BEFORE THE DIRECTOR OF THE DEPARTM E NT OF P E STICI D E REGUL A T I ON STAT E OF CALIFORNIA

In the Matter of the Respon sible F a rmers Coa lition’s Request for Approval of Reduced Volatile Organic Compound Em issions Field Fum i gation Methods

DECISION (Californ i a Code of Regulations, T i tle 3, section 6452)

RESPONSI BLE F A RMERS CO ALITION Mr. John Guerard c/o Bolthou s e Farms 7200 East Brundage Ro ad Bakersfield, California 93307 ______________________________/

Summary

The Responsible Farm ers Coalition s u bm itted a s t udy to th e Departm e nt of Pesticide Regulation ( D PR) titled “Field Vola tility of MIT C Af ter Applica tion of Metam

- Sodium by Che m igation and Shank Injection C o mp aring Standa rd W a ter Sealing and Pulsed W a ter Sealing” dated October 18, 2007. As part of DPR’s effort s to reduce volatile organic compound (VOC)

em issions, most night applications of m e thyl is othiocyanate (MITC)-con tain ing pes tic ides a r e prohibited w ithin several ozone nonattainm ent ar eas (NAAs) during May–October, under Title 3, California C ode of Regulations (3 C CR) s ection 6450.1(c). H o wever, the regulations also include a provision for the DPR Di rector to grant interim approva l of fumigation m e thods that reduce VOC em issions (3 CCR section 6452). DPR has co mpleted its evaluation of the two fum i gation m e thods described in the study as specified in 3 C CR section 6452. The subm itted study indicates high uncertainty as to exact em issions for the two m e thods. Despite the uncertainty of the data, DPR has determ ined that the m e thods m eet the ultim a te test for approval as interim methods, as describe d below. Effective May 1, 2008, DPR grants approval for interim use of the shallow shank injection m e thod desc ribed in the study in all five ozone NAAs. Effective May 1, 2008, DPR grants approval for inte rim use of the sprinkler m e thod described in the study for the Sacramento Metro and South Coast ozone N AAs, but not the San Joaquin Valley, Southeast Desert, or Ventura ozone NAAs during May–October. The em ission ratings assigned to these m e thods will be equ a l to the hig h est rating f o r any currently app r oved m e thod for m e tam

- s odium in each specific area. The m e t hods describ e d in the stu dy m a y be used for three years f r om the effe ctive date, contingent on the subm ittal of an additional study to m o re accurately d o cum e nt the em issions from these fum i gation m e thods.Responsible Farm ers Coalition Page 2

Background

VOCs contribute to the form ation of ozone, a m a jor air pollutant in several regions of California. Under the fe deral Clean Air Act, California’s S t ate Implem entation Plan for ozone includes an elem ent to track and reduce VOC e m i ssions fr om pesticides. On January 25, 2008, DPR adopted regulations to control VOC e m issions from fu migants during the May–October peak ozone season in five ozone NAAs: Sacram ento Metro, San Joaquin Valley, Southeast Desert, South Coast, and Ventura.

The Responsible Farm ers Coalition s u bm itted co mments for DPR’s regulations du rin g the rulem a king process. During this rulem a king process, DPR modified its orig inally proposed text and provided the public an opportunity to comm e n t on the m odifications. As part of their comments, the Responsible Farm ers Coalition in cluded a study on field em issions from several experim e nta l application s of m e tam

- sodium at night, “Fie ld Volatility of MITC Af ter Application of Metam

- Sodium by Chem igation a nd Shank Injection Comparing Standard W a ter Sealing and Pulsed W a ter Sealing” dated October 18, 2007. This study and comments on night applications of m e ta m

- sodium were not relevant to the m odifi cations, and therefore, no revisions to the regulations were considered at that tim e. DPR has since adopted th e regulations, including a provision prohibiting most ni ght applications of MITC-c ontaining pesticides [3 CCR section 6450.1(c)]. However, the regulations also include a provision for interim approval of fum i gation m e thods with em issions no greater that the field fum i gation methods allow e d in the regulations in the respectiv e areas (3 CCR section 6452).

Regulatory Standards and Considerations

Title 3, CC R section 64 52 sets dif f

e rent s t anda r d s by which to evalu a te whether a ne w fum i gation m e thod will be allowed, one for the Sacram ento Metro and S outh Coast ozone NAAs and one for the San Joaquin Valley, Southeast Desert, and Ventura ozone NAAs. Sa cram ento Metro and S outh Coast h a ve a less stringent s t and a rd becau se no further VOC reductio ns from pesticides are needed in thes e ozone NAAs. Both “low-em i ssion” and “high-em ission” m e thods can be used in these two areas. Only “low-em i ssion” m e thods are allowed in the San Joaquin Valley, Southeast Desert, and Ventura ozone NAAs during the May–October peak ozone season. The key inform ation is the em ission rating (percent of the fum i gant applied that is em itted to the air) and the em ission rate (em i ssion rating m u ltiplie d by the m a xim u m applic a tion ra te). Either the em ission rating or the em ission rate can be no greater than the current m e thods allowed within the ozone NAAs by the regulations. The f o llowing table shows the standard for approval of an interim m e thod for MITC, base d on DPR’s current em ission estim ates.Responsible Farm ers Coalition Page 3

Oz one Nonattainment Area Maximum Allow e d MITC Emission Ratin g (percentag e ) Maximum Allow e d MITC Emission Rate (pounds/acre) Sacram ento Metro, South Coast 77 140 San Joaquin Valley, Southeast Desert, Ventura 28 51

In assessing whether the new m e thod m eets the standard, DPR m u st assess the scientific data subm itted to estab lish th e em ission rating, no rm a lly cons istin g of field monitoring data. In evaluating this data, 3 CCR section 6452 require s DPR to consider the following factors:

• whether th e inf o rm ation is suf f i cient to estim a te em issions.

• whether th e results are v a lid as i ndicated by the quality control data.

• whether the conditions studied re present agricultural fields.

Summary and Evaluation of the Submitted Information

The Responsible Farm ers Coalition s u bm itted th e study entitled “Field V o latility of MITC After Application of Metam

- S odium by Che m igation and Shank Injection Comp aring Standard W a ter Sealing and Pulse d W a ter Sea ling” by Dr . David Sulliv an and Dr. Husein Ajwa, dated October 18, 2007, to support its request to allo w m e ta m

- sodium applications at night. Dr. Sullivan and Dr. Ajwa m easure d the MITC em issions f o r two m e tam-sodium f

u m i gation

m e thods: shallow injection using tractor shan ks and chem igation using sprinklers. All applications were initiated on July 26, 2007, between 1:00 a.m. and 2:00 a.m ., and completed between 1:45 a.m

. and 6:00 a.m

. In addition to the two fum i gation m e thods, Dr. Sullivan and Dr. Ajwa measured em i ssions fr om “standard” water treatments (continuous water application) and “pulsed” water treatm ents (a lternating periods of water and no water application). Two water
trea tm ents were applie d f o r all f our applic a tions, one imm e diately af ter a pplica tion a nd the second during the evening of the day of applicat ion. All four applications were approxim ately 2.5 acres in size, separated by 900-1,600 feet, located in Kern County, and with m e tam

- sodium applied at 75 gallons/acre (320 pounds active ingred ient/acre). Using a combination of integrated horizon tal f l ux and of f

- site back -calc u lation tech niques, Dr. Sullivan and Dr. Ajwa estim ated the following em issions for MITC over the four-d ay study period (em i ssion rating and em ission
rate ):

• night sprinkler with two pulsed water tr eatm ents: 37.65 percent and 67 pounds/acre.

• night sprinkler with two standard water treatm e nts: 35.68 percent and 64 pounds/acre.

• night shallow injection with two pulsed water treatm ents : 2.22 percent and 4.0 pounds/acre.

• night shallow injection w ith two standard water tr eatm ents: 2.10 percent and 3.7 pounds/acre.Responsible Farm ers Coalition Page 4

The report s u bm itted on October 18, lacked som e key inform a tion. DPR requested add i tional inform ation in Novem b e r2007 and received it in Decem ber 2007. After several m o re phone calls and e- m a il exchanges, DPR staf f had a f i na l dis c ussio n with Dr. Sulliv an and Dr. Ajwa on February 13, 2008, and the last requested in form ation was received on February 15, 2008.

DPR’s scien tif ic r e view of th e report describes several shortcom ings, both with the design and execution of the study. T h e m o stcritical issues include:

• uncertainty of the air co ncentration s due to nonlinear calibration curves f o r the laboratory instrum e nt.

• uncertainty of the air concentr ations due to variable recove ries (28–175 percent) of samp les containing known a m ounts of MITC (spiked samples).

• samp ling halted when sprinklers were running.

• uncertainty in the em issions for some periods due to an insufficient num ber of valid samp les or air concentrations that inc r eased with heigh t

. Additional work by the study autho r s or rev i ew of additional inform ation by DPR would not further resolve these issu es. Even with these shortcom ings, m a ny of the results are reasonably consistent w ith the results from other studies, pa rticularly for the sprink ler application. While not preferred by the scientific staff, it is possible with a reasonable am ount of certainty to set an upper-bound for the em ission rates th at will not b e exceeded f o r these application m e thods. The attached m e morandum c ontains the detailed review.

Findings

The inform a tion provided, particularly the quality control data, indicate s h i gh uncertain ty with the exact emissions for these fum i gation m e thods . However, DPR staff is confident that the

em issions are no greater than other fum i gation m e thods currently in use. T h erefore, DPR has assigned the following em ission ratings to these m e thods:

• MITC night shallow injection m e thod: 28 percen t (based on current shallow injection m e thod with two post-f u m i gation water trea tm ents).

• MITC night sprinkler m e thod: 77 percent (based on current sprinkler m e thod with one post-f u m i gation water tre a tm ent).

Conclusions

The em ission ratings and the current m a xim u m a pplication rate of 320 pounds per acre of

m e ta m

- sodium and 350 pounds per acre of m e tam

- potassium support approval of these fum i gation m e thods. Effective May 1, 2008, the MITC night shallow injection m e thod is approved for use in all five ozone NAAs. Eff ective May 1, 2008, the MITC night sprinklerResponsible Farm ers Coalition Page 5

m e thod is approved for use in the Sacram ento Metro and South Coast ozone NAAs, b u t not the San Joaquin Valley, Southeast Desert, or Ve ntura ozone NAAs duri ng May–October. These fu m i gation m e thods m a y be used anytim e outsi de of ozone NAAs and within any ozone NAA outside the May–October period, consistent with all VOC fu m i gation m e thod restrictions.

In addition, the fum i gation m e thod descriptions and photographs for the shallow injection

m e thod show significant differences from the me thods currently described in the regulations. Growers and applicators fum i gating with the ni ght shallow injection m e thod m u st follow the regulatory recomm endat i ons for equipm ent and proce dures described in part VI of the atta ched

m e morandum.

DPR grants interim approval of these fum i gation m e thods for three years f r om the effe ctive date. Due to the high uncertainty of the em ission estim a tes, continued use of these fum i gation m e thods beyond three years is co ntingen ton the subm itta l of an additional acc eptable study to more accurately d o cum e nt the em issions. Since DPR mu st adopt regulations to include th ese new

m e thods prior to th e exp i ration of th e interim approval, the addition a l s t u dy should be subm itted within 12 months. The addition a l s t u dy should in clude a comp arison of th e shallow injection

m e thod used for this study and the typical shal low injection m e thod previously m onitored (as described in the series of studies by D

. L. Merricks in 1999, 2001, and 2002). DPR recomm ends that the Res ponsible Farm ers Coalition subm it a dr aft proto c ol for DPR scientific staff review prior to initia ting the study.

By:

___ fo r

_______ Date:______ 2/29/08

___________ Mary-Ann War m erdam, Director Departm e nt of Pesticide Regulation

Attachm e nt

# Department of Pesticide Regulation

Mar y -A nn W a r m erdam 

### M E M O R A N D U M Arnold Schwarze negger Director Go v e rno r

TO: Randy Segawa Environm ental Program Manager I Environm ental Monitoring Branch

FROM: Pa m e la W o fford Original signed by Senior Environm ental Scientist Environm ental Monitoring Branch (916) 324-4297

DATE: April 23, 2008

SUBJECT: AMENDM ENT TO REVIEW OF “FIELD VOLATILITY OF METHYL ISOTHIOC YANATE AFTER APP L ICAT ION OF METAM-SODIUM BY CHEMIGATION AND SHANK INJE CTION C O MPARING STANDARD WAT E R SE ALING W I TH PUL S E D WATER SEALING”

In a m e m o ra ndum to you dated February 26, 2008, Terrell Barry, Shifang Fan, and I described a review of a study on the em issions of m e thyl is othiocyanate from two m e t a m

- sodium fum i gation

m e thods: night shank injection with two water tr eatm e nts and night sprinkler application with
two water treatm e nts. We m i stakenly described part of the configura tion of the application tractor used for the shank in jection portion of the study. The comp action equipm ent was described as:

“The application tool bar(s) are followed by a ring roller with four gauge wheels controlled by hydraulic cy linders to co ntrol d e pth and or pressu re to seal the chisel trace that is as least as wide as the app lic ation tool ba r. The ring r o lle r will b e f o llowed with a coil p ack er tha tis as least as wide as the application tool bar.”

The comp ac tion equipment and recommended perm it conditions should instea d be described as

“The application tool bar(s) are followed by a ring roller with four gauge wheels controlled by hydraulic cy linders to co ntrol d e pth and or pressu re to seal the chisel trace that is as least as wide as the application tool bar, or a co il p acker that is as leas t as w i de as the application tool bar.”

100 1 I Street • P.O. Box 4015 • Sacramen to, Californ i a 9 581 2-40 15 • www

. c dpr.c a.g o v
A Depart m e n t of the California En vironm ent al Prot ection Agency

Prin te d o n re cycled p a p e r , 10 0 % p o s t-consu m e r--p ro ce sse d ch lorin e

- fre e

.

# Department of Pesticide Regulation

Mar y -A nn W a r m erdam 

### M E M O R A N D U M Arnold Schwarze negger Director Go v e rno r

TO: Randy Segawa Environm ental Program Manager I Environm ental Monitoring Branch

FROM: Terrell Barry, Ph.D., Re search Scien tist III Original signed by Environm ental Monitoring Branch

Shifang Fan Ph.D., Environm ental Scientist Original signed by Environm ental Monitoring Branch

Pa m e la W o fford, Senior Environm ental Scientist Original signed by Environm ental Monitoring Branch (916) 324-4297

DATE: February 26, 2008

SUBJECT: REVIEW OF “FIELD VOLATILI T Y OF MET HYL ISOT HIOCYANATE AF TE R APPLICATION OF METAM-SODI UM BY C H EMIGATION AND SHANK INJECTION COMPARING STANDARD WATER SEALING W I TH PULSED WAT E R SE ALING”

I. Backgrou nd

This field study had two m a in objectives: (1) m easure flux from night m e tam sodium applications, and (2) comp are ev ening watering-in that is applied over a two hour period with pulsed watering-in applied over a four hour period (30 m i nutes on/30 m i nutes off).

The original report did not contain enough detail to fully review the results. For example, the on-field m a st m easured air concentrations are show n in a plot but not in a table. In addition, the f l ux calculations were no t inc l uded. S ubsequently the autho r s s u bm itted f o r

review th e quality assurance/quality control (QA/QC) data collect ed for the study and the spreadsheets and calculations used to estim a te the flux for both met hods. A review of those da ta is included in this

m e morandum.

This is th e first nigh t time shank application stud y subm itted. In addition, the application rig is signif i can tly dif f

e rent f r om the typica l rig us ed in Calif ornia. The applic ator has subm itted photographs and the rig specifications to the De partm e nt of Pesticide Regulation (DPR) for review. Before night shank applications usi ng this rig are allowed, a second study should be conducted to verify that the em issions are reliably as low as those m easured in this study since the results are so different from previous sha nk application m e thod results. The additional study should include both the application rig used in this study (W e s tern Farm s rig) and the typical application rig used in the Me rricks studies (Merricks, 1999; Merricks, 2001; Merricks, 2002).

100 1 I Street • P.O. Box 4015 • Sacramen to, Californ i a 9 581 2-40 15 • www

. c dpr.c a.g o v
A Depart m e n t of the California En vironm ent al Prot ection Agency

Prin te d o n re cycled p a p e r , 10 0 % p o s t-consu m e r--p ro ce sse d ch lorin e

- fre e

.Randy Segawa February 26, 2008 Page 2

Due to considerable unce r ta inty in the labora t ory QA/QC and irregulari ties in the fieldwork (both discussed in detail below) , it should be assum e d that e m i ssions for this new rig are the

sam e as the typical rig. However, the typical ri g used for m e t a m sodium a pplications should not be allowed f o r night applications.

When differ e nces in tim ing of the application ar e considered the sprink ler results are reasonably sim ilar to the previous sprinkler results. The flux and concentrations are high during the night application. These results do not su pport allowing night sprinkler applications unl ess m a ss loss in the context of the volatile or ganic compound (VOC) regulations includes a large uncertainty factor. Acute exposure and buffer zones to protec t persons off-site are not addressed in this review. Concentrations and flux decreases during the day and first the evening. As observed in previous s t u d ies, th e inte rm ittent watering- in pe rf orm e d early the f i rs t eve n ing damp s the increase in f l ux and air concentrations that has been observed for m e tam i n standard w a tering-in studies. Th e s e resu lts in dicate tha tthe tota l m a ss loss of app r oxim a tely 3 7 % f o r the s p rinkler application m e thod used in this study is less than the standard day sprinkler m e thod (77%) but more than th e inte rm itten twater i ng- in day sprink le r app lic ation (28%). U n certainty in the quality of these results infers a m a ss loss larger than the 37% estim a ted in this study.

Detailed review of the laboratory QA /QC and th e fieldwork are presen te d separa tely b e low.

II. Laboratory Quality Assurance and Quality Control Comments

This part of the review is focused on quality m easures of m e thyl isothiocyanate (MIT C) monitoring. During review, we had telephone, e-m a il and a teleconference call exchanges with the Univers i ty of Calif ornia, Da vis laboratory to obtain m o re deta iled inform ation concerning the laboratory analysis.

QA/QC measures for field samp les included 12 duplicate samp les at one samp ling station, triplicates of field blank, and tripli cates of trip spikes and field sp ikes each of three levels. QA/QC

m easures for laborato r y analys is included determination of the dete ction lim it as 2 μg/sample and 44 lab spike samp les prepared by adding 10 μl of 10.8 μg M I TC/μl of a standard fortification solution to the m i ddle of the charcoal tube on th e day the field samp les arrived in the laboratory. The spiked tubes were stored, extracted and analy zed the s a me as the field samp les. One laboratory s p ike was an alyzed with every ten fi eld samp les. Based on the revised protocol for MITC analy s is, the s e lab o ratory spik es were us ed “as standard QC/QA to confirm MI TC storage stability on charcoal, extract ion efficiency, and the GC m easurem ent accuracy.”Randy Segawa February 26, 2008 Page 3

DPR has seven m a jor concerns a bou t the labo rato ry prac tic es:

1. Spiked samples at different concentrations shou ld have been analyzed prior to the study to validate the gas chrom a tograph/m a ss spectrom e try (GC/MS) m e thod used for this study. According to e-m a il communication: “the la boratory has been running MITC analyses following the Morse protocol using the NP de tector since 2002, the GC/MS used for this study is a n e w GC purchased early last year. Th e laboratory u s ed this GC because it w a s not expected that the con centrations were m u ch lower than prev io us st udies.” The laboratory spikes m e ntioned above could not serve as anal ytical m e thod validation since all spikes were at one concentration level of 108 μg MITC/tube . Standard laboratory practice is three to seven different levels for anal ytical m e thod validation studies to cover concentration ranges of field samples. The reported results of fi eld samples in this study ranged from 1 to 160 μg/tube.

2. A trapping efficiency study should have been conducted. The field spikes m i ght provide inform ation for trapping efficiency; however th ey were samp led in the field for only four hours and the results of the field spikes were highly variable. The field samples ran from three to eight hours.

3. The results of the single concentration laborator y spikes sho w a declin in g trend with analys is sequence (Figure 1). This indicates a system atic bias th at in creases ov er tim e

.

4. The field QA/QC sa mp l e s showed variable results and indicate possible problem s. The results of field blank s a mples rang ed from 0 to 0.87 μg/tube. Positive field blanks ind i cate a contam ination problem . Recoveries of several tr ip spikes were high, ranging from 84.4% to 174.8%. Plus, these are inconsistent with the field spike results that showed low recoveries, ranging from 27.7% to 109%.

5. The laboratory standard calibration curves used to calcu late the samp le results wer e n o t linea r (R 2 =0.9793) (Figure 2). For side-by-side co mp arison, a typical standard calibration curves (R 2 =0.9997) from the California De partm e nt of Food and Agri culture’s laboratory is shown in Figure 3. Using a linear model for the nonlinea r ca libr a tion cur v e leads to incorrect

samp le concentra tion res u lts, pa rticularly a tlow c oncentr ation s

.

6. There is an inconsistency in MITC air conc entrations between the data on page 77 of Sullivan En vironm ental Consulting, Inc.’s re port and the data DPR calculated us ing th e laboratory analysis results. Vi a e-m a il comm unications, it tur n ed out tha tthe incon s is tency was due to a subtraction of 0.6 μg/ m l (6 μg/tube ) from all analysis re sults including both on-field and off-field samples. This subtraction of 0.6 μg/ m l was based on the average of differences between the results calcu l ated by subtracting the y-in tercept versus those calcu lated b y forcing the slope th rou gh zero for the on-field s a mp les. The differences of eachRandy Segawa February 26, 2008 Page 4

paired data ranged from -4.38 to 0.96 μg/m l. Th e investigators m a de these adjustm e nts in an
attemp t to c o rrec tthe no nlinea r prob lem s of the calibration curve discussed in num be r 5. DPR does not believe that either forcing the slope through zero or subtracting 6 ug/tube is an appropriate adjustm e nt for this problem . In addition, m a king both adjustm e nts appears to double-correct the resu lts, underestimating the true c oncentrations. Attemp ting any

reca lcula tio n of the resu lts a tth is tim e is problem atic.

7. One of purposes of this study was to comp ar e MITC em ission from different application

m e thods, chem igation versus shank injection an d standard w a ter sealing versus pulsed water sealing. However, all samples of chem igation were analyzed in one period (July 31, 2007, 15:38 to August 1, 2007, 11:03) and results we re calculated using one standard curve (calibration slope); all samples of shank injection were analyz ed in another period (August 1, 2007, 15:44 to August 3, 2007, 3:10) and results we re calculated using a different standard curve (calibration s l ope). This samp le analys is schedule m a y introduce system atic errors that would confound comp arison of di ffer e nt application m e thods.

The following are specific comm ents on the different docum ents:

On Revised Protocol:

1. Page 1, the paragraph of Stock Solution, the la st sentence: This stoc k solution should contain 0.995 m g MITC /m l since the purity is 99.5%.

2. Page 2, the first paragraph: Either the con centration unit of the sp iking standard or the procedure was wrong. If following the procedure, the spike standard solution concentration should be 10 μg/m l, not 10 μg/μl. Also the purity of the MITC analytical standard should be considered.

3. Page 2, the paragraph of Field Samp le Fortificat ion: If following the procedure that 10 μl of 0.05, 1.0, and 20 μg/m l MITC standard solutions wa s spiked, the fortified tubes should have contained 0.0005, 0.01, and 0.2 μg/tube MITC, not 0.5, 10, and 200 μg/tube. It is possible that the concentration unit of the spiking solutions was wrong.

On Report:

1. Page 33, the m e dian values were used for fi eld spike recovery values, 95.2 to 109.2%. W ith only three samples, a range should have been reported instead of the m e dia n.

2. Page 35, the last sentence: it is unclear how the 2 μg/tube was converted to 20 μg/m 3 . W ith a flow rate of 1 liter/m inute, the samp ling tim e would be only 100 m i nutes. However, most

samp les ran approxim a tely 200-500 m i nutes.Randy Segawa February 26, 2008 Page 5

3. Page 36, the analytical standard purity, date of expiration, and certifi cate of analysis w e re docum ented in the laboratory files: except fo r the purity provided in revised analysis protocol, other inform ation was not provided anywhere.

Laboratory spreadsheet:

1. In the on-field samp le sheet, all dup A1 should be dup B1.

2. Two sets of data were the sam e , but labeled diffe rently. One s e t were the r e sults in th e colum n s of P, Q, and R of each worksheet of the Laborat o r y spread sheet_MITC_7 _07_Bakersfield.x ls file. Via phone conversation, these results were fr om the 10 ppm of the standard solution for continuous standard calibration control (as in page 36 of the report). The other set of data was actually co llected from all th e resu lts on the P, Q, and R of each workshee t of the Lab o ratory spreadsheet_MITC_7_07_Bakersfield.xls file and lis ted on the Standard fortified laboratory

samp les worksheet of the MITC-stds. xls file as the results of the laboratory spike samp les analyzed with every 10 field samp les.

III. Fieldw ork Comments

Page 14

. First Paragraph . This paragraph states that for the evening watering-in periods on-field samp lers were not run when the sprinkl ers were running. W h ile th is is reasonable to avoid dam a ge to the samplers, the study design s hould have been planned to have sufficient off-site samplers to provide a back-calculated es tim a te of the flux. It is completely unknown how much m a ss loss was m i s s ed due to the lack of sa mplers during the irrigation events. In addition, the pump running tim es for the standard watering-i n treatm ents are not cl ear. The field history sheets are d i fficult to decipher.

Page 28

. Chemigation P l ots (#1 and #2) . This paragraph states that Plot #2 was completed at 10:40 a.m

. However, Table 2 indicates that the in itial watering-in was finished at 0800 hours. It is unclear w h ether the 10:40 a.m

. refers to th e completion of setting up th e sonic an emom eter tower ra ther than the wa tering- in.

Page 29

. First paragraph . This paragraph states that Appendix F contains confirm a tory results for periods 3-6. However, Appendix F shows onl y figures and the head ing of Appendix F “Confirm a tory Modeling versus Measured Plots (Per iods 4-6)” is in confli ct with the caption of the very first plot where is states th at the plo t is for Period 3. T h ese sorts of m i stakes lead to doubt about the correctness of the rem a inder of the report.

Page 29

. Last paragrap h . The irrigation paragraph indicate s that the irrig a tion was qu ite variable with the shank applica tions receiving less water than the planned am ount. The authors end by saying that if the irrigation is averaged ac r o ss fie lds th at resu lts were generally close toRandy Segawa February 26, 2008 Page 6

design am ounts. However, the authors also pr ovide unsupported speculation that if the shank applications had not received 14% to 21% less water than planne d that the shank results would show even lower em issions. So, the author’s st atem ents are in conflict. E ithe rthe av erage

am ount across fields is acceptab l e an d the variati on is judged to not be significant o rthe shank received significantly less, not both.

Page 34

. Tables 7 and 8 . Field Fortifications, Blanks, and Duplicates. The authors conclude that the fi eld blank and duplicate results are acceptable. However, the Field Spike results are quite variable, showing recove ries between 28% and 175%. The Field Blanks

are con t am inated. The Duplicates are not in as cl ose agreement as inferred in the tex t–f or the range of concentrations observed in most samp les in this study the duplicates differ by an average 12 %.

Pages 35

– 36

. Table 9 . This table indicates that recoveries for samp les with 0.5 ug/tube are acceptable. Yet on Page 35 the tex tstates that , based upon Merricks (199 9), any on-field tubes with 2 ug/tube or less were defa ulted to a “flux value” of <1 ug/m 2 /sec. The flux and the resu lts should use all observations above the detection lim it for this laboratory (University of California, Davis) and this study.

Page 37

. Section 3.0 . T h is section states that Appendix C co ntains tabular results of all on-field and am bient m easured concentration s . First, Ap pendix C is not labeled as such. Second, no off-site air concentration s are shown in what appears to be Ap pendix C. Third, the off-site air

samp les are not am bient samp les by DPR definiti on. Am bient samp les are taken to characterize regional sub

- chronic and chronic exp o sures. The samp les taken in this study represent acute exposures and are simp ly off-site air concentrations.

Page 37

– 50

. Section 4.0 . Section 4.2–the flux is estim ated by back-calculation, not the “am bient

m e thod.”

Page 43

, 44

, and 79 . The shank em ission profile analysis shows 13 of the 18 periods where the air con centration p r ofile does not behave acco rding to the ass u mp tion of decreasing air concentrations with height. The ai r concentrations for m o st of th ese 13 periods are sim ilar to the lower concentrations in the sprinkler em ission pr of iles. However, with the exception o f the last

samp ling interval, the sprinkler em ission profiles do show decreas ing air concentrations with height. It is noted in review of the laboratory QA /QC that all the spr i nkle r samp les were analyzed together over several days followed by all the shank samp les analyzed tog e th er days later. This can lead to system atic laboratory differences that confound re sults. It cannot be ruled out tha tthis occurr ed in these labo ratory analys es and the em ission prof ile s m a y illustr a te th at problem . Specifically, in the figur es on Page 79, there are times wh en the 3 ft or 1 ft samp les show air concentrations higher than the 0.5 ft sa mpler or when the 1 ft sampler shows an air concentration higher than the 3 ft sampler. The key samp ling period for the shank m e thod onRandy Segawa February 26, 2008 Page 7

field 4 (Period 2), estimated flux with only 2 samples. This is not acceptable. In futu re stud ies th e on-site air concentrations should be m easured at more than three levels for the IHF method. That way if one samp ler is los tthe results will still be acceptable. Mo st IHF studies in the litera t ure use at leas t 5 m easurement heigh t s.
Page 47

. Figure 14A . These resu lts seem suspect. For the sh ank fields th e “upwind” air concentrations are higher than the on-site concentrations. In addition, the shank on-site air concentratio ns are subs ta ntia lly lowe r than sp rinkler onsite concentrations but the “upwind”

samp lers for shank and sprinkler show concentrations of sim ilar m a gnitude. It m a kes no sense that off-site air con centrations are h i gher than those m easured on-site (see page 89). This m a y indicate laboratory problem s a nd/or cross-field plot contam ina tion. These field plots were m u ch closer than DPR would advise a nd the potential for cross-field c ontam ination is significant (see page 92). The authors m a y have justified the orie ntation and spacing of th ese field plots based on consulting prevailing wind patterns in the area. However, prevailing winds m ean nothing when

m easuring air concentrations over m o re than a few hours. This study was conducted over four days.

Page 49

. Section 4.6 an d Figure 15 . The percen t of MITC em itted results shown in Figure 15 were checked using the f l ux estim a tes for each sampling interval prov ided by the auth ors in an Excel spreadsheet. The exact m a ss loss calcu lations for all four fields w e re not provided so it was difficult to verify the results shown in Fi gure 15. The recalculated m a ss loss estim ates were slightly different from that shown in Figur e 15. There appears to be two reasons for the differences: (1) the authors used a conversi on of 4.2 pounds of m e ta m sodium per gallon of product rather than the label conversion of 4.26 pounds per gallon and (2) it appears that the authors used a uniform 75 gallons per acres a pplication rate for all four applications to calculation the percent loss. However, both shank applic atio ns rece ived less than 75 gallon per acres. Thus, the sprinkler m a ss loss estim ates ar e virtu a lly ide n tica l due to the very sm all difference between 4.2 and 4.26 lbs m e ta m sodi um per gallon product and the shank estim ates differ slightly due to both the pounds m e tam sodi um per gallon difference and the difference in
tota l m a ss applied.

Although comparisons of the sprinkler m a ss loss re sults with previous sprinkler studies is difficult, the results do seem reasonable base d upon trends in thos e previous studies. Comp arisons between the results from the spri nkler application in th is study and the night application studies in DPR data base, Wofford (1994) and Sulliv an (2006), are difficult because the tim i ng of the applications were significantly different. The W o fford app lica tion wa s star ted a t 1940 hours on August 3, so, the entire application, the watering-in and several hours after were under dark hours. This w ould lead to substa ntial m a ss lost, 73.3% loss w a s observed through the first nigh t. T h e Sulliv an (2006) study applicati on was started at 0400 hour s and comp leted after sunrise. The first watering-in was applied duri ng daylight hours. Total m a ss loss in Sullivan (2006) was 39.1%. The applications in this re port were started at 0100 hours and Table 2Randy Segawa February 26, 2008 Page 8

indicates that the watering-in was completed at 0800 hours. This m eans that the period following the watering in was during daylight. The additi onal watering-in on the first evening would be expected to further redu ce the loss. The W o ff ord loss through the watering-in was 53%, for Sullivan (20 06) loss thro ugh the in itial watering-in was 10%. Tota l lo ss for this study was about 37% with a loss through initial wate ring-in of approxim a tely 13%.

These shank loss results are not c onsistent with any of the shank results DPR already has. The shank application m a ss loss result in this study is substantially less than any of the previous shank studies. In fact, these shank mass losses ar e sim ilar to the drip application losses observed in Levine et al. (2005), and Li et al. (2006). DPR has no other night shank application data. Other than the cha nge in r i g, n o thing in the report i ndicates reasons for the extrem ely sm all m a ss loss. These extrem ely low mass loss estim ates for night shank application should be verified with a second trial before DPR uses th ese results for VOC calculations.

Page 51

. Conclusions . E ach conclusion is discussed below:

1. Shank injection/comp action . . .produced excellent retention of MITC . . .

This conclu s i on cannot b e m a de until the QA/QC i ssues are resolved. Unfortunately, it is not like l y labo ra tory QA/QC issues c a n b e comp letely resolved.

2. Relatively sm all differences were observed between the pulsed and continuous water seals for chem igation.

These resu lts seem inter n ally con s is tent. I tis unlikely corrections for the QA/QC wou l d change this conclusion.

3. The use of on-field profiles and the integrated horizontal flux m e thod produced a high degree of precision . . .

The authors are placing importance o n precis i on to the exclusion of accuracy. The precision of these results is unimportant if the accuracy is un acceptable. Even the precision is at issue due to the sign if ica n t QA/QC issues.

4. In order to quantify very low levels of e m issions . . .

See comm e n ts on the detection lim it above. Ther e is conflicting inform ation relating to the detec tion an d quantif ica t ion lim its.

5. Nighttim e applica tions based on sha nk injec tion . . .well m a naged of f

- gassing ra tes.Randy Segawa February 26, 2008 Page 9

This conclu s i on cannot b e m a de until the QA/QC i ssues are resolved. Unfortunately, it is not like l y labo ra tory QA/QC issues c a n b e comp letely resolved.

6. Nighttim e applic ation s using chem igation woul d benef it by modif i ed water se aling p r actices in order to b e tte r re tain MITC in the heat of the day . . .

A field study would need to dem ons trate th at this additional wa ter application would signif i can tly reduce the loss. The f i rs t two samp li ng intervals, as expected, showed the highest flux. If the results are taken as they are, th e loss in this study is sim ilar to Sullivan (2 006).

IV. Discussion

Previous studies (Merricks, 1999; Merricks 2001, and Merricks 2002) have indicated that total

m a ss loss for sprinkler and shank are sim ilar. Th is study shows widely differing results between sprinkler and shank. The shank applications would be expected to show the sam e increase in flux during the day that was shown by th e sprink ler. However, measured air concentrations for shank were so low that no trend was dem o nstrated. A second study should be conducted to confirm that the new rig is the reason for the very low em i ssion obtained f o r shank. Period 2 (the critical period) shank flux was estim ated using only two points. A simple stra igh tlin e was f i t to characterize the concen tration p r of ile because one of the three samp les was lost. This , in addition to the con s id erable uncer tain ty in th e labor atory Q A /QC cast significant doubt on the shank results.

V. Technical Recommendations

There ar e tw o alte rnative s regard ing the data in th is repo rt:

1. Reject the report due to labor atory QA/QC issues and irregular ities in the f i eld study conduct. This is m o st defensible f r om a scientific standpoint and our preference.

2. Use the m a s s loss results but add uncertain ty f actors to th e re sults. The recommended uncertainty f actors for the VOC program only ar e as f o llows: (a) as sum e the sprink ler m a ss loss is the sam e as standard sprink ler, and (b) assu m e the shank m a ss loss is the sam e as interm ittent shank. Acute exposure o f persons off-s ite is no t addressed in this rev i ew. These results are not of sufficient quality to allow an assessm ent of r e quired acute exposure buffer zones for these m e thods. Use of this alternat ive is a comp letely qualitative m a nage m e nt decision.

Regardless of which alternative is chosen above , because th e shank m a s s loss reported in th is study is substantially less than losses observe d in any prior shank study, a second field studyRandy Segawa February 26, 2008 Page 10

should be conducted to confirm these results. The second study should directly comp a r e the standard shank m e thod to the W e stern Farm rig used in this study.

VI. Regulatory Recommendations

If a nighttime application is to be allowed, it m u st adher e to the spec if ica tions used in the application studies. Therefore, the following regu lato ry requ irem ents are recomm ended for these fum i gation m e thods:

For Night Sprinkler Application with Two Post-Fum igation W a ter Trea tm ents

• the field m u st receive an init ial irrigation at a ra te of 0.20 inches imm e diately prior to applic ation

• the application period m u st be initiated no ear lier than 0100 hrs and be applied at a m i nim u m rate of 0.20 acre-inches/hour

• post-fum i gation water treatm ents m u st be cons istent with the requirem e nts described in Title 3, California Code of Regulatio ns, section 6 450.1(d)(2 ) *

For Night Shank Application w i th Tw o Post-Fumigation Water Treatments

• application must start no earlier than 0100 hours

• post-fum i gation water treatm ents m u st be cons istent with the requirem e nts described in Title 3, California Code of Regulatio ns, section 6 450.1(d)(2 ) *

• the following fum i gation equipm ent and procedures m u st be used

i. Before application, thoroughly cultivate th e field to rem ove clods with a disc or spring tooth bar. Soil m u st contain adequate m o isture (as stated in regulations) prior to application

ii. The applic ation equ i p m ent m u st m eet the f o llowing criter ia: The shanks must be set on a single o r m u ltiple ba rs so the r e is an ef f

ective spacing of no m o re than 4 inches between shanks. Injection depth is 3 inches, 6 inches, and 9 inches. Nitrogen m u st be used to purge the system befor e applicator bar is lifted out of the ground at any tim e

.

* The 0. 2 0 i n c h es f o r

t h e p o st

- f um i g at i on wat e r tr eat m e nt s d e scri be d i n t h e reg u l a t i ons s h o u l d be c h a nge d t o 0. 40 in ch es, so it is co nsisten t with th e water treatmen t s for t h is an d prev iou s m o n ito rin g stud iesRandy Segawa February 26, 2008 Page 11

iii. Comp action equipm ent The application tool bar(s) are followed by a ring roller with f our gauge wheels controlled by hydraulic cylinders to contro l depth and or pressure to seal the chisel trace that is as leas t as wi de as the application tool bar. The ring ro ller will be f o llowed with a coil p acker that is as least as wide as the application tool bar.

Ne w Method Codes for Field Fumigation Methods

Since both application m e thods are n e w, the fo llo wing will be used for the fum i gation code on the Pesticide Use Reporting and the F i eld Fum i gant VOC Em i ssion Allow a nce form s:

Method code Em ission Rating (%) Regula tion Section Field Fum i gation Method

1452 77 6452 (b)(1) Night Sprinkle r/Broadcast or Bed/ Two W a ter Treatm e nts

1455 28 6452 (b)(1) Night Nontarpaul in/Shallow/Broadcast or Bed/ Two W a ter Treatm entsRandy Segawa February 26, 2008 Page 12

References

Levine, J., D. Ki m , and P. Lee. 2005. Monitori ng an untarped bedded drip application of

m e ta m

- sodium in Merced Country. Californi a E nvironm ental Protection Agency. DPR. Environm ental Monitoring Branch. 1001 I Street , P.O. Box 4015, Sacram ento, California 95812. EH05-03.

Li, L., T. Barry, K. Mongar, and P. Wofford. 2006. Modeling Methyl Is othiocyanate Soil Flux and Em ission Ratio from a Field following a Chem igation of Metam

- Sodium . Journal Environm ental Quality. Volum e 35:707-713.

Merricks, D.L. 1999. Determ ination of m e thyl isothiocyanate offsite air m ovem e nt from application of Metam

- s odium through shank in jection and sprinkler irrigation. Agrisearch Incorporated, 5734 Industry Lane, Fred rick, Maryland 21704-7293. December 14, 1999.

Merricks, D.L. 2001. Determ ination of m e thyl isothiocyanate offsite air m ovem e nt from application of Metam

- s odium through shank inj ection. Agrisearch Incorporated, 5734 Industry Lane, Fredrick, Maryland 21704-7293. March 1, 2001.

Merricks, D.L. 2002. Determ ination of m e thyl isothiocyanate offsite air m ovem e nt from application of Metam

- s odium through sprinkl er irrigation. Agrisear ch Incorporated, 5734 Industry Lane, Fredrick, Maryland 21704-7293. January 10, 2002.

Sullivan, D. 2006. Field volatility of MITC after application of m e tam

- sodium at the Edison Road field site, Mettler, Califor nia. Departm e nt of Pesticide Regulation registration volum e

num b er 50150-0163.

Wofford, P., K.P. Bennett, J. Hernandez, a nd P. Lee. 1994. Air Monitoring for Methyl Isothiocyanate During a Sprinkler App lication of Metam

- Sodium . 1994. California Environm ental Protection Agency. DPR. Envir onm ental Monitoring Branch. 1001 I Street, P.O. Box 4015, Sacram ento, California 95812. EH94-02.Randy Segawa February 26, 2008 Page 13

Figure 1. Recoveries of the laborator y spikes in analysis sequ ence

0 10 20 30 40 50 60 70 80 90 100 110

0 1 0 2 0 3 0 4 0 5 0
An a l y s i s s e q u e n c e%recoveryRandy Segawa February 26, 2008 Page 14

Figure 2. One copy of standard curves for laborat ory analysis data calc ulation in Bakersfield study, 2007

7/31/07 M i t c St andard C u rv e

y

= 1. 8509x
R 2 = 0. 9793

0 5 10 15 20 25 30 35 40Corrected Area

0 5 10 15 20 25

PPMRandy Segawa February 26, 2008 Page 15

Figure 3. A typical MIT C standard curve fr om the California Departm e nt of Food and Agriculture ’s labo ratory analysisBEFORE THE DIRECTOR OF THE DEPARTMENT OF PESTICIDE REGULATION STATE OF CALIFORNIA

In the Matter of Grimmway Farms Request for Approval of Reduced Volatile Organic Compound Emissions Field Fumigation Methods

DECISION (Title 3, California Code of Regulations section 6452)

GRIMMWAY FARMS Mr. Sean McNally Vice President Corporate and Government Affairs 14141 Di Giorgio Road P.O. Box 81498 Bakersfield, California 93380-1498 ______________________________/

Summary

Grimmway Farms submitted a request to allow ch emigation applications of metam-sodium and metam-potassium (methyl isothiocyanate [M ITC]-containing pesticides) based on a study previously submitted to the Department of Pe sticide Regulation (DPR). The Metam-Sodium Task Force and Amvac Chemical Corporation su bmitted a study to DPR titled “Field Volatility of MITC After Application of Metam-Sodium at the Edison Road Field Site, Mettler California” dated July 2006. The application was made by chemigation with a 4:00 a.m. start time, which qualifies as a night application. As part of DPR’s efforts to reduce volatile organic compound (VOC) emissions, most night applicat ions of MITC-containi ng pesticides are prohibited within several ozone nonattainment ar eas (NAAs) during May–October, under Title 3, California Code of Regulations (3 CCR) s ection 6450.1(c). However, the regulations also include a provision for DPR’s Dir ector to grant interim approva l of fumigation methods that reduce VOC emissions (3 CCR section 6452). DP R has completed its evaluation of the fumigation method described in the study as specified in 3 CCR section 6452. The DPR has determined that with applicati on rate modifications the method meets the standard for approval as an interim method, as described below. Effective August 1, 2008, DPR grants approval for interim use of the metam 4:00 a.m. start chemig ation method described in the study in all five ozone NAAs. The method described in the study may be used for three years from the effective date.

Background

VOCs contribute to the formation of ozone, a major air pollutant in several regions of California. California’s State Implementation Plan for the fe deral Clean Air Act ozone standard includes anGrimmway Farms Page 2

element to track and reduce VOC emissions fr om pesticides. On January 25, 2008, DPR adopted regulations to control VOC emissions from fu migants during the May–October peak ozone season in five ozone NAAs: Sacramento Metr o, San Joaquin Valley, Southeast Desert, South Coast, and Ventura. The regulations in clude provisions that only allow fumigation methods for which DPR has adequate data to de termine the VOC emission rates. However, the regulations include a provision for interim approval of fumigation methods with emissions no greater than the field fumigati on methods allowed in the regula tions in the respective areas (3 CCR section 6452).

On June 16, 2008, DPR received a ve rbal request from representa tives of Grimmway Farms and other carrot growers to approve an interim method for nighttime chemigation applications using metam-potassium and metam-sodium. DPR r eceived a subsequent written request from Grimmway Farms on July 31, 2008. The fumigation method is critical to carrot and potato farming operations since a label restriction regard ing ambient air temperature limits the times of day that the pesticide may be applied in certa in regions of Californi a. Between this label restriction and the prohibiti on of nighttime chemigation, growers in NAAs have a narrow window to treat their acreage.

Regulatory Standards and Considerations

Title 3, CCR section 6452 sets different standards by which to evaluate whether a new fumigation method will be allowed, one for the Sacramento Metro and South Coast ozone NAAs and one for the San Joaquin Valley, So utheast Desert, and Ventura ozone NAAs. Sacramento Metro and South Coast have a less stringent standard because no further VOC reductions from pesticides are needed in these ozone NAAs. Both “low-emission” and “high-emission” methods can be used in thes e two areas. Only “low-emission” methods are allowed in the San Joaquin Valley, Southeast Desert, and Ventura oz one NAAs during the May–October peak ozone season. The key information is the em ission rating (percent of the fumigant applied that is emitted to the air) a nd the emission rate (emission rating multiplied by the maximum application rate). Either the emissi on rating or the emission rate can be no greater than the current methods allowed within the ozone NAAs by the regulations. The following table shows the standard for approval of an interim method for MITC-generating pesticides, based on DPR’s current emission estimates.

Ozone NAA Maximum Allowed MITC Emission Rating (percentage) Maximum Allowed MITC Emission Rate (pounds/acre) Sacramento Metro, South Coast 77 140 San Joaquin Valley, Southeast Desert, Ventura 28 51Grimmway Farms Page 3

In assessing whether the new me thod meets the standard, DPR must assess the scientific data submitted to establish the emission rating, normally consisting of field monitoring data. In evaluating this data, 3 CCR section 6452 require s DPR to consider the following factors:

• whether the information is sufficient to estimate emissions.

• whether the results are valid as i ndicated by the quality control data.

• whether the conditions studied re present agricultural fields.

Summary and Evaluation of the Submitted Information

The Metam-Sodium Task Force and Amvac Ch emical Corporation submitted a study to DPR titled “Field Volatility of MITC After Applicat ion of Metam-Sodium at the Edison Road Field Site, Mettler California” dated July 2006. The application was made by chemigation with a 4:00 a.m. start time, which qualifies as a night application. AMVAC Me tam 42 (Metam Sodium 42 percent w/w) was applied at a rate of 75.35 ga llons/acre (319.5 lbs active ingredient/acres) by sprinkler (chemigation) to a 10.17-acre field. The application was finished at 10:00 a.m. After a 15 minute flushing of the sprinkle r lines with water a “water ca p” of 0.23 acre inch was applied between 10:15 a.m. and 11:30 a.m. This applicat ion method also includes an additional “water cap” of 0.46 acre inch between 6:00 p.m. and 8:30 p.m.

Twenty air samplers were positioned off-site at distances of 30 meters to 150 meters from the field edge. The Quality Control/Quality Assura nce results were reviewed and found to be acceptable. A four-day MITC flux profile wa s developed and total MITC mass loss was estimated using the ISCST model and the back -calculation method in two different ways:

• using all 20 air samplers: 283.1kg MITC ma ss loss/33.79 percent and 61.1 pounds/acre.

• using only the 12 forecast samplers (sampl ers expected to be downwind): 292.71kg MITC mass loss/34.93 percent and 63.2 pounds/acre.

Findings

The information provided indicates that th e emissions for this fumigation method are approximately 35 percent of the available MITC . Therefore, DPR has assigned the following emission ratings to this method:

• metam-sodium and metam-potassium sprinkl er 4:00 a.m. start method: 35 percent.

Low-emission application methods must achieve an emission rating of 28 percent or less. Therefore, this application method cannot be considered a low-emission method based upon the emission rating. However, this method can be considered a low-emission method if the maximum application rate is adjusted to a leve l that ensures the emission rate (emission ratingGrimmway Farms Page 4

multiplied by the maximum application rate) does not exceed 51 pounds of MITC per acre, equivalent to 290 pounds of metam-potassium activ e ingredient (A.I.) pe r acre or 260 pounds of metam-sodium A.I. per acre. Table 1 shows the equivalent product application rates.

Conclusions

The 35 percent emission rating and an applicatio n rate limit support approval of this fumigation method. Effective August 1, 2008, the metam sprinkl er 4:00 a.m. start application method is approved for use in the San Joaquin Valley, Sout heast Desert, and Ventura ozone NAAs with the following restrictions du ring May 1–October 31:

• metam-potassium application rate must not exceed 290 pounds A.I. per acre.

• metam-sodium application rate must not exceed 260 pounds A.I. per acre.

• fumigations must start no earlier than 4 a.m.

• two post-fumigation water treatments as spec ified in 3 CCR section 6450.1(d)(2) must be applied.

• pesticide use reports must id entify these applications us ing field fumigation method code 1472.

Effective August 1, 2008, the metam sprinkler 4:00 a.m. start application method is approved for use in the Sacramento Metro and South Coast oz one NAAs with the following restrictions during May 1–October 31:

• fumigations must start no earlier than 4:00 a.m.

• two post-fumigation water treatments as spec ified in 3 CCR section 6450.1(d)(2) must be applied.

• pesticide use reports must id entify these applications us ing field fumigation method code 1472.

The only restriction, other than labeling requirements, outside th e May 1–October 31 period is to include field fumigation method co de 1472 on pesticide use reports.

DPR grants interim approval of this fumigation me thod for three years from the effective date.

By: __

___ Date: _____08/14/2008

_____ Mary-Ann Warmerdam, Director

AttachmentTable 1. Maximum product application rates ingallons per acre to meet low emissionMITC mass loss criteria of 51 pounds MITC peracre in the San Joaquin Valley, Southeast Desert, and Ventura NAAs during May–October.Metam Sodium ProductsCompany Product Name Reg No. lbs A.I./gal Conversion factor1Maximum application rate(gal/ac)2AMVAC AMVAC Metam 5481-420-AA 3.18 0.8163 80AMVAC AMVAC Metam 426 5481-423-AA 4.26 1.0935 60AMVAC METAM SODIUM 5481-350-ZA 3.18 0.8163 80AMVAC VAPAM 5481-466-AA 3.18 0.8163 80AMVAC VAPAM HL 5481-468-AA 4.26 1.0935 60BuchmanLaboratoryBUSAN 1020 1448-85-AA 3.2 0.8214 80Taminco, Inc. Metam CLR 42% 45728-16 4.25 1.0909 60TessenderloKerley, Inc.SECTAGON 42 61842-6 4.22 1.0832 60Metam Potassium ProductsCompany Product Name Reg No. lbs A.I./gal Conversion factorMaximum application rate(gal/ac)AMVAC K-PAM HL 5481-483-AA 5.8 1.3154 50TessenderloKerley, Inc.SECTAGON-K54 61842-7-AA 5.8 1.3154 50173 . . 1* *129 . . 2.2046product lb MS MITCmol wt kgconversion factorgal MSmol wt lbs=2allowed application rate = (65.7kg MITC/ac)/(conversion factor)BEFORE THE DIRECTOR OF THE DEPARTMENT OF PESTICIDE REGULATION STATE OF CALIFORNIA

In the Matter of Ratto Brothers, Inc. Request for Approval of Reduced Volatile Organic Compound Emissions Field Fumigation Method

DECISION (California Code of Regulations, Title 3, section 6452)

RATTO BROTHERS, INC. Mr. Raymond A. Ratto, Jr. Ratto Brothers, Inc. 6312 Beckwith Road Modesto, California 95358

Summary

Ratto Brothers, Inc., submitted a request to allo w drench applications of potassium N-methyl dithiocarbamate (metam-potassium). As part of the Department of Pesticide Regulation’s (DPR’s) efforts to reduce volatile organic compound (VOC) emissions, this fumigation method is not allowed within several ozone nonattainment areas (NAAs) during May–October, under Title 3, California Code of Regulations (3 CCR) sec tion 6450.1(c). However, the regulations include a provision for the DPR Director to grant interim approval of fumi gation methods with emissions no greater than the field fumigati on methods allowed in the regula tions (3 CCR section 6452). DPR has completed its evaluation of the fumigation me thod as specified in 3 CCR section 6452. No data was submitted, but even assuming 100 percent VOC emissions, the application rate is low enough to meet the requirements for approval as an in terim method. Effective immediately, DPR grants approval for interim use of the drench applic ation method using either metam-potassium or metam-sodium, with limits on the application rate . The emission rating assigned to this method is 100 percent. This method may be used for three year s from the date of this decision. Continued use beyond three years is contingent on the submittal of an acceptable study to document the emissions from this fumigation method.

Background

VOCs contribute to the formation of ozone, a major air pollutant in several regions of California. Under the federal Clean Air Act, California’s State Implementation Plan for ozone includes an element to track and reduce VOC emissions fr om pesticides. On January 25, 2008, DPR adopted regulations to control VOC emissions from fu migants during the May–October peak ozone season in five ozone NAAs: Sacramento Metr o, San Joaquin Valley, Southeast Desert, South Coast, and Ventura. The regulations in clude provisions that only allow fumigation methods for which DPR has adequate data to de termine the VOC emission rates. However, theRatto Brothers, Inc. Page 2

regulations include a provision for interim approval of fumigation methods with emissions no greater than the field fumigati on methods allowed in the regula tions in the respective areas (3 CCR section 6452).

In a letter dated April 24, 2008, Ra tto Brothers, Inc., requested th at DPR approve an exemption for a soil drench application method using pot assium N-methyl dithiocarbamate (metampotassium; methyl isothiocyanate [MITC]-gen erating pesticide). Th e fumigation method is critical to Ratto Brothers farming of specialty crops like leafy green vegetables, herbs, and root vegetables because most other pesticide products are not registered for use on these crops. Ratto Brothers, Inc., asserts th at other fumigation methods al lowed probably have higher VOC emissions.

Regulatory Standards and Considerations

Section 6452, 3 CCR, sets different standards by which to evaluate whether a new fumigation method will be allowed; one for the Sacramento Metro and South Coast ozone NAAs, and one for the San Joaquin Valley, S outheast Desert, and Ventura ozone NAAs. Sacramento Metro and South Coast have a less stringent standard because no further VOC reductions from pesticides are needed in th ese ozone NAAs. Both “low-emission” and “highemission” methods can be used in these two area s. Only “low-emission” methods are allowed in the San Joaquin Valley, Southeast Desert, a nd Ventura ozone NAAs during the May–October peak ozone season. The key information is the em ission rating (percent of the fumigant applied that is emitted to the air) and the emission rate (emission rating multiplied by the maximum application rate). Either the emission rating or the emission rate can be no greater than the current methods allowed within the ozone NAAs by the regulations. The following table shows the standard for approval of an interim me thod for MITC, based on DPR’s current emission estimates.

Ozone Nonattainment Area Maximum Allowed MITC Emission Rating (percentage) Maximum Allowed MITC Emission Rate (pounds/acre) Sacramento Metro, South Coast 77 140 San Joaquin Valley, Southeast Desert, Ventura 28 51Ratto Brothers, Inc. Page 3

In assessing whether the new me thod meets the standard, DPR must assess the scientific data submitted to establish the emission rating, normally consisting of field monitoring data. In evaluating this data, 3 CCR section 6452 require s DPR to consider the following factors:

• whether the information is sufficient to estimate emissions.

• whether the results are valid as i ndicated by the quality control data.

• whether the conditions studied re present agricultural fields.

Summary and Evaluation of the Submitted Information

Ratto Brothers, Inc., proposes to apply K-Pam (metam-potassium) using a drench application method. K-Pam label requirements for this methodinclude pre-irrigation to achieve 50 to 80 percent field capacity and an application rate of 30 to 60 gallons of K-Pam per treated acre. Ratto Brothers, Inc., applies K-Pa m using low-pressure booms with nozzles 9 to 10 inches above the top of the beds at a rate of 15 to 23 gallons of K-Pam in 1,900 gallons of water per acre. However, additional information from Ratto Brothers , Inc., indicates that th eir application rate is on a broadcast acre basis, not treat ed acre basis. Applications are made in the early morning and are followed by a 0.15 to 0.20-inch water treatment within 30 minutes of the application and three additional water treatments over the firs t 24 hours. Ratto Brothers, Inc., proposes to fumigate up to 15 acres per day for a tota l of 1,000 to 1,500 acres using this method.

NOTE: The application rates desc ribed in this document are based on broadcast applications, unless otherwise noted. Drench applications are normally applied to beds or rows, and labels frequently refer to application rates on a treated acre basis. Application rates on a treated acre basis must be converted to the broadcast equivale nt (bed/row treated area plus furrow untreated area) to determine compliance with specified application rate limits.

Ratto Brothers, Inc., did not submit any data doc umenting the VOC emissions ratings associated with a MITC drench application. DPR is not aware of any emissions data for this fumigation method. In addition, this method is substantiall y different from any other fumigation method with available data. DPR staff are not confident in using other data as a surrogate for this fumigation method. However, the proposed applicati on rate is very low. Even if the emission rating is 100 percent, the VOC emission rate would range from 43 to 66 pounds of VOCs per broadcast acre, depending on the application rate. A metam-pot assium application rate of 98 pounds active ingredient per broa dcast acre (17 gallons/acre of K-Pam) would be equivalent to the San Joaquin Valley’s maximum allowed MITC emission rate of 51 pounds of VOCs per broadcast acre.Ratto Brothers, Inc. Page 4

Findings

Ratto Brothers, Inc., did not submit any data doc umenting the VOC emissions associated with a MITC drench application and no data is ava ilable to reliably estimate the emission rating. Therefore, the emission rating assigned to MITC drench applications is 100 percent.

Conclusions

The 100 percent emission rating and proposed application rate of 87 to 133 pounds active ingredient per broadcast acre of metam-potassi um support approval of this fumigation method. Effective immediately, the MITC drench appl ication method is approved for use in the San Joaquin Valley, Southeast Desert, and Ventura ozone NAAs with the following restrictions during May 1–October 31:

• Metam-potassium application rate must not exceed 98 pounds active ingredient per acre.

• Metam-sodium application rate must not exceed 90 pounds active ingredient per acre.

• Soil moisture at the time of application mu st meet the requirements described in 3 CCR section 6450.1(b).

• Fumigations must start no earli er than one hour after sunrise and must be completed no later than one hour before sunset.

• Two post-fumigation water treatments as sp ecified in 3 CCR secti on 6450.1(d)(2)(A) must be applied.

• Pesticide use reports must id entify these applications us ing field fumigation method code 1413.

Effective immediately, the MITC drench appl ication method is approved for use in the Sacramento Metro and South Coast ozone NAAs with the following restrictions during May 1–October 31:

• Metam-potassium application rate must not exceed 270 pounds active ingredient per acre.

• Metam-sodium application rate must not exceed 246 pounds active ingredient per acre.

• Soil moisture at the time of application mu st meet the requirements described in 3 CCR section 6450.1(b).

• Fumigations must start no earli er than one hour after sunrise and must be completed no later than one hour before sunset.

• Two post-fumigation water treatments as sp ecified in 3 CCR secti on 6450.1(d)(2)(A) must be applied.

• Pesticide use reports must id entify these applications us ing field fumigation method code 1413.Ratto Brothers, Inc. Page 5

The only restriction, other than labeling requirements, outside th e May 1–October 31 period is to include field fumigation method co de 1413 on pesticide use reports.

DPR grants interim approval of this fumigation method for three years from the date of this decision. Continued use of this fumigation me thod beyond three years is contingent on the submittal of an acceptable study to document the emissions. Since DPR must adopt regulations to include these new methods prior to the expira tion of the interim approval, the study should be submitted within 12 months. DPR recommends that Ratto Brothers, Inc., submit a draft protocol for DPR scientific staff review prior to initiating the study.

By: _______

___ for ______________ Date: _____ 05/15/08

______ Mary-Ann Warmerdam, Director Department of Pesticide Regulation

# Department of Pesticide Regulation

Mary-Ann Warmerdam Director 

### M E M O R A N D U M Arnold Schwarzenegger Governor

1001 I Street • P.O. Box 4015 • Sacramento, California 95812-4015 • www.cdpr.ca.gov
A Department of the California Environmental Protection Agency TO: John S. Sanders, Ph.D. Environmental Program Manager II Environmental Monitoring Branch Original signed by Pam Wofford FROM: Randy Segawa for Environmental Program Manager I Environmental Monitoring Branch 916-324-4137

Terrell Barry, Ph.D., Research Scien tist III Original signed by Environmental Monitoring Branch

DATE: April 29, 2010

SUBJECT: METHYL IODIDE (IODOMET HANE) MITIGATION EVALUATION AND OPTIONS

Summary

The Department of Pesticide Regu lation’s (DPR’s) risk assessment for methyl iodide describes several exposure scenarios of concern, including exposure to bystanders. DPR’s Environmental Monitoring Branch (EMB) staff evaluated several alternatives to reduce methyl iodide bystander exposure to acceptable levels. The evaluation in cluded an assessment of fumigations using virtually impermeable film (VIF) to suppre ss emissions. EMB staff found that three methyl iodide studies using VIF likely underes timate the air concentrations and flux, and use poor methodology, as indicated by the quality contro l results. In additio n, the studies did not include measurements during tarp cutting or rem oval. Despite the study problems, changing from standard tarps to VIF likely redu ces methyl iodide flux 30–40 percen t (%). The registrant (Arysta LifeScience North American Corporation; Arysta ) estimates a 68% reduc tion due to VIF based on the studies. EMB staff estimated buffer zones for various application me thods. Restrictions to mitigate potential groundwater contamination by iodide breakdown product may be needed.

Background

Methyl iodide is a soil fumigant pesticide used prior to planting agricultural fields for controlling a variety of pests including weeds, nematodes, insects, and diseases. DPR is considering four products for registration: Midas EC Gold (33% methyl iodide, 62% chloropicrin); Midas 33:67 (33%methyl iodide, 67% chloropi crin); Midas 50:50 (50% methyl iodide, 50% chloropicrin); and Midas 98:2 (98% methyl i odide, 2% chloropicrin). This evaluation does not address mitigation of chloropicrin. DPR’s risk assessmen t for methyl iodide describes several exposure scenarios of concern, including e xposure to bystanders. EMB staff evaluated various options to reduce bystander exposure to methyl iodide. Due to its volatility, the main route of exposure is inhalation. Similar to mitigation for other fumigants, the primary measures to reduce bystanderJohn S. Sanders, Ph.D. April 29, 2010 Page 2

exposure is to modify application methods a nd/or implement buffer zones. Both mitigation measures are normally based on air monitoring data , specifically studies that determine the flux or emission rate from treated fields. Flux estimates are used in conjunction with weather data and computer modeling to estimate downwind ai r concentrations for various scenarios. For methyl iodide, Arysta conducted several studies that include VIF to re duce flux. As potential mitigation measures, the VIF studies were not pr eviously reviewed or included in the risk
assessment.

Virtually Impermeable Film Study Reviews

Arysta conducted three studies that included direct and indi rect flux measurements for methyl iodide applications that use VIF. Methyl iodide was a pplied with a Symmetry tractor using a bed-shank method, and three different VIF tarps. Studies were done in Dover, Florida, January 2007; Bainbridge, Georgia, March 2007 ; and Hart, Michigan, May 2007. While out of state, the study conditions were similar to Califo rnia. Arysta determined that these three studies had an average peak 24-hour flux of 11 ug/m 2 -sec normalized to a 100 lb s/acre application rate (8.5% of the amount applied). In comparison, three other Arysta studies of a standard tractor rig and standard tarp had an aver age peak 24-hour flux of 74 ug/m 2 -sec normalized to a 100 lbs/ac application rate (57% of the amount applied). Arysta believes these st udies demonstrate that Symmetry and VIF combined reduce methyl i odide flux by 85 percent (difference between 74 and 11 ug/m 2 -sec) and that 80% of the reduction is due to VIF. Arysta estimates that VIF reduces flux by 68% compared to standard tarps.

Environmental Monitoring Branch’s Staff Re view of the Three Methyl Iodide Virtually Impermeable Film Studies Indicates Several Major Issues

Breakthrough–There appears to be significant breakthrough from the front sampling bed to the back sampling bed. Not all back sections were analyzed. Arysta believes this is due to contamination of the back sections during stor age. Arysta provided additional information for this explanation, but the data are not conclusive. Specifically, some of the front and back sections were stored together and analyzed at the same tim e. It is unlikely that the back sections were contaminated, but the front secti ons were not. No field blanks we re collected that would provide conclusive evidence of contamination.

Spikes and recovery adjustment–The lab spikes were prepared in an unusual manner and do not indicate method performance. Trapping efficiency and field spikes were variable, ranging from 64% to 86% recovery. The trapping efficiency te sts may overestimate recoveries because they were run for 6 hours. Most field samples were run for 12 hours. Field sample results were not adjusted for trapping efficiency or field spike recoveries.John S. Sanders, Ph.D. April 29, 2010 Page 3

Storage stability - Storage stability results were variable, with recoveries ranging from 47% to 76% after one week. Sample extracts of back s ections were held much longer than the storage stability test duration.

Field results–Some results we re atypical. Highest concentrat ions for methyl iodide and chloropicrin sometimes occurred at different locations. The unusual results may be due to poor sampler placement. Some of the chloropicrin re sults were very unusual and cannot be used to determine the flux. The tarps were not cut or re moved during the studies. The flux calculations were not checked.

EMB staff found that the studies likely underestimate the air concentrations and flux, and used poor methodology.

Virtually Impermeable Film Flux Estimation

Despite the problems with the studies, it is po ssible to use them to estimate the maximum possible flux for VIF applications. EMB staff have not verified the flux calculations, but even if there are some errors, they woul d have little or no impact on th e relative adjustments described below. Table 1 shows the fluxes estimated by Arysta.

Table 1. Methyl iodide flux estimated by Arysta for Symmetry bed-sh ank VIF method, assuming 100 lbs/acre application rate (Exponent memo dated 2/1/10).

24-hr peak flux for 100 lbs/ac app rate Study ug/m 2 -sec lbs/ac-day % of applied Total flux (lbs/ac and % of applied) FL 15.6 12 12 29 GA 10.9 8.4 8.4 23 MI 6.5 5.0 5.0 33 Average 11.0 8.5 8.5 28 Max possible flux estimated by DPR* 38.9 30 30 100

*Max possible flux estimated by adjusting th e average measured flux by 3.57x, increasing the

total flux from 28 to 100% of the amount applie d and increasing the 24-hour peak flux from 8.5 to 30% of the amount applied.

A reliable adjustment to account for breakthrough, spike recoveries, and stor age stability cannot be determined. A maximum worst- case flux can be estimated by assuming that the total flux is 100% of the amount applied. For exam ple, if the application rate is 100 lbs/acre, the total flux is 100 lbs/acre over the entire 6-day study period. This is 3.57x higher than the 28 lbs/acre totalJohn S. Sanders, Ph.D. April 29, 2010 Page 4

flux estimated by Arysta as the average for th e three VIF flux studies. Applying the same 3.57x adjustment factor increases the averag e 24-hour peak flux value from 11.0 ug/m 2 -day (8.5 lbs/acre or 8.5% of the amount applied) to 38.9 ug/m 2 -day (30 lbs/ac-day or 30% of the amount applied). The maximum worst-case 24-hour peak flux for methyl iodide applied with the bed-shank method using a Symmet ry rig and VIF is 30 percent of the amount applied. For comparison, Table 2 shows the fluxes estimated by Arysta (and verified by EMB staff) for the other studies.

Table 2. Methyl iodide flux estimated by Arysta (and verified by EM, except as noted) for all studies.

Location Fumigation Method Peak 24-hr Flux (% of applied) Total Flux (% of applied) Manteca, CA Broadcast-shank, std tarp 51 93 Watsonville, CA Broadcast-shank, std tarp 35 57 Guadalupe, CA Bed-shank, std tarp 60 96

Oxnard, CA Bed-shank, std tarp 54 102 Plant City, FL* Bed-shank, std tarp 56 71 Camarillo, CA Drip, std tarp 50 83 La Selva Beach, CA Drip, std tarp 42 62 Guadalupe, CA Drip, std tarp 71 100

Average Broadcast-shank, std tarp 43 75 Average Bed-shank, std tarp 56 98 Average Drip, std tarp 54 82 Average (estimated by Arysta) Bed-shank, Symmetry, VIF 8.5 28 Average (estimated by EM) Bed-shank, Symmetry, VIF 30 100 * Plant City flux not included in the average du e to rainfall and other problems with the study.

However, this makes little or no diffe rence in the average flux estimate.

The average 24-hour peak flux from two bed-shan k studies (Guadalupe an d Oxnard) that used standard tractor rigs and standard tarps was 56% of the amount applied (74 ug/m 2 -sec for a 100 lbs/ac application rate). Th erefore, the combined effect of the Symmetry rig and VIF reduced the 24-hour peak flux from 56% of the amount applied to no more than 30% of the amount applied (74 ug/m 2 -sec to 39 ug/m 2 -sec). The difference between the two values is a 47% reduction in flux. The relativ e contribution of the Symmetry rig and VIF to flux reduction cannot be determined with the available data, but the majority of the reduction is likely due toJohn S. Sanders, Ph.D. April 29, 2010 Page 5

VIF. Changing from standard tarps to VIF (w ithout Symmetry rig) may reduce methyl iodide flux between 30 and 40%.

All of these estimates are consistent with th e variation in the appa rent VIF reduction for other fumigants. Arysta provided a list of VIF studies for other fumigants, but most of these studies used chambers or other unacceptable methods to measure flux (Arysta note dated February 24, 2010). Similarly, tarp permeability data provided by Arysta cannot be used to estimate flux under field conditions. Lab permeab ility measurements indicate that VIF flux should be several orders of magn itude lower than standard tarps. Field studies show less than 10x reduction. Table 4 summarizes the flux reduction meas ured for other field st udies that likely used acceptable flux measurement methods. Complete repor ts are not yet available, so none of these studies have been reviewed or accepted.

Table 4. Approximate flux reduction from other VI F field studies. Reduction based on difference between two nearby simultaneous plots, one with standard tarp and one with VIF.

Location/Year Fumigant Fumigation Method VIF Reduction of Peak Flux (%) Santa Maria 2006 Chloropicrin Drip VIF 68 Salinas 2007 Chloropicrin Drip VIF 88 Oxnard 2007 1,3-D Drip VIF 44 Oxnard 2007 Chloropicrin Drip VIF 70 Salinas 2008 Methyl bromide Drip TIF* 37 Salinas 2008 Chloropicrin Drip TIF* 33 Wasco 2009 Methyl bromide Broadcast shallow shank TIF* 66 Wasco 2009 Chloropicrin Broadcast shallow shank TIF* 19 Ventura 2009 1,3-D Broadcast shallow shank TIF* 25 Ventura 2009 Chloropicrin Broadcast shallow shank TIF* 44 * TIF – totally impermeable film

Flux estimates for all fumigation methods

EMB previously reviewed and verified Arysta ’s flux estimates for the standard fumigation methods. EMB’s review of the VIF studies ar e described above. Table 5 summarizes the flux estimates, including various assumpti ons of the reduction due to VIF.John S. Sanders, Ph.D. April 29, 2010 Page 6

Table 5. Estimates of flux for each fumigation me thod and various assumptions of reduction due to VIF.

Fumigation

Method Flux with Standard Tarp (% of applied) Flux with 30% VIF Reduction (% of applied) Flux with 40% VIF Reduction (% of applied) Flux with 50% VIF Reduction (% of applied)Broadcastshallow shank 43 30 26 22

Bed-shallow shank 56 39 34 28 Drip 54 38 32 27 Auger probe Not determined Not determined Not determined Not determined

Buffer zones

EMB staff calculated approximate buffer zones fo r several application methods, with standard tarps and with VIF. Buffer zones were calculated with the PERFUM model. The PERFUM model buffer zones are the 95th percentile ma ximum direction buffer zones calculated using mean flux profiles and 5 years of Ventura weat her data. Flux profiles developed by Arysta for each of the seven accepted studies were used (Tab le 2). The mean flux profiles were developed for each application method as follows: (1) each flux profile used was aligned with 0800 hours and (2) the flux for each hour was averaged. The average flux profile was input into PERFUM and the 95th percentile maximum direction buffer zone for desired application rates of each application method were determined. The buffe r zone distances using PERFUM for a 24-hour target concentration of 32 parts per billion (ppb) (C. Andrews, pers onal communication) are shown in Attachment 1.

Buffer zones for auger probe applications (tree and vine replacement) cannot be determined due to lack of monitoring data. It is likely that the flux is approx imately the same as a standard shallow shank injection method. Auger probe applications are deeper than shallow shank (12 inches versus. 18-24 inches), but without a tarp. The label does not cl early state the number of applications allowed. It a ppears that the maximum number is 53 sites and 106 pounds per acre (2 pounds per injection site, and injection s ite every 100 square feet). Determining the appropriate buffer zone is more difficult than the other application methods due to the uneven number of sites treated across a field. There are at least three buffer zone alternatives for auger probe applications. (1) Use the same buffer zone s as broadcast-shallow shank or bed-shallow shank applications, (2) Limit the number of auger probe applicati ons, and (3) Establish the same buffer zone around each individual injection site.John S. Sanders, Ph.D. April 29, 2010 Page 7

The monitoring data indicates that peak concen trations occur within the first two days of fumigation, and flux is minimal on later days, in cluding the day standardtarps are cut. Air concentrations at the edge of treated areas should be less than the 32 ppb target concentration two days after fumigation. The 48-hour buffer z one duration specified on labels should be sufficient, assuming the flux is minimal wh en VIFs are cut (see next section).

DPR’s methyl bromide regulations specify that two nearby fumiga tions should be combined to determine the buffer zone, if the fumigations are se parated by less than 1320 feet (1/4 mile) or 36 hours. EMB staff determined this separation distance based on consistency of wind direction and the probability of the plumes from two 40-acr e fields would overlap a significant period of time. Air concentrations should be less than th e 32 ppb target concentration with the same separation requirements, assuming the treated fiel d size is no more than 40 acres. The proposed label requirement to prohibit ov erlapping buffer zones would likely provide adequate separation if the minimum buffer zone is large enough a nd the field size is less than 40 acres.

Virtually Impermeable Film Tarp Cutting and Removal

The other main shortcoming with the VIF studies is the lack of measuremen ts during tarp cutting and removal, for both flux and worker exposure. Several of the VIF studi es listed above show a secondary peak of emissions when tarps are cut. Buffer zones or work er protection measures may be needed when tarps are cut. Arysta pr ovided air concentration measurements under VIF from a separate study (Arysta memorandum da ted March 14, 2010). These data have minimal value due to small plot size, unusual methods to measure air concentrations, and lack of quality control data. Air concentrations under the tarps reached no detectable levels ten days after application for each of the seven types of VIF measured. Two studies monitored both soil concentrations and air concentrations following a pplications using standard tarps. Emission rates were also estimated. Those results are discu ssed in a separate memoranda by Barry dated April, 29, 2010 and indicate that after 14 days fo r a standard tarp appl ication that both soil concentrations and emissions are minimal. It is po ssible that the half-life of MeI in the soil will be longer for applications using VIF tarps. A lo nger soil half-life may lead to higher emission rates when the tarp is cut and/or removed.

Groundwater

As described in the risk assessment, EMB’s ev aluation indicates virtually no possibility of groundwater contamination by methyl iodide. The groundwater contamination by the iodide anion breakdown product is uncertain due to the lack of adequate field dissipation data, but potentially high based on a conservative mass-bala nce calculation. Use of VIF could increase the retention of methyl iodide and amount of i odide in the soil, causing higher groundwater concentrations than estimated in the risk assessment. Any groundw ater contamination would take years to occur. An adequate field dissipation study would provide data to better estimateJohn S. Sanders, Ph.D. April 29, 2010 Page 8

groundwater concentrations, followed by mitiga tion measures if n eeded. Alternatively, mitigation measures could be implemented i mmediately. Mitigation me asures should include buffer zones around wellheads, and irrigation re strictions in ground wa ter protection areas.Page 9

Attachment 1–Estimated Buffer Zone Distances

Methyl iodide buffer z one distances (feet) for 32 ppb , 24-hour exposure. Buffers calculated using PERFUM model and Ventura weather data. Buffers longer than 4723 feet (1440 meters) estimated by extrapolation. Distances represent the 95th perc entile in the maximum direction. Broadcast-shallow shank fumigation method. Flux is average of Manteca and Watsonville studie s (43% of applied amount for peak 24 hrs).

Table 1-1. Broadcast-shallow shank method with standard tarp

Buffer Zone (feet) for Various Field Sizes Broadcast app rate (lbs MeI/acre) 1 acre 5 acres 10 acres 20 acres 30 acres 40 acres 51 67 296 480 793 1,034 1,269 75 162 532 841 1,318 1,665 2,055 100 236 734 1,154 1,788 2,241 2,770 125 319 937 1,464 2,239 2,782 3,443 176 462 1,306 2,031 3,075 3,795 4,704

Table 1-2. Broadcast-shallow shank with VIF (30% flux reduction)

Buffer Zone (feet) for Various Field Sizes Broadcast app rate (lbs MeI/acre) 1 acre 5 acres 10 acres 20 acres 30 acres 40 acres 50 14 162 274 489 666 811 75 92 360 578 937 1,207 1,485 100 166 546 863 1,352 1,707 2,107 125 227 705 1,108 1,717 2,151 2,659 175 343 1,009 1,577 2,411 2,995 3,708

Table 1-3. Broadcast-shallow shank with VIF (40% flux reduction)

Buffer Zone (feet) for Various Field Sizes Broadcast app rate (lbs MeI/acre) 1 acre 5 acres 10 acres 20 acres 30 acres 40 acres 50 13 150 255 455 619 754 75 70 310 503 830 1,082 1,328 100 129 470 750 1,201 1,535 1,891 125 211 656 1,031 1,597 2,001 2,473 175 319 937 1,464 2,239 2,782 3,443

Table 1-4. Broadcast-shallow shank with VIF (50% flux reduction)

Buffer Zone (feet) for Various Field Sizes Broadcast app rate (lbs MeI/acre) 1 acre 5 acres 10 acres 20 acres 30 acres 40 acres 50 12 93 170 340 489 590 75 65 289 469 774 1,009 1,239 100 121 439 700 1,120 1,433 1,765 125 180 591 934 1,465 1,849 2,283 175 289 870 1,363 2,095 2,612 3,232Page 10

Methyl iodide buffer z one distances (feet) for 32 ppb , 24-hour exposure. Buffers calculated using PERFUM model and Ventura weather data. Buffers longer than 4723 feet (1440 meters) estimated by extrapolation. Distances represent the 95 th percentile in the maximum direction. Bed-shallow shank fumigation method. Flux is average of Guadalupe and Oxnard studie s (57% of applied amount for peak 24 hrs).

Table 1-5. Bed-shallow shank me thod with standard tarp Buffer Zone (feet) for Various Field Sizes Broadcast app rate (lbs MeI/acre) 1 acre 5 acres 10 acres 20 acres 30 acres 40 acres 50 157 588 965 1,507 2,273 2,418 75 300 951 1,502 2,198 3,315 3,527 100 417 1,275 1,993 2,865 4,321 4,597 125 538 1,575 2,432 3,422 5,160 5,489 176 754 2,140 3,274 4,528 6,827 7,262

Table 1-6. Bed-shallow shank with VIF (30% flux reduction) Buffer Zone (feet) for Various Field Sizes Broadcast app rate (lbs MeI/acre) 1 acre 5 acres 10 acres 20 acres 30 acres 40 acres 50 81 397 684 1,145 1,728 1,839 75 198 698 1,132 1,731 2,611 2,778 100 308 976 1,541 2,254 3,400 3,617 125 401 1,224 1,913 2,751 4,148 4,413 175 579 1,696 2,619 3,685 5,557 5,911

Table 1-7. Bed-shallow shank with VIF (40% flux reduction) Buffer Zone (feet) for Various Field Sizes Broadcast app rate (lbs MeI/acre) 1 acre 5 acres 10 acres 20 acres 30 acres 40 acres 50 76 369 636 1,065 1,607 1,710 75 168 630 1,034 1,614 2,435 2,591 100 261 884 1,419 2,134 3,219 3,425 125 357 1,133 1,788 2,617 3,946 4,198 175 538 1,575 2,432 3,422 5,160 5,489

Table 1-8. Bed-shallow shank with VIF (50% flux reduction) Buffer Zone (feet) for Various Field Sizes Broadcast app rate (lbs MeI/acre) 1 acre 5 acres 10 acres 20 acres 30 acres 40 acres 50 41 299 543 971 1,466 1,560 75 157 588 965 1,507 2,273 2,418 100 244 825 1,324 1,992 3,005 3,197 125 333 1,057 1,669 2,442 3,683 3,919 175 497 1,482 2,301 3,267 4,926 5,240Page 11

Methyl iodide buffer z one distances (feet) for 32 ppb , 24-hour exposure. Buffers calculated using PERFUM model and Ventura weather data. Buffers longer than 4723 feet (1440 meters) estimated by extrapolation. Distances represent the 95 th percentile in the maximum direction. Drip fumigation method. Flux is average of Camarillo, La Selva, Guadal upe studies (54% of applied amount for 24 hrs).

Table 1-9. Drip with standard tarp Buffer Zone (feet) for Various Field Sizes Broadcast app rate (lbs MeI/acre) 1 acre 5 acres 10 acres 20 acres 30 acres 40 acres 51 47 175 340 530 707 878 75 116 346 588 911 1,173 1,451 100 170 486 805 1,245 1,591 1,966 125 230 634 1,018 1,572 1,991 2,457 176 334 896 1,409 2,174 2,734 3,371

Table 1-10. Drip with VIF (30% flux reduction) Buffer Zone (feet) for Various Field Sizes Broadcast app rate (lbs MeI/acre) 1 acre 5 acres 10 acres 20 acres 30 acres 40 acres 50 9 79 198 311 437 546 75 65 221 408 634 834 1,035 100 119 355 603 934 1,203 1,488 125 163 467 773 1,195 1,527 1,887 175 248 682 1,097 1,693 2,144 2,646

Table 1-11. Drip with VIF (40% flux reduction) Buffer Zone (feet) for Various Field Sizes Broadcast app rate (lbs MeI/acre) 1 acre 5 acres 10 acres 20 acres 30 acres 40 acres 50 8 74 184 289 406 508 75 49 184 356 555 740 919 100 92 295 528 819 1,069 1,325 125 152 434 719 1,112 1,420 1,755 175 230 634 1,018 1,572 1,991 2,457

Table 1-12. Drip with VIF (50% flux reduction) Buffer Zone (feet) for Various Field Sizes Broadcast app rate (lbs MeI/acre) 1 acre 5 acres 10 acres 20 acres 30 acres 40 acres 50 7 29 127 202 305 384 75 46 171 332 518 690 858 100 86 276 492 764 998 1,236 125 129 384 654 1,012 1,304 1,612 175 192 538 875 1,351 1,717 2,120