Page 1 of 17 OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION U. S. ENVIRONMENTAL PROTECTION AGENCY WASHINGTON D.C., 20460

PC Code: 101701
DP Barcode: D414467

MEMORANDUM April 21, 2015

SUBJECT: Propyzamide (Pronamide): Tier II Drinking Water Exposure Assessment in support of the Proposed Use of Propyzamide on Leaf Lettuce

TO: Wilhelmena Livingston, Chemical Review Manager Kevin Costello, Acting Branch Chief Risk Management and Implementation Branch IV
Pesticide Re-evalua tion Division (7508P)

Ideliz Negrón-Encarnación, Ph.D., Chemist Danette Drew, Senior Chemist Stephen Dapson, Ph.D., Toxicologist Mike Metzger, Branch Chief
Risk Assessment Branch V and VII Health Effects Division (7509P)

CC: Keri Grinstead, Risk Manager Tawanda Maignan, Emergency Response Team Leader Minor Use and Emergency Response Branch Registration Division (7505P)

Mindy Ondish, Risk Manager Kathryn Montague, Product Manager Daniel Kenny, Branch Chief
Herbicide Branch Registration Division (7505P)

FROM: Karen Milians, Ph.D., Chemist
Environmental Risk Branch IV
Environmental Fate a nd Effects Division (7507P )

REVIEWED
BY: Jim Carleton, Ph.D., Senior Scientist
Environmental Risk Branch IV
Environmental Fate a nd Effects Division (7507P)Page 2 of 17 APPROVED
BY: Jean Holmes, DVM, MPH, Branch Chief
Environmental Risk Branch IV
Environmental Fate a nd Effects Division (7507P)

The Environmental Fate and Effects Division (EFE D) has completed a review of a proposed new use of propyzamide (Kerb ® 3.3 SC, EPA Reg. No. 62719-578, 35.6 % active ingredient) on leaf lettuce. The proposed single application rate ranges from 0.5 to 2.0 lbs a.i./acre. Because leaf lettuce may be cropped twice per year, this use represen ts a maximum annual app lication rate of 4.0 lbs
a.i./acre.

In the previous drinking water assessment (D WA), estimated concentrations (EDWCs) of propyzamide in surface water and in ground wa ter were generated based upon maximum use patterns of propyzamide (USEPA, 2007). That a ssessment used a total toxic residues (TTR) approach to estimate exposure to the residues of concern, i.e. propyzamide and all of its degradates that contain the 3,5-dichlorobenzoyl moiety (U SEPA, 2002; 2007). In th e current assessment, available monitoring data on propyzamide are review ed, and up-to-date models used to estimate residues in surface and ground water-based drinking wa ter. Like the previous assessment, this one uses a TTR approach in estimating exposures to propyzamide residues of concern (USEPA, 2002; 2007). Various procedural and informational changes have been incorporated into this assessment, resulting in EDWCs that differ from those genera ted previously. These changes include a new batch equilibrium study (OCSPP 835.1230), input paramete r guidance (USEPA, 2009), use of the PRZMGW model to generate ground water EDWCs (U SEPA, 2012a), new percen t cropped area (PCA) adjustment factors (USEPA, 2012b) and new o ff-site spray drift gui dance (USEPA 2013).

Current propyzamide labels fail to state maximum a pplication rates for certain crops in annual terms. Application rates for these crops are instead given on a per season ( e.g. , for turf, leaf lettuce) or per crop basis (e.g., head lettuce, endive, escarole, and ra dicchio greens), or else are not given in terms of any particular time frame ( e.g., alfalfa seed). For these crops, conservative assumptions were employed to estimate plausible maximum annual application rates.Page 3 of 17 1. EXECUTIVE SUMMARY

The Environmental Fate and Effects Division (EFE D) has reviewed a request for a new use of propyzamide (also referred as pronamide) on leaf le ttuce. The maximum proposed single application
rate for leaf lettuce is 2.0 lbs a. i./acre, however neither a maximum number of applications annually, nor a maximum annual rate are specified on the proposed label. For assessment purposes, EFED assumed two leaf lettuce growing seasons may occu r per year, resu lting in a maximum annual rate
of 4.0 lbs a.i./acre. In this assessment the articho ke use was also modeled because this use allows the maximum application rate (for any crop) of 8 lbs a.i./acre ( i.e ., 4 lbs a.i./acre x 2 assumed applications/yr). Table 1 show the estimated drinking water concentrations in surface water and ground water (including values using Sci- Grow and PRZM-GW for ground water. The recommended estimated drinking water concentrati ons (EDWCs) for the Health Effects Division’s (HED) dietary assessment is 102 ppb for the acute dietary assessment and 47.0 ppb for the chronic and cancer dietary assessments.

Table 1. Tier II Total Residue of Concern EDWCs in Surface Water and Ground Water from Propyzamide Uses on New Uses (Maximum EDWCs in Bold). Drinking Water Source (Model, Use, Modeled rate) Scenario EDWCs
Acute (μg/L) Chronic (μg/L) Cancer (μg/L)
Surface Water (SWCC, Artichokes, 4 lb a.i./A x 2 applic.; total of 8 lb/A/yr) CA row crop RLF (aerial application) 61.4 33.4 26.0

Surface Water (SWCC, Leaf Lettuce, 2 lb a.i./A x 2 applic.; total of 4 lb/A/yr) CA lettuce (aerial application) 102 47.0 33.6

Ground Water (PRZM-GW, Artichokes, 4 lb a.i./A x 2 applic.; total of 4 lb/A/yr) WI sands 21 18.6 18.6

Ground Water (SCI-GROW, Artichokes, 4 lb a.i./A x 2 applic.; total of 8 lb/A/yr) N/A 0.802 0.802 0.802

Ground Water (SCI-GROW, Leaf Lettuce, 2 lb a.i./A x 2

applic.; total of 4 lb/A/yr) N/A 0.401 0.401 0.401

N/A= Not Applicable Values in bold show the EDWCs recommended for HED’s acute (102 ppb) and chronic (47.0 ppb) and cancer (33.6 ppb) dietary risk assessment as they are considered protective of all the registered uses of pronamide.

The standard all-agricultural PCA of 1.0 was used for all other uses because they are not limited to specific regions of the U.S. Surface water ED WCs were calculated using the Surface Water Concentration Calculator (SWCC). Ground water EDWCs were calculated using both SCI-GROW
and PRZM-GW.Page 4 of 17 Monitoring data on propyzamide ha ve revealed concentrations in the environment consistent with the peak (3.7-10.3 μg/L) and annual mean (0.53-4.45 μg /L). Monitoring data are not available on any degradates of propyzamide. Ther efore, concentration estimates for total toxic residues cannot be directly compared against available monitoring data.

Propyzamide is an organochlorine herbicide (pre-emergence and early postemergence control of winter annual and perennial gra sses and chickweed) that is typi cally applied aerial or ground, and wetted in, during the fall or winter months. The major routes of degradation of pare nt appear to be aerobic microbial degradation in so il (44.6 d) and photolysis in wate r (217 d). Four major degradates of propyzamide have been identified (R H-24644, RH-24655, RH-24580 and RH-26059, with a maximum applied radioactivity of 31.9%, 27.3%, 32.2%, and 15.0%, re spectively). The Health Effects Division (HED) found all de gradates of propyzamide that contain the 3,5-dichlorobenzoyl moiety to be of risk concern, assuming that their toxicity is similar to that of propyzamide parent (USEPA, 2002; 2007). A total toxic residues (TTR) approach was therefore used to generate EDWCs that reflect residues, in dr inking water, of the parent com pound plus all such degradates of

concern.

Propyzamide has relatively lo w vapor pressure (8.5 x 10 -5 torr; 25°C) and is so luble in water up to 15 mg/L (25°C). The compound is stable to hydroly sis, relatively resistan t to soil photolysis (t 1/2 = 249 d), and moderately susceptib le to aquatic photolysis (t 1/2 = 42 d). Propyzamide degrades relatively readily in aerobic soil environments (t 1/2 = 20-44.6 d), but is more persistent in anaerobic environments (t 1/2 = 127-450 d) and aquatic environments (aerobic aquatic and anaerobic aquatic half-lives of 119 d and 450 d, respectively). Sorp tion to soils is a function of organic carbon. Soil sorption also correlates with cati on exchange capacity. Nonetheless the compound is mobile in soil [K F range = 3.15 (1/n=1.22) – 10.1 (1/n=1.00)], and thus presents a potential groundwater concern in some areas, e.g ., those with sandy soils and high water ta bles. Propyzamide has been detected in both surface water and groundwater.

EDWCs based on total toxic residues for propyzamide likely exceed act ual concentrations in most drinking water supplies due to the screening (con servative) nature of the exposure models, use national PCA (1.0), and limited acceptable environmen tal fate data. In accordance with EFED’s Input Parameter Guidance, degradation half-liv es employed in the models are 90 percent upper
confidence limits on mean values.

2. USE CHARACTERIZATION

Propyzamide is a systemic, organochl orine herbicide. There are two active registrations (EPA Reg. No. 62719-578 and 62719-397), allowing use on alfalfa, apples, globe artichokes (CA), birdsfoot trefoil, blackberry/boysenberry/rasbe rries (IH, OR, WA), blueberries, cherries, clover, crown vetch, endive, escarole, grapes, fallow land, head lettu ce, nectarines, peaches, pears, plums, prune, radicchio greens, raspberries, rhub arb, sainfoin, winter peas, woody ornamentals, nursery stock of ornamentals, and Christmas trees.

Propyzamide is formulated as a wettable powder in water soluble pouches and can be applied preplant, pre-emergence, and post-emergence by gr ound or aerial spray equipment, depending on the use. Wetting in of applications is recommended with rainfall or irri gation. The maximum annual application rate for propyzamide uses is 8 pounds of active ingred ient per acre (lbs a.i./A) onPage 5 of 17 artichokes. The use on artichoke s which are only grown in Calif ornia, can involve up to two applications per season for a maximum annual applica tion rate of 8 lbs a.i./A (aerial and/or ground application).

The uses on lettuce (leaf and h ead) and artichokes are the maximu m use patterns affecting surface water and ground water exposure ( Table 2 ).

Table 2 displays the maximum use patterns of th e current labels (EPA Reg. No. 62719-578).

Table 2. Maximum Use Patterns for Current Propyzamide Uses.

Use
Pattern Single App. Rate (lbs a.i./A) Number of Apps per

Year. 1 Annual App. Rate (lbs a.i./A) Minimum
Retreatment
Interval

(days) Application
Method Comments

Artichoke 4 2 8 Not specified Aerial/ground In CA only
Leaf
Lettuce 2 2 4 183 d Aerial/ground Assuming two crops/year

1 Assumed

3. ENVIRONMENTAL FATE AND TRANSPORT CHARACTERIZATION

The environmental fate and transport-related properties of propyzamide are shown in Table 3

. Parent propyzamide is slightly to moderately mobile (FAO 2000), and moderately labile to degradation under aerobic conditions in soil, and via photolysis in wate r. Half-lives for total toxic residues generally range from mont hs to years, in part because all identified degradates except
carbon dioxide are considered to be of risk concern due to the 3,5- dichlorobenzoyl moiety (USEPA, 2007).

Table 3. General Chemical Properties a nd Environmental Fate Parameters of Propyzamide.
Chemical/Fate Value Source

Chemical name 3,5-dichloro-N-(1,1- dimethylprop-2-ynyl)benzamide USEPA, 1994

Molecular mass 256.13 g/mol USEPA, 1994 Vapor pressure (25  C) 8.5 x 10 -5 torr USEPA, 1994 Solubility (25  C) 15 mg/L USEPA, 1994 Octanol-water partition coefficient (K O W ) 1000-2000 MRID 46413408

Freundlich soil-water distribution coefficient (K F ) ;

Freundlich organic carbon partitioning coefficient (K FOC ) in L/ kg OC 700
1026
1150
1317
1586
2283
2287
5383 MRID 49126805

Hydrolysis half-life at pH 4.7, 7.4 and 8.8 (20  C) No significant degradation MRID 00107980Page 6 of 17 Table 3. General Chemical Properties a nd Environmental Fate Parameters of Propyzamide.
Chemical/Fate Value Source

Aqueous photolysis half-life;
Total toxic residues half-life 41.7 d; 217 d MRID 40420301, MRID
40320601 Soil photolysis half-life;

Total toxic residues 249 d; No significant degradation MRID 41913504

Aerobic soil metabolism halflife;
Total toxic residues half-life (soil texture) 20.1 d; 64.9 d (sandy loam) 21.5 d; 96.6 d (silty clay loam)

44.6 d; 166 d (loamy sand) MRID 46413407

Anaerobic soil metabolism halflife;
Total toxic residues half-life (soil texture) 450 d; No significant degradation (sandy loam) MRID 41913505

Aerobic aqueous metabolism half-life;
Total toxic residues half-life (sediment texture) 69.0 d; 899 d (silt loam) 119 d; 782 d (sand) MRID 46427901

Anaerobic aqueous metabolism half-life;
Total toxic residues half-life (soil texture) 127 d; 402 d (loamy sand) MRID 46413408

Terrestrial field dissipation halflife (soil texture) 18-24 d (sandy loam) 34-53 d (loam) MRID 44078601

Propyzamide is a soluble chemical (15 mg/L in water at 25  C; USEPA, 1994) that is not expected to volatilize significantly due to the compound’ s relatively low vapor pressure of 8.5 x 10 -5 torr (25  C; USEPA, 1994). Propyzamide is slightly to mode rately mobile, with Freundlich soil-water partitioning coefficients (K F ) that ranged from 18.3 (1/n=0.96) to 47.2 (1/n=0.96). Additionally, organic carbon partitioning coefficients (K FOC ) ranged from 700 to 5383 L/kg OC . These values range in classification from moderately mobile to sl ightly mobile (FAO 2000). Mobility is partially explained by affinity to organic matter, as the coefficient of variation (CV) across six soils for K FOC (40%) is less than that for K F (47%). The compound may also have greater mobility in sandy, claypoor soils, as K F values for propyzamide correlate with cation exchange capacity (R 2 = 0.9214). In general, compounds with K F values less than five are sufficiently mobile to present a potential ground water concern, especially in areas with soils that are sandy a nd where water tables are close
to the surface.

Propyzamide is stable to hydrolysis at pH 5, 7, and 9, relatively persistent w ith respect to photolysis on soil (t 1⁄2 = 249 d), but moderately susceptible to degradation by aquatic photolysis (t 1⁄2 = 41.7 d). Two major photodegradates were identified: RH-26059 and RH-24580.

Parent propyzamide is slightly persistent (Goring scale, 1975) in aerobic soils (t 1⁄2 = 20.1-44.6 d) and moderately persistent in aerobic aquatic systems (t 1⁄2 = 69.0-119 d). Propyzamide is also moderately persistent in anaerobic aquatic systems (t 1⁄2 = 127 d), and persistent in anaerobic soils (t 1⁄2 = 450 d).Page 7 of 17 Major degradates of propyzamide (>10% of th e applied radioactivit y) include RH-24644, RH24580, RH-26059, and carbon dioxide. Six minor degrad ates have also been identified: RH-24655, RH-20839, RH-26521, RH-25891, RH-26702, 3,5-dichlorobe nzamide. A batch equilibrium study on RH-24644 and RH-24580 indicates that RH-24644 has similar to lower mobility compared to propyzamide (K F range = 2.34 (1/n=0.98) to 55.1 (1/n=0.86); K FOC range = 993-3910 L/kg OC ), whereas RH-24580 is unambiguously mo re mobile than propyzamide (K F range = 0.283 (1/n=0.83) to 2.36 (1/n=0.87); K FOC range = 96.3-210 L/kg OC

.

The two major degradates observed in metabolis m studies were RH-24580 at up to 32.2% of the applied, and RH-24644 at up to 31. 9% of the applied. Carbon dioxide was also formed, at up to 50.4% of the applied. Both RH-24580 and RH-24644 a ppear to degrade no mo re quickly than the parent based on biotic studies.

The 2002 TRED and the HED memorandum (USEPA, 2007) state that for human dietary risk assessment, propyzamide and its metabolites cont aining the 3,5-dichlorobe nzoyl moiety are the residues of concern (USEPA, 2002). Because all identified orga nic degradates of propyzamide contain the 3,5-dichlorobenzoyl mo iety, and toxicity data for thes e degradates are unavailable, HED assumes that they have toxicity equivalent to th at of parent propyzamide, and are thus residues of concern (USEPA, 2007). A total toxic residues approach was therefore used in the current assessment to evaluate potential expo sures to people via drinking water.

4. DRINKING WATER MODELING

EDWCs were generated for this assessment using EF ED’s standard suite of models. The last DWA for propyzamide was conducted in 2007. Since th en, new input parameter guidance has been developed, Drinking Water Intake watershed PCAs have been developed, and new surface water modeling (SWCC) and ground water modeling (PRZM- GW) tools have become available. This DWA reflects these changes in the form of ne w EDWCs. Model input parameters listed in Tables
4 and 5 were generated based upon the fate proper ties discussed in the previous section.

Models

Exposure estimates were revised with the recently released Surface Water C oncentration Calculator (SWCC). SWCC estimate pe sticide concentrations in water bodi es that result from pesticide applications to land. The SWCC uses PRZM ve rsion 5.0+ (PRZM5) and the Variable Volume Water Body Model (VVWM).

Groundwater EDWCs for propyzamide based upon the ch emical’s labeled uses were derived using PRZM-GW (Pesticide Root Z one Model for Groundwater, ve rsion 1.0, August 31, 2012). PRZMGW is a one-dimensional leaching model that estimat es potential concentrations of pesticides in groundwater. The model accounts for pesticide sorpti on and decay during vertical transport through the crop root zone and deeper soil profile, to a shal low water table aquifer. In keeping with standard practice, PRZM-GW was used to simulate 30 or mo re years of repeated propyzamide applications in six standard scenarios that represent esp ecially leaching-vulnerabl e areas: the Delmarva Peninsula, coastal GA, coastal NC, WI “corn”, FL “potato” and FL “citrus ”. Input parameters employed in the model are listed in Table 6 . The model generated the greatest single-day maximum concentration and the average breakth rough for the WI sands scenario ( Table 9 ).Page 8 of 17 Tier 1 groundwater EDWCs for propyzamide we re also developed using the Screening Concentration In GROund Water (SCI-GROW v2.3, Jul. 29, 2003) model. SCI-GROW is a regression model used as a screeni ng tool to estimate pesticide concentrations in leaching-vulnerable groundwater. SCI-GROW was developed by fitti ng a linear model to monitored groundwater concentrations, with the Relative Index of Leachi ng Potential (RILP) as the independent variable.
Groundwater concentrations were taken from 90-day average high c oncentrations from Prospective Ground Water monitoring studies. The RILP is a f unction of a pesticide’s aerobic soil metabolism and soil-water partition coefficient. The outp ut of SCI-GROW repres ents pesticide residue concentrations that might occur in shallow, unc onfined aquifers underlying sandy soils, following a single year’s application. Such lo cations are representative of gr oundwater that is likely to be maximally vulnerable to pesticide contamina tion. SWCC, PRZM-GW and SCI-GROW were run to estimate screening-level concentrations of t otal toxic residues of propyzamide in potential drinking

water sources.

Input Parameters

Input parameters used in the SWCC modeling appear in Table 4 and Table 5 . In addition, Table 6
and 7 present the input parameters for the gro undwater models (PRZM-GW and SCI-GROW, respectively). Explanations of various mode l input parameters are discussed below.

Table 4. SWCC Application-Specific I nput Parameters for Propyzamide

Uses PRZM Scenario Max App rate in lbs a.i./A (kg a.i./ha) # Apps/ye

ar Interval

(days) % Drift/ Efficiency Date of 1 st of application

Artichoke 1 CA row crop
RLF 8 (8.96) 2 120 0.135/0.95 Feb 1

Leaf Lettuce CA Lettuce 2 (2.24) 2 183 0.135/0.95 Feb 1

1. There is not a standard scenario availabl e for the artichoke group. The CA row cr op RLF scenario was used because this scenario was felt to provide the clos est representation of agricultural pract ices for artichokes from among available EFED-approved scenarios.

Table 5. SWCC Input Parameters for Propyzamide (TTR approach). Source Data are in Table 3. Input Parameter Value Justification Source
Molecular Mass (g/mol) 256.13 Product chemistr y data USEPA, 1994

Vapor Pressure at 25°C (torr) 8.5 x 10 -5 Study value USEPA, 1994

Solubility in Water at
25 o C (mg/L) 15.0 Product chemistry data USEPA, 1994

Organic Carbon
Partition Coefficient (K OC ) (L/kg OC ) 1966 Represents the mean
K FOC for propyzamide parent as an estimate of the partition coefficient
for the total residues. MRID 40211103Page 9 of 17 Table 5. SWCC Input Parameters for Propyzamide (TTR approach). Source Data are in Table 3. Input Parameter Value Justification Source
Aerobic Soil
Metabolism Half-life (days) 165 Represents the 90 percent upper confidence limit on the mean (two soils) total
residue half-life. MRID 46413407

Aerobic Aquatic
Metabolism Half-life (days) 1020 Represents the 90 percent upper confidence limit on the
mean total residue halflife. MRID 46427901

Anaerobic Aquatic
Metabolism Half-life (days) 1210 Represents 3 times the single available total
residue half-life. MRID 46413408

Hydrolysis Half-lives at pH 5, 7 and 9 (days) Stable No measureable degradation in study. MRID 00107980

Aqueous Photolysis Half-life (days) 217 Represents the single
environmental phototransformation
total residue half-life. MRID 40420301

Currently approved SWCC scenarios were used for the drinking (surface) water modeling. The California Row Crop regional scenario was used to model use on artichokes, becaus e this scenario was parameterized to represent row crop vegeta bles and propyzamide may only be applied to
artichokes in California. The California lettuce s cenario was used to mode l application to leaf lettuce, as this scenario was de signed to be nationally protective for use on lettuce (IPM, 2013).

Application methods, rates and time of application were obtained/derived from proposed labels for leaf lettuce uses (EPA Reg. No. 62719-578). The s econd seasonal application to lettuce represents application to a second crop planted 183 days after the first; all appli cations were modeled as aerial.

Chemical property input values were chosen in accordance with current EFED input parameter guidance (USEPA, 2009 and USEPA, 2013). Based on analysis of total toxic residues , the upper 90%
confidence limit on the mean half-life was selected as the model input value for aerobic soil and aerobic aquatic metabolism pathways (165 d and 1,020 d TTR half-lives respectively). For the anaerobic aquatic metabolism pathway (used to re present decay within the benthic zone of the receiving water body), the single av ailable half-life was multiplied by 3 (producing a value of 1,210 d) to account for uncertainty associated with limited data.

Standard percent cropped area (PCA) adjustment f actor was used for these uses. These constitute conservative estimates of the crop acreage portions of watersheds in which specific crops or crop combinations are grown (USEPA, 2012b). The na tional all-agriculture PCA of 1.0 was employed to adjust results for all uses, because these uses are not as confined to specific regions of the country.

Input parameters used in PRZM-GW and SCI-GROW appear in Table 6 and Table 7, respectively. Data sources and justification accompany values for each parameter.Page 10 of 17 Table 6. PRZM-GW Input Parameters Parameter (units) Input Value Data Source Application Rate (lbs a.i./A) 4 Label Number of Applications/yr 2 Label Application Dates (month/day) Feb 1 and Aug 1 IPM center

Hydrolysis Half-life (days) Stable (0) MRID 00107980

Soil Metabolism Half-life (days) 165 (upper 90 percent confidence limit on the mean) MRID 46413407

K oc (mL/g oc ) 1966 (average) MRID 40211103

Table 7. SCI-GROW Input Para meters for Propyzamide.

Input Parameter Value Comment Source

Application Rate (lbs a.i./A) Artichoke: 4 (4.48) Leaf Lettuce: 2 (2.24) Label directions Proposed and
current labels

Applications per Year 2 applic. for Artichoke and Lettuce and the rest just one application Label directions Proposed and
current labels

Organic Carbon Partition Coefficient (K OC ) (L/kg OC ) 1451 Represents the median of eight
values MRID 40211103

Aerobic Soil Metabolism Half-life (days) 109 Represents the mean of three
values for total toxic residues MRID 46413407

Modeling Results

The proposed use pattern and the maximum applic ation rate were modeled for surface water and groundwater exposure estimates, as described above. Tables 8 list EDWCs for the highest use patterns of propyzamide, which are also reported in Tables 1 . The maximum use patterns that yielded the maximum surface water and groundwate r EDWCs for use in drinking water exposure
estimation were lettuce and articho kes, respectively. Model input/ output data for these estimates
are attached in Appendix A and B

.

Table 8. Tier II Total Residue of Concern EDWCs in Surface Water and Ground Water from Propyzamide Uses on New Uses (Maximum EDWCs in Bold). Drinking Water Source (Model, Use, Modeled rate) Scenario EDWCs

Acute (μg/L) Chronic (μg/L) Cancer (μg/L) Surface Water (SWCC, Artichokes, 4 lb a.i./A x 2 applic.; total of 8 lb/A/yr) CA row crop RLF (aerial application) 61.4 33.4 26.0

Surface Water (SWCC, Leaf Lettuce, 2 lb a.i./A x CA lettuce (aerial application) 102 47.0 33.6Page 11 of 17 2 applic.; total of 4 lb/A/yr)Ground Water (PRZMGW, Artichokes, 4 lb a.i./A x 2 applic.; total of 4 lb/A/yr) WI sands 21 18.6 18.6

Ground Water (SCIGROW, Artichokes, 4 lb a.i./A x 2 applic.; total of 8 lb/A/yr) N/A 0.802 0.802 0.802

Ground Water (SCIGROW, Leaf Lettuce, 2 lb a.i./A x 2 applic.; total of 4 lb/A/yr) N/A 0.401 0.401 0.401

N/A= Not Applicable Values in bold show the EDWCs recommended for HED’s acute (102 ppb) and chronic (47.0 ppb) and cancer (33.6 ppb) dietary risk assessment as they are considered protective of all the registered uses of pronamide. Surface water EDWCs based on total toxic residues and maximum annual application rates were highest for leaf lettuce (102, 47.0 and 33.6 ppb, fo r peak concentration and chronic values, respectively).

The groundwater EDWCs listed in Table 8 are smaller than those reported in the most recent DWA (USEPA 2007), mainly because of a new batch equilibrium data that demonstrated a more immobile compound compared to the previous study subm itted. Using PRZM-GW, the acute groundwater EDWC (21.0 ppb) do not exceeds the acute surface water EDWC (102 ppb) for artichokes at the maximum annual application rate (8 lbs a.i./A). Th is groundwater EDWC is a ssociated with the WI sands scenario. The potential for groundwater contamin ation is expected to be greatest in areas where soils are relatively permeable and the water table is relatively close to the surface.

5. MONITORING DATA

A cursory review of both groundwater and surf ace water monitoring data on propyzamide was conducted as part of the 2002 TRED (USEPA, 2002a). The current a ssessment contains additional review of currently available monitoring data. The USGS NAWQA national database contains monitoring data of pesticides through 2005 (USGS, 2006). In surf ace water, propyzamide (only parent) was detected above the level of quantita tion in 2.2% of samples (459 of 20,720 samples).
The maximum measured surface water concentra tion was 1.12 μg/L in Shelby County, Tennessee in January, 2003. In groundwater, propyzamide was de tected above the level of quantitation in 0.05% of samples (5 of 9624 samples). The maximu m concentration measured in groundwater was 0.820 μg/L in Benton County, Arkansas in April, 1994.

The USGS NASQAN national database contains mon itoring data of pesticides by regional basin from 1996 to 2000 (USGS, 2006a). The maximum con centration of propyzamide detected in this program was 0.125 μg/L in the Colorado Basin in June, 1997. Concentrations of propyzamide were detected above the reporting limit in the Columb ia, Colorado, Rio Grande, and Mississippi River basins; however, detections only occurre d in the Northwes t and Southwest.Page 12 of 17 The California Department of Pesticide Regula tion (DPR) Surface Water Database contains monitoring data of pesticides in California from 1990 to 2005 (CDPR, 2006). Propyzamide was detected in 8% of 1678 samples coll ected in the state, w ith the majority of detections occurring in water bodies within the Sacramento Valley. The maximum concentration of propyzamide reported in this database was 0.25 μg/L, detect ed in Yolo County in February, 1994.

Propyzamide was detected in one Oklahoma reservoi r out of twelve which were monitored in the Pilot Reservoir Monitoring Program due to their particular vulne rability to pesticide contamination (USEPA, 2002a). The compound was detected at up to 0.044 ppb in 83% of 41 raw water samples and up to 0.012 ppb in 42% of 19 finished water samples.

Propyzamide was not detected in 432 ground water wells from 1984 to 1990, according to the EPA Pesticides in Ground Water Database (USEPA, 1992). Propyzamide is not a regulated chemical under the Safe Water Drinking Act (SWDA) or related statutes. Therefore, it is not listed in the EPA Safe Drinking Water Information System (SDWIS /FED) database (USEPA , 2007a) nor is it found in the EPA Unregulated Contaminants Monitori ng Rules (UCMR) chemical monitoring database (USEPA, 2006b).

The available monitoring data show peaks of 3.7-10.3 μg/L and annual mean of 0.53-4.45 μg/L parent propyzamide EDWCs generated in support of the 2002 TRED (USEPA, 2002a). Recently, an article published by Smalling, K.L. et al. 2013 mentioned that propyzamide was detected in water samples analyzed (at Santa Maria estuary in California, N=19), however, no pesticide concentrations were provided (Smalling, 2013). Monito ring data are not available on the degradates of propyzamide. Therefore, exposure estimates of total toxic residues cannot be directly compared against monitoring data.

Recently, water and sediment (both bed and susp ended) were collected from January 2008 through October 2009 from 12 sites in 3 of the largest wate rsheds along California’s Central Coast (Pajaro, Salinas, and Santa Maria Rivers) and analyzed fo r a suite of pesticides by the U.S. Geological Survey in cooperation with the California State Water Resources Control Board. Propyzamide was detected in more than 50% of the samples in the Salinas and Pajaro Rivers and greater than 95% in
Santa Maria River. The maximum concentra tions of propyzamide ranged from 30.4 to 14,000 ng/L (14 ppb) during summer dry season and 47. 8 to 1,390 ng/L (1.3 ppb) in storm events in Pajaro and Santa Maria Estuarie s, respectively (USGS, 2011).

Drinking Water Treatment

Some data on the effects of drinking water trea tment on propyzamide concentrations are available from the Pilot Reservoir Monitoring Program (USEPA, 2002a). The compound was detected twice as often in raw water samples as in finished water samples. However, monitored treatment data carry some inherent uncertainty due to variability in treatment faci lity design. Collecting analogous samples of water before and after treatment for purposes of comparison is challenging due, among other things, to dilution and transit time effects.

Flocculation and sedimentation might be expected to be effective at removing some propyzamide
residue concentrations due to th e chemical’s weak affinity fo r organic carbon. Activated carbonPage 13 of 17 filtration might similarly decrease propyzamide re sidue concentrations, a lthough this technique is not employed in most water treatment operations. Changes in pH are not expected to affect propyzamide, as the compound is stable to hydrolysis. Data regarding the eff ects of specific drinking water treatment practices on propyza mide residues of risk concern have not been provided to the Agency, and have not been found in the published literature.

6. CONCLUSION

The EDWCs reported here are based on ar tichoke (CA) and leaf lettuce uses. Tables 1 and 2 reflect the most conservative (highest) EDWCs for su rface and groundwater, whic h are recommended for use in HED’s dietary assessment. The leaf lett uce use generated the hi ghest surface water and groundwater EDWCs. The total toxic residues of propyzamide include propyzamide parent and all degradates with the 3,5-dichlorobenzoyl moiety, whic h are assumed to have t oxicity similar to that of propyzamide parent. The recommended estimated drinking water conc entrations (EDWCs) fo r the Health Effects Division’s (HED) dietary assessment is 102 ppb fo r the acute dietary assessment and 47.0 ppb for the chronic and cancer dietary assessments.Page 14 of 17 LITERATURE CITATIONS

CDPR. 2006. Surface Water Database. Californi a Department of Pesticide Regulation, Surface Water Protection Program. Online at: ht tp://www.cdpr.ca.gov/docs/sw/surfdata.htm

Jones, R. D., S. Abel, W. R. Effland, R. Matzner, R. Parker. 1998. An Index Reservoir for Use in Assessing Drinking Water Exposure. Proposed Methods for Basin- scale Estimation of Pesticide Concentrations in Flowing Water a nd Reservoirs for Tolerance Reassessment. Presentation to FIFRA Science Advisory Panel, June 29-30, 1998. Online at: http://www.epa.gov/scipol y/sap/1998/index.htm

IPM, 2013. NSF Center for Integrated Pest Manage ment (host). U.S. Department of Agricultre Pest Management Centers. Last updated: September 16, 2013. Online at: http://www.ipmcenters.org/cropprofiles/CP_form.cfm

USEPA. 1992. Pesticides in Ground Water Databa se: A Compilation of Monitoring Studies: 1971- 1991: National Summary. U.S. Environmen tal Protection Agency. Washington, DC.

USEPA. 2002. Report of FQPA Tolerance Reasse ssment Progress and Interim Risk Management
Decision: Pronamide. U.S. Environmenta l Protection Agency, Office of Prevention, Pesticides, and Toxic Substances, Mar. 8, 2002.

USEPA. 2002a. Tier II Drinki ng Water Assessment to Support TRED for Pronamide (Propyzamide). U.S. Environmental Protec tion Agency, Office of Pesticide Programs,
Environmental Fate and Effect s Division, Memorandum, Jun. 5, 2002.

USEPA. 2002. SCIGROW: Users Manual. Online at: http://www.epa.gov/oppefed1/models/water/#scigrow

USEPA. 2005. PRZM 5: Users Manual. Online at: http://www.epa.gov/oppefed1/models/water/#przm

USEPA. 2005. EXAMS 2.98.04.06: Users Manual. Online at: http://www.epa.gov/oppefed1/models/water/#exams

USEPA. 2006. Water models PE Vers ion 5: User Manual. Online at: http://www.epa.gov/oppefed1/models/water/pe5_user_manual.htm

USEPA. 2009. Guidance for Selecting Input Parame ters in Modeling the Environmental Fate and Transport of Pesticides. U.S. Envir onmental Protection Agency, Office of chemical Safety and Pollution Prevention, Office of Pe sticide Programs, Environmental Fate and Effects Division, Oct. 22, 2009. Online at: http://www.epa.gov/oppefed1/models/w ater/input_parameter_guidance.htm

USEPA. 2006a. Water Models. U.S. Environmen tal Protection Agency, Pesticides: Science and Policy. Last updated: July 9, 2013. Online at: http://www.epa.gov/oppefed1/models/water/Page 15 of 17 USEPA. 2006b. Unregulated Contaminant Monitoring Rules (UCMR). U.S. Environmental Protection Agency, Unregulated Contaminan t Monitoring Program. Last updated: Nov. 24, 2006. Online at: http://www.epa.gov/sa fewater/data/ucmrgetdata.html

USEPA. 2007. Clock-Rust, M. Residues of Con cern for Pronamide (Propyzamide) for Drinking
Water. DP Barcode: 328077. HE D Memorandum to EFED.

USEPA. 2007a. Safe Drinking Water Information System/Federal Version (SDWIS/FED). U.S. Environmental Protection Agency. Last updated: September 19, 2013. Online at: http://www.epa.gov/safewater/data/getdata.html

USGS. 2006. National Water-Quality Assessment (N AWQA) Program. U.S. Geological Service. Last updated: Oct. 19, 2006. Online at: http://infotrek.er.usgs.gov/tr averse/f?p=136:1:1779537078393353::NO:::

USGS. 2006a. Kelly, V., R. Hooper, B. Aulenbac h, and M. Janet. Concentrations and Annual Fluxes for Selected Water-Quality Constituents from the USGS National Stream Quality Accounting Network (NASQAN) , 1996-2000. U.S. Geological Survey. Last updated: Nov. 20, 2006. Online at: http://pubs.us gs.gov/wri/wri014255/re sults/detect.htm

USGS. 2011. Smalling, K.L. and Orlando, J.L.; Ocu rrence of Pesticides in Surface Water and
Sediment from Three Central Calif ornia Coastal Watersheds, 2008-2009.

USEPA. 2012a. Guidance for Selecting Input Parameters fo r Modeling Pesticide Concentrations in Groundwater Using the Pesticide Root Zone Model. Office of chemical Safety and Pollution Prevention, Office of Pesticide Pr ograms, Environmental Fate and Effects Division, and Health Canada Pesticide Management Regulatory Agency, Oct.15, 2012.

USEPA. 2012b. Development and Use of Percent Cropped Area Adjustment Factors in Drinking Water Exposure Assessments. U.S. Environmen tal Protection Agency, Office of chemical Safety and Pollution Prevention, Office of Pe sticide Programs, Environmental Fate and Effects Division, September 9, 2010. Online at: http://www.epa.gov/oppefed1/models/w ater/pca_adjustment_dwa.html \

USEPA. 2013. Guidance for Modeling Offsite Deposition of Pesticides via Spray Drift for Ecological and Drinking Water Assessments. Office of chemical Safety and Pollution Prevention, Office of Pesticide Programs, Environmen tal Fate and Effects Division, Dec. 20, 2013.

Smalling, K.L.; Kuivila, K. M.; Orlando, J.L.; Phill ips, B.M.; Anderson, B.M.; Siegler, K.; Hunt, J.W.; Hamilton, M. Environmental fate of fungicides and othe r current-use pesticides in a central California. Marine Pollution Bulletin 73 (2013) 144–153.

FAO, 2000. Food and Agriculture Organization of th e United Nations. Pesticide Disposal Series 8. Assessing Soil Contamination: A Reference Manual . Appendix 2. Parameters of pesticides that influence processes in the soil. Editorial Group, FAO Info rmation Division: Rome, 2000. http://www.fao.org/docrep/003/X2570E/X2570E00.htm

.Page 16 of 17 Appendix A. SWCC Input/Output Data for Drinking Water Exposure Assessment

.



## Summary of Water Modeling of Pronamide and the USEPA
Standard Reservoir

Estimated Environmental Concentrations for Pron amide are presented in Table 1 for the USEPA
standard reservoir with the CAle ttuceSTD field scenario. A graphi cal presentation of the year-toyear peaks is presented in Figure 1. These va lues were generated with the Surface Water Concentration Calculator (SWCC Version 1.106). Critical input values for the model are
summarized in Tables 2 and 3.
This model estimates that about 1.8% of Pronamide applied to the field eventually reaches the water body. The main mechanism of transport from the field to the water body is by runoff ( 70% of the total transport), followed by sp ray drift (22.2%) a nd erosion (7.8%). In the water body, pesticide dissipates with an eff ective water column half-life of 91.7 days. (This value does not include dissipation by transport to the benthic region; it includes only processes that result in removal of pesticide from the co mplete system.) The main source of dissipation in
the water column is volatiliza tion (effective average half-lif e = 157.7 days) followed by washout (245.1 days), metabolism (2259.2 days), and photolysis (27914 days). In the benthic region, pesticide dissipation is negligible (2680. 1 days). The main source of dissipation in the benthic region is metabolism (effective average half -life = 2680.1 days). The vast majority of the pesticide in the benthic region (99.53%) is sorbed to sediment rather than in the pore water.

Table 1. Estimated Environmental Con centrations (ppb) for Pronamide.

Peak (1-in-10 yr) 102.

4-day Avg (1-in-10 yr) 97.0

21-day Avg (1-in-10 yr) 82.5

60-day Avg (1-in-10 yr) 69.1

365-day Avg (1-in-10 yr) 47.0

Entire Simulation Mean 33.6

Table 2. Summary of Model Inputs for Pronamide.

Scenario CAlettuceSTD

Cropped Area Fraction 1

Koc (ml/g) 1966.5

Water Half-Life (days) @ 25 °C 1020

Benthic Half-Life (days) @ 25 °C 1210

Photolysis Half-Life (days) @ 40
°Lat 217Page 17 of 17 Hydrolysis Half-Life (days) 0

Soil Half-Life (days) @ 25 °C 165

Foliar Half-Life (days) 0

Molecular Wt 256.13

Vapor Pressure (torr) 8.5e-5

Solubility (mg/l) 15

Table 3. Application Sc hedule for Pronamide.

Date (Mon/Day) Type Amount (kg/ha) Eff. Drift

2/1 Foliar 2.24 0.95 0.135

8/1 Foliar 2.24 0.95 0.135

Figure 1. Yearly Peak Concentrations