UNITEDSTATESENVIRONMENTALPROTECTIONAGENCYWASHINGTOND.C.,20460SEP2 72012MEMORANDUMSUBJECT:FROM:THRU:TO:ReviewofSulfonylUrea(SU)PlantReproductionStudiesElizabethRiley,Co-chair,PlantTechnicalTeam(PTT)RobinSternberg,Co-chair,PTTNancyAndrews,ManagementRepresentative,PTTEnvironmentalFateandEffectsDivisionDonaldBrady,DivisionDirectorEnvironmentalFateandEffectsDivision(7507P)MichaelGoodis,AssociateDivisionDirectorPesticideRe-evaluationDivision(7508P)OFFICEOFCHEMICALSAFETYANDPOLLUTIONPREVENTIONInthepast,theAgencyhashadconcernsthatsulfonylurea(SU)herbicidesmayhaveeffectsonplantreproductionatrateslowerthanthosethatcausevisualphytotoxiceffectstovegetativevigor(i.e.,growth).TheseconcernswerehighlightedintheRegistrationEligibilityDecision[RED]forchlorsulfuron(D330621)andsulfometuron-methyl(D354292).Asaresultoftheuncertaintiesassociatedwithreproductiveeffects,aData-Call-In(DCI)forplantreproductionstudieswasissuedforthesechemicals.Informationfromopenliteraturesourcesavailableatthattimewasreviewedandreported.However,acomprehensivereviewofthepotentialforreproductiveeffectsatratesrelativetoeffectsonvegetativevigorhadnotbeenconducted.AsadditionalSUsenteredtheregistrationreviewprocess,andadditionalplantreproductionstudieswererequested,athoroughreviewoftheavailableinformationbecameahighpriority.Additionally,thechlorsulfuronDCIstudywassubmittedtotheAgencyforreview.Asaresultofthispriority,thePTTwastaskedwithconductingareviewoftheavailableinformationinordertodeterminewhetherthereissufficientinformationtosupporttheriskhypothesisthatexposuretoSUherbicidesduringreproductivelyactivelife-stageswillresultinmoresensitiveendpointsthanexposureduringvegetativelyactivelife-stages.ThePTThasfinalizedacomprehensivereviewoftheavailableregistrant-submittedandopenliteratureplantreproductionstudiesconductedwithSUherbicides(describedinfurtherdetailintheSupportingDocumentationsectionbelow).Thisreviewfocusedonthecomparisonofeffectsendpoints between

plants exposed
during

the vegetative

and reproductive

stages, respectively. The available information
indicates

that although
effects

on plant reproductive
endpoints

are possible

for the SU herbicides

(as well

as other types

of systemic herbicides included

in the studies),

they occur

at concentrations

similar

to the regulatory vegetative

vigor endpoints.

Based on this review,

PTT concluded

that risk hypothesis

is not supported

and additional

studies

on the effects

of SU herbicides

on plant reproduction

are not needed

at this time. StOS

\

**~** qj;?, In lieu

of requesting additional

studies,

the PTT recommends

inclusion

ofthe following language in Problem Formulations

for the SU herbicides: EFED's

Plant Technical

Team (PTT) conducted

an analysis

of available

SU plant reproduction data from

the open literature

and

the registrant-submitted

data for chlorsulfuron

and concluded that data .from

the 850.4150 vegetative

vigor guideline

study

are sufficiently protective

of potential impacts

to plant reproduction. Acetolactate

synthase

(ALS) inhibitors primarily

affect metabolically-active

meristem
tissues.

When plants

are exposed

at

a young, vigorously growing life-stage,

effects

are expressed primarily

as inhibition

of vegetative

growth

(i.e. biomass,

shoot length).

As plants mature

these effects

are less pronounced.

However,

as plants
enter their reproductive
life-stage,

the metabolically-active

tissue

will include flower

and seed production. Plants exposed

to SU herbicides

during

the reproductive

life stage

are likely

to exhibit adverse effects

on reproduction,

generally expressed

as reduced

seed number

or reduced

seed weight. Based

on the latest data analysis,

these effects

are expected

to occur

at similar concentrations

to those effects determined

in the guideline vegetative

vigor studies (850.4150)

so further

data

are not requested

at this time. Supporting Documentation Summary

of Registrant Submitted

Data E.

I. DuPont

De Nemours

& Company

has submitted

several studies

to evaluate

the effects

of chlorsulfuron

applied

at various

crop growth stages. Effects

from both vegetative

and reproductive

exposure

on growth

and yield responses
(MRID 48776902)

and seed viability (MRID 48776903)

of soybean
grown under greenhouse conditions

are the studies considered most relevant

to address

the risk hypothesis.

These studies indicate

that soybean

is no more sensitive

to chlorsulfuron

applied

at the reproductive

stage

of growth

than

at the vegetative growth
stage. These special studies confirm

that
the endpoint determined

in the guideline vegetative

vigor study

for chlorsulfuron

is protective

of the inhibitory

effects

of exposure

at reproductive

stages. Summary

of Open Literature

Data In addition

to the aforementioned

review

of the DuPont

study,

PTT conducted

a thorough
review of the available

open literature

plant reproduction

studies.
Table

1 provides

a summary

of the relevant information

from each study

that was used

to compare

the vegetative

and reproductive endpoints.

For reference,

the associated regulatory endpoint

from

the guideline

study

is provided where available.

For this comparison,

a vegetative

growth endpoint

(e.g., height, weight,

orphytotoxicity)thatisgreaterthanthereproductiveendpointprovidesevidencethatplantreproductiveeffectsmayoccuratlevelsbelowvegetativegrowtheffects.WhiledatafromopenliteraturestudiesdoprovidesupportfortheargumentthatexposuretoSUherbicides(aswellasothertypesofsystemicherbicides)canleadtoreproductiveeffects,amajorityoftheopenliteraturedatadidnotallowformeaningfulcomparisonbetweenvegetativegrowthandreproductiveendpointsordidnotaddresstheriskhypothesisduetooneormoreofthefollowing:1.Avegetativeorreproductiveendpointwasnotprovidedinthestudy.2.Endpoint(s)wasnon-definitive(i.e.,greaterthanorlessthanvalue).3.Thevegetativegrowthendpointwasbasedonphytotoxiceffectsonly.Manyofthestudiesutilizedsomeformofplantinjuryindexbasedonsemi-quantitativeobservationsofphytotoxicity.Sinceplantheightanddryweightcanbemoresensitivethanobservationsofphytotoxicity,theseendpointsdonotreduceuncertaintyastowhetherreproductiveeffectsmayoccuratlevelsbelowvegetativegrowtheffects.4.Severalstudiesexposedplantsduringthevegetativelyactivelife-stage(e.g.,the2-,4-,or6-leafstage)andmeasuredvegetativegrowthandreproductiveendpointspostflowering.ThesestudiesprovideinformationthatsuggestsplantsexposedtoSUherbicidesduringthevegetativevigorlife-stagemayexperiencelingeringeffectsonreproduction;however,theydonotaddressthequestionbeforethePTT.Althoughamajorityoftheopenliteraturestudiesdidnotallowfordirectcomparisonbetweenvegetativegrowthandreproductiveendpoints,thereweresevenstudiesthatappeartoaddresstheriskhypothesisdirectlyandwereamenabletocomparisonacrossendpoints.Foreachofthesestudies,plantswereexposedduringeitherthevegetativeor reproductivestages,vegetativedatawerecollectedinamannerconsistentwithguidelinestudies,andIC2svalueswerereportedforthemostsensitivevegetative(e.g.,height)andreproductive(e.g.,seedweight)endpoints.Dataforthreeofthesestudiesindicatedthatreproductiveendpointsareequivalenttovegetativeendpoints,whereasresultsfromthreestudiessuggestthatthevegetativeendpointsarelesssensitivebutwithinafactorof3ofthereproductiveendpoints.Giventhevariabilityassociatedwithplantstudies,endpointswithinafactorof3ofeachotherarenotconsideredsubstantiallydifferent.Datafromonestudy(Olszyketal.2009),however,didsuggestthatreproductiveendpointsaretwoordersofmagnitudemoresensitivethanvegetativeendpointswhenpeaswereexposedtosulfometuron-methyl.Sincetheresultsofthisstudywereinsharpcontrasttotheresultsoftheremainingstudies,PTTrequestedtherawdatafromthestudyauthorstoconductamorethoroughreview,asdiscussedinthefollowingsection.

# Table 

# 1. C 

# om 1ar1son o fSUR, duction Stud·

' 

# Vegeg.tive

' 

# Growth ' Reproductive Regulatory Study, addresses risk €hemical, Species* IC1sl End{loint Endpoint (R)

**VG >R?**  

# Endp,oint** hypothesis 1 and l is amenable Reference (Reference) f NOAE€



# ~G) (lb a,i./A) (lb a.i./A) 

# to comparison across 

# I Ob a.i./A) endpoints?

Registrant-Submitted Studies

IC25 2

. 34x1o-' 9.55 x1o-' Yes, VG conducted the same MRIDs Chlorsulfuron Soybean (1.36 x10- 5

- (5

. 24 x10- 5

- No 280 x10- 5 48776902 and (C. 

# I.) 4.04 x10- 5 ) 

# 17.31 x10- 5 ) as guideline. 48776903 Open Literature Studies

No, plants treated at 4- to 6-
Black NOAEC 2.0 x10- 5 2.0 x10- 5 No NR leaf stage

. Measurements MRID 48915011 bindweed taken at 3 1 days post

treatment.

No, VG not conducted the

Canola NOAEC 4.0 xl0- 5 2

. 0 x10- 5 Yes 0.9 x10- 5

same as guideline. Treatment MRID 48915009

at reproductive stage only.

Chlorsulfuron Cherry NOAEC NR 4

. 0 x10- 5 NP NR No, VG endpoints not MRID 48915006 reported.

No, endpoints non-definitive.

Foxtail NOAEC 

# < 9.0x10- 3 

# < 9.0x10- 3 

# NP NR VG endpoints based on visual MRID 48915010 injury index only.

No, VG measurements for

post-emergence application

Pea NOAEC NR 8

. 0 x10- 5 NP 72.0 x10- 5 not reported. R endpoint based MRID 48915005

on mean yield less than 75%

of control.

No, VG not conducted the

Pea NOAEC 2.0 x10 4 

# 0

. 08 x10 4 

# Yes 7.20 x10 4 

# same as guideline. Treatment MRID 48915008 at 6-leaf stage with visible

flower buds.

Chlorsulfuron No, VG not conducted the Soybean NOAEC 2

. 0 x1o-s 2.0 x10- 5 No 14.0 x10- 5

same as guideline. Treatment MRID 48915009

at reproductive stage only.

No, VG not conducted the

Sunflower NOAEC 2.0 xlo- 5 4

. 0 xl0- 5 No NR same as VV. Treatment at MRID 48915009 reproductive stage only

. Smartweed NOAEC 

# < 2.0

**xlo-~** 

# < 2

. 0

**xlo-~** 

# No NR No, endpoints non-defmitive, MRID 48915009

# Table 1. C om**~ariSOD** 

# 0 

# fSUR duction Stud·

Vegetative Study addresses risk Growth Reproductive ' 

# Regulatory Chemical Species* :IC2s/ Endpoint Endpoint (R) 

# VG>R? Endpoint** hypothesis and is amenable Reference (Reference) NOAEC**(V~)** 

# (lb a.i./A) (lb a.i./A) to comparison across

(lb a.i./A) endpoints?

VG 

# not conducted the same as guideline. Treatment at reproductive stage only.

Yes (by No, VG 

# endpoints based on
Sweet NOAEC 2.0 xl0-4 0.7xl0-4 order of NR visual injury index only. MRID 48915006 cherry magnitude) Application to mature tree

branches.

Metsulfuron Foxtail NOAEC 

# < 9.0 xl0" 3 

# < 9.0 xl0" 3 

# No, endpoints non-definitive.

NP NR VG 

# endpoints based on visual MRID 48915010 injury index only.

Nicosulfuron Soybean NOAEC 1.0 xl0· 3 

# 4.0 xl0· 3 

# No NR No, VG 

# not conducted the MRID 48915004

same as guideline.

Pea IC25 6.0 xl0-4 1.2 xl0-4 Yes (within NR Yes, VG 

# conducted the same MRID 48915012 (S.E.) (2.0 xl0-4) (2.0 xl0-4) factor of2) as guideline.

No, R endpoint not reported.

Primisulfuron Soybean NOAEC 4.0xl0-4 NR NP NR VG 

# not conducted the same as MRID 48915004 guideline.

IC25 3.9 xl0-4 No, R endpoint not reported.

Potato (S.E.) (2.0 xl0-4) NR NP NR VG 

# conducted the same as MRID 48915001

. guideline.

I



# IC25 1.5 xl0-4 0.8 xl0-4 Yes (within Yes, VG 

# conducted the same Study I (0.5 xl0-4- (0.2 xl0-4- 2.4lxl0-4 raw data from (C.I.) 4.6 xl0-4) 3.6 xl0-4) factor of2) as guideline. MRID 48915012

Pea IC25 6.0**xlo-~** 

# 2.0**xto·~** 

# Yes (within Yes, VG 

# conducted the same Study2
(2.0 xto· 5

- (0.4 xto· 5

- 24.1 xi0- 5

raw data from (C.I.) 36 xl0- 5 ) 8.0 xl0" 5 ) factor of3) as guideline. MRID 48915012 Sulfometuron IC25 9.0 xto·' 3.0 xlO"' Yes (within Yes, VG 

# conducted the same (S.E.) (20 xl0- 5 ) (2.0 xl0- 5 ) factor of3) 24.1 xto· 5

as guideline. MRID 48915002

Potato IC25 0.07**xlo-~** 

# 3.0**xto·~** 

# No NR Yes, VG 

# conducted the same MRID 4891500 I (S.E.) (0.08 xi0- 3 ) 

# (5.0 xl0- 3 ) 

# as guideline.

Soybean IC25 2.0 xl0-4 2.0 xl0-4 No 0.000018 Yes, VG 

# conducted the same MRID 48915002 (S.E.) (2.0 xl0-4) (2.0 xl0-4) as guideline.

Thifensulfuron Canota IC25 0.0005 NR NP 0.000048 No, R endpoints not reported. Wall, 

# eta/., 1995

# Table 1. C om

**~ar1son** 

# o fSUR, duction Stud'

I 

# Vegetative

I 

# Study

**address~** 

# risk I 

# I l€i&st GrowtbJ Reproductive Regulatory I 

# €hemical

' Species* Endpoint

**Endp~int** 

# (iR) 

# VG

. >R? Endpoint** hy,pothesis and

. is 1 

# amenable I 

# Reference

**~eference)** 

# r I 

# NO.AEC '

**tvG~** 

# @b a.i./A) l 

# @ba.UA) to • comparison across

I 1 

# (tb a.tJA)

, I 

# endp"oints?

IC 25 calculated for fresh and 

# dry weight. VG conducted similarly to guideline.

No, VG measurements for

Pea NOAEC NR 5.0 xl0-4 

# NP 9

. 8 xl0-4 post emergence application

not reported

. R endpoint based MRID 48915005

on mean yield less than 75%

of control.

No, R endpoint not reported

.
Canol a IC2s l.Oxl0-4 NR NP 1.0 xl0-4 IC2s calculated for fresh and Wall, 

# eta/

. , 1995 

# dry weight. VG conducted similarly to guideline.



# Tribenuron No, endpoints non-definitive

. Foxtail NOAEC 

# < 9.0 xto· 3 

# < 9.0 xl0" 3 

# NP NR VG endpoints based on visual MRID 48915010

injury index only.

IC2s 2.0 xl0" 5 No, R endpoint not reported

. Potato (S.E.) (1.0 xl0" 5 ) NR NP NR VG conducted the same as MRID 4891500 I guideline.

NR = 

# value not reported; C.l. = 

# confidence interval; S.E. = 

# standard error
NP 

# = comparison is not possible either because a VG orR endpoint was not provided or because endpoints are less than or greater than values that do not allow
for direct comparison

*Scientific names for the tested species are: soybean 

# (Glycine max), black bindweed 

# (Polygonum convolvulus), canola 

# (Brassica napus), cherry 

# (Prunus avium),
foxtail 

# (Setaria spp.), pea 

# (Pisum sativum), sunflower 

# (Helianthus annuus), smartweed 

# (Polygonum persicaria), and potato 

# (Solanum tuberosum). **Comparable endpoint from the guideline study.Summaryof0/szyketa/(2009)DataReviewandRe-AnalysisTakenatfacevalue,thereviewofthisopenliteraturestudyseemstoindicatethat,forsulfometuronmethyl,peareproductioneffectsfromexposureattheonsetoffloweringaregreaterthaneffectsonvegetativegrowthfromexposureatthetypicalvegetativevigorstage(i.e.,guidelinestudy850.4150).However,theanalysisofthedatapooledacrosstwoseparateexperimentswasnotconsistentwithstandardEFEDanalyses.Theprimaryauthorofthestudy,DavidOlszykofORD'sWesternEcologyDivision, providedtherawdatawhichallowedthePTTtoanalyzethedatainamannerconsistentwithstandardEFEDpractice.Foreachstudy,theeffecton21-dayplantheight,theonlyvegetativevigorendpointthatwassimilarto850.4150,wasanalyzedforplantsexposedatthevegetativevigorstagetoobtainICzsvalues.Inaddition,theeffectonseedweight,themostsensitivereproductionendpoint,wasanalyzedforplantsexposedattheonsetofthereproductivelife-stagetoobtainICzsvalues.ThisanalysisallowedthePTTtomakedirectcomparisonsbetweentheeffectofexposuretimingonthemostsensitiveendpointsforeachlife-stageandaddresstheresearchquestionofwhetherourcurrentguidelinestudy(i.e.,vegetativevigor)issufficientlyprotectiveofeffectsseenatexposureattheonsetofflowering,anotherparticularlysensitivelifestage.Theresultsofthisanalysis(Table2)indicatethattherearenoappreciabledifferencesbetweentheratesatwhich25%inhibition(ICzs)occursateachparticularexposurelife-stageandendpoint.Itisimportanttonotethat21-daybiomasswasnotameasurementendpointinthesestudies.Intheguidelineregulatorystudyforsulfometuron-methyl,peabiomasswasanorderofmagnitudemoresensitivethanpeaheight.12lba.i./AHowever,thedatadoindicatethatplantsexposedtoSUherbicidesatthevegetativeactivelylifestagemayalsoresultinlowerseedweightandsmallerseedsthaninthecontrol,suggestingthatsensitiveplantsexposedearlyinlifemayexperienceadverseimpactsonfruit/seednumbersand/orfruit/seedweight.However,thisissueisseparatefromthequestionofwhethercurrentguidelinestudiesareprotectiveofreproductiveeffectsandneedstobeexploredmorethoroughlybythePTTinthefuture.References MRID 48915004 MRID 48915005 MRID 48915006 MRlD 48915007 MRID 48915008 MRlD 48915009 MRID 48915010 MRID 48915011 MRlD 48915012 MRlD 48915001

Al-.Khatib,

K. and

D. Peterson.

1999. Soybean (Glycine

max) response

to simulated

drift from selected sulfonylurea herbicides, dicamba, glyposate, and glufosinate.

Weed Technology,

13: 254-270. Al-.Khatib,

K. and

A. Tamhane.

1999.

Dry pea (Pisum sativum

L.) response

to low rates

of selected
foliar-

and soil- applied sulfonylurea

and growth regulator herbicides.

Weed Technology,

13: 753-758. Bhatti, M.A.; Al-.Khatib,

K.; Felsot,

A.S.; Parker,

R. and

S. Kadir.

1995. Effects

of simulated chlorsulfuron

drift

on fruit yield

and quality

of sweet cherries (Prunus
avium

L.). Environmental
Toxicology

and Chemistry,

14 (3): 537-544. Fletcher,

J.S., T.G. Pfleeger,

and H.C. Ratsch.

1993. Potential environmental

risks associated

with

the new sulfonylurea herbicides. Environ.

Sci. Technol. 27:2250-2252. Fletcher,

J.S.; Pfleeger,

T.G.

and H.C. Ratsch.

1995. Chlorsulfuron influence

on garden

pea reproduction. Physiologia Plantarum,

94: 261- 267. Fletcher,

J.S.; Pfleeger,

T.G.; Ratsch,

H.C.;

and

R. Hayes

. 1996. Potential impact

of low levels

of chlorsulfuron

and other herbicides

on growth

and yield

of nontarget

plants. Environmental
Toxicology

and Chemistry,

15 (7): 1189-1196. Khan,

M. and W.W. Donald.

1992. Sulfonylurea herbicides

reduce survival

and seed production

of green

and yellow foxtails (Setaria

spp.). Weed Technology,

6: 284-290. Kjaer,

C. 1994. Sublethal

effects

of chlorsulfuron

on black bindweed (Polygonum convolvulus

L.). Weed Research,

34: 453-459. Olszyk,

D.; Pfleeger,

T.; Lee, E.H.;

and

M. Plocher.

2009.

Pea (Pisum sativum)

seed production

as an assay

for reproductive

effects

due

to herbicides. Environmental
Toxicology

and Chemistry,

28 (9): 1920-1929. Olszyk,

D.; Pfleeger,

T.; Lee, E.H.;

and

M. Plocher.

2010. Potato (Solanum tuberosum) greenhouse

tuber production

as an assay

for asexual reproduction

effects

from herbicides. Environmental
Toxicology

and Chemistry,

29 (1): 111-121.MRID48915002Pfleeger,T.;Olszyk,D.;Lee,E.H.;andM.Plocher.2011.Comparingeffectsoflowlevelsofherbicidesongreenhouse-andfield-grownpotatoes(SolanumtuberosumL.),soybeans(GlycinemaxL.),andpeas(PisumsativumL.).EnvironmentalToxicologyandChemistry,30(2):455-468.Wall,D.A.,D.A.Derksen,andL.F.Friesen.1995.Canola(Brassicanapus)responsetosimulatedsprayercontaminationwithThifensulfuronandThifensulfuron:Tribenuron(2:1).WeedTechnology,9:468-476.