due to their low severity grade and lack of associated findings. This conclusion is 

supported by the rat combined chronic toxicity/carcinogenicity study (MRID #45910024). At 

3000 ppm, the highest dose tested, an increased incidence of slight to moderate lipofuscin 

deposition was observed in kidney proximal tubule cells, with no evidence of alterations to 

urinalysis/clinical chemistry parameters, kidney weight, or other kidney histopathology. Foam 

cell accumulation in lungs of males and females was also observed at 3000 ppm with no apparent 

adverse consequences. 

The LOAEL is 6000 ppm (equivalent to 354.8/395.5 mg/kg/day in males/females), based on 

decreased body weights and body weight gains in both sexes, and on urinalysis findings in 

females suggesting toxicity to the kidney. The NOAEL is 3000 ppm (equivalent to 

176.7/201.0 mg/kg/day in males/females). 

This study is classified acceptable/guideline and satisfies the guideline requirements for a 90-

day oral toxicity study (OPPTS 870.3100a; OECD 408) in the rat. 

870.3200 21-Day Dermal Toxicity - Rat

In a 21-day dermal toxicity study (MRID 47945762) in rats, kasugamycin technical (71.5% a.i., 

free base), Batch No. KMB 0808) was applied to the clipped skin of 10 animals/sex/dose. The 

test substance was applied at dose levels of 0 (vehicle control), 50, 250, or 500 mg/kg/day 

(males) and 0, 50, 250/100, or 500/200 mg/kg/day (females) over a 6-hour exposure period daily 

for 21 consecutive days. In females, because of severe dermal effects observed on Day 7, the 

dose levels in the 250 and 500 mg/kg/day test groups were reduced to 100 and 200 mg/kg/day, 

respectively, on Day 8 and for the remainder of the treatment period. 

Reddening and scabbing of the dose site were observed in both sexes in the mid- and high-dose 

groups beginning on Day 5 and Day 7 for females and males, respectively. These observations 

generally persisted in a dose-dependent manner throughout the treatment period. On Day 7, 40% 

and 90% of the females in the mid- and high-dose groups, respectively, had very slight to severe 

erythema and/or edema (dose-dependent) at the dose site; eschar and coriaceousness were 

observed in the high-dose group. Following reduction of the dose in the mid- and high-dose 

female groups, the frequency and severity of the dermal findings decreased in the mid-dose 

group, while the effects in the high-dose group varied in severity (increased, decreased, or were 

unchanged). On Day 7, 40% of the males in the high-dose group showed very slight to slight 

erythema and/or edema at the dose site. The frequency and severity of these observations were 

reported to increase over the course of the treatment; with 80% of the males showing very slight 

to severe erythema and/or edema by Day 21; eschar and encrustation also were observed in the 

high-dose group males by Day 21. Microscopic observations of treated skin showed 90% of the 

males and 70% of the females in the high-dose groups had acanthosis, acute inflammation and/or 

ulceration at the dose site at the end of the treatment period. No test-substance-related 
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microscopic findings were seen in either sex in the low- and mid- dose treatment groups. No 

macroscopic test substance-related dermal findings were reported for the low-dose groups. 

The LOAEL for dermal toxicity for kasugamycin technical (expressed as active ingredient) 

in rats is 500 mg/kg/day for males and 500/200 mg/kg/day for females, based on adverse 

dermal lesions at the dose site (erythema, edema, eschar, encrustation, ulceration, 

coriaceousness, and/or scabbing), with correlating microscopic findings (acanthosis, acute 

inflammation, ulceration and/or granulomatous inflammation) in both sexes. The NOAEL 

for dermal toxicity for kasugamycin technical (expressed as active ingredient) is 250 

mg/kg/day for males and 250/100 mg/kg/day for females. 

There were no effects on clinical observations or on mean body weight, food consumption, 

absolute and relative organ weights, hematological parameters, clinical chemistry, or urinalysis 

determinations in either sex at any dose level associated with exposure to kasugamycin technical. 

A few microscopic observations in animals in the high-dose groups (mild myeloid hyperplasia in 

the sternal and femoral bone marrow of one male, minimal lymphoid necrosis of the thymic 

cortex and minimal vacuolation of the adrenal cortex in one male, and minimal lymphoid 

necrosis in the thymus of 2 females) were considered to be secondary to dermal inflammation or 

stress responses to dose application and handling procedures, and not directly test substancerelated. Statistically significant differences in some hematological parameters in males were 

attributed to individual outlier values resulting from tissue inflammation or necrosis not 

associated with test substance treatment. A 5.4% decrease in the mean body weights of males in 

the high-dose group (not statistically significant) compared with controls was not considered to 

be treatment-related. There was over a 22% decrease in body weight gain in males and over a 

19% decrease in females at the highest dose tested. However the severe irritation at this dose 

lessens the biological significance of this finding. Three unscheduled mortalities occurred 

during the treatment period (one control male, one low-dose male, one mid-dose female); these 

deaths also were not considered to be treatment-related. 

The NOAEL for systemic effects for kasugamycin technical (expressed as active ingredient) 

is greater than 500 mg/kg/day for males and greater than 500/200 mg/kg/day for females, 

the highest tested doses, based on body weight, food consumption, absolute and relative 

organ weights, clinical observations, hematological parameters, clinical chemistry, and 

urinalysis determinations. A LOAEL for systemic effects could not be determined (i.e., 

greater than the highest tested doses). 

This 21-day dermal toxicity study in the rat is acceptable/guideline and satisfies the guideline 

requirement for a 21-day dermal toxicity study (OPPTS 870.3200) in rats. 

A.4.2 Developmental toxicity 

870.3700b Developmental Toxicity – Rabbit (updated summary)
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In a developmental toxicity study (MRID #46030303), kasugamycin hydrochloride hydrate 

(62.7% ai, Lot #KP-570) in distilled water was administered daily by oral gavage to 15 female 

New Zealand White rabbits/dose in a dose volume of 10 mL/kg at dose levels of 0, 1, 3, or 10 

mg/kg bw/day on GD 6 through 19. All surviving does were killed on GD 29; their fetuses were 

removed by cesarean section and examined. Dosing was based on the results of a range-finding 

study (MRID 46428701). Initially doses of 0, 250, 500 or 1000 mg/kg/day were administered to 

4 pregnant rabbits/dose group, but due to excessive maternal toxicity, additional groups were 

added at 0, 10, 30 and 100 mg/kg/day. 

Maternal toxicity: In the main study, there were no treatment-related effects on maternal 

mortality, clinical signs, body weight, food consumption or gross pathology. Although effects 

were not seen at the highest dose tested, a new developmental toxicity study in the rabbit is not 

required because treatment-related effects were seen at dose levels of 30 mg/kg/day and higher in 

the preliminary study. At 10 mg/kg/day, one female was sacrificed in extremis on GD 27 but 

gross examination at necropsy showed evidence of a gavage error. At 30 mg/kg/day, one female 

was found dead on GD 11, but this animal also showed evidence of gavage error. Decreased 

maternal body weight (up to 10% below controls) due to weight loss, primarily in the first week 

of dosing (from GD 6-14, control to high dose 0.11, 0.02, -0.08 and -0.38 kg, respectively) were 

observed. Food consumption was also lower during the early portion of treatment. One doe 

aborted on GD 22; this was considered secondary to the body weight effects. At 100 mg/kg/day, 

one female was sacrificed in extremis on GD 21 – this death was considered treatment-related, 

based on lack of evidence of gavage error at necropsy. Body weight loss was marked during 

dosing and 3 of 4 animals aborted on GD 18, 19 and 27, secondary to the weight effects. All 

animals administered doses of ≥250 mg/kg/day in the initial dosing groups were sacrificed on 

GD 14 to 16 due to sharply reduced food consumption (<10% of controls) and weight loss (body 

weight decreases exceeding 10% relative to GD 6 weights). Females that died or were sacrificed 

during the study showed fluid and gaseous distension of the gastrointestinal tract. The maternal 

toxicity LOAEL is 30 mg/kg/day, based on weight loss and decreased food consumption 

during dosing and an abortion following weight loss in the range-finding study. The 

maternal toxicity NOAEL is 10 mg/kg/day based on lack of effects in the main study and 

the range-finding study. 

Developmental toxicity: In the main study, there were no treatment-related effects on fetuses. In 

the range-finding study, at 30 mg/kg/day fetal mean body weight was reduced (15% below 

controls) in the two litters that were available for evaluation. Due to mortality and abortions at 

doses ≥100 mg/kg/day, no litters were available for examination. No treatment-related fetal 

abnormalities were reported. The developmental toxicity LOAEL is 30 mg/kg/day, based on 

decreased mean fetal weight in the range-finding study. The developmental NOAEL is 10 

mg/kg/day, based on lack of effects in the main study and the range-finding study. 

This study is classified acceptable/guideline and satisfies the guideline requirements for a 

developmental toxicity study (OPPTS 870.3700b; OECD 414) in the rabbit, when the main study 

is considered together with the range-finding study. 
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A.4.3 Reproductive toxicity 

870.3800 Reproductive Toxicity – Rat (updated summary)

In a two-generation reproduction toxicity study (MRID #45910023), kasugamycin hydrochloride 

hydrate (81% ai; Lot #KP-913) was administered continuously in the diet to Crl:CD®BR 

VAF/Plus® rats (25 rats/sex/dose) at dose levels of 0, 200, 1000, or 6000 ppm (equivalent to 0/0, 

13.7/16.2, 70.3/82.9, 425.3/503.4 mg/kg bw/day [M/F]). The P and F1 parents were dosed for 10 

weeks before they were mated to produce the F1 and F2a litters, respectively. The F1 pups were 

weaned on post-natal day (PND) 21, and 25 pups/sex/group (1 pup/sex/litter as nearly as 

possible) were randomly selected as parents of the F2 generation. Because of low fertility of the 

F1 parents during the production of the F2a litter, the F1 adults were paired again six days 

following weaning of the F2a litter to produce the F2b litter. F1 males that did not sire a litter in 

the first (F2a) mating were paired with proven females, and females that failed to deliver an F2a

litter were paired with proven males. 

In the P generation, 1000 ppm male body weights were decreased (-6 to -7%; p0.05) during 

Weeks 4 to 9 and Week 11, and 6000 ppm male body weights were decreased (-5 to -6%; 

p0.05) during Weeks 6 to 9. P generation cumulative body weight gains were decreased in the 

1000 ppm males for Weeks 3 to 9 (8%; p0.05) and in the 6000 ppm males for Weeks 3 to 14 

(11%; p0.05). In the F1 generation, cumulative body weight gains were decreased in the 6000 

ppm males (p0.05) during Weeks 1 to 3, 5 to 6, and 9 to 11 of the pre-mating period for the F2b

litter (28% below controls, week 0-11; p0.01). Based on the marginal body weight and weight 

gain decreases relative to controls (<10%) observed at 1000 ppm in only one parental generation, 

the decreases observed at this dose, although treatment-related, were not considered adverse. 

Red and swollen skin around the anal opening was observed exclusively in the 6000 ppm group 

in both sexes and in both generations. This clinical sign was first noted at Week 10 in the P 

males (16 to 28%) and P females (13 to 100%), and it was first seen at Week 5 in the F1 males (8 

to 75%) and F1 females (12 to 100%). Gross examination of the animals in this dose group 

revealed red foci/areas on the rectum in both sexes and both generations (80 to 100% treated vs 0 

controls), as well as thickened walls of the rectum in the F1 males (46% treated vs 0 controls). 

Microscopically, chronic active inflammation and ulceration of the rectum were observed in both 

sexes of both generations (88 to 100% treated vs 0 controls). Additionally, in the P males at this 

dose, squamous cell hyperplasia was observed at the ano-rectal junction (38% treated vs 0 

controls). 

At 6000 ppm, testes that were small (38%) and containing fluid (67%) were observed (compared 

to 0% of controls) in the F1 males at necropsy. Microscopically, atrophy/degeneration was noted 

in the testes in the P (12% treated vs 0% controls) and F1 (63% treated vs 0% controls) males. 

This atrophy/degeneration was marked to severe in the F1 generation and was characterized by 
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complete loss of the germinal epithelium, atrophy of the seminiferous tubules, persistence of 

Sertoli cells, and variable amounts of intertubular edema. Additionally in the 6000 ppm F1

males, pelvic dilatation of the kidney and chronic progressive nephropathy were observed 

microscopically (21% treated vs 4% controls). 

The LOAEL for parental toxicity is 6000 ppm (equivalent to 425.3/503.4 mg/kg/day [M/F]), 

based on decreased body weights and body weight gains in the P and F1 generation males, 

increased incidence of pelvic dilatation of the kidney and chronic progressive nephropathy 

in F1 males, and lesions of the anal opening in P and F1 animals of both sexes. The 

NOAEL is 1000 ppm (equivalent to 70.3/82.9 mg/kg/day [M/F]). 

In F1 female pups, adjusted body weights were decreased (-6%; p0.05) at 6000 ppm on PND 

21. This decrease was minor and occurred only at the end of the lactation period. Furthermore, 

there were no treatment-related effects on body weights in the F2a or F2b females or in the male 

pups of either generation at this dose. Thus, this decrease is not considered adverse. Pup 

weights at 1000 ppm in both sexes and generations were comparable to controls. 

It should be noted that several parameters were not examined in the offspring, including sexual 

maturation, developmental landmarks, organ weights, and histopathology. 

Based on the parameters investigated, the LOAEL for offspring toxicity was not observed. 

The NOAEL is 6000 ppm (equivalent to 425.3/503.4 mg/kg/day).

In the F1 generation, male and female fertility and fecundity indices were decreased at 6000 ppm 

for the F2a litter (64 to 67% treated vs 88 to 96% controls) and the F2b litter (36 to 39% treated vs

88 to 100% controls). Additionally, in the F1 generation, the pre-coital interval during the 

mating period to produce the F2b litter was longer (p0.01) at 6000 ppm (5.73 days) compared to 

controls (2.23 days). 

The LOAEL for reproductive toxicity was 6000 ppm (equivalent to 425.3/503.4 mg/kg/day 

[M/F]) based on testicular atrophy in P and F1 males, decreased fertility and fecundity in 

the F1 parents for both litters and increased pre-coital interval during the mating period 

for the F2 litter. The NOAEL is 1000 ppm (equivalent to 70.3/82.9 mg/kg/day [M/F]). 

This study is classified as acceptable/guideline and satisfies the Guideline requirements 

(OPPTS 870.3800; OECD 416) for a two-generation reproduction study in the rat. 
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A.4.4 Neurotoxicity 

870.6200a Acute Neurotoxicity Screening Study - Rat

In an acute neurotoxicity study (MRID # 47945767), Kasugamycin technical (purity 71.5% free 

base, Lot no. KMB-0808) was administered at doses of 0, 500, 1000 or 2000 mg/kg body weight 

dissolved in deionized water to Crl:CD(SD) rats (12 rats/sex/dose) by oral gavage. The dose 

volume was 10 mL/kg for all groups. All animals were observed twice daily for mortality and 

morbidity, clinical observation recorded daily and body weights recorded weekly. A functional 

observational battery (FOB) and locomotor activity evaluations were performed prior to 

exposure (pretest on Day -7), approximately 1 hour following dose administration (time to peak 

effect) on study Day 0, and on Days 7 and 14. At study termination, 6 animals/sex in the control 

and 2000 mg/kg groups were euthanized and perfused in situ for neuropathological evaluations. 

Brain weights and measurements were recorded for all animals and central and peripheral 

nervous system tissues were examined for microscopic changes. 

No deaths occurred in any of the four groups of animals, nor were there any Kasugamycinrelated effects on clinical condition, body weights or body weight gains. No test substance dose 

related effects were recorded in brain weights or brain dimensions in perfused animals. 

Functional observational battery (FOB) and total motor activity revealed no treatment-related 

effects in male and female rats at any dose levels of 500, 1000, and 2000 mg/kg on study Days 0, 

7, and 14. No dose related macroscopic finding were observed in male and female rats at 

necropsy. At 2000 mg/kg, no treatment-related histological changes were observed in the central 

or peripheral nervous system tissues. 

The results of the current study suggest that the NOAEL for neurotoxicity of Kasugamycin 

is 2000 mg/kg body weight in the rat. The LOAEL is not determined. 

This study is classified as acceptable and satisfies the guideline requirement (870.6200; OECD 

424) for neurotoxicity screening battery in rats. 

870.6200b Subchronic Neurotoxicity Screening Study - Rat

In a 90-day dietary neurotoxicity study (MRID # 47945768), Kasugamycin technical (purity 

71.5% free base, Lot no. KMB-0808) was administered continuously in the diet at doses of 0, 

300, 3000 or 6000 ppm to Crl:CD(SD) rats (12 rats/sex/dose) for at least 90 consecutive days 

(approximately 13 weeks). All animals were observed twice daily for mortality and morbidity. 

Clinical observations, body weights, and food consumption were recorded weekly. A functional 

observational battery (FOB) and locomotor activity evaluations were performed prior to 

exposure (pretest on study week -1) and during study weeks 1, 3, 7, and 12. At study termination, 

6 animals/sex in the control and 6000 ppm groups were euthanized and perfused in situ for 

neuropathological evaluations. Brain weights and dimensions were recorded for all animals and 
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central and peripheral nervous system tissues were examined for microscopic changes. 

No deaths occurred in any of the four groups of animals, nor were there any Kasugamycinrelated effects on clinical condition during the weekly detailed physical examinations. No testsubstance-related effects were apparent on mean male and female rats food consumption at any 

exposure levels. There was a significant (p<0.05 or p<0.01) reduction in mean male body 

weights in the 6000 ppm group during study weeks 2-13 whereas mean female body weights 

were significantly (p<0.05) reduced on study week 4 only compared to control group. In 

addition, mean body gains were significantly (p<0.01) reduced during study weeks 1-2, 3-4, and 

4-5 for the males and study week 3-4 for the females following Kasugamycin exposure. Mean 

body weights for the male rats in the 300 and 3000 ppm groups were consistently lower and 

showed an exposure related trend, however they were not statistically different from controls. 

The average calculated test substance consumption (intake) was 21, 210, and 439 mg/kg/day for 

males and was 23, 238, and 486 mg/kg/day for females. Functional observational battery (FOB) 

and mean ambulatory and total motor activity revealed no effects in male and female rats at any 

dose levels of 300, 3000, and 6000 ppm on study weeks 1, 3, 7, and 12. No test substance dose 

related effects were recorded in brain weights or brain dimensions in perfused animals. No dose 

related macroscopic finding were observed in male and female rats at necropsy. At 6000 ppm, no 

treatment-related histological changes were observed in the central or peripheral nervous system 

tissues. 

The results of the current study suggest that the NOAEL for subchronic toxicity of 

Kasugamycin is 3000 ppm for males (210 mg/kg body weight/day) and females (238 

mg/kg/day). The LOAEL is 6000 ppm, based on decreased body weight and body weight 

gain. The NOAEL for subchronic neurotoxicity is 6000 ppm for males (439 mg/kg/day) and 

females (486 mg/kg/day). 

This study is classified as acceptable and satisfies the guideline requirement (870.6200; OECD 

424) for neurotoxicity screening battery in rats. 

A.4.5 Mutagenicity

870.5100 Bacterial Reverse Gene Mutation

(1) In a toxicity study (MRID 47945764), kasugamycin (active ingredient/free base purity of 

71.5%) was tested in the Bacterial Reverse Mutation Assay using Salmonella typhimurium tester 

strains TA98, TA100, TA1535 and TA1537 and Escherichia coli tester strain WP2 uvrA in the 

presence and absence of Aroclor-induced rat liver S9. 

The assay had two phases, using the plate incorporation method. The first phase, the initial 

toxicity-mutation assay (Experiment B1), was used to establish the dose-range for the 

confirmatory mutagenicity assay and to provide a preliminary mutagenicity evaluation. 
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The second phase, the confirmatory mutagenicity assay (Experiment B2), was used to evaluate 

and confirm the mutagenic potential of the test article. Dosing formulations were adjusted for 

purity using a correction factor of 1.4 (50 mg kasugamycin x 1 mg kasugamycin technical/0.715 

mg kasugamycin active ingredient = 70 mg kasugamycin technical). 

The test article formed a soluble and clear solution in water at approximately 50 mg/mL 

kasugamycin technical, the maximum concentration tested in the solubility test. 

The dose levels tested were 1.5, 5.0, 15, 50, 150, 500, 1500 and 5000 μg kasugamycin active 

ingredient per plate. Maximum dosage was achieved using a concentration of 50 mg/mL and 

100 μL plating aliquots. In the initial toxicity-mutation assay, no positive mutagenic response 

was observed. 

In the confirmatory mutagenicity assay, no positive mutagenic response or precipitate was 

observed. Toxicity was observed beginning at 500 or 1500 μg per plate. 

Positive controls induced the appropriate responses in the presence and absence of S9 activation. 

The results of this study indicate the test article, Kasugamycin technical, was concluded to 

be negative in the Bacterial Reverse Mutation Assay. 

This study was conducted in compliance with the testing guidelines of the OECD (1998) and the 

US EPA Health Effects Guidelines OPPTS 870.5100 (1998). 

870.5375 In Vivo Mammalian Cytogenetics

Kasugamycin, Technical, was tested in the chromosome aberration assay (MRID 47945765) 

using Chinese hamster ovary (CHO) cells in both the absence and presence of an Aroclorinduced S9 activation system. A toxicity test was performed to establish a dose range for the 

chromosome aberration assay. The chromosome aberration assay was used to evaluate the 

clastogenic potential of the test substance. The dosing preparations were adjusted for the purity 

(71.50%) of the test substance using a correction factor of 1.4. Cytotoxicity in the preliminary 

and definitive chromosome aberration assays was determined by relative increase in cell counts. 

Water was the solvent and the test substance was soluble in water at a concentration of 43.4 

mg/mL, the maximum concentration prepared in the assay. 

In the preliminary toxicity assay, the maximum dose tested was 4340 μg/mL (10 mM). The test 

substance was soluble in water and in the treatment medium at all dose levels tested at the 

beginning and conclusion of the treatment period. Substantial toxicity (i.e., at least 50% cell 

growth inhibition, relative to the solvent control) was not observed at any dose level in all three 

exposure groups. 
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In the chromosome aberration assay, the cells were treated for 4 and 20 hours in the nonactivated test system and for 4 hours in the S9-activated test system. All cells were harvested 20 

hours after treatment initiation. The test substance was soluble in water and in the treatment 

medium at all dose levels tested at the beginning and conclusion of the treatment period. In the 

absence of both test substance precipitation in the treatment medium and at least 50% toxicity, 

the highest dose level evaluated was 4340 μg/mL Two additional lower dose levels were 

included in the evaluation. The percentage of cells with structural or numerical aberrations in the 

test substance-treated groups was not significantly increased relative to solvent control at any 

dose level (p>0.05, Fisher's Exact test). 

The results of this study indicate the test article, Kasugamycin Technical, was negative for 

the induction of structural and numerical chromosome aberrations in CHO cells in both 

non-activated and the S9-activated test systems. 

This study was conducted in compliance with the testing guidelines of the OECD 473 (1998) and 

the US EPA Health Effects Guidelines OPPTS 870.5375 (1998). 

A.4.6 Immunotoxicity 

870.7800 Immunotoxicity - Mouse

In a 28-day dietary immunotoxicity study (MRID 48132601), kasugamycin technical (71.5% 

free base/a.i., Batch No. KMB-0808) was administered to two study groups (AFC and NK) of 

female Crl:CD-1 mice in the diet at concentrations of 0 (vehicle and positive control groups), 

300, 3000 or 10,000 ppm (10 animals/dose/study group) as the active ingredient, for 28 

consecutive days. Because of severe weight loss in the AFC and NK groups dosed with 10,000 

ppm, the dietary concentration in the high-dose groups was reduced from 10,000 ppm to 7000 

ppm on Day 16 (AFC group) or Day 15 (NK group). The average daily dose of kasugamycin 

(a.i.) was 0, 70, 755, or 2468 mg/kg/day for the AFC dose groups, and 0, 68, 691, or 2531 

mg/kg/day for the NK dose groups. 

On Day 24, animals in the AFC study group received a single dose of sheep red blood cells (1 x 

108

 SRBCs in 0.2 mL of Earl’s Balanced Salt Solution with HEPES buffer solution) via a tail 

vein, with the exception of one animal in the 10,000/7000 ppm group that received an 

intraperitoneal injection. Animals in the AFC positive control group also were administered 

cyclophosphamide monohydrate by intraperitoneal injection once daily on Days 24-27 at a dose 

rate of 50 mg/kg/day. Animals in the AFC study group were used to evaluate the effect of 

kasugamycin technical on the T-cell dependent antibody response (humoral immunity). Animals 

in the NK positive control group were dosed with a single intravenous injection (0.2 mL) of antiasialo GM1 formulation (1:10 dilution of a reconstituted anti-asialo GM1 vial) on Day 27. 

Animals in the NK study group were used to evaluate the effect of kasugamycin technical on 

innate immunity. 
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Three animals in the high-dose AFC group were euthanized in extremis on Days 21, 23, and 25, 

respectively, because of significant body weight losses and clinical findings. There were no 

other unscheduled mortalities in any other AFC dose group or at any dose level in the NK study 

group. Animals in the both the AFC and NK high-dose groups had significantly decreased 

(p≤0.01) mean body weights during Weeks 2, 3, and 4; decreased mean cumulative body weight 

gains during Weeks 0-2, 0-3, and 0-4; and decreased mean terminal body weights when 

compared with the vehicle control. There were no test substance treatment-related effects on 

food consumption in the low- and mid-dose AFC and NK groups. The effect of the test 

substance on food consumption by the high-dose AFC and NK groups could not be determined. 

Test substance treatment- related changes in hematological parameters were seen in the highdose NK group. Mean corpuscular hemoglobin and mean corpuscular volume were significantly 

lower than the control values (p≤0.01 and p≤0.05, respectively); mean hemoglobin distribution 

width and mean absolute and percent neutrophil counts were significantly higher (p≤0.01) than 

control values. Hematological changes seen in the mid-dose group, including decreases in mean 

corpuscular hemoglobin and mean corpuscular volume, and increases in mean hemoglobin 

distribution width (not statistically significant), and statistically significant increases in mean 

total white blood cell and absolute lymphocyte counts (p≤0.05 and p≤0.01, respectively) were 

considered to be possibly related to test substance treatment. There were no test substancetreatment-related effects on hematological parameters in the low-dose NK group. Hematological 

parameters were not evaluated in the AFC study group. 

There were no test substance treatment-related gross macroscopic findings reported for any AFC 

or NK treatment group. There were no statistically significant effects of test substance treatment 

on absolute and relative mean spleen and thymus weights in any of the NK dose groups. A 

significant decrease in mean absolute spleen weight (p≤0.05) was seen in the high-dose AFC 

group (absolute and relative thymus weights and relative spleen weights were not evaluated); 

however, the measurement of spleen weights of immunized animals was not considered to be the 

most appropriate way to evaluate the effect of a test substance on spleen weight. 

For systemic toxicity related to treatment with kasugamycin technical, the LOAEL for 

female mice is 10,000/7000 ppm (highest tested dose, equivalent to 2468 and 2531 

mg/kg/day active ingredient, for the AFC and NK groups, respectively), based on clinical 

observations, mean body weights, and mean hematological parameters (NK study group). 

The NOAEL is 3000 ppm (equivalent to 755 and 691 mg/kg/day active ingredient, for the 

AFC and NK groups, respectively) based on these parameters. 

In the AFC assay (AFC study group), there were no statistically significant decreases in immune 

response in the test substance treatment groups when evaluated as Specific Activity (AFC/106

spleen cells). A statistically significant decrease (p≤0.05) in Total Spleen Activity (AFC/spleen) 

was seen in the high-dose AFC group when compared with the control. Because the decreased 

mean body weights in the high-dose group exceeded the maximum tolerated dose, the results 

were considered inconclusive regarding potential immunotoxicity. There were no statistically 
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significant test substance treatment-related effects on NK cell activity at any dose level (NK 

study group). 

For immunotoxicity related to treatment with kasugamycin technical, the NOAEL for 

female mice is 10,000/7000 ppm (highest dose tested, equivalent to 2468 and 2531 

mg/kg/day active ingredient, for the AFC and NK groups, respectively) based on the 

overall weight-of-evidence: no effect on natural killer cell activity (NK assay) and no 

statistically significant effect on absolute and relative thymus weights in the NK group; no 

effect on mean Specific Activity (AFC assay), and inconclusive evidence of test substance 

treatment effects on mean Total Spleen Activity (AFC assay) and mean absolute spleen 

weights in the AFC group. The LOAEL for immunotoxicity is greater than 10,000/7000 

ppm, highest tested dose. 

This 28-day dietary immunotoxicity study in the mouse is acceptable/guideline and satisfies the 

guideline requirement for a 28-day immunotoxicity study (OPPTS 870.7800) in mice. 

APPENDIX B: Metabolism Summary Tables 

TABLE B.1 Chemical Names and Structures of Compounds Detected in the Goat Metabolism and 

 Confined Rotational Crop Studies. 

Common Name 

Matrix 

Chemical Name Chemical Structure 

Kasugamycin 

Goat kidney, liver, and 

renal fat. 

Rotated lettuce, wheat 

forage, hay, straw, and 

grain. 

3-O-[2-amino-4-[(carboxyiminomethyl)amino]-2,3,4,6-tetradeoxyα-D-arabino-hexopyranosyl]-Dchiro-inositol 

Kasugamycinic 

Acid 

Wheat hay. 

N-[5-amino-2-methyl-6-(2,3,4,5,6-

pentahydroxycyclohexyloxy)tetrahydro-pyran-3-

yl]-oxallamic acid *

* Chemical name generated using naming software from ISIS/Draw (refer to D308573; W.T. Drew; 17 August 

2005; PP#3E6579). 
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TABLE B.2 Chemical Names and Structures of Compounds Detected in the Rat and Tomato 

 Metabolism Studies. 

Common Name [Code] 

% Total Radioactive Residues

Chemical Name Chemical Structure

Kasugamycin, 

Parent Compound [TM-416]

Rat

Essentially 100% TRR 

Tomato (Fruit)

90-94% TRR (2-hour, 1-day) 

69% TRR (7-day) 

55-60% TRR (14-, 21-, 28-day)

Tomato (Foliage)

75-84% TRR (2-hour, 1-day) 

70% TRR (7-day) 

52-57% TRR (14-, 21-, 28-day)

3-O-[2-amino-4-

[(carboxyiminomethyl)amino]-2,3,4,6-

tetradeoxy-α-D-arabinohexopyranosyl]-D-chiroinositol 

Kasugamycinic acid 

[KA-2] 

Tomato (Fruit)

10% TRR (21-day) 

12% TRR (28-day)

Tomato (Foliage)

2-7% TRR (all PHIs) 

N-[5-amino-2-methyl-6-

(2,3,4,5,6-pentahydroxycyclohexyloxy)-tetrahydropyran-3-yl]-oxalamic acid 

Kasuganobiosamine 

•2HCl [KB-2] 

Tomato (Foliage)

1% TRR (1- to 28-day)

6-(3,5-diamino-6-methyltetrahydro-pyran-2-yloxy)-

cyclohexane-1,2,3,4,5-pentol 

hydrochlorate 

O

O

OH

OH

OH

OH

HO

H C3

N

H

NH

HO

O

NH2

O

O

OH

OH

OH

OH

HO

H C3

N

H

O

HO

O

NH2

O

O

OH

OH

OH

OH

HO

H C3

H N2

NH2

. 2 HCl
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TABLE B.2 Chemical Names and Structures of Compounds Detected in the Rat and Tomato 

 Metabolism Studies. 

Common Name [Code] 

% Total Radioactive Residues

Chemical Name Chemical Structure

2-N-acetyl-kasugamycin [KN-2] 

Tomato (Foliage)

1-2% TRR (14-, 21-, 28-day)

[5-acetylamino-2-methyl-6-

(2,3,4,5,6-pentahydroxycyclohexyloxy)-tetrahydropyran-3-ylamino]-iminoacetic acid 

Tomato metabolism: MRID #45910006. Single, foliar broadcast application of [14C]-kasugamycin to tomato plants 

at 0.17 lb ai/A (roughly 3X the proposed maximum seasonal rate); fruit and foliage harvested at PHIs of 2 

hours, 1, 7, 14, 21, and 28 days. 

Rat metabolism: MRID #46030306. Oral gavage dosing of [14C]-kasugamycin at a single low dose (100 mg/kg 

bw); a single radiolabeled high dose (1000 mg/kg bw); repeated unlabeled low doses (100 mg/kg bw) for 

14 days in the diet, plus 100 mg/kg bw radiolabeled single dose; or repeated unlabeled high doses (1000 

mg/kg bw) for 14 days in the diet, plus 1000 mg/kg bw radiolabeled single dose. 

APPENDIX C: Physical/Chemical Properties 

TABLE C Physicochemical Properties of the Technical Grade Test Compound (Kasugamycin 

Hydrochloride Hydrate). 

Parameter Value Reference 

Molecular Weight 433.8 PP#3E6579 administrative materials 

Melting Point/Range 202-230oC (decomposing) (MRIDs #45910004 and -05) 

pH 4.35 at 24.5oC (1% wt/vol solution) 

Density 0.43 g/mL at 24.5oC 

Water Solubility g/100 mL

pH 5 20.7 

pH 7 22.8 

pH 9 43.8 

Solvent Solubility g/100 mL

Methanol 0.744 

Hexane <1 x 10-5

Acetonitrile <1 x 10-5

Methylene chloride <1 x 10-5

O

O

OH

OH

OH

OH

HO

H C3

N

H

NH

HO

O

NHCOCH3
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TABLE C Physicochemical Properties of the Technical Grade Test Compound (Kasugamycin 

Hydrochloride Hydrate). 

Parameter Value Reference 

Vapor Pressure <0.013 mPa at 25oC 

Dissociation Constant (pKa) pKa1 = 3.23 

pKa2 = 7.73 

pKa3 = 11.0 

Octanol/Water Partition Coefficient 

(Log [KOW]) 

<1.96 at 23oC and pH 5 

UV/Visible Absorption Spectrum Not available 

APPENDIX D: Review of Human Research 

This risk assessment relies in part on data from studies in which adult human subjects were 

intentionally exposed to a pesticide or other chemical. These data, which include studies from 

the Pesticide Handlers Exposure Database Version 1.1 (PHED 1.1), the Agricultural Handler 

Exposure Task Force (AHETF) database, and the Agricultural Re-entry Task Force (ARTF) 

database are subject to ethics review pursuant to 40CFR §26, have received that review, and are 

compliant with applicable ethics requirements. For certain studies, that review may have 

included review by the Human Studies Review Board. Descriptions of data sources, as well as 

guidance on their use, can be found at: http://www.epa.gov/pesticides/science/handler-exposuredata.html and http://www.epa.gov/pesticides/science/post-app-exposure-data.html.