### UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D.C. 20460

MEMORANDUM Date : October 31, 20 1 3 OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION



### SUBJECT: Tefluthrin: Revised Response to C omments by the Syngenta Crop Protection , LLC on the Registration Re view for Tefluthr in PC Code: 128912 Decision No.:Lt17??R 

### Petition No.: N/A Risk Assessment Type: N/A TXRNo.: N/A MRID No.: N/ A
FROM: C hri s Schlosser, Toxicologist Risk Assessment Branch VI 

### DP Barcode: D41 1269 Registration No.: N IA 

### Regulatory Action: N/A Case No.: N/A CAS No.: 79538-32-2 40CFR: N/A

and**_,..-.........._~** 

### Charles Smith, Branch Chief 

# c_**~** 

# · Risk Assessment Bran ch I Health Effects Divis ion (7509P) Office of Pe sticide Programs THROUGH : Jeffery Dawson, Acting Branch C hief Risk Assessment Branch VI 

### Health Effects Division (7 509P) Office of Pesticide Programs T O: Molly Clayton, Chemical Review Manager Risk Management and Implementation Branch 3 Pesticide Re-Evaluati on Division (7508P) Office ofPesticide Program s This memo re sp ond s to the TFL Dermal Toxic ity Assessment submitted by Syngenta Crop Protection, LLC to support the Regi s tration Review ofTefluthrin. 

### In the recent Hea l th Effects Division (HED) 20 12 Human Healt h Risk Assessment for Proposed Section 3 Registration on Sugar Beat Seed (No n-Food Use), the Agency u sed a N OAEL 

### ofO
. l mglkg based on evidence of " splayed gait" as the point of departure for short
-term dermal

Page 1 of2exposure ofthe granular formulation. In the current submission Syngenta has proposed the following: "We believe the evidence from these studies and the additional information provided demonstrates that the fmding of "splayed gait" in the dermal study was not reflective of a systemic effect and therefore, not appropriate for risk assessment purposes". Additionally, Syngenta has identified that : "These daily observations were performed as part of a general assessment of toxicity; they were not conducted by technical stafftrained to perform specific neuro logic observations such as the functional observational battery (FOB)"
. HED response: Upon re - evaluation ofthe two 21-day dermal toxicity studies (1985 and 1989) 1
, HED concurs with Syngenta that daily observations of clinical toxicity were conducted by staff that was not specifically trained to identify neuro logic observations, such as those in the Functional Observationa l Battery (FOB). Upon consultation with EPA's Office of Research and Development (ORD), several inconsistencies have been identified with the results reported in the clinical observations. Anatomically, it is unclear how downward curvature ofthe spine and tiptoe gait could occur simultaneously as reported
. In addition, without further clarification on the timing of the observed effects, it is difficult to interpret how both upward and downward curvature ofthe spine could occur in the same animals (i.e., 10/10 animals at the higher two dose levels). As effects related to the FOB are critical to assess the neurotoxic potential of pyrethroids, HED has determined that the dermal toxicity studies are inappropriate to assess the neurotoxic potential of tefluthrin via dermal application. HED acknow ledges that the margins

_ of exposure (MOE) for the granular formulation as reported in the 2012 human health risk assessment are below the level of concern for dermal exposure . As an alternative approach, HED will use the NOAEL of 0.5 mg/kg/day from chronic dietary study in Beagle dogs, used to assess the dermal exposure of the microencapsulated formulation, with a default pyrethroid dermal apsorption value of 5%. Use of 5% is consistent with the default pyrethroid dermal absorption factor utilized in the pyrethroid cumulative risk assessment (USEPA; 1 0/4111 ). In general, pyrethroid dermal absorption estimates based on potency comparisons between oral and dermal studies within the same rat strain, direct measures of in vitro skin penetration (Hughes and Edwards 20 10), or penetration rates based on lower dermis levels of skin that are more likely to be absorbed by the body are <5%. HED is confident that use of a 5.0% dermal absorption factor for granular tefluthrin formulations i s health protective.

1 EPA MRID 40141306 : Southwood, J. (1985): Subacute Dennal Tox i city to Rats: Laboratory Project ID: CTUP/1147
. Prepared by ICI Central Toxicology Laboratory 314 p. Unpublished EPA MRID 41080002: Leah, A. (1989) Teluthrin: 21-Day Dennal Toxi city to the Rat: Pro-ject ID: Report No
. CTUP/2488; Study No
. LR0524
. Prepared by ICI Central Toxicology Laboratory. 589 p. U npublished Page 2 of2