UNITED STATES ENVIRONMENTAL PROTECTION AGENC Y WASHINGTON D.C.

, 20460

OFF I CE OF CHEMICAL SAFETY AND PO L LUTION PREVEN T ION

PC Code: 128850 DP Barcode: 401123 Date: 28 January 2013

Subject: Preliminary Ecological Risk Assessment for the Registration Review of the Herbicide, Glufosinate-ammonium

To: Katie Weyrauch, Chemical Review Manager Margarita Collantes, Acting Team Leader Risk Management and Implementation Branch III Pesticide Re-evaluation Division (Mail Code 7508P) 

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# . Chuck Peck, Environmental Engineer

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Thru: Environmental Fate and Effects Division (Mail Code 7507P)

Jim Carleton, Ph.D., Senior Scientist // ·

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# L/ l/2"r/.Jotl 1 Thomas Steeger, Ph.D., Senior

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## /~s I I 3 Mar ietta Echeverria, Branch Chief 1\1\ 

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### r 2 1 1..) Environmental Fate and Effects Division (Mail Code 7507P)

T he Environmenta l Fate and Effects Division (EFED) has completed the preliminary environmental fate and ecological risk assessment (attached) for the Registration Review of the herbicide, glufosinate-arnmonium (PC Code 128850)
, hereafter referred to as g lufosinate

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The preliminary problem formulation (2008) identified uncertainties regarding the potential
to xicity of glufosinate degradates. Recently reviewed aquatic ecotoxicity data are s ummari zed in the risk assessment. These data demonstrate that glufosinate degradates (MPA, MPP, NAG) are generally equally or less toxic than glufosinate technical grade active ingredient (TGAI) but may

cause adverse effects through acidification of the aquatic environment through the formation of these degradates. With this in mind, the preliminary ris k assessment only evaluates exposure and risk to the parent compound, glufosinate, as exposure to the parent below the levels of concern should be protective of any exposure to the degradates.

The preliminary assessment identifie s potential chronic risk to mammals from most registered

uses of glufosinate and risk to terrestrial and wetland plants from multiple agricultural and nonagricultural us es; th ese risks are substantiated by multiple li nes of evidence including RQ values that exceed the Agency's Levels of Concern (LOCs). Certain uses of glufosinate may also result" in acute risk to mammals and chronic risks to birds, reptiles, and terrestrial -phase amphibiansTransmittal Memo fo r the Registration Review PRA – Glufosinate-ammonium



### 2 exposed to glufosinate in the diet . The potential for acuterisk to birds, reptiles, and terrestrialphase amphibians is based on sublethal effects (lethargy and diarrhea) through oral exposure estimates and is uncertain given the relatively hi gh dietary exposure levels that would need to occur for animals foraging on a treated field to appr oach the equivalent oral dose. No mortalities or sublethal effects were observe d in subacute dietary toxicity tests with birds at the limit dose (5,000 mg/kg diet). Acute risk to mammals and risks to birds are likely to be below the Agency’s LOCs when glufosinate is applied at“typical” application rates (and intervals).

Off-site transport of glufosinate to surface water presents risk that exceeds the LOC for federally listed threatened and endangered sp ecies (hereafter referred to as “listed”) of aquatic nonvascular plants ( e.g. , algae). While there are cu rrently no listed species of aquatic nonvascular plants, the degree to which direct effects on the aquatic plant community may result in indirect effects on other organisms is uncertain. Risks to aquatic nonvascular plants may be reduced below the listed species LOC by reducing the number of applic ations for certain uses. Risks to aquatic animals are not expected except as associated withthe direct application of glufosinate to rice paddies. Uses on rice present risk to estuarine/marine invertebrates that exceeds the acute risk to listed species LOC, although the pot ential co-location of estuarin e/marine invertebrates with treated rice paddies and receiving waters imme diately downstream is uncertain. Overall, formulated glufosinate is generally more toxic to aquatic and terrestrial animals than the TGAI. Typical end-use product (TEP) data indicate that the use of fo rmulated glufosinate on rice triggers additional risks for fish and amphibians th at exceed the acute risk to listed species LOC.

Finally, a spatial co-occurrence analysis that compares the best available data regarding glufosinate potential and documented use areas and listed species occurrence is needed to more explicitly address potential risk to listed species of concern.

Additional Considerations for Listed Species

At this stage of the Registration Review process, it is premature to make effects determinations for listed species until further refinements are conducted. In order to make effects determinations for individual sp ecies, useful refinements may in clude analyses of 1) more detailed, species-specific ecological and biol ogical data; 2) more detailed and accurate information on glufosinate use patterns; and 3) sub-county level spatial proximity data for the cooccurrence of potential effects ar eas and listed species and any designated critical habitat. Examples of such refinements are described below.

EFED is currently developing tools that are exp ected to further refine the assessment and are designed to support effects determinations for individual listed species and their designated critical habitats (where applicable). Scien tific information obtained from the U.S. Fish & Wildlife Service (USFWS), the National Marine Fisheries Service (NMFS) , and other reliable sources is being collated by EFED to address all currently listed sp ecies. The information will be stored in an Office of Pesticide Programs Pe sticide Registration Information SysteM (PRISM) knowledgebase. The listed species knowledgebase w ill consist of an information repository that houses biological and behavioral information relevant to individual species ( e.g. , habitat, diet, and life history, including specific temporal and spatial associations) an d a document repository that contains supporting documents ( e.g ., USFWS recovery plans) and electronic information ( e.g ., GIS data files). For terrestr ial taxa, the biological information relevant to risk quotient (RQ) calculations ( e.g ., diet and body weight) wi ll be used to parameteri ze exposure estimates toTransmittal Memo fo r the Registration Review PRA – Glufosinate-ammonium



### 3 derive species-specific RQs us ing a method consistent with cu rrently used methods in the TREX and T-HERPS models.

Refinements may also include more detailed analyses of the registered uses and their use patterns that result in LOC exceedances for federally list ed species in the screening-level assessment. The analyses may include more information on wh ere, when, and how glufosinate is used for agricultural and non-agricultural applications. Actual usage data (when available) and national land-cover datasets that indicate potential use sites [ e.g ., national land cover dataset (NLCD), crop data layer (CDL)] may be used to support a more refined analysis of where glufosinate is reasonably expected to be used. Similarly, refi nements for the timing of applications and how glufosinate is used may be base d on the analysis of additiona l usage data, beyond what were available at the time of the screening-level as sessment, and a more in-depth exploration of agronomic practices.

In addition, a committee of the National Res earch Council (NRC) has been tasked with providing advice on ecological risk assessment tool s and scientific approaches under ESA and FIFRA (Project Identification Number DELS-B EST-11-01). The committee has been asked to review the use of “best available data”; me thods for evaluating subl ethal, indirect, and cumulative effects; the state of the science regarding assessment of mixtures and pesticide inert ingredients; the development, application, and in terpretation of results from predictive models; uncertainty factors; and what constitutes authoritative geospatial and temporal information for the assessment of individual species and habitat e ffects. The Agency anticipates that this NRC report, tentatively expected in Spring 2013, will provide recommendations to ensure the scientific soundness and maximize the utility of risk assessment refinements for listed species.

The refinements based on individu al species data; additional, detailed usage information, when available; and further recommendations from th e NRC report are expected to help to more accurately identify potential areas of effect and to bette r inform effects and habitat determinations for listed species and any designated critical habitats. For example, if glufosinate is used when a particular species of concern is not present ( e.g ., it is migratory) or is not colocated in space, then risk of potential direct effects to the sp ecies may often be precluded. If LOCs are still exceeded for taxa after conducting the refined analyses, further analyses of the potential spatial and te mporal co-occurrence of listed spec ies of concern (and any designated critical habitat) may be conducted. The extent of possible refinement in the analyses ofspatial/temporal co-occurrence will largely depend on the scale and quality of the available subcounty level use site ( e.g ., NLCD, CDL) and species location data

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