 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

OFFICE OF 

PREVENTION, PESTICIDES AND 

TOXIC SUBSTANCES

MEMORANDUM	DATE:  May 17, 2006

	PC CODE: 098801

	DP BARCODE: 323825

			

SUBJECT:	Drinking Water Assessment for Chlorflurenol Growth Regulator
and Herbicide

TO:	Richard Griffin, Risk Assessor

	RB2 (7509C)

	Health Effects Division		

FROM:	Ronald D. Parker, Ph.D. Senior Environmental Engineer

ERB5 (7507C)

		Environmental Fate and Effects Division

THRU:	Mah Shamim, Branch Chief

ERB5 (7507C)

		Environmental Fate and Effects Division

EXECUTIVE SUMMARY: 

This memo summarizes estimated drinking water concentrations (EDWCs) for
Chlorflurenol Methyl Ester from surface water and groundwater sources.
Chlorflurenol is a plant growth regulator (retardant) and herbicide. It
retards the growth of turf, trees, grass, shrubs, ornamentals, grassy
weeds, conifer release and non-agricultural rights-of way, and it
controls broadleaf weeds.

Groundwater concentrations were estimated using the Tier I SCIGROW
model. Surface water concentration values were estimated using the
linked, Tier II PRZM and EXAMS models. See model descriptions below. The
environmental fate information for chlorflurenol is incomplete.
Conservative default values have been substituted for missing data in
order to proceed with this assessment. The only acceptable environmental
fate studies indicate that Chlorflurenol has a Koc in the range of 65
L/mg and is stable to hydrolysis. See Table 1 below. The OPP/EFED
Florida turf scenario was selected for this assessment as a reasonable
worst case based on the available usage and environmental fate
information. It is likely that a more complete database for this
chemical would lead to reduced estimates of Chlorflurenol concentrations
in drinking water. For this assessment, it was assumed that 8
applications of chlorflurenol were applied to turf grass at a rate of
3.0 pounds active ingredient per acre with a 28-day spacing between
applications. See Table 3 below. The acute and chronic ground water
concentration of 2050 ppb (2.05 ppm) is the highest of the estimated
values. This would represent a maximum concentration in a shallow,
private well in a high usage area. Surface water concentrations are
acute: 386 ppb; chronic non-cancer: 236 ppb; and chronic cancer: 176
ppb. See Tables 2, 4 and 5 below. 

Usage of Chlorflurenol

Chlorflurenol is an herbicide and plant growth regulator (PGR). Products
containing chlorflurenol methyl ester have been reported to exhibit
varying biological properties. For example, they retard growth of many
grasses and control broadleaf weeds and vines. Some products are
recommended for use on areas where regular mowing and trimming are
difficult. Such locations would include areas under security fences and
guard rails, around sign posts, delineator posts, culverts,
rights-of-way, median strips and ditches and steep banks. Some products
are intended for bark banding to inhibit tree growth, induce seedless
fruit set in all-female cultivars of pickling cucumbers, and are used
for control of broadleaf weeds in ornamental turfgrass. One product,
Maintain CF 125, produces vegetative planting material for pineapples
and is registered in Hawaii under Section 24(c) for use on pineapples
(see Reg. No.: 000400 HI-83-0011)

Identity of the Active Ingredient:

Chemical Name:		9H-Fluorene-9-carboxylic acid, 2-chloro-

				9-hydroxy-, methyl ester

Synonym:			Methyl 2-chloro-9-hydroxyfluorene-

				9-carboxylate

Common Names:		Chlorflurecol-methyl ester

				Chlorflurenol-methyl ester (ISO)

CAS Reg. No.:			2536-31-4

EPA Chemical Code:		098801

EPA Case Name:		Chlorflurenol, methyl ester

EPA Case Number:		2095

Chemical Structure:

 

  SEQ CHAPTER \h \r 1 Background Information on SCIGROW:

SCI-GROW is a screening model used by the EPA Office of Pesticide
Programs (OPP) to estimate pesticide concentrations in vulnerable ground
water. The model provides an exposure value that is used to determine
the potential risk to the environment and to human health from drinking
water contaminated with the pesticide. The SCI-GROW estimate is based on
environmental fate properties of the pesticide (aerobic soil degradation
half-life and linear adsorption coefficient normalized for soil organic
carbon content), the maximum application rate, and existing data from
small-scale prospective ground-water monitoring studies at sites with
sandy soils and shallow ground water.

Pesticide concentrations estimated by SCI-GROW represent conservative or
high-end exposure values because the model is based on ground-water
monitoring studies which were conducted by applying pesticides at
maximum allowed rates and frequency to vulnerable sites (i.e., shallow
aquifers, sandy, permeable soils, and substantial rainfall and/or
irrigation to maximize leaching). In most cases, a large majority of the
use areas will have ground water that is less vulnerable to
contamination than the areas used to derive the SCI-GROW estimate. 

The SCI-GROW value is likely to be exceeded only under exceptional
circumstances in a small percentage of the use area. No more than a few
percent of U.S. agricultural land consists of sandy soils overlying
shallow ground water like those selected for reasonable worst-case,
small-scale prospective groundwater monitoring studies (source: STATSGO
soils database).

Background Information on Linked PRZM/EXAMS Models

The linked EPA PRZM-EXAMS models estimate aquatic concentrations in a
one hectare pond that is two meters deep next to a ten hectare plot. The
pond receives simulated drift, runoff and eroded soil from the adjacent
field.  PRZM models terrestrial pesticide fate and transport and EXAMS
models the aquatic portion.

The Pesticide Root Zone Model (PRZM) is a one-dimensional, dynamic,
compartmental model that can be used to simulate chemical movement in
unsaturated soil systems within and immediately below the plant root
zone.  It has two major components: hydrology (and hydraulics) and
chemical transport. The hydrologic component for calculating runoff and
erosion is based on the Soil Conservation Service curve number technique
and the Universal Soil Loss Equation. Evapotranspiration is estimated
either directly from pan evaporation data, or based on an empirical
formula. Evapotranspiration is divided among evaporation from crop
interception, evaporation from soil, and transpiration by the crop.
Water movement is simulated by the use of generalized soil parameters,
including field capacity, wilting point, and saturation water content.  

Exposure Analysis Modeling System (EXAMS) is a model that can receive
progressive PRZM runoff concentration output to further predict aquatic
pesticide concentrations in a simulated pond.  The predicted
concentrations over the period of time (usually 30 years) can be
averaged over time to produce peak and time averaged concentrations that
take into account aquatic degradation.

Table 1. Input Parameters for PRZM/EXAMS and SCIGROW Models

Parameter	

Input	

Source



Hydrolysis t1/2 @ pH 7 (days)	

Stable	

MRID 43496201



Aerobic soil t1/2 (days)	

Stable	

EFED Default



Aerobic aquatic t1/2 (days) 	

Stable	

EFED Default



Photolysis t1/2 in water (days)	

Stable	

EFED Default

Organic carbon partition coefficient - Koc (mL/g)	

65	

MRID 43496202



Application rates (lb a.i./Acre)	3.0 lbs a.i./acre	

Label maximum rate



Applications / year	

8	Typical maximum number applications



Application spacing	

28 Days	Label minimum spacing



Table 2. Simulated drinking water concentrations for surface and ground
water.

Model	Chlorflurenol Drinking Water Concentration (ppb)

Exposure Duration	Acute

	Chronic

Non-cancer	Chronic

Cancer

No. Annual Turf Applications 	8 Apps

@28 Days	8 Apps

@28 Days	8 Apps

@28 Days

PRZM/EXAMS

(Surface Water)	386	236	176

SCIGROW

(Ground Water)	2050	2050	2050



Table 3. Chloroflurenol Uses and Application Rates

Chloroflurenol:  Uses and Application Rates

Crop	EPA Reg. No.	Max. Application Rate	Specific Instructions Regarding
Intervals	Likely Applications per Unit Area per Year	Likely Applications
by Occupational or Residential Applicator per Year

Occupational Uses

Turf:  ornamental and lawns	69361-1

water dispersible solution	1.0 lb ai/acre	Apply when weeds are actively
growing	8 (FL)	40 (FL)

	69361-3

dry	0.26 lb ai/acre	Wait at least 4 weeks before 2nd application

Apply anytime weeds actively growing and temp is >60°F	8 (FL)	40 (FL)

	69361-6

liquid	3.0 lb ai/acre	Apply when grass just beginning to green up. 
Apply throughout growing season.	8(FL)	40 (FL)

Turf:  golf courses	69361-1

water dispersible solution	1.0 lb ai/acre	Apply when weeds are actively
growing	8 (FL)	40 (FL)

Weed Turf:

growing in culverts, ROW, median strips, ditches, under security fences
69361-6

liquid	3.0 lb ai/acre	Apply throughout growing season	6	60

Weed Hardwoods:

growing under utility lines, as screens or ground cover, adjacent to
highways	69361-6

liquid	1.0 lb ai/100 gallons	Retards growth up to 1 year	1	10

Weed Hedges:

growing under utility lines, as screen	69361-6

liquid	1.0 lb ai/100 gallons	Retards growth up to 2 months	6	60

Weed Vines

growing under utility lines, as screens or ground cover, ROW, hedgerows 
69361-6

liquid	1.0 lb ai/100 gallons	Retards growth up to 6 months	2	20

Weed Gymnosperms	69361-6

liquid	0.25 lb ai/100 gallons	Must be treated before buds expand	1	10

Trees:

bark banding to inhibit growth	69361-6

liquid	depends on trunk diameter & tree type

1	10

Agricultural Uses

Turf:  sod farms	69361-6

liquid	3.0 lb ai/acre	Apply throughout growing season beginning when
turf is just beginning to green up. (REI 48 hours)	6	30

Pineapple plants:

for plant material production (non food use)	69361-6 (SLN)

liquid	1.0 lb ai/acre	A 2nd application may be made after an interval of
10-12 days.  Apply to mature pineapple plants at time of forcing, and 6
months prior to desired planting material harvest.   	2	10

Residential Uses

Turf:  lawns	69361-3

dry	0.26 lb ai/acre	Wait at least 4 weeks before 2nd application

Apply anytime weeds actively growing and temp is >60°F	6	6



Table 4. PRZM/EXAMS Output File

Stored as FLTurfIR.out

Chemical: Chlorflurenol

PRZM environment: FLturfC.txt	modified Monday, 16 June 2003 at 14:48:06

EXAMS environment: ir298.exv	modified Thuday, 29 August 2002 at 15:34:12

Metfile: w12834.dvf	modified Wedday, 3 July 2002 at 10:04:28

Water segment concentrations (ppb)

Year	Peak	96 hr	21 Day	60 Day	90 Day	Yearly

1961	126	125	121	117	112	53.93

1962	278	276	267	248	234	133

1963	286	284	275	268	262	201

1964	289	287	281	266	266	217

1965	218	216	211	203	197	162

1966	445	443	432	423	418	267

1967	390	387	375	349	331	260

1968	292	290	281	269	267	227

1969	402	399	386	359	339	216

1970	272	270	262	244	237	190

1971	213	212	205	195	190	150

1972	284	282	274	259	250	196

1973	262	260	252	235	222	177

1974	336	334	323	300	284	200

1975	261	259	251	234	222	193

1976	354	352	340	316	300	236

1977	293	291	282	268	256	210

1978	279	277	270	257	254	219

1979	270	268	262	250	239	207

1980	184	183	178	166	160	148

1981	158	156	152	147	142	112

1982	227	225	219	215	211	166

1983	263	261	258	249	240	193

1984	309	307	297	276	270	232

1985	218	216	210	196	189	166

1986	194	193	188	182	181	136

1987	177	175	170	163	159	141

1988	113	112	109	107	104	99.33

1989	103	102	99.08	96.51	94.54	81.82

1990	123	122	118	114	110	77.43

Sorted results

Prob.	Peak	96 hr	21 Day	60 Day	90 Day	Yearly

0.032258064516129	445	443	432	423	418	267

0.0645161290322581	402	399	386	359	339	260

0.0967741935483871	390	387	375	349	331	236

0.129032258064516	354	352	340	316	300	232

0.161290322580645	336	334	323	300	284	227

0.193548387096774	309	307	297	276	270	219

0.225806451612903	293	291	282	269	267	217

0.258064516129032	292	290	281	268	266	216

0.290322580645161	289	287	281	268	262	210

0.32258064516129	286	284	275	266	256	207

0.354838709677419	284	282	274	259	254	201

0.387096774193548	279	277	270	257	250	200

0.419354838709677	278	276	267	250	240	196

0.451612903225806	272	270	262	249	239	193

0.483870967741936	270	268	262	248	237	193

0.516129032258065	263	261	258	244	234	190

0.548387096774194	262	260	252	235	222	177

0.580645161290323	261	259	251	234	222	166

0.612903225806452	227	225	219	215	211	166

0.645161290322581	218	216	211	203	197	162

0.67741935483871	218	216	210	196	190	150

0.709677419354839	213	212	205	195	189	148

0.741935483870968	194	193	188	182	181	141

0.774193548387097	184	183	178	166	160	136

0.806451612903226	177	175	170	163	159	133

0.838709677419355	158	156	152	147	142	112

0.870967741935484	126	125	121	117	112	99.33

0.903225806451613	123	122	118	114	110	81.82

0.935483870967742	113	112	109	107	104	77.43

0.967741935483871	103	102	99.08	96.51	94.54	53.93

0.1	                    386.4    383.5      371.5	345.7	327.9	235.6

Average of yearly averages:	175.6

Inputs generated by pe4.pl - 8-August-2003

Data used for this run:

Output File: FLTurfIR

Metfile:	w12834.dvf

PRZM scenario:	FLturfC.txt

EXAMS environment file:	ir298.exv

Chemical Name:	Chlorflurenol

Description	Variable Name	Value	Units	Comments

Molecular weight	mwt	300	g/mol

Henry's Law Const.	henry	3.0e-10	atm-m^3/mol

Vapor Pressure	vapr	3.0e-8	torr

Solubility	sol	 18	mg/L

Kd	Kd		mg/L

Koc	Koc	65	mg/L

Photolysis half-life	kdp	0.0	days	Half-life

Aerobic Aquatic Metabolism	kbacw	0.0	days	Halfife

Anaerobic Aquatic Metabolism	kbacs	0.0	days	Halfife

Aerobic Soil Metabolism	asm	1000000	days	Halfife

Hydrolysis:	pH 5	0.0	days	Half-life

Hydrolysis:	pH 7	0.0	days	Half-life

Hydrolysis:	pH 9	0.0	days	Half-life

Method:	CAM	2	integer	See PRZM manual

Incorporation Depth:	DEPI		cm

Application Rate:	TAPP	3.37	kg/ha

Application Efficiency:	APPEFF	.99	fraction

Spray Drift	DRFT	.05	fraction of application rate applied to pond

Application Date	Date	01-03	dd/mm or dd/mmm or dd-mm or dd-mmm

Interval 1	interval	28	days	Set to 0 or delete line for single app.

Interval 2	interval	28	days	Set to 0 or delete line for single app.

Interval 3	interval	28	days	Set to 0 or delete line for single app.

Interval 4	interval	28	days	Set to 0 or delete line for single app.

Interval 5	interval	28	days	Set to 0 or delete line for single app.

Interval 6	interval	28	days	Set to 0 or delete line for single app.

Interval 7	interval	28	days	Set to 0 or delete line for single app.

Record 17:	FILTRA	

	IPSCND	1

	UPTKF	

Record 18:	PLVKRT	

	PLDKRT	

	FEXTRC	0.5

Flag for Index Res. Run	IR	IR

Flag for runoff calc.	RUNOFF	total	none, monthly or total(average of
entire run)

Table 5. SCIGROW Output File.

                                      

				SCIGROW              

                     VERSION 2.2: NOVEMBER 1, 2001                

   RUN No.   1 FOR Chlorflurenol       ** INPUT VALUES **       

   --------------------------------------------------------  

    APP RATE   APPS/   TOTAL/     SOIL   AEROBIC SOIL METAB  

    (LBS/AC)    YEAR    SEASON    KOC       HALFLIFE (DAYS)    

  
------------------------------------------------------------------------
---------   

      3.000             8             24             65.0           
100000.00

   GROUND-WATER SCREENING CONCENTRATION (IN UG/L - PPB)  

  
------------------------------------------------------------------------
------------------  

                                                  2051.633000

  
------------------------------------------------------------------------
------------------

