2 Comment regarding the drinking water assessment

Reference: Page 4, Section 4.2 (also noted on Page 17, Section 8.1.2). Document states: The Health Effects Division (HED) recommends the normal and reverse acid are appropriate to include in the drinking water asse ssment along with parent dithiopyr.

DAS Comment: The mono-acid degradates are formed only at significant levels (e.g., >10% applied radioactivity) in the aqueous photolysis study [5]. Since photolysis is only possible in surface water, these degradates would be unlikely to be formed in ground water, and therefore the mono-acids are not applicab le to the drinking water asse ssment. This conclusion is supported by the New York ground water monito ring study [3], in which neither normal nor

reverse monoacid metabolites were detected. This study can be provided to the EPA upon

request.

References: MRID 40638628. Solsten, R. T. The Photolysis of MON 7200, 3,5-pyridine- dicarbothioic acid, 2-(difluoromethyl)-4-(2-methylpropyl )-6-(trifluromethyl)-S,S- dimet hyl ester in Water and inSoil. Monsanto unpublished report number MSL7049, 1988.

Petrecz, T. and W. Zogorski. Ground Water Monitoring Study for Dithiopyr in Nassau and Suffolk Counties, New York: Final Report. Dow AgroSciences unpublished report number 110487, 2005.

EFED Response: In addition to percent formation, degradat e toxicity is also a determinant in selecting degradates of concern for the drinking water assessment. The toxicities of the normal and reverse acids are assumed to be comparable to that of dithiopyr because they maintain the core pyridine structure of dithi opyr (structure comparison: page 7 of the problem formulation). Since both acids are more polar than parent dithiopyr and are formed in aerobic terrestrial environments (MRIDs 40638629, 41001517), they have the ability to move freely through the soil column into groundwater. In the absence of toxicity data, the normal and reverse acids will be added into the tolerance expression along w ith the parent dithiopy r as recommended by the Health Effects Division. EFED requests DAS to submit the mentioned groundwater monitoring study for dithiopyr.

Comments regarding ecological incidents

Reference: Pages 15-16, Section 6.1 and Table 6-3. Document states: In the risk assessment,

the incidents will be further evaluated to determ ine if the reported incidents represent current patterns of use for dithiopyr. Examples of additional considerations are mitigation ( e.g ., reduced application rates), product cancell ations, and changes in use pattern s that have occurred since the date of the repor ted incident(s).

DAS Comment : The majority of the lis ted incidents occurred in 1992 when Monsanto was the primary technical registrant. It is important to note that the use sites indicated in 28 of the 323 incidents in Table 6-3 relate to applications made to golf greens. DAS labels for dithiopyr either 1) explicitly prohibit uses on putting greens or 2) clearly lay out detailed restrictions and procedures for effective use on putting greens. The development and implementation of this label language is intended to en sure undesirable effects do not o ccur. Based on the ecological

incidents noted in Table 6-3 of the EFED Pr oblem Formulation document, DAS believes it is reasonable to assume that the absence of repor ted incidents relating to putting greens for over 20 years is an indicator of the positive effect of the label language used.

Of the remaining four incident s, the two that occurred in 2003 and 2005 involved tank mixes and

therefore it cannot be concluded that dithiopyr was the cause.

One incident was the result of accidental misuse wh ich has not been repeated and the legality of the remaining incident is undetermined. Therefor e, DAS concludes that the incidents listed are not representative of registered uses of dithiopyr.

Reference: Pages 15-16, Section 6.1 and Table 6-3. Document stat es: For dithi opyr, registrants have reported 6 minor fish and wildlife inci dents, 27 minor plant incidents, and 0 other nontarget incidents. Unless additional information on these aggregated incidents becomes available, they will be assumed to be representative of regi stered uses of dithiopyr in the risk assessment.

DAS Comment: In our review of aggr egated incident reports, DAS believes there are specific examples of incidents due to off-label use. Additionally some claims of adverse effects are unlikely based on available relevant scientific studies. Further, there appears to be a relatively low number of reported incidents over the 23 year history of use in the United States. There

should not be an adverse effects concern with registered uses of dithiopyr products based on current Dow AgroSciences product labels. DAS is willing to discuss in more detail if the Agency has specific questions or concerns on this topic.

EFED Response: The total number of actual incidents asso ciated with the us e of dithiopyr may be higher than what is reported to the Agenc y. Incidents may go unreported since effects may not be immediately apparent and/or readily attributed to the use of a chemical. Therefore, a lack of reported incidents should not be taken as an indicator of little or no ecological risk.

As stated in the problem formulation, the incide nts will be further evaluated at the time of the risk assessment to determine if the reported incidents represent current patterns of use for dithiopyr. The Agency will consider the registrant’s comments during this evaluation.

Comments regarding the environmental fate of dithiopyr and associated studies

Reference: Page 19, Table 11-1, Row 5. Do cument states: 835.4200 Anaerobic soil metabolism - Stability will be assumed in the absence of data.

DAS Comment: DAS agrees with the Agency assessment and assumption to be made in the absence of data. Stability is assumed, and a defa ult half-life of 1000 days will be acceptable in

the risk assessment.4 EFED Response: Stability will be assumed in the absence of anaerobic soil metabolism data. In the current environmental exposure models, th e input value is zero, wh ich represents stable compounds. Please note, the anaerobic soil metabolism data will continue to be a data gap and OCSPP Guideline 835.4200 will remain outstanding.

Reference: Page 19, Table 11-1, Row 6. Docu ment states: EPA has identified the following data gap: 835.4300 Aerobic aquatic metabolism.

DAS Comment: A flooded soil metabolism study was conducted for dithiopyr in 1989 [6]. The study examined two unique flooded soils and demons trated an average half life of 440 days (490 d in Arkansas clay soil, 390 d in volcanic ash- paddy soil). This study can be provided to the EPA upon request.

Reference: Pantano, L. K. The Flooded Ae robic Soil Metabolism of MON 7200, 3,5- Pyridinedicarbothioic Acid, 2-(difluoromethyl)-4-(20methylpropyl)-6- (t rifluoromethyl)-,S,S-dimethyl Ester. Monsanto unpublished report number MSL-8196, 1989.

EFED Response: EFED requests DAS to submit the men tioned flooded aerobic soil metabolism study to the Agency for review and consideration.

Reference: Page 19, Table 11-1, Row 7. Document states: 835.4400 Anaerobic aquatic metabolism - Stability will be assumed in the absence of data.

DAS Comment: DAS agrees with the Agency assessment and assumption to be made in the absence of data. Stability is assumed, and a defa ult half-life of 1000 days will be acceptable in

the risk assessment.

EFED Response: Stability will be assumed in the absence of anaerobic aquatic metabolism data. In the current environmental exposure models, th e input value is zero, wh ich represents stable compounds. Please note, the anaerobic aquatic meta bolism data will continue to be a data gap

and OCSPP Guideline 835.4400 w ill remain outstanding.

Reference: Page 19, Table 11-1, Row 9. Do cument states: 835.1410 Volatility–Field - The registrant should submit analytical data for th e soil and turf grass surfaces to confirm the application rate and the rate of volatilization. If this data can not be provided, a new study is requested.

DAS Comment: Although a field volatility (FV) study is not a required guideline study for dithiopyr registration, the initia l registrant (Monsanto) conducted a FV study to obtain a more complete picture of the dissipation of dithiopyr under field conditions [7]. FV studies were conducted at three sites; one n ear Atlanta, GA, one near Colu mbus, OH and one near Cleveland,5 OH. Applications of the EC formulation of dithi opyr were made on fescue turf plots at a rate of 1 pound of active ingredient per acr e (2x the current maximum label rate) at all three locations. Air samples were collected at the center of th e treated plots at hei ghts of 30.5, 61, and 183 cm above ground surface and analyzed for dithiopyr. Samples were collected at eight times; 0, 3h, 1, 2, 3, 7, 14, and 30 days after dithiopyr application. Samples were collected at the warmest time of the day to ensure that the maximum vol atilization rates would be observed. Cumulative dithiopyr emissions were calculated to be 38.2, 19.5 and 12.5% of applied at Atlanta, Columbus, and Cleveland, respectively. As much as 10.9% volat ilized from the Atlanta site in the first day and helps explain the low ‘day 0’ recoveries observed in the terr estrial field dissipation study. The maximum concentration of dithiopyr observe d at the 30.5 cm height was 7.82 μg/m3 at the Atlanta site, 2.6 μg/m3 at the Columbus site and 5.13 μg/m3 at the Cleveland site, on the day of application. Concentrations then declined monotonically to < 0.1 μg/m3 by 30 days after application at all three sites.

The maximum concentration at the 30.5 cm height at the Atlanta site is approximately 10% of the saturated vapor concentration (SVC) of dith iopyr (86.2 μg/m3), and represents a reasonable

worst case concentration for use in an inhalation ri sk assessment. This is consistent with the EPA SAP’s [8] comments; “ Volatile flux from crops will result in concentrations that are substantially below the saturation vapor pressure of most vapors .” Therefore using the SVC of dithiopyr as the exposure endpoint for an inhalation risk assessme nt is extremely conservative, and using the maximum concentrat ion observed 30.5 cm directly ove r the treated field represents a realistic worst case scenario for inhalation exposure.

The EPA’s request for the soil and turf grass analytical data was addressed by Monsanto [9] in which they presented the data that could be used to confirm the a pplication rate of dithiopyr in the FV studies. The data are summarized again here:

1. The same spray mixture of dithiopyr M ON15104 EC formulation and water and the same spraying equipment were used to spray the plot s in the FV study and th e foliar dissipation study. The MON15104 formulation contains 1 pound of dithi opyr per gallon. The app lication rate to all plots was one pound of dithiopyr per acre.

2. The assay of the lot number of the MON 15104 formulation used and the volumes of water and formulation mixed together were pres ented in the volatility report, MRID 416151601.

3. The volume of MON 15104 and water in the tank mix, and the volume of tank mix remaining after each application along with th e area of the plot were used to calculate the application rate and confirm that the nominal ap plication rate of 1 pound of dithiopyr per acre was obtained at each site. These data are presented in attachments 2, 3, and 4 in MRID 43043301.

4. It was noted that the EPA Pesticide Reject ion Rate Analysis for field volatility studies discusses the rejection fact or of inadequate soil da ta to confirm the application rate and states on page 142: “ Therefore, soil analysis or other means such as known weights or volumes of pesticide applied to the soil may be used to co nfirm the rate of applica tion, provided that the calibration and performance of the application equipment is verified .”6 Because the Pesticide Treatment Calculations reported in Attachments 2, 3, and 4 in MRID 43043301 provide the data needed to calculate the application rate and also to verify the performance of the spray equipment, the regist rant believes that the Agency has adequate information to conclude that the applicat ion rate was one pound of dithiopyr per acre.

Reference: MRID 416151601. Fleschar, E. M. Volatiliz ation of Dithiopyr Residues Following Applications to Turfgrass. Monsan to unpublished report number MSL-9686, 1990.

EPA, 2009. FIFRA SCIENTIFIC ADVISORY P ANEL (SAP), December 1 – 3, 2009. Docket Number: EPA-HQ-OPP-2009-0687 http://www.epa.gov/scipoly/sap/

MRID 43043301. Fleschar, E. M. Response to Ag ency Reviews of the Previously Submitted Study: "Volatilization of Dithiopyr Residues Following Applications to Turfgrass" MRID 416151601. Monsanto unpublished report number MSL-9686, 1993.

EFED Response: EFED appreciates the data furnished by DAS confirming the application rate

and the rate of volatil ization of dithiopyr.

References: Page 19, Table 11-1, Row 9. Docu ment states: 835.1410 Volatility–Field - The registrant should submit analytical data for th e soil and turf grass surfaces to confirm the application rate and the rate of volatilization. If this data can not be provided, a new study is requested.

Page 3, Section 1 (also noted on Page 5, Table 1, Row 4 of the Preliminary Work Plan). Document states: Major findings include data needs and the uncertainty described below: OCSPP Guideline 835.1410 (TGAI) Volatility-laboratory.

DAS Comment: DAS would like to seek clarity on the perceived uncertaintie s, proposed data gaps, and data needed to conduct the risk assessment relating to volatility. 40 CFR §158.1300 cites field and lab volatility st udies as conditionally required fo r terrestrial nonfood use patterns and not required for residential outdoor use pa tterns. DAS believes that a clear understanding of exposure and toxicity have been outlined from existing studies/publicat ions [7-10], supportive factual information (Henry’s law constant and va por pressure, as defined in Table 5-1 of EFED Problem Formulation), and additional comments ma de in this document (Comment #7 to EFED Problem Formulation, Comment #2 to HED Scoping Document).

Reference: MRID 416151601. Fleschar, E. M. Volatiliz ation of Dithiopyr Residues Following Applications to Turfgrass. Monsan to unpublished report number MSL-9686, 1990.

EPA, 2009. FIFRA SCIENTIFIC ADVISORY P ANEL (SAP), December 1 – 3, 2009. Docket Number: EPA-HQ-OPP-2009-0687 http://www.epa.gov/scipoly/sap/7 MRID 43043301. Fleschar, E. M. Response to Ag ency Reviews of the Previously Submitted Study: "Volatilization of Dithiopyr Residues Following Applications to Turfgrass" MRID 416151601. Monsanto unpublished report number MSL-9686,

1993.

MRID 40638610. Yoshida, M. MON 7200 Acute Inha lation Toxicity Study in Rats. Monsanto unpublished report number ET-87-124, 1988.

EFED Response: EFED appreciates the data furnished by DAS concerning field volatility. The data provided will be reviewed by the Agency to characterize the volat ility of dithiopyr for

environmental risk assessments.

Comments regarding the ecological effect s of dithiopyr and associated studies

Reference: Page 22, Table 11-2, Row 1. Docu ment states: 850.1350 Saltwat er invertebrates life cycle - In the absence of these data, estuary/ma rine invertebrate chr onic toxicity data for surrogate pesticides – starting with da ta for closely related pesticides ( e.g. , pyridine herbicides) and proceeding to data for less related pesticid es – may be used to characterize the chronic toxicity of dithiopyr to estuary/marine invertebrates.

Reference: Page 23, Table 11-2, Row 1. Docu ment states: 850.1350 Saltwat er invertebrates life cycle - In the absence of these data, sediment-d welling invertebrate chronic toxicity data for surrogate pesticides – starting with da ta for closely related pesticides ( e.g. , pyridine herbicides) and proceeding to data for less related pesticid es – may be used to characterize the chronic toxicity of dithiopyr to sedi ment-dwelling invertebrates.

Reference: Page 23, Table 11- 2, Row 2. Document states: 850.4400 Aquatic plant toxicity test using Lemna spp. - In the absence of these data, Lemna toxicity data for surrogate pesticides – starting with data for clos ely related pesticides ( e.g. , pyridine herbicides) and proceeding to data for less related pesticides – may be used to ch aracterize the chronic toxicity of dithiopyr to aquatic vascular plants.

Reference: Page 23, Table 11-2, Row 3. Docu ment states: 850.4500 Algal toxicity - In the absence of these data, diatom toxicity data for su rrogate pesticides – starting with data for closely related pesticides ( e.g. , pyridine herbicides) and proceeding to data for less related pesticides – may be used to characterize the ch ronic toxicity of dithiopyr to freshwater and marine diatoms.

Reference: Page 24, Table 11-2, Row 1. Do cument states: 850.4550 Cyanobacteria - In the absence of these data, cyanobacteria toxicity data for surrogate pesticides – starting with data for closely related pesticides ( e.g. , pyridine herbicides) and proceeding to data for less related pesticides – may be used to characterize the ch ronic toxicity of dith iopyr to cyanobacteria.

Reference: Page 24, Table 11-3, Row 1. Document states: 850.2100 Av ian oral toxicity - In the absence of these data, passerine toxicity data fo r surrogate pesticides – starting with data for8 closely related pesticides ( e.g. , pyridine herbicides) and proceeding to data for less related pesticides – may be used to characterize the chro nic toxicity of dithiopyr to passerine species.

DAS Comment: DAS is in favor of not sacrificing mo re organisms in toxicity testing if EPA can determine that the use of surrogate data will not significantly impact the current available use patterns of dithiopyr. In the absence of such assertion, DAS w ill conduct the tests upon a request

from EPA.

EFED Response: As stated in the executive summary of the problem formulation, EFED

considers the above studies to be “data needs” for conducting the Regist ration Review ecological risk assessment. Only in the absence of data specific to dithiopyr will data for surrogate pesticides be used to characterize the toxicity of dithiopyr to terrestrial and aquatic organisms. The use of data for surrogate pesticides may result in conservative a ssumptions regarding the toxicity of dithiopyr. Therefore, how the use of data for surrogate pesticides will affect risk conclusions for dithiopyr is unknown. In respons e to a Data Call-In (D CI) for an ecological effects study, the registrant may submit a waiver request that includes an analysis of surrogate toxicity data for consideration towards fulfilling the need for dithiopyr-specific data.

Reference: Page 22, Table 11-2, Row 3. Docu ment states: 850.1400 Saltwat er fish early-life stage - In the absence of these data, an acute-t o-chronic ratio derived fr om toxicity data for freshwater fish may be used to estimate the chronic toxi city of dithiopyr to estuarine/marine fish. This methodology may yield a conservative estimate of the chronic toxicity of dithiopyr to estuarine/marine fish given the non- definitive acute toxicity endpoint from sheepshead minnow.

DAS Comment: DAS is in favor of not sacrificing mo re organisms in toxicity testing if EPA

can determine that the use of an acute-to-chronic ratio derived from toxicity data for freshwater fish will not significantly impact the current availa ble use patterns of dithiopyr. In the absence of such assertion, DAS will conduct th e tests upon a request from EPA.

EFED Response: EFED anticipates using an acute-to-chr onic ratio derived from toxicity data

for freshwater fish to estimate the chronic toxici ty of dithiopyr to estuarine/marine fish. As noted in the problem formulation, this met hodology may yield a conservative estimate of the chronic toxicity of dithiopyr to estuarine/mari ne fish given the non-definitive acute toxicity endpoint for sheepshead minnow. Th e registrant may submit an analys is of existing toxicity data for dithiopyr and/or surrogate pes ticides to be considered for char acterizing the chronic toxicity of dithiopyr to estu arine/marine fish.

Reference: Page 25, Table 11-3. Document states : EPA has identified the following data needed to conduct the risk assessment. ...adult honey bee acute oral toxicity da ta are not available.

DAS Comment: An adult honey bee acute oral and a further contact toxicity study were conducted in 2013 according to OECD guidelines 213 and 214 and GLP standards in order to satisfy the requirements for China [11]. The acute oral and acute c ontact 48- hour LD50 of dithiopyr technical was found to be > 119 μg a.i. /bee and > 100 μg a.i./bee, respectively. These9 endpoints provide evidence that dithiopyr is pr actically non-toxic to adult honey bees. This study can be provided to the EPA upon request.

Reference: Verge, E. Acute Oral and Contact Toxicity to the Honeybee Apis mellifera L. (Hymenoptera, Apidae) under Laboratory Conditions. Eurofins unpublished report number S13-00206, 2013.

EFED Response: EFED encourages the registrant to submit the above referenced study ( i.e.

, Verge, 2013) for consideration towards fulfilling th e need for honey bee acute oral toxicity data.

Reference: Page 25, Table 11-3. Document stat es: The “White Paper in Support of the Proposed Risk Assessment Process for Bees” as submitted to the FIFRA Scientific Advisory Panel proposes a screening-level risk assessment process that includes acute cont act and oral toxicity

tests with adult bees and an acute oral toxicity test with larval bees. Larval and adult honey bee acute oral toxicity data are not available. In the absence of these data, honey bee oral toxicity data for surrogate pesticides – starting w ith data for closely related pesticides ( e.g. , pyridine herbicides) and proceeding to data for less relate d pesticides – may be used to characterize the oral toxicity of d ithiopyr to honey bees.

DAS Comment: As dithiopyr has a herb icide mode of action and is not an insect growth regulator, it is not expected to impact terrestrial invertebrate s. This is supported by the 850.3020 compliant study referenced in EPA-HQ-OPP-20 13-0750-0003 [12], as well as two additional GLP studies available [11], which provide eviden ce that dithiopyr is pr actically non-toxic to adult honey bees and does not cause sub-lethal effects or behavior al differences. Therefore it is reasonable to assume that if residues are pres ent in nectar and polle n, during flowering, those residues would similarly be practic ally non-toxic to adult honey b ees and that any residues taken back to the hive would also be pr actically non toxic to honey bee larvae.

Additionally, dithiopyr is a pre-emergence and early post-emergence herbicide not applied during flowering growth stages and, therefore, applications are expected to have negligible impact on foraging worker bees.

DAS disagrees that an acute oral toxicity test with larval bees is necessary based on the available

information.

References: MRID 40638626. Hoxter, K. A. MON 7200 An Acut e Contact Toxicity Study with the Honey

Bee. Wildlife Internationa l unpublished report number 139-236, 1987.

Verge, E. Acute Oral and Contact Toxicity to the Honeybee Apis mellifera L. (Hymenoptera, Apidae) under Laboratory Conditions. Eurofins unpublished report number S13-00206, 2013.

EFED Response: At this point, EFED does not have an understanding of the relative sensitivity

of the adult and larval life st ages of honey bees. Even though th e mode of action of dithiopyr on10 target species would not be of concern for adult bees, it may ha ve an unintended mode of action that could impact larvae.

In regards to exposure, DAS did not provide e nough information to preclude an exposure to larvae. There may be exposure if it is applied to areas adjacent to plants that are flowering. In addition, since dithiopyr is systemic, there may be exposure if it is pers istent enough in treated plants to still be present at th e time of flowering (and therefore be present in nect ar and pollen).