UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON D.C., 20460 

PC Code: 112602 

DP Barcode: D423472 

Date: November 18,2014 

MEMORANDUM 

SUBJECT: 

TO: 

FROM: 

Response to Public Comments on the Trinexapac-ethyl Proposed Interim 

Decision 

Brittany Pruitt, Chemical Review Manager 

Avivah Jakob, Team Leader 

Patricia Parrott, Branch Chief 

Risk Management and Implementation Branch III 

Pesticide Re-Evaluation Division 

Office of Pesticide Programs (7508P) 

(' ~~1. {t.vV'~ ,. ~0~ '2.£)11 

Christopher M. Koper, M.S., Chemist ~'f\1'{· fY' W" 

Meghan Radtke, Ph.D., Acting RAPL ~~ _ V.,.,(/~{;f I ( I~ II'( 

Sujatha Sankula, Ph.D., Branch Chief ""'"\\, ..... )\£-...---'"'-. n\18! 11 

Environmental Risk Branch I · 

Environmental Fate and Effects Division (7507P) 

Office of Pesticide Programs 

In response to the Proposed Interim Decision for Trinexapac-ethyl (case number 7228), Syngenta 

Crop Protection submitted two comments regarding the ecological risk assessment in support of 

Registration Review (D409748) and the Environmental Fate arid Effects Division response to 

public comments on the risk assessment (D416981). This memo addresses Syngenta's 

comments in the context of the proposed interim decision. 

Syngenta's Comment: As per the EPA response to Public Comments document (DP Barcode: 

D416981 ), Page 3, Residues of Concern, EPA Response #2, "Only those degradates identified in 

the abiotic hydrolysis study at pH 7 are included in the total toxic residue (TR) abiotic hydrolysis 

half-life." Syngenta believes that the major degradation products included in the TTR, CGA313458 and M3, will only form under acidic conditions (MRID 46809301 ); and therefore should 

not be included as part of the stressor of concern. 

EFED Response: As mentioned in the Agency's response, "only those degradates identified in 

the abiotic hydrolysis study at pH 7 are included in the total toxic residue (TR) expression", the 

unidentified degradate M3, will not be included the TR calculation, since it is formed at pH 5. 

The degradate CGA-313458 will be included into the tolerance expression as it fonns in the 
aqueous photolysis study (MRID 46809302) and has been identified as a degradate of concern by 

the Residues of Concern Knowledgebase Subcommittee (ROCKS) of EPA's Health Effects 

Division (HED) (0390 12 1 ). 

Syngenta's Comment: Syngenta comment to the EPA Response to Public Comments document 

(DP Barcode: 0416981 ), page 5, T -REX Modeling, EPA Response # 16 regarding the potential 

exposure of birds to granules on corn versus turf environments: 

Granules may be ingested accidentally when birds forage for food or they may be ingested 

intentionally if they are mistaken for food (e.g., grains and weed seeds) or when birds are 

foraging for grit. Syngenta cited the example from Fisher and Best (Environ. Toxicol. And 

Chern. 11:1495-1508, 1995) to represent a reasonable worst-case scenario where birds may 

indiscriminately consume granules while selecting for grit in a field with sufficient bare ground. 

EPA suggested that turf is expected to contain less bare ground and, therefore, have less 

available natural grit. In EPA's response to comments, the Agency also provided useful citations 

from ECOFRAM on the Granule Grit Preference factor. In the EPA response it is discussed that 

birds could be more likely to selectively take up granules as grit in a turf scenario vs. bare 

ground. However, Best (National Wildlife Research Center Repellents Conference 1995) stated 

that birds greatly favor silica granules for grit rather than much softer granular products that are 

comprised of gypsum or clay 

(http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article= 1 005&context=nwrcrepellants). The 

preferable silica granules are readily available on bare soils, as indicated by EPA, or, for turf 

applications, in sand traps found on golf courses. In addition, granules applied on turf areas of 

golf courses are less visible than those on bare ground. Erbach et al. (Transactions of the ASAE 

39: 11-15., 1996) demonstrated that, within one hour after application, only 67% of granules 

were visible on greens and only 38% and 15% of granules were visible on fairways and rough, 

respectively. Visibility decreased further upon irrigation. These fmdings by Best (1995) and 

Erbach et al. (1996) support the discussion that granule consumption by birds on golf courses 

would be less than that on bare ground. This limited exposure, in addition to the relatively low 

toxicity oftrinexapac-ethyl to birds, indicates that risk to avian species from consumption of 

granules is correspondingly low. 

EFED Response: The LDso/ff analysis is used to estimate the dose that a bird receives through 

all potentially complete exposure routes. The most obvious exposure routes include direct 

ingestion of granules as grit or incidental ingestion of granules as a matter of course during 

feeding or preening. However, granules are a mechanism to deliver trinexapac-ethyl to turf and 

consequently it is reasonable to expect that the pesticide will be released from the granules to the 

surrounding environment. Therefore, exposure is also possible through I) ingestion of pesticide 

residues in animal and vegetative food items through uptake of a pesticide from granule-released 

pesticide in the soil matrix, 2) direct dermal contact with granules and pesticide released to the 

soil matrix, 3) consumption of pesticide with drinking water in contact with pesticide granules or 

pesticide released to soil or vegetative matter, and 4) inhalation of dust or vapor phase pesticide. 

The information about grit size arid location may help refine the assessment for some specific 

exposure routes (i.e. direct ingestion for granules as grit), but the information does not address 

other potentially complete exposure routes. In the absence of data regarding the other possible 

routes of exposure that would preclude them as being complete, EFED cannot rely solely on the 

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information provided to set aside the LD50/ft2 analysis. Further, trinexapac-ethyl is registered 

for turf, which may include landscapes other than golf courses (e.g., residential yards, parks, 

recreational areas, and business parks) and the provided analysis is silent about the completeness 

of any exposure routes for these potential sites. 

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