## Nick Poletika a



## Brian Bret a 

## Mike Winchell b

a Dow AgroSciencs LLC b Stone Environmental, Inc.

1

# Background

 

### Pronamide ( propyzamide ) is a soil

- applied herbicide registered for use on numerous crops to control a wide 

### variety of weeds.

 

### It is difficult to pass an FQPA dietary risk assessment due to a cancer endpoint attributed to total residues of 

### concern (parent + multiple metabolites) and modeled 30
- year average drinking water exposure estimates that range from 10.8 to 105 μg L

- 1 

### for surface water sources.

 

### Regulatory approval of use on leaf lettuce cannot be granted unless exposure can be shown to be negligible.

2

# Proposed Methodology for An Alternative to Monitoring

 

### California is primary market for pronamide, with most of that use occurring in the Central Coastal valleys.

 

### Preliminary review of source water protection reports indicated that coastal California production areas were unlikely to have agriculture listed as potential sources 

### of contaminants by Community Water Systems (CWS)

 

### Propose that existing public records and data sets can be used to document potential for pronamide 

### contamination of surface water sources on the central California coast from use on lettuce

3

# Presentation of Sensitive Drinking Water Information

 

### US EPA has a policy on sensitive drinking water information (US EPA, 2005; US GAO, 2006) that we will follow using an approach consistent with the one 

### EPA is considering for sharing information products with a wide public audience that is based on the concept of drinking water indicators ( Cooter et al., 

### 2011)

 

### Example: Watershed Boundary Dataset subwatershed HUC12 drainage areas , 160,000 estimated for US ( Laitta et al., 2004)

 

### We use this as our indicator

4

# Data Sources

 UC Extension list of coastal counties with historical lettuce production a

 Historical CWS intake locations pre

- 9/11/2001

 Safe Drinking Water Information System (SDWIS)

 UC Davis Drinking Water Source Assessment and Protection Program and On

- Line Mapping Tools

 USGS NHD Flowline , Waterbody , and HUC12 data

 Cal EPA/Department of Pesticide Regulation Pesticide Use Reports (PUR) 2007

- 2009 average use in a section

 Google Earth (for place names)

 Internet search: Google (for reports to customers and contacts)

 Employees at CWS

5 a Contra Costa, Monterey, San Benito, San Luis Obispo, Santa Barbara, Santa Clara, Santa Cruz

# Procedure

 

### Start with historical intake locations and PUR data

 

### Check against current SDWIS active CWS list

 

### Three categories

 No longer active: remove from list

 Remain active: check for accuracy (NHD, Google Earth)

 New active CWS not on historical list: investigate location (NHD, Google Earth, Google, employees)



###  

### After locations of all current intakes are found, then 

### examine for exposure potential based on use and NHDFlowline Hydro Net flow direction

6

# Procedure

– Decision Tree for 

# Location

7 

### If Use in 

### County, Compare Historic to Current 

### SDWIS Currently

Active Historic

–

Check 

### Location

New

– Find Location No Longer Active (Done)



### Ground Truth, if Necessary8 Example of No Use in County9 Example of Currently Active Accurate Historical Intake Location in County Represented by HUC12 Indicator with Use in County (1

- Mile Sections)10 Example of Information Obtained from Google Search for New Location SLO Co. Master Water Plan “Lopez Reservoir provides supplies to ... Grover Beach ...

# Procedure

– Decision Tree for 

# Exposure Potential

11 

### Intake Locations SW Hydrologic

Connection Upstream from Use Sites* 

### (Done)

Downstream from Use Sites No SW 

### Hydrologic Connection (Done) 

### Ground Truth, if

Necessary *And with protected conveyance if water transported.12 Example of No SW Hydrologic Connection from Google Search SLO Co. Master Water Plan “Lopez Reservoir provides supplies to ... Grover Beach ... via the Lopez pipeline system

.13 Example of No SW Hydrologic Connection from Map14 Example of SW Hydrologic Connection with Location Upstream from Use Sites15 Many CWS Receive Water from Remote Sources

# Results for 223 Locations Evaluated: None 

# with Exposure Potential

16 Lines of Evidence Used to Make Determination (% of Total Number of Sites) Not Active Internet Map Ground Truth

5.4 26.9 55.6 12.1

# Review of 223 Active Intakes Suggests a Consistent Pattern

17

Photo credit: Rohm and Haas/DAS

## Implication of Different EDWC Assumptions for Dietary Risk

 

### No exposure potential for drinking water sourced from surface water suggests that the SCI

- GROW estimated drinking water concentration (EDWC) can be used for dietary risk assessment.

18 EDWC Exposure Estimation Method EDWC from

Lettuce Use (μg/L) Dietary

Exposure (mg/kg/day) Anticipated

Cancer Risk

PRZM/EXAMS 64.1 a 0.001359 b 4 x 10 - 5 SCI

- GROW 0.699 0.000026 6.78 x 10

- 7 No water (food only) 0 0.000012 3.14 x 10 - 7

a Surface water 30

- year mean exposure (EFED). b EDWC + HED dietary exposure estimate.

# Conclusions and Recommendations

 

### Zero exposure potential from surface water from the lines of evidence evaluated

 

### Approach could be extended to other areas of California 

### (PUR for actual use) and other regions with western irrigated agriculture (CDL or CLU for potential use)

 

### Routine updates needed to demonstrate no change has occurred

 

### A significant amount of work was involved to address the new sites without sensitive location data available to the public.

 

### Suggest that EPA/USGS conduct future similar analyses, 

### when appropriate, as they have access to the sensitive location data

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# Acknowledgements

 

### Olivier de Cirugeda Helle, Dow AgroSciences

– GIS and internet searches

 

### Kay Mercer, KMI

– Ground truthing

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# References

 Cooter , W, Everett, K, Chrest , D, Rineer , J, Bergenroth , B, Anzzolin , A. 2011. Examples of Cross

- Program Approaches for Sharing Drinking Water Indicators. ESRI International User Conference , San Diego, CA, July 11

- 15, 2011. Paper Number 3063.

 Laitta , M, Legleiter

, K, Hanson, K. 2004. The National Watershed Boundary Dataset. HydroLine , Summer 2004, p. 1. ESRI Water Resources Group. http://www.esri.com/library/newsletters/hydroline/hydroline_summer2004.pdf.

 U.S. EPA. 2005. Policy to Manage Access to Sensitive Drinking Water

Related Information. Office of Water, Michael Shapiro, Deputy Assistant Administrator, April 5, 2005, Washington, DC.

 U.S. GAO. 2006. Information Sharing: The Federal Government Needs to Establish Policies and Processes for Sharing Terrorism

- Related and Sensitive but Unclassified Information. GAO

- 06

- 385. U.S. Government Accountability Office, Washington, DC.

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