UNfTED STATES E VIRONMENTAL PROTECTION AGENCY 

WASHINGTON D.C., 20460 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

PC Code: 128888 

DP Barcode: 423503 

December 02, 2014 

MEMORANDUM 

SUBJECT: 

TO: 

FROM: 

Response to Comments Regarding the Lactofen Registration Review Preliminary Risk 

Assessment that Were Submitted During the Registration Review Proposed Interim 

Decision Public Comment Period 

Kelly Ballard, Chemical Review Manager 

Neil Anderson, Chief 

Risk Management and Implementation Branch I 

Pesticide Reevaluation Division {7508P) 

1 

J 

Brian Kiernan, Biologist ~I}~ ( ~ 2 { 'i 

Andrew Shelby, Physical Scientist Jf. ·l.. • I"( 

Mark Corbin, Branch Chief 

Environmental Risk Branch VI 

Environmental Fate and Effects Division (7507P) 

The Environmental Fa,te and Effects Division (EFED) has reviewed the comments submitted by Valent 

U.S.A. Corporation, dated 9/22/14, regarding the proposed interim registration review decision on the 

herbicide lactofen (PC code 128888). The comments on the EFED Preliminary Risk Assessment (PRA) 

component are addressed in this document. Valent makes a number of comments critiquing EFED's risk 

assessment models and procedures as well as several specific comments. 

Valent expressed concern that the PRA relied on only high-end and marginal (Section 24c, Special Local 

Needs registrations) use patterns (e.g. Florida fruiting vegetables) in describing potential risk from 

lactofen uses. EFED responds that while the highest risk estimates result from some of the more limited 

use patterns, the PRA described risk estimates from all use patterns identified on the labels. The more 

limited uses tended to have higher application rates, resulting in higher risk estimates, but EFED 

describes the spatial limitations of the high-application use patterns in the PRA, and will continue to 

note these limitations in the upcoming endangered and threatened (Listed) species risk assessment. 

Further, Valent states that "the Agency did not conduct an assessment of aquatic exposure following the 

use of the product in soybeans" (p 5 of the 9/22/14 comment). EFED's response is that indeed all use 

patterns were considered in the assessment of aquatic risk, but that since no risk to aquatic animals was 

identified for any of the registered use patterns, there was no need to list out individual use patterns. 
The exception to the finding of low risk to aquatic animals was for chronic fish exposure under high-UV 

light conditions based on the fact lactofen is a light dependent peroxidizing herbicide {LDPH); the 

document extensively describes both the conditions {high UV light) and the taxon for which the finding 

is valid (fish via chronic exposure). EFED will adhere to the appropriate guidance at the time of the 

listed species risk assessment regarding the LDPH issue. Risk estimates for aquatic plants were bounded 

in the assessment (e.g." RQs ranging from 1.36 to 3.70"), and the PRA specifically stated that the LOC 

was exceed for aquatic plants for all scenarios. 

Valent also comments on effects endpoints used in the PRA, specifically for terrestrial plants {MRIDs 

47919602 and 47919601) and avian reproduction (MRID 48223101). EFED went back to the data 

evaluation records (DERs) for these studies and confirmed that the correct endpoints were drawn from 

the DERs. However, EFED disagrees with Valent's suggestion that the original study author's reported 

values be used in risk assessment rather than the conclusions from EFED's DERs. EFED independently 

evaluates submitted studies and applies consistent statistical procedures to all data submitted, including 

lactofen. Results from these internal analyses are used in selecting endpoints for the risk assessment. 

The DERs from these lactofen studies should have been sent to Valent at the time of the reviews (early 

2012), but should be made available for Valent's review. 

One additional specific comment was that the model T-HERPS should have been used in the assessment. 

EFED responds that the model, which modifies T-REX to account for dietary and metabolic differences 

between birds and repti le and terrestrial-phase amphibians, is by guidanc~, not used in screening-level 

risk assessments. The model could have been used in a refinement to the risk assessment, however 

such refinements were not requested to support the lactofen interim registration review decision. The 

listed species risk assessment process is still being determined, but the accepted methodology will be 

applied at the time of that assessment. 

General Comments on EFED Risk Assessment Approaches and Methods 

Valent makes numerous comments on the methods, tools and assumptions used by EFED in assessing 

risk to non-target species from pesticides. These methodological comments are generally broken down 

into broad categories of model sufficiency, model assumptions, use pattern relevance, and 

characterization of exposure values. As a general response, it should be noted that EFED's exposure 

assessment methods, tools and assumptions have evolved over time and have been well documented 

and peer reviewed. Where appropriate, EFED attempts to characterize the relevance of results from 

exposure outputs. EFED also notes that the tools, methods and models employed in risk assessments 

are not static and are constantly evolving and where appropriate, the general methodological comments 

noted by Valent will be considered.