change specific parts of the Registration Review Problem Formulation. This document contains responses only to those comments submitted related to the ecological risk assessment or the drinking water exposure assessment outlined in the problem formulation. Given the large number of comments and the similarity between comments, comments ha ve been grouped together and summarized by common topic.



### 2OPP RESPONSE TO PUBLIC COMMENTS :



### 1. Comment Summary: C 

### hlorothalonil drift from treated fields to areas where bystanders (including frogs) may live, work or frequently visit should be considered as part of the registration review process.

ID Number: EPA-HQ-OPP-2011-0840-0010; Commenter: Carol Ashley; Organization : none

OPP RESPONSE: Potential chlorothalonil spray drift will be assessed during the registration review process. In addition, data on the pote ntial volatilization of chlorothalonil following application has been requested. The potential risks associated with drift and volatilization will be assessed as part of the registration review process.



### 2. Comment Summary: Based on the cited reference (Holt et al ., 2010) the levels found should be expressed as 39 ng Σ PCDD/F g -1 AI.

ID Number: EPA-HQ-OPP-2011-0840-0016; Commenter: Syngenta; Organization : Syngenta

OPP RESPONSE: As stated in the problem formulation, “(t)hese chemicals have been found in technical grade chlorothalonil, as well as formulated chlorothalonil products ; however, the levels are low (39 ng DF/g a.i.). 1 ” The unit/term “DF” was defined as “polychlorinated dioxins (D) and dibenzofurans (F)” in the same paragraph as th e quoted text. The difference in the expressions used by EPA in the problem formulation and that suggested by Syngenta does not impact data requirements or the conceptual m odel for conducting risk assessment.



### 3. Comment Summary: The correct chemical name for R419492 is 4-amido-2,5-dichloro-6- cyanobenze.

ID Number: EPA-HQ-OPP-2011-0840-0016 ; Commenter : Syngenta; Organization : Syngenta

OPP RESPONSE: The typo has been corrected.



### 4. Comment Summary: Chlorothalonil application rate corrections were provided for several crops: banana, cherry, filbert (hazelnut), golf cour se, papaya, passion fruit, plantain, squash, and

stone fruits.

ID Number: EPA-HQ-OPP-2011-0840-0016 ; Commenter : Syngenta; Organization : Syngenta

OPP RESPONSE: EFED confirmed that the use (applicati on rates) information provided by Syngenta is correct. During the registration review process EFED will assess all uses as specified on the registered labels current at the time of the assessment is completed.



### 5. Comment Summary: The studies given as the source for several environmental fate studies (00071625, 00071627, 00087369, 00087301 and 00087332) could not be confirmed or located in either the Syngenta electronic or hard-copy archives. MRID 00087332 presents data for both a laboratory study, which provided the product iden tification, and a field study, which quantified

the environmental concentrations of the identified products.

1 Holt. E.; Weber, R.; St evenson, G.; Gaur, C. Environ. Sci. Technol. 2010, 44 , 5409-5415.



### 3ID Number: EPA-HQ-OPP-2011-0840-0016 ; Commenter : Syngenta; Organization : Syngenta

EFED RESPONSE: The listed environmental fate MR ID references (00071625, 00071627, 00087369, 00087301 and 00087 332) are correct, and are studies previously submitted to support chlorothalonil. The information provided for MRID 00087332 is correct. This study is classified as supplemental as stated in the problem formulation.



### 6. Comment Summary: The referenced studies presented monitoring data from the Central Valley of California and surrounding areas (EPA footnotes 19, 20 and 21, Pages 46-47), which indicated the potential for long-range atmospheri c transport of pesticides. Sparling et al . (2001) and Fellers

et al . (2004) provided data for several organophosphorous and organochlorine pesticides, but did not provide monitoring data specific to chloroth alonil (EPA footnotes 20 and 19, respectively).

Lenoir et al . (1999), EPA footnote 21, did present chlorothalonil monitoring data but a mechanism for transport was not identified. The st atement should be clarified to reflect that only

LeNoir et al . (1999), EPA footnote 21, presented information on chlorothalonil.

ID Number: EPA-HQ-OPP-2011-0840-0016 ; Commenter : Syngenta; Organization : Syngenta

OPP RESPONSE: The referenced literature articles (Sparling, et al

. 2 and Fellers et al

. 3 ) were used in general terms as a means to highlight the potential for pesticide volatilization and subsequent off site transport. These two articles did not specifically look for chlorothalonil; therefore, the presence or absence of the chemical cannot be confirmed. One of the referenced articles (Lenoir et al

. 4 ) includes detections of chlorothalonil. While this study does not suggest a transport mechanism, the detection of chlorothalonil in air cannot be dismissed. Furthermore, additional citations were provided that suggest chlorothalonil is getting into the air following application and may be transported offsite. Th is suggests that chlorothalonil may volatilize from

treated field.



### 7. Comment Summary: As part of the response to Chlorothalonil Salmonid BiOP, Syngenta reviewed the available monitoring data (Synge nta Report TK0026829). Details are available in the report, but in general, water monitoring data collected across 18 years, including multi-year national surveys (NAWQA), targeted state su rveys (WSDA and USGS) and academic surveys and upwards of 10,00 collective samples indicate no residues in water above 0.71 ppb.

ID Number: EPA-HQ-OPP-2011-0840-0016 ; Commenter : Syngenta; Organization : Syngenta

OPP RESPONSE: OPP uses mathematical models as well as monitoring data to generate exposure estimates for drinking water a nd aquatic exposure asse ssments. Modeling and monitoring data are both important tools that by and large provide different types of information that can be used for assessing pes ticide concentrations in water.

Mathematical models are used to generate e xposure estimates for drinking water and aquatic

environments to better understand the extent to which monitoring data may underestimate

2 Sparling, D.W., Fellers, G.M., McConnell, L.L., 2001. Pesticides and amphibian population declines in

California USA. Environ. Tox. Chem. 20: 1591-1595.

3 Fellers, G.M, L.L. McConnell, D. Pratt, S. Datta. 2004. Pesticides in Mountain Yellow-Legged Frogs (Rana Mucosa) from the Sierra Nevada Mountains of California, USA. Environ. Tox. Chem. 23 (9):2170-2177.

4 LeNoir, J.S., L.L. McConnell, G.M. Fellers, T.M. Cahill, J.N. Seiber. 1999. Summertime Transport of Current-use pesticides from California’s Central Va lley to the Sierra Nevada Mountain Range, USA. Environmental Toxicology & Chemistry 18(12): 2715-2722.



### 4exposures, both spatially and temporally. Mode ls, specifically PRZM-EXAMS, calculate EDWCs using laboratory data that describe how fast a pesticide breaks down to other chemicals and how it moves in the environment. In addition, modeling provides an efficient tool for exploring the impact of different environmental factors such as soil type and meteorological conditions on estimated pesticide concentrations in water. Although computer modeling provides an indirect estimate of pesticide concentrations, these con centrations can be estimated continuously over long periods of time, and for places that are of most interest for a particular pesticide. Modeling is a useful tool for characterizing vulnerable sites, and can be used to estimate peak concentrations from infrequent, large storms.

Monitoring data can elucidate what is happeni ng under current use practices and under typical conditions. Although monitoring data can provide a direct estimate of the concentration of a pesticide in water, it does not always provid e a reliable estimate of peak exposures because sampling may not occur where the highest pesticide concentrations are found and/or sampling may not occur when the pesticide concentrations ar e the highest. It is also important to consider the design of the monitoring program where there is use information available and where it was targeted to chemical specific use areas.

EFED will evaluate all available monitoring data for chlorothalonil during the registration review process. Monitoring data and modeling estimates w ill be used together to characterize the potential exposure to chlorothalonil. It would not be appropriate to rely solely on monitoring data; for the reasons explained above, not to menti on the fact that it would be inefficient and ineffective, if not impossible, to capture all rele vant scenarios, site and meteorological conditions, soil types, etc ., in a monitoring program.



### 8. Comment Summary: The final report [for the PGW stud y] was submitted February 9, 1998 (MRID 44483401).

ID Number: EPA-HQ-OPP-2011-0840-0016 ; Commenter : Syngenta; Organization : Syngenta

OPP RESPONSE: This study will be reviewed as part of the registration review process. Thank you for providing the MRID.



### 9. Comment Summary: The final report [for the PGW stud y] was submitted February 9, 1998 (MRID 44483401). Field dissipation data for SDS- 3701 can be obtained from the submitted PGW study (MRID 44483401).

ID Number: EPA-HQ-OPP-2011-0840-0016 ; Commenter : Syngenta; Organization : Syngenta

OPP RESPONSE: This study will be reviewed as part of the registration review process and may provide useful information on the dissipation of SDS-3701 in the environment. The acceptability of these data (PGW study) are not exp ected to impact the risk assessment approach explained in the problem formation



### 10. Comment Summary: Syngenta provided additional information relating to the deficiencies identified in the terrestrial field dissipation study. “ Syngenta Comment: Several points can be addressed: (1) a final report for the freezer-storage stability study conducted over 4 years was submitted (MRID No. 44483402); (2) and (3) th e PGW study (MRID No. 44483401) presented the results of shallow- and deep-core sampling conducted from 0 to 24 MAA from which rates of dissipation for chlorothalonil and SDS-3701 could be derived. During the conduct of the PGW



### 5study, (4) analytical methods for determination of residues of chlorothalonil, SDS-3701, SDS19221, SDS-47525 and SDS-46851 were developed.”

ID Number: EPA-HQ-OPP-2011-0840-0016 ; Commenter : Syngenta; Organization : Syngenta

OPP RESPONSE: (1) MRID 44483402 will be reviewed as part of the registration review process. Thank you for providing the MRID. The acc eptability of these data (storage stability) are not expected to impact the risk assessment appr oach explained in the problem formation nor does it change the data requirements. (2) and (3) the design of a PGW study is to examine the leaching potential of a pesticide and its transformation pr oducts through a vertical soil profile in a soil highly vulnerable to leaching; however, it is not a terrestrial field dissipation study and does not consider other dissipation routes and site conditions that should be c onsidered in a terrestrial field dissipation study. (4) If the analytical methods used in the PGW are representative suitable environmental chemistry methods and have been i ndependently validated, then a waiver for the environmental chemistry methods requirement should be submitted to EPA that includes the reports and methods along with th e independent lab validation.



### 11. Comment Summary: A field volatility study is not trigge red per EPA guidance and; therefore, the study should not be required.

ID Number: EPA-HQ-OPP-2011-0840-0016 ; Commenter : Syngenta; Organization : Syngenta

OPP RESPONSE: There are monitoring data available that suggest that chlorothalonil is present in air as well as precipitation samples. These real wo rld data suggest that chlorothalonil may be volatilizing off treated fields. In order to acc ount for this dissipation route and the potential exposure to chlorothalonil as a result of volatilization a field study is needed.

This study (field volatilization) may be combined with a standard terrestrial field dissipation study.



### 12. Comment Summary: Urban exposure and runoff of chlorothalonil was overlooked.

ID Number: EPA-HQ-OPP-2011-0840-0021 ; Commenter : Janet B. O’Hara; Organization : San Francisco Bay Regional Water Control Board

ID Number: EPA-HQ-OPP-2011-0840-0015; Commenter: Sipcam Agro USA, Inc.; Organization: Sipcam Agro USA, Inc.

OPP RESPONSE: EFED is currently further exploring me thods to assess urban and residential

uses on a national basis. EFED will consider comment s regarding the need to include models that consider transport of runoff from impervious su rfaces and stormwater drainage systems while it develops these methodologies. At the present time , EFED considers the use of the impervious scenario (a Pesticide Root Zone Model (PRZM) modeling scenario) as the most suitable available modeling approach for impervious runoff and h as used this approach for some assessments completed for Endangered Species in California. The PRZM impervious scenario may be used in the Tier 2 coupled aquatic models PRZM/Expos ure Analysis Modeling System (EXAMS) along

with a residential or other suitable scenario su ch as rights-of-way (ROW) to obtain Estimated Environmental Concentrations (EECs). The c onceptual model for the residential scenario integrates simultaneous modeling of the individual use scenario with an impervious scenario. This approach assumes that no watershed is complete ly covered by either the 1⁄4 acre lot (the basis



### 6for the residential scenario) or undeveloped land (t he basis for the ROW scenario) for residential and ROW use patterns; therefore, differential amount s of runoff will occur within the watershed. The impervious scenario was developed to repr esent the paved areas within a watershed not including roads, parking lots, sidewalks, and buildings outside the 1⁄4 acre lot (the 1⁄4 acre lot scenario accounts for impervious surfaces such as buildings with in the represented area). By modeling a separate scenario for impervious surf aces, it is also possible to estimate that amount of exposure that could occur when the pesticid e is oversprayed onto this surface. Using two scenarios in tandem requires post-processing of the m odeled output in order to derive a weighted EEC that represents the contri bution of both the pervious ( i.e., residential and ROW scenarios) and the impervious surfaces. Exposure from both scenarios can also be weighted and aggregated. The daily time series from each model run from the times series file (NAME_TS.out) generated from the PRZM graphical user interface (PE5.pl) residential and impervious surface scenarios are combined using Microsoft EXCEL. The time seri es data are weighted based on percentage of impervious surface, the percentage of the pervious surface treated, and an adjusted time series is created. Rolling averages for the relevant durations of exposure ( e.g. , 21-day and 60-day averages) are calculated, and the relevant one-in-ten year EEC is generated from these

distributions.

The Agency intends to use available non-agric ultural use and usage data, such as the Kline database, the California Department of Pestic ide Regulation’s (CDPR) Pesticide Use Reporting Data and Pest Control Operator’s usage survey , and the Residential Joint Venture Task Force homeowner survey data (2003), to make certa in reasonable assumptions regarding various applications and information related to urban/resi dential use are made. Due to the limited data available, exposure to the environment and uncertainties will be characterized. Detailed information on non-agricultural use and usage of chlorothalonil would be useful in order to

reduce those uncertainties for the final envir onmental risk assessment for chlorothalonil.

As stated in the problem formulation, AD anticipates requiring data on the leaching of chlorothalonil from treated wood. The leach rate from other material preservative uses ( e.g ., stucco, paint, coating, and caulk) is desired but in the absence of leaching data, the wood leaching

results will be used to assess all of the outdoor antimicrobial uses. When the registered antimicrobial chlorothalonil products are used in urban settings, AD will consider using the approach outlined above. Please see the conceptual models outlined in the problem formulation

for more information.



### 13. Comment Summary: The risk assessment must include analysis of products contaminants including dioxins, furans, and hexachloroben zene) and transformation products (particularly SDS-3701).

ID Number: EPA-HQ-OPP-2011-0840-0021 ; Commenter : Janet B. O’Hara; Organization : San Francisco Bay Regional Water Control Board

OPP RESPONSE: The problem formulation identified stressors of concern including

contaminants and transformation products (including SDS-3701) an d how they will be assessed in

the final risk assessment.



### 14. Comment Summary: In the problem formulation EFED reco mmends that the Agency work with registrants to establish the level of known impurities. Sipcam comments that “ 

### The levels of HCB in currently registered technical produc ts are well establishe d: current technical products are produced to a specification of < 40ppm HCB. Sipcam Agro USA, Inc. has

7ID Number: EPA-HQ-OPP-2011-0840-0015; Commenter: Sipcam Agro USA, Inc.; Organization: Sipcam Agro USA, Inc.



### OPP RESPONSE: The Agency encourages the registrants to submit relevant information at any time or, at the very latest, at the time of the data call-in associated with this registration

review.



### 15. Comment Summary : The identified NOEC (1.3 μg a.i./L) for the chronic fish toxicity study (MRID 00030391) in the problem formulation is not supported by the cited study as the NOEL was calculated to be 3 μg a.i./L based on significant effects on reproduction and hatchability.

ID Number: EPA-HQ-OPP-2011-0840-0016 ; Commenter : Syngenta; Organization : Syngenta

OPP RESPONSE : There was a 79% and 88% decrease in the mean number of eggs per female in the 3.0 and 6.5 μg/L treatment groups, respectiv ely, compared to the negative control group. However, due to inherent variability in egg pr oduction and that the study only utilized two replicates per treatment, the statistical analysis could only detect a 110% difference from the control. Therefore, the 79% and 88% decrease s were not statistically significant (p>0.05, Dunnett’s). EFED considers these decreases to be biologically significant and a NOEC of 1.3 μg

a.i./L will be used in the risk estimation of th e risk assessment. If the re gistrant has evidence or

information that demonstrates that decreases of these magnitudes do not have an impact on the fitness of the fish population, then EFED will consider such information.



### 16. Comment Summary: The chronic NOEC for freshwater invertebrates is identified as 0.6 μg a.i./L (MRID 45710222) which is classified as supplemental and was not included in the RED (U.S. EPA 1999) for chlorothalonil. This endpoi nt is not consistent with the core chronic invertebrate study (MRID 00115107) which demons trated a NOEC of 39 μg/L. The registrant considers the study with the NOEC of 39 μg/L the best available data.

ID Number: EPA-HQ-OPP-2011-0840-0016 ; Commenter : Syngenta; Organization : Syngenta

OPP RESPONSE: EFED has re-evaluated the toxicity data for MRID 45710222. This study

was not included in the 1999 RED as it was not submitted to the Agency until June 20, 2002 

### (however, it has been used in subsequent risk assessments) . In the study report, the estimated ‘no observed effect concentration’ value was 0.6 μg/L, based on direct lethal effects ( ≤ 20% immobility). Although the test concentrations dissipated betw een renewal periods thereby, introducing uncertainty into the actual exposure concentrations, EFED considers the immobilization toxicity observed to be treatment-related based on: 1) a decreasing trend (monotonic response) in survival as the concentr ation increased; 2) the effect was consistent between replicates within test concentrations; a nd 3) survival in both controls (negative and solvent) was 93%. Survival in the treatment gr oups ranged from 95% at the lowest treatment (0.6 μg/L) to 40% at the highest (75 μg/L). Immobili zation of the parental generation was statistically significantly (p<0.05, using Dunnett’s and William’s test) at concentrations ≥ 1.8 μg/L (75% survival); therefore, the NOAEC value is 0.6 μg /L based on immobilization. Significant effects (p<0.05) on reproduction (number of live young pe r adult) were also reported for the 75 μg/L treatment group. The NOAEC value of 0.6 μg/L is considered to be adequate for quantitative

use. EFED uses the lowest effect value obser ved from all available studies that have been



### 8deemed appropriate for quantitative use, which may include studies that have an overall study classification of core (acceptable) or supplemental , for calculating risk quotients (RQs) in a risk assessment. Therefore, the NOAEC value of 0.6 μg /L will be used in calculating the RQ value while the NOAEC value of 39 μg/L observe d in study MRID 00115107 will be used in characterizing risk.



### 17. Comment Summary: The chronic NOEC for birds is identified as 153 mg/kg-diet (MRID 45710218) in the problem formulation. This study was not included in the RED (U.S. EPA 1999) for chlorothalonil and is not statistically supported.

ID Number: EPA-HQ-OPP-2011-0840-0016 ; Commenter : Syngenta; Organization : Syngenta

OPP RESPONSE: The results of this study (MRID 45710218) were not included in the chlorothalonil RED, because it was not submitte d to the Agency until after the RED was completed (submitted on June 20, 2002 and it has b een used in subsequent risk assessments). A NOAEC of 153 mg a.i./kg-diet and a LOAEC of 624 mg a.i./kg-diet were based on a reduced number of egg laid per hen. Although the endpoints were not statistically significantly different than the controls (p>0.05), the differences were considered biologically significant (there was an 18% reduction in the number of eggs laid/hen at the 624 mg a.i./mg-diet concentration when compared to the controls). The NOAEC value of 153 mg/kg-diet was used in the chronic avian RQ calculations (using the T-REX model) for the California red-legged frog risk assessment (CRLF RA) (EPA 2007). If the registrant has ev idence or information that demonstrates that a decrease of this magnitude does not have an impa ct on the fitness of the bird population, then

EFED will consider such information.



### 18. Comment Summary: Syngenta previously submitted 16 studies with formulation specific toxicity data for fish (rainbow trout) and invertebrates (Daphnia) for consideration.

ID Number: EPA-HQ-OPP-2011-0840-0016 ; Commenter : Syngenta; Organization : Syngenta

OPP RESPONSE: The Agency has received the data a nd will consider the information as part of the risk assessment for the regist ration review of chlorothalonil.



### 19. Comment Summary : A formation rate of 34% of SDS-3701 was assumed based on formation observed in soil metabolism studies (MRIDs 00040547 and 00087351). The available data demonstrate that residue levels on plant foliage do not support the highly conservative formation rate of 34% on potential food items.

ID Number: EPA-HQ-OPP-2011-0840-0016 ; Commenter : Syngenta; Organization : Syngenta

OPP RESPONSE : A discussion about the formation of SDS-3701 on avian and mammalian food items is presented in the 1999 RED and 2007 CRLF risk assessment. Studies that evaluated the amount of SDS-3701 that may form after chlorothalonil application to peanut hay, turf, and grass grown for seed are available. However, these studies do not provide a dependable basis for estimating the amount of SDS-3701 that may fo rm on avian and mammalian food items as described in the 1999 U.S. EPA RED. In a peanut hay study (MRID 43843601), SDS-3701 residues were reported at a maximum of 24% of the parent chlorothalonil residues. The 1999 RED reported that use of a 10% formation rate would be conservative; however, it also stated that due to the observed formation of 24% in the p eanut hay study, it is conceivable that under different conditions, residues of SDS-3701 could reach higher levels.



### 9

### 10 As previously stated in these documents, there ar e insufficient residue study data to characterize with certainty how much SDS-3701 will form on avian and mammalian food items. Most of the available residue studies were designed to measu re the amount of SDS-3701 that is taken up by crops and how much accumulates in vegetable ite ms associated with human consumption such as beans and fruits. Unfortunately, most of these studies do not provide a dependable basis for estimating how much SDS-3701 will form on avia n and mammalian food items in the days immediately following treatment with chlorothal onil, as measurement of chlorothalonil and its degradates generally occur days up to months after the last chlorothalonil application (RED, EPA 1999). Typically, a minimum of three reliable residue studies which measure residues immediately after application are needed to adequate ly evaluate potential magnitude of formation.

As the residue data was deemed to not be sufficient, the available laboratory data were used to estimate the amount of SDS-3701 that may form on terrestrial organism food items. Soil metabolism studies suggest that SDS-3701 could form at levels of approxi mately 34% of applied parent material. SDS-3701 was observed in several of the submitted aerobic soil metabolism studies (MRIDs 00087351/00040547, 4387960, 47207702, and 47207703. The maximum concentration ranged from <10% to 34.1% (n=14) in various soils and time points. In four of the test systems the concentration of SDS-3701 was >20%. The second highest concentration of SDS-3701 observed was 28.4%, thereby, sugges ting that 34% is an appropriate maximum

formation value.



### 20. Comment Summary: Sipcam provided citations for exis ting public literature studies on the leaching of chlorothalonil from treated wood and requested guidance with regards on the methods

and substrates that should be used to conduct th e leaching studies anticipated to be required.

ID Number: EPA-HQ-OPP-2011-0840-0015; Commenter: Sipcam Agro USA, Inc.; Organization: Sipcam Agro USA, Inc.

OPP RESPONSE: The Agency encourages the registrants to submit relevant studies and applicable waivers in response to the data call-in associated with this registration review. At that time, the Agency will review the information to determine if the wood leaching data requirement is adequately met and can be waived. In the event the literature studies are not sufficient, the Agency recommends that the registrant c onduct the study according to the AWPA E11-06 method for addressing leaching from wood submerged in water. As stated in the problem formulation, the Agency anticipates utilizing these data “to determine the leach rate of chlorothalonil and its major toxic transformati on products, and impurities of concern out of preserved wood for use in modeling loading to soil from rain washoff of antimicrobial applied wood preservatives.”