INFORMATION and REPORT concerning

S-METOLACHLOR

submitted to the

PESTICIDE REGISTRATION EVALUATION

COMMITTEE

pursuant to the

PESTICIDE CONTAMINATION PREVENTION ACT

by

SYNGENT A CROP PROTECTION, LLC Greensboro, North Carolina

February 27, 2016

SUMMARY

This report concerning S-metolachlor and its degradation products is submitted by Syngenta Crop Protection, LLC ("Syngenta"), in response to a September 23, 2016 Notice of Metolachlor/S-metolachlor Degradation Product Residue Detections in California Groundwater and Registrant Opportunity to Request a Hearing ("Notice") issued by the Department of Pesticide Regulation ("DPR" or "Department") pursuant to the Pesticide Contamination and Prevention Act ("PCPA"), Cal. Food & Agric. Code§§ 13141-13152. (Attachment 1). The Notice stated that DPR detected residues of two degradation products of the active ingredients metolachlor and S-metolachlor in groundwater, and that detections were due to legal agricultural use of the pesticide products containing metolachlor and S-metolachlor. Syngenta filed a timely response on October 19, 2016, requesting a hearing. (Attachment 2). DPR notified Syngenta that it will conduct a hearing to support the continued sale and use of Syngenta's metolachlor and S-metolachlor products on March 28, 2017. (Attachment 3). To prepare for the hearing, and pursuant to Section 13150 of the PCPA, Syngenta submits this report, which includes all information requested by DPR (Attachment 4).

This report focuses on the herbicide S-metolachlor; however, metolachlor and S­metolachlor can be used interchangeably to discuss their environmental behavior and toxicological endpoints (USEPA, 2015). USEPA's Environmental Fate and Effects Division ("EFED") concluded that both have similar physical and chemical properties and environmental behavior; therefore, environmental fate data can be bridged from metolachlor to S-metolachlor. Similarly, USEPA' s Health Effects Division ("HED") Hazard Indentification Assessment Review Committee ("HIARC") and Metabolism Assessment Review Committee ("MARC") concluded that even though existing toxicological data are primarily composed of studies conducted with metolachlor, toxicity profiles of metolachlor and S-metolachlor are comparable and interchangeable (USEPA, 2003).

S-metolachlor was registered in California in 2000. Two degradation products of S­metolachlor, M-ESA and M-OXA have been detected in some well water samples in California. This is a threshold finding under the PCPA, which requires no further regulatory action if the material detected in groundwater, at the levels detected "has not polluted, and does not threaten to pollute, the groundwater of the state in any region within the state." Cal. Food & Agric. Code § 13150(a)(2) (Attachment 1).

The term "pollute," according to Section 13142G) of the Code, "means to introduce a pesticide product into the groundwaters of the state resulting in an active ingredient, other specified ingredient, or a degradation product of a pesticide above a level that does not cause adverse health effects, accounting for an adequate margin of safety." (Emphasis added.) Syngenta demonstrates herein that detected groundwater concentrations of S-metolachlor, M­ESA, and M-OXA do not exceed this level; therefore, no further regulatory action is required to prevent pollution of groundwater in California by S-metolachlor or its degradation products.

From monitoring in 2001, 2004, 2009, 2015, DPR detected M-ESA and M-OXA in 62 of 282 groundwater wells (-22%) in relatively high use areas of California (S-metolachlor was not detected). The highest concentration -- 20.2 parts per billion (ppb) -- was detected in 2001. In 2004, 2009 and 2015, maximum M-ESA and M-OXA concentrations were 1.1, 2.8, and 1.7 ppb, respectively. Majority (69%) of M-ESA and M-OXA detections were in three California counties: San Joaquin, Solano, and Stanislaus. During the same monitoring period, S­

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metolachlor was not detected. The Drinking Water Equivalent Level ("DWEL") -- which is the life-time exposure level at which adverse health effects would not be expected to occur -- is 3500 ppb. The Health Advisory ("HAL") which is the concentration in drinking water that is not expected to cause any adverse effects for a lifetime of exposure -- is 700 ppb. Even though no water quality standards (DWEL, HAL) exist for M-ESA and M-OXA, toxicology studies indicate that M-ESA and M-OXA are 3- to 100-fold less toxic than S-metolachlor depending on the studies compared.

Clearly, the maximum detected level of S-metolachlor degradation products (20.2 ppb) is conservatively 34-fold lower than the HAL (700 ppb) and 173 times lower than the DWEL (3500 ppb ). S-metolachlor "has not polluted . . . the groundwater of the state in any region within the state."

Restricting the use of S-metolachlor, whether through cancellation or mitigation requirements, has potential to cause significant economic impact to California producers. S­metolachlor is used on numerous crops grown in California, and plays a vital role in controlling key weeds in a variety of those crops. Continued use of S-metolachlor is justified based on the weeds controlled, wide-array of crops on which it is used, and its contribution to weed resistance management. It is imperative that S-metolachlor remain registered as an herbicide option for growers in California.

Current labels (e.g., Attachment 5) include a groundwater environmental hazard statement and directions for use that are intended to minimize potential leaching of S­metolachlor to groundwater while maintaining efficacy and optimal weed control in key crops grown in California. Labels include significant and sufficient user restrictions to prevent groundwater pollution, based on the definition mentioned above. These restrictions have been on the S-metolachlor label for 16 years and demonstrate an on-going commitment by Syngenta to respond to regulatory evaluation of leaching potential.

Monitoring data collected by DPR suggest that legal agricultural use of S-metolachlor according to its label results in relatively infrequent shallow groundwater concentrations of two degradation products (M-ESA, M-OXA) well below conservative HAL and DWEL levels. S­metolachlor label instructions appear to successfully minimize S-metolachlor, M-ESA, and M­OXA transport to groundwater in California, and do not appear to trigger further action under the PCPA. As a result, Syngenta has not proposed mitigation measures, and requests that DPR continue registration of S-metolachlor without additional mitigation requirements or listing under Cal. Code Regs., tit.3, § 6800(a).

Moreover, given the relatively short-lived degradative nature of S-metolachlor, M-ESA, and M-OXA, the current, mature use rates for S-metolachlor in California, and monitoring data collected to-date, there is no evidence to suggest that S-metolachlor would potentially threaten to pollute groundwater in the state going forward. Thus, S-metolachlor "has not polluted" and no evidence exists to suggest that it will "threaten to pollute" groundwater in the state.

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REPORT AND DOCUMENTED EVIDENCE

A. ACTIVE INGREDIENT

"Name ofactive ingredient."

The active ingredients detected, according to the Notice, are metolachlor (CASRN 51218-45-2) and S-metolachlor (CASRN 87392-12-9).

B. REGISTRANT(S)

"Name and address of registrant."

The name of the registrant for the products identified below is Syngenta Crop Protection, LLC, also referred to as "Syngenta." The company is located in Greensboro, North Carolina.

C. CONTACT PERSON

The Syngenta contact person with responsibility for this matter is Ms. Debbie Stubbs. Ms. Stubbs' contact information follows:

Ms. Debbie Stubbs SYNGENTA CROP PROTECTION, INC.

410 Swing Road Greensboro, North Carolina 27409 Phone: (336) 632-2449 Email: debbie.stubbs@syngenta.com

D. S-METOLACHLOR REGISTRATIONS

"Name, EPA registration number, and label of each of your product( s) containing the detected active ingredient, other specified ingredient or associated degradation product, registered in California for agricultural use."

At the present time, Syngenta holds nine active registrations for pesticide products containing S-metolachlor and no registrations for products containing metolachlor. Information regarding these products follows.

1. Bicep II Magnum was registered on September 9, 2013 with DPR registration number 100-817-ZC, and remains active. This product has a DPR registration Type A-Section 3 Regular Registration in the Category C-Chemical. Its formulation is a flowable concentrate, and the product has an agricultural use as an herbicide. Health hazards associated with this product include skin, eye, and oral precautions. Environmental hazards involve drift, ground water, application directly to water, and aquatic organisms. The active ingredient is S­

102588243 \ V-1 Page 4 of 33

metolachlor at 26.1 percent; atrazine at 33.0 percent; other related atrazine at 0.7 percent; and inert ingredients make up the remaining 40.2 percent of the product.

2. Dual II Magnum was registered on March 29, 2012 with DPR registration number 100-818-ZB, and remains active. This product has a DPR registration Type A-Section 3 Regular Registration in the Category C-Chemical. Its formulation is an emulsifiable concentrate, and the product has an agricultural use as an herbicide. Health hazards associated with this product include skin, eye and oral precautions. Environmental hazards involve drift, ground water, and the application directly to water. The active ingredient is S-metolachlor at 82.4 percent, and inert ingredients make up the remaining 17.6 percent of the product.

3. Dual Magnum Herbicide was registered on July 22, 2011 with DPR registration number 100-816-ZC, and remains active. This product has a DPR registration Type A-Section 3 Regular Registration in the Category C-Chemical. Its formulation is an emulsifiable concentrate, and the product has an agricultural use as an herbicide. Health hazards associated with this product include skin, eye, and oral precautions. Environmental hazards include ground water and the application directly to water. The active ingredient is S-metolachlor at 83.7 percent, and inert ingredients make up the remaining 16.3 percent of the product.

4. Halex GT Herbicide was registered on January 1, 2013 with DPR registration number 100-1282-AA, and remains active. This product has a DPR registration Type A­Section 3 Regular Registration in the Category C-Chemical. Its formulation is a capsule suspension, and the product has an agricultural use as an herbicide. Health hazards associated with this product include inhalation, skin, and eye precautions. Environmental hazards include drift, ground water, and the application directly to water. The active ingredient is S-metolachlor at 20.50 percent; mesotrione at 2.05 percent; glyphosate at 20.50 percent; and inert ingredients make up the remaining 56.95 percent of the product.

5. Medal EC was registered on July 20, 2011 with DPR registration number 100­816-ZB, and remains active. This product has a DPR registration Type A-Section 3 Regular Registration in the Category C-Chemical. Its formulation is an emulsifiable concentrate, and the product has an agricultural use as an herbicide. Health hazards associated with this product include skin, eye, inhalation, and oral precautions. Environmental hazards involve children/humans, drift, groundwater, and the application directly to water. The active ingredient is S-metolachlor at 83.7 percent, and inert ingredients make up the remaining 16.3 percent of the product.

6. Medal II ATZ was registered on April 26, 2012 with DPR registration number 100-817-ZB, and remains active. This product has a DPR registration Type A-Section 3 Regular Registration in the Category C-Chemical. Its formulation is a flowable concentrate, and the product has an agricultural use as an herbicide. Health hazards associated with this product include skin, eye, and oral precautions. Environmental hazards involve drift, groundwater, aquatic organisms, and the application directly to water. The active ingredient is S-metolachlor at 26.1 percent; atrazine at 33.0 percent; other related atrazine at 0.7 percent; and inert ingredients make up the remaining 40.2 percent of the product.

7. Medal II EC was registered on May 3, 2012 with DPR registration number 100­818-ZC, and remains active. This product has a DPR registration Type A-Section 3 Regular Registration in the Category C-Chemical. Its formulation is an emulsifiable concentrate, and the product has an agricultural use as an herbicide. Health hazards associated with this product

102588243 \ V-1 Page 5 of33

include skin, eye, and oral precautions. Environmental hazard lists the application directly to water. The active ingredient is S-metolachlor at 82.4 percent, and inert ingredients make up the remaining 17.6 percent of the product.

8. Pennant Magnum Herbicide was registered on February 7, 2012 with DPR registration number 100-950-ZB, and remains active. This product has a DPR registration Type A-Section 3 Regular Registration in the Category C-Chemical. Its formulation is an emulsifiable concentrate, and the product has an agricultural use as an herbicide. Health hazards associated with this product include skin, eye, and oral precautions. Environmental hazards include children/humans, drift, groundwater, and the application directly to water. The active ingredient is S-metolachlor at 83.7 percent, and inert ingredients make up the remaining 16.3 percent of the product.

9. Sequence Herbicide was registered on November 1, 2011 with DPR registration number 100-1185-ZA, and remains active. This product has a DPR registration Type A­Section 3 Regular Registration in the Category C-Chemical. Its formulation is an emulsion in water, and the product has an agricultural use as an herbicide. Health hazards associated with this product include skin and eye precautions. Environmental hazards lists drift, groundwater, and the application directly to water. The active ingredient is S-metolachlor at 29.0 percent; glyphosate at 21.8 percent; and inert ingredients make up the remaining 49.2 percent of the product.

In addition to registrations detailed above, Syngenta has held 28 other registrations for 15 S-metolachlor and 13 metolachlor pesticide products, which the Company has cancelled voluntarily or allowed to lapse over the years. Because those registrations are no longer active, we have provided only product names and registration numbers.

S-METOLACHLOR

PRODUCT NAME DPR REGISTRATION NUMBER

DUAL MAGNUM HERBICIDE 100- 816-AA

DUAL II MAGNUM 100- 818-AA

BICEP II MAGNUM 100- 817-AA

PENNANT MAGNUM HERBICIDE 100- 950-AA

MEDAL HERBICIDE 100- 964-AA

BICEP II MAGNUM 100- 817-ZA

DUAL MAGNUM HERBICIDE 100- 816-ZA

DUAL II MAGNUM 100- 818-ZA

PENNANT MAGNUM HERBICIDE 100- 950-ZA

MEDAL HERBICIDE 100- 964-ZA

MEDAL II AT HERBICIDE 100- 1165-AA

MEDAL II HERBICIDE 100- 965-AA

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S-METOLACHLOR

PRODUCT NAME DPR REGISTRATION NUMBER

SEQUENCE HERBICIDE 100- 1185-AA

MEDAL II HERBICIDE 100- 965-ZA

MEDAL HERBICIDE 100- 964-ZB

BICEP 100-590-AA

METOLACHLOR

PRODUCT NAME DPR REGISTRATION NUMBER

BICEP6L 100-645-AA

BICEP HERBICIDE 100- 645-ZA

CYCLE HERBICIDE 100- 716-AA

DUAL 100-673-AA

DUAL25G 100-638-AA

DUAL6E 100-583-AA

DUAL SE 100-597-AA

MEDAL HERBICIDE 100-688-AA

MILOCEP 100-604-AA

ONTRACK8E 100-610-AA

PENNANTSG 100-665-AA

PENNANT LIQUID HERBICIDE 100- 691-AA

In addition to registrations held by Syngenta, DPR records show eight active registrations for metolachlor and S-metolachlor pesticide products held by five other companies. Registrations are listed below by product name, registration number, and registrant. Syngenta' s response is intended to support other S-metolachlor registrations listed below.

PRODUCT NAME REGISTRATION NUMBER REGISTRANT

Drexel Me-Too-Lachlor Herbicide

19713-548-ZA Drexel Chemical Company

Drexel Me-T oo-Lachlor II Herbicide

19713-549-ZA Drexel Chemical Company

Parallel Herbicide 66222-87 -AA Makhteshim Agan of North America, Inc. (d/b/a ADAMA Agricultural Solutions Ltd.)

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PRODUCT NAME REGISTRATION NUMBER REGISTRANT

Parallel PCS Herbicide 66222-86-AA Makhteshim Agan of North America, Inc. (d/b/a ADAMA Agricultural Solutions Ltd.)

Stalwart Herbicide 60063-24-AA Sipcam Agro USA, Inc.

Brawl Herbicide 100-816-AA-55467 Tenkoz Inc.

Brawl II Herbicide 100-818-AA-55467 Tenkozinc.

Agrisolutions Charger Basic 1381-207-AA Winfield Solutions, LLC

E. DATE OF INITIAL REGISTRATION OF EACH PRODUCT IN CALIFORNIA

"Date of initial registration of each product in California, if known."

Initial date of registration for all of Syngenta' s products:

PRODUCT NAME REGISTRATION NUMBER DATE OF REGISTRATION

Bicep II Magnum 100- 817-ZC September 9, 2013

Dual II Magnum 100- 818-ZB March 29, 2012

Dual Magnum Herbicide 100- 816-ZC July 22, 2011

Halex GT Herbicide 100- 1282-AA January 1, 2013

Medal EC 100- 816-ZB July 20, 2011

Medal II ATZ 100-817-ZB April 26, 2012

Medal II EC 100-818-ZC May 3, 2012

Pennant Magnum Herbicide 100-950-ZB February 7, 2012

Sequence Herbicide 100-1185-ZA November 1, 2011

Dual Magnum Herbicide 100- 816-AA October 29, 1998 Inactive: December 31, 2004

Dual II Magnum 100- 818-AA September 15, 1999 Inactive: December 31, 2003

Bicep II Magnum 100- 817-AA September 15, ·1999 Inactive: December 31, 2003

Pennant Magnum Herbicide 100- 950-AA March 1, 2000 Inactive: December 31, 2004

Medal Herbicide 100-964-AA July 4, 2000 Inactive: December 31, 2004

102588243 \ V-1 Page 8 of 33

PRODUCT NAME REGISTRATION NUMBER DATE OF REGISTRATION

Bicep II Magnum 100- 817-ZA July 30, 2001 Inactive: December 31, 2015

Dual Magnum Herbicide 100- 816-ZA August 31, 2001 Inactive: December 31, 2013

Dual II Magnum 100- 818-ZA August 31, 2001 Inactive: December 31, 2013

Pennant Magnum Herbicide 100- 950-ZA September 10, 2001 Inactive: December 31, 2013

Medal Herbicide 100- 964-ZA September 10, 2001 Inactive: December 31, 2013

Medal II AT Herbicide 100- 1165-AA April 21, 2005 Inactive: December 31, 2013

Medal II Herbicide 100- 965-AA May 5, 2005 Inactive: December 31, 2013

Sequence Herbicide 100- 1185-AA May 10, 2005 Inactive: December 31, 2013

Medal II Herbicide 100- 965-ZA November 1, 2011 Inactive: December 31, 2014

Medal Herbicide 100- 964-ZB February 7, ?012 December 31, 2014

Bicep 100-590-AA February 23, 1978 Inactive: December 31, 1992

Bicep 6L 100-645-AA April 24, 1984 Inactive: December 31, 1991

Bicep Herbicide 100-645-ZA September 30, 1992 Inactive: December 31, 1997

Cycle Herbicide 100- 716-AA September 4, 1990 Inactive: December 31, 1994

Dual 100-673-AA March 31, 1988 Inactive: December 31, 1999

Dual 25G 100-638-AA July 11, 1982 Inactive: December 31, 1996

Dual 6E 100-583-AA No registration date listed. Inactive: November 30, 1982

Dual SE 100-597-AA July 24, 1980 Inactive: December 31, 1999

102588243 \ V-1 Page 9 of 33

PRODUCT NAME REGISTRATION NUMBER DATE OF REGISTRATION

Medal Herbicide 100-688-AA September 28, 1988 Inactive: December 31, 1995

Milocep 100-604-AA No registration date listed. Inactive: January 1, 1987

Ontrack SE 100-610-AA No registration date listed. Inactive: January 1, 1987

Pennant SC 100-665-AA September 4, 1986 Inactive: December 31, 1997

Pennant Liquid Herbicide 100- 691-AA September 28, 1988 Inactive: December 31, 1999

F. EVIDENCE THAT MATERIAL DETECTED IN SOIL AND GROUNDWATER DOES NOT

POLLUTE OR THREATEN TO POLLUTE GROUNDWATER

"Documented evidence that the material detected in soil does not threaten to pollute ground water in any region of the state when used according to terms under which it is registered; and that the material detected in ground water has not polluted, and does not threaten to pollute, ground water in any region of the state when used according to terms under which it is registered."

l. Statutory Standards for Determining When a Material Detected in Soil or Groundwater "Does Not Pollute" or "Threaten to Pollute the Goundwater"

The PCPA does not require that a pesticide product's registration be cancelled, or that the product be subjected to use restrictions or mitigation measures, simply because the pesticide has been detected in one or more wells. Such detection in monitoring wells initiates a process in which the pesticide product's registrant has an opportunity to demonstrate that notwithstanding such detection, the pesticide product in question "has not polluted, and does not threaten to pollute, the groundwater of the state ..." Food & Agric. Code Section 13150(a)(2). "Pollute," in tum, is defined in Food & Agric. Code Section 13142G) as "to introduce a pesticide product into the groundwaters of the state resulting in an active ingredient, other specified ingredient, or a degradation product of a pesticide above a level that does not cause adverse health effects, accounting for an adequate margin of safety."

In this case, there were no detections of the parent S-metolachlor. As for M-ESA and M-OXA, Syngenta can demonstrate convincingly that reported levels are so far below levels at which any adverse health effects are conceivable (i.e., corresponding HAL and DWEL values) that the subcommittee should find and recommend, and the Director should determine, that S­metolachlor, M-ESA, and M-OXA do not pollute or threaten to pollute the groundwater of the state. See Food & Agric. Code Section 13150(b),(c)(l).

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As demonstrated below, USEP A established a lifetime HAL (700 ppb) in drinking water at which humans will suffer no adverse effects assuming they are exposed at that level over their entire lifetimes. The HAL already incorporates an "adequate margin of safety," as required by Food & Agric. Code Section 13142U), in that it incorporates an "uncertainty factor" of 100 times the level at which metolachlor showed "no observed adverse effects" in test animals, and an additional five-fold factor in that it assumes that human lifetime exposure to metolachlor will be primarily by routes other than ingestion of drinking water (80% ), and only allows 20% of exposure by ingestion of drinking water (DWEL=3500 ppb). No water quality standards exist for M-ESA and M-OXA; however, M-ESA and M-OXA are 3- to 100-fold less toxic than the parent compound.

Given the degradation characteristics of S-metolachlor, M-ESA, and M-OXA, current use rates for S-metolachlor in California since it was registered in 2000 (Figure 1), and monitoring data collected to-date, there is no evidence to suggest that S-metolachlor would potentially threaten to pollute groundwater in California going forward. From soil dissipation field studies conducted in agricultural soils of California, average and median (n=6) half-life values for metolachlor were 29.6 and 32.9 days, respectively (Honeycutt, 1986). Furthermore, under a lab setting, metolachlor and S-metolachlor half-life values were similar, 7 .8 and 8.8 days, respectively (Clark, 1995). Half-life values for M-ESA and M-OXA ranged from 30.5­33.6 and 10.9-37.8 days, respectively. Thus, S-metolachlor, M-ESA, and M-OXA are relatively short-lived in agricultural soils of California. For historical and current use rates for S­metolachlor over the last 16+ years, monitoring data to-date demonstrates that the maximum detected M-ESA and M-OXA concentration (20.2 ppb) was significantly below HAL and DWEL levels. Considering the conservatism embodied in the HAL, the Director should conclude that S-metolachlor, M-ESA, and M-OXA do not pollute California groundwater with an adequate margin of safety. Clearly, reported levels detected do not satisfy the statutory definition of "pollute." Equally clear, given degradation characteristics of S-metolachlor, M­ESA, and M-OXA mentioned above and assuming monitoring data over the past 16+ years at historical and current use rates are predictive of future groundwater monitoring results in California, there is no potential for the continued use of S-metolachlor to "threaten to pollute" groundwater because S-metolachlor, M-ESA, and M-OXA residues will not accumulate in soil and groundwater over time to a level remotely near the adverse effects level, given the adequate margin of safety.

2. S-Metolachlor Has Not Polluted Groundwater in Any Region of the State

In September, 2016, DPR notified Syngenta that two degradation products (M-ESA, M­OXA) of the pesticide active ingredients metolachlor and S-metolachlor had been detected in groundwater as a result of legal agricultural use. This finding triggers a requirement that the registrant submit evidence supporting the continued registration, sale, and use of metolachlor and S-metolachlor. Evidence must support the conclusion that "any active ingredient, other specified ingredient, or degradation product that has been found in groundwater has not polluted, and does not threaten to pollute, the groundwater of the state in any region within the state in which the pesticide may be used according to the terms under which it is registered." Food & Agric. Code Section 13150(a)(2).

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Bergin (2016) summarized DPR' s groundwater monitoring of metolachlor, S­metolachlor, and two degradation products (M-ESA, M-OXA) in support of the notice Syngenta received from DPR. Briefly, DPR analyzed 433 samples from 282 wells located in relatively high use areas for metolachlor and S-metolachlor with no detections of metolachlor or S­metolachlor, despite metolachlor and S-metolachlor being registered in California for 39 years (since 1977) and 16 years (since 2000), respectively.

In total, DPR detected M-ESA and M-OXA in 62 of 282 groundwater wells (-22%), during four sampling years (2001, 2004, 2009 and 2015). DPR commonly targets shallow wells for sampling based on the assumption that they have the highest potential for contamination via pesticide applications (Troiano et al., 2001; Bergin, 2016). For example, in 2009, the 68 wells sampled averaged 40 feet in depth to groundwater (range: 9-115 feet) (Bergin and Nordmark, 2012). Most of the M-ESA and M-OXA detections (43 of 62 wells, 69%) were in three CA counties: San Joaquin, Solano, and Stanislaus counties. M-ESA and M-OXA were detected in 36, 30, and 60% of wells in each respective county.

Based on 2001, 2004, 2009, and 2015 monitoring data (Bergin, 2016), M-ESA and M­OXA were detected in 23 (67%) and 8 (33%) of the well samples. Metolachlor or S­metolachlor were not detected in any samples. M-ESA and M-OXA maximum concentrations ranged from 0.05-20.2 ppb. The maximum reported concentration (20.2 ppb) is conservatively 34 and 173 times lower than HAL (700 ppb) and DWEL (3500 ppb) values, respectively. From the distribution of the highest M-ESA and M-OXA concentrations from 2001, 2004, 2009, and 2015, average and median concentrations were 1.3 and 0.583 ppb, respectively. From that same distribution, 96% of the highest M-ESA and M-OXA concentrations were :54.02 ppb; 90% of those same concentrations were ~1.98 ppb. Also, the three highest M-ESA and M-OXA detections (20.2, 10.03, 4.02 ppb) reported were from 2001. Maximum M-ESA and M-OXA concentrations for 2001, 2004, 2009, and 2015 were 20.2, 1.1, 2.83, and 1.67 ppb, respectively. Excluding the data for 2001, average and maximum peak concentrations for 2004, 2009, and 2015 were 0.64 and 2.835 ppb, respectively.

DPR suggested that groundwater monitoring results used to support the September 2016 notice mirrored groundwater monitoring results for metolachlor, S-metolachlor, M-ESA, and/or M-OXA across the nation (Bergin, 2016). Metolachlor, M-ESA, and M-OXA data from four states (Georgia, Iowa, Minnesota, Wisconsin) were compared. On average, metolachlor, M­ESA, and M-OXA detection frequencies (range) were 16.3 (7-36%), 75.5 (60-91 %), and 46% (25-86%), respectively. On average, maximum concentrations for metolachlor, M-ESA, and M­OXA detections (range) were 5.1 (0.13-10 ppb), 17.3 (8-24.3 ppb), and 13.8 ppb (4.42-23 ppb), respectively. The maximum detected M-ESA concentration reported from the four states (24.3 ppb) is conservatively 29 times lower than HAL (700 ppb) and 144 times lower than DWEL (3500 ppb) values. This concentration (24.3 ppb) is also 20% higher than the maximum concentration in California (20.2 ppb ), which, as noted above, is conservatively 34 and 173 times lower than HAL (700 ppb) and DWEL (3500 ppb ). Given these data, one would conclude that California groundwater concentrations of metolachlor, S-metolachlor, M-ESA and/or M­OXA are lower than corresponding concentrations in other states.

Additional data establish that groundwater concentrations of metolachor, M-ESA and M-OXA in California are somewhat lower than corresponding concentrations in other states. Metolachlor, M-ESA, and M-OXA were part of a 7-yr (1995-2001) groundwater monitoring program in seven midwestern states (Illinois, Indiana, Iowa, Kansas, Minnesota, Nebraska,

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Wisconsin) (de Guzman et al., 2005). Depth to groundwater ranged from 5-75 ft; 62% of the 182 wells ( 112 wells) had an average depth to groundwater of <25 ft. Of the 112 wells, 60 had an average depth to groundwater of <10 ft.; and 22 wells had an average depth of <5 ft.

Over the seven-year study, metolachlor was detected in all seven states and in 30 of 182 wells (-16%). Metolachlor was detected in 396 of 10,054 samples (-4%); 99 samples were <LOQ (0.5 ppb ), 95 samples were between LOQ and 0.10 ppb, and 202 samples were >LOQ. M-ESA was detected in all seven states and in 106 of 182 wells (-58%). M-ESA was detected in 976 of 1961 samples (-50%), 248 of which were <LOQ. M-OXA was detected in all seven states and in 63 of 182 wells (-35%). M-OXA was detected in 407 of 1961 samples (-21 %), 268 of which were <LOQ.

Syngenta initiated a groundwater study (Francis and Johnson (2001) in 1996 to evaluate mobility and fate of S-metolachlor in a worst-case, hydrogeologically-vulnerable area used for com production in Minnesota. The - 2A test plot included 17 monitoring wells and four observation wells, with water table depths of 20-24 ft. Com was planted in year 1 of the study, then the site was left bare for the remainder of the 60 month study. S-metolachlor was applied at the maximum labeled yearly use rate.

S-metolachlor was not detected in groundwater above the LOQ (0.1 ppb); M-OXA and M-ESA were detected above the LOQ. M-OXA was first detected in shallow monitoring wells (-20 ft.) at five months after application (MAA) and peaked at an average concentration of 5.3 ppb. By 45 MAA, M-OXA was below the LOQ in shallow monitoring wells. M-OXA was first found in deep monitoring wells (-30 ft. ) at 14 MAA and peaked at an average concentration of 0. 9 ppb at 16-17 MAA. By 45 MAA, M-OXA was below the LOQ in deep monitoring wells. M-ESA was first found in shallow monitoring wells at five MAA and peaked at an average concentration of 15.6 ppb at 19 MAA. By 51 MAA, M-ESA was found only at levels slightly above the LOQ in shallow monitoring wells.

Francis and Johnson (2001) concluded that S-metolachlor degraded relatively rapidly in soil and has a low potential to impact underlying groundwater systems. Also, M-ESA and M-OXA were more mobile than S-metolachlor and were detected in shallow and deep monitoring wells (peaked at average concentrations of 5.3-15.6 ppb). Peak concentrations were significantly below levels (at least 44 times lower than the HAL of 700 ppb and at least 224 times lower than the DWEL of 3500 ppb) that could cause adverse human health effects.

Another Syngenta study (Gold et al., 1999) evaluated the mobility and fate of metolachlor in groundwater in a worst-case, vulnerable area typically used for peanut production in Georgia. T he -3A test plot included 16 monitoring wells, with water table depths of 10-20 ft. Peanuts were planted in year 1 of the study, then the site was left bare for the remainder of the 3-yr study. Metolachlor was applied at the maximum labeled yearly use rate.

Metolachlor was not detected in groundwater; M-OXA and M-ESA were detected, but at very low concentrations. For M-ESA, the maximum concentrations detected in shallow and deep wells were 24 ppb (-15 MAA) and 8.8 ppb (-13 MAA), respectively. The highest concentration of M-OXA in shallow wells was 2.9 ppb; the highest concentration in deep wells was 1.4 ppb. The average concentration of M-ESA and M-OXA during the highest residue levels for three consecutive months was 8.8 and 0.98 ppb, respectively.

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Gold et al. (1999) concluded that metolachlor had a relatively short half-life of 24 days, and would not be expected to leach to groundwater under worst case conditions. Also, M-ESA and M-OXA reached groundwater, yet their respective maximum concentrations (M-ESA=24 ppb; M-OXA=2.9 ppb) were significantly below HAL (700 ppb) and DWEL (3500 ppb) levels.

Comparing monitoring data for metolachlor, M-ESA, M-OXA in California (Bergin, 2016) to that in eight other states (Iowa, Georgia, Wisconsin, Nebraska, Minnesota, Illinois, Indiana and Kansas), M-ESA and M-OXA are detected more frequently than metolachlor, with M-ESA detected more frequently than M-OXA. Average (range) frequency of detection for M­ESA in eight states and CA was 73% (50-99%) and 47% (23-67%), respectively. Average frequency of detection for M-OXA in the eight states and CA was 43% (21-86%) and 17% (8­33%), respectively. Average frequency of detection for metolachlor in the eight states was 19% (4-57%); conversely, metolachlor and S-metolachlor were not found in California groundwater samples. Maximum concentrations in California (M-ESA, M-OXA) (Bergin, 2016); Georgia, Iowa, Minnesota and Wisconsin (Bergin, 2016); Minnesota (Francis and Johnson, 2001); Georgia (Gold et al., 1999); and Illinois, Indiana, Iowa, Kansas, Minnesota, Nebraska, Wisconsin (de Guzman et al., 2005) (1999 only) were 20.2, 24.3, 15.6, 24, and 23 ppb, respectively. All cited maximum concentrations are below HAL (700 ppb) and DWEL (3500 ppb) levels. Thus, frequency and maximum concentrations detected in California were generally 19-26% and 14-20% lower than those from eight other states. As a result, maximum concentrations of metolachlor, M-ESA, M-OXA in California (20.2 ppb) have not polluted groundwater based on HAL and DWEL values and terms defined by the Section 13142(j) of the Pesticide Contamination Prevention Act. Likewise, maximum concentrations of metolachlor, S-metolachlor, M-ESA, and M-OXA in other Midwestern and Southeastern states have not polluted groundwater based on HAL and DWEL values.

3. S-metolachlor Does Not Threaten to Pollute Groundwater

Given the degradation characteristics of S-metolachlor, M-ESA, and M-OXA, current mature, relatively constant use rates for S-metolachlor in California since it was registered in 2000 (Figure 1), and monitoring data collected to-date, there is no evidence to suggest that S­metolachlor would potentially threaten to pollute groundwater in California going forward. As previously mentioned, S-metolachlor, M-ESA, and M-OXA are relatively short-lived in agricultural soils of California. Given historical and current use rates for S-metolachlor over.the last 16+ years, monitoring data to-date demonstrates that the maximum detected M-ESA and M­OXA concentration (20.2 ppb) was well below conservative HAL and DWEL levels. Because S-metolachlor, M-ESA, and M-OXA are relatively short-lived and assuming monitoring data over the past 16+ years at historical and current use rates are predictive of future groundwater monitoring results in California, there is no potential for the continued use of S-metolachlor to "threaten to pollute" groundwater because S-metolachlor, M-ESA, and M-OXA residues will not accumulate in soil and groundwater over time to a level remotely near the adverse effects level, given the margin of safety.

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G. MITIGATION MEASURES

"The registrant may submit potential mitigation measures and rationale for their adoption, including proposed restriction or agricultural use modification for certain areas of the state or for the entire state. "

Syngenta has not proposed any mitigation measures at this time for the following reasons: First, S-metolachlor, M-ESA, and M-OXA exposure data reported in California groundwater are conservatively and significantly below toxicological endpoints (HAL=700 ppb; DWEL=3500 ppb ). Second, the successful management of S-metolachlor by growers and Syngenta demonstrate that the current S-metolachlor label sufficiently protects against the potential for S-metolachlor, M-ESA, and M-OXA to be detected at concentrations that "pollute" or "threaten to pollute" California groundwater. Finally, any mitigation implemented at this time would not be cost-effective for California growers.

H. ECONOMIC HARDSHIP

"The registrant may submit evidence that agricultural use modification or cancellation of the product( s) will cause severe economic hardship on the state 's agricultural industry. Such evidence should show why the registrant's product is the preferred material for use and also the additional costs to growers if agricultural use modifications are made or alternative products are used. "

S-Metolachlor is an important member of the chloroacetamide class of herbicides and is used as a selective, pre-emergence herbicide to control a broad spectrum of grass and small seeded broadleaf weeds. S-metolachlor is especially effective for control of yellow nutsedge in many crops grown in California, and is the only option for controlling this weed. Also, S­metolachlor is also effective for control of nightshades, common lambsquarters, barnyardgrass and Italian ryegrass which are difficult to control in many crops grown in California.

S-Metolachlor is a flexible herbicide that can be applied safely to crops either pre- or post-emergence. In California, S-metolachlor is registered for use on 85+ food crops (Table 1) and 100+ non-food crops (Table 2). The only other Group 15 herbicide registered for use in California is dimethenamid-p, and this compound is labeled for use on only 11 of the food crops currently registered for S-metolachlor. Elimination of S-metolachlor would leave growers of 70+ food crops without access to a Group 15 herbicide for control of weeds and management of herbicide-resistant weeds. Loss of S-metolachlor for use in California would be a significant economic impact to grower's ability to effectively control weeds on many crops.

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