Document ID: EPA-HQ-OPP-2007-0872-0007
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2008-04-23T04:00Z

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

OFFICE  OF 

PREVENTION, PESTICIDES AND 

TOXIC SUBSTANCES

							

							PC Code No.:		085651

							DP Barcode:		D 342613

							Date:			March 5, 2008

MEMORANDUM				

	

SUBJECT:	Estimated Drinking Water Concentrations of Parent Cyazofamid
and its Degradates CCIM, CCIM-AM and CTCA for Use in Human Health Risk
Assessment (Carrot use pattern).

FROM:	Mohammed A. Ruhman, Agronomist, Ph.D.

		Environmental Risk Branch V

		Environmental Fate and Effects Division (7507P)

THROUGH:	Mah T. Shamim, Ph.D., Chief

		Environmental Risk Branch V

		Environmental Fate and Effects Division (7507P)

TO:		Dan Rosenblatt, Chief

		Susan Stanton, Risk Manager Reviewer

		Risk Integration, Minor Use and Emergency

		Response Branch

		Registration Division (7505P)

AND:		Kelly O’Rourke

		Registration Action Branch 3

		  SEQ CHAPTER \h \r 1 Health Effects Division (7509P)

Summary

This memo presents the Estimated Drinking Water Concentrations (EDWCs)
for Parent Cyazofamid and degradates CCIM, CCIM-AM and CTCA for use in
an FQPA human health risk assessment. Cyazofamid fungicide and/or
degradates may reach both surface and groundwater under some conditions.
The registrant is seeking registration for use of this chemical on
carrot. It is noted that EDWCs were previously estimated for:

Turf and ornamentals (EFED Memo to HED dated September 6, 2004); and

Cucurbits, potatoes, and tomatoes (EFED Memo to HED dated April 28,
2004).

It is noted that maximum EDWCs were determined previously for cyazofamid
use on turf and ornamentals.  In comparison to turf and ornamental use
pattern, EDWCs for the current use pattern on carrots are much lower as
values are 17% for the surface water acute; 5% for the surface water
non-cancer chronic, and 7% for the cancer chronic. Furthermore, the
acute/chronic value for ground water is 25% of the values assigned for
the turf and ornamentals use pattern. 

The screening level surface water and ground water estimates are
calculated using tier 2 linked PRZM/EXAMS models and the tier 1 SCI-GROW
model, respectively. Resultant Estimates are presented in Table 1 for
three scenarios as follows:

(1) 1st scenario (parent) assuming application of the maximum rate as
parent;

(2) 2nd scenario (each of the degradates CCIM, CCIM-AM, and CTCA)
assuming application of the molar equivalent of the parent for each of
the degradate by dividing the rate between the degradates based on
molecular ratios and adjusted maximums found in fate studies; and

(3) 3rd scenario (the terminal degradate CTCA) assuming application of
100% molar conversions of the parent into this terminal degradate CTCA.

Table 1 Resultant maximums of surface/ground water EDWCs for cyazofamid
and each of its major degradates

Scenario

	Chemical	Surface water EDWCs (ppb)	Ground water EDWC (ppb)

Acute	Chronic “non-Cancer”	Chronic “Cancer”

	1st  Scenario	Parent	4.038	0.064	0.035	0.00294

2nd  Scenario 	CCIM	1.652	1.226	1.078	0.00015

	CCIM-AM	0.554	0.200	0.140	0.00069

	CTCA	4.826	4.761	2.654	0.13100

3rd  Scenario 	CTCA	18.025

8.347*	6.546	5.457	0.545

EDWC	6.244	6.546	5.457	0.545

* Chronic “non-cancer” maximum was taken from one run while chronic
“cancer” maximum from another.

Based on the results presented in Table 1 above and time-line of
exposure, the surface water acute EDWC is 6.244 ppb (total value= Parent
“4.038 ppb” + CCIM “1.652 ppb” + CCIM-AM “0.554 ppb”).  CTCA
is not included in the surface water acute number because it is not
expected to be present at this time frame. The surface water non-cancer
chronic is 6.546 ppb and the cancer chronic is 5.457 pp (equal to values
for the terminal degradate CTCA). For ground water, the acute/chronic
value is 0.545 ppb (equal to the value for the terminal degradate CTCA).

The above stated values represent upper-bound estimates of the parent,
individual degradates and/or terminal degradate CTCA concentrations that
might be found in surface water and groundwater due to the use of
cyazofamid on carrot EFED emphasizes that this is a tier 1 screening
level analysis, and should there be a need by HED, additional
refinements can be made.

Environmental Fate of Cyazofamid

Available environmental fate studies suggest cyazofamid is not very
mobile and quickly degrades into a number of degradation products under
different environmental conditions. Among the three major degradates for
Cyazofamid (CCIM, CCIM-AM and CTCA), the two terminal ones are CCIM and
CTCA. CCIM is expected to be the major terminal degradate in water
bodies with low biological activity because it forms as a result of
abiotic hydrolysis of the parent. In contrast, CTCA is expected to be
the major terminal degradate in biologically active soils and
water/sediment systems. Both CCIM and CTCA are stable to abiotic
hydrolysis and susceptible to leaching but only CCIM is highly
susceptible to biodegradation. Given these fate characteristics,
cyazofamid could potentially reach surface water via spray drift or
runoff under certain environmental conditions but the potential for it
to reach ground water is very low. CCIM and/or CTCA could potentially be
the terminal degradates in surface water bodies affected by spray drift
and/or runoff depending on the level of biological activity. However,
only CTCA has a high potential to contaminate groundwater due to its
high persistence and mobility. This assessment addresses exposure to
parent cyazofamid and its degradation products CCIM, CCIM-AM and CTCA.

Procedure for calculating EDWCs for cyazofamid and its degradates

Cyazofamid is a relatively new fungicide and no surface water monitoring
data are available.  For this reason, the Agency based this report on
simulated screening values using modeling.  The screening level surface
water and ground water estimates are calculated using tier 2 linked
PRZM/EXAMS models and the tier 1 SCI-GROW model, respectively.  It
should be noted that: 

(1) Water numbers for cyazofamid and its degradates were generated from
the models in which the Koc and aerobic soil half-life values used were
obtained from supplemental studies; 

(2) Solubility of the degradates were considered to be the same as
parent (0.107 ppm); 

(3) Direct photolysis half-life for the degradate CCIM was estimated
from its formation and decline curve in the aqueous direct photolysis
study of the parent (half-life= 31.52 days); 

(4) The degradates CCIM-AM and CTCA were considered to be stable to
direct photolysis in water as it was not identified in parent aqueous
direct photolysis and therefore, half-lives could not be calculated; and

(5) The initial residue levels for degradates used in the models were
based on molecular ratios; assuming time zero 100% conversion of parent
to a mixture of degradates based on weight adjusted maximums in fate
studies.  EFED acknowledges that this assumption is reasonable but
conservative. The calculated initial residue levels are presented in
Table 2.

Table 2 An example for calculating the initial residue levels used in
modeling (i.e. application rates)

Chemical	Molecular Weight *	Molecular Ratio	Determined Maximum (% Parent
Equivalent)	Example Application Rate** (lb a.i./Acre for carrot)

	Value	Adjusted Value	Fate Study Used

	Parent	324.79	1	100%	100%	Assumed	0.15612

CCIM	217.66	0.6702	83%	63%	Hydrolysis	0.0659

CCIM-AM	235.67	0.7256	17%	13%	Anaerobic Aquatic	0.0147

CTCA	236.66	0.7287	31%	24%	Aerobic Aquatic	0.0273

Total	131%	100%

CTCA	236.66	0.7287	100%	100%	Assumed	0.1138

* Molecular Weights for degradates of cyazofamid were calculated by
deduction of elements lost from parent structure.

** Rate for each degradates= Parent Rate x Molecular Ratio x adjusted
maximum found in fate studies; for example the rate for CCIM= 0.1562 x
0.6702 x 63% = 0.0659 lb a.i/A.

Based on the procedure explained by Table 2, application rates, model
runs and other parameters are calculated and included in Table 3. 

 

Table 3 Modeling parameters for cyazofamid and degradates

Scenario	Modeled Chemical	Max. Single Rate (kg/ha)*	Other parameters

First	Parent	0.1750	Maximum number of applications: 5

Minimum intervals: 14-day

Scenario: FL carrots, CA row crops, and South Texas Vegetables 

Application dates: January 14 for the CA scenario and September 14 for
the FL and S-TX scenarios**

Second	CCIM	0.0739

CCIM-AM	0.0165

CTCA	0.0306

	Third	CTCA	0.1275

	*    By multiplying label rates in lb/A by 1.121 for example: 
0.15612x1.121= 0.1750 kg/ha.

** These dates were chosen from maximums of multiple runs (13 runs each)
with varied application dates

Fate and transport input parameters are summarized in Table 4.

  SEQ CHAPTER \h \r 1 Table 4 Cyazofamid: PRZM/EXAMS input parameters
for modeling surface water EDWCs

Input Parameter	Chemical	Value	Reference

Molecular Weight (gram mole -1)	Parent	324.79	MRID 454090-38

	CCIM	217.66

CCIM-AM	235.67

CTCA	236.66

	Vapor Pressure (torr)	All	1.316x10-10	MRID 454090-38

Aerobic Soil Metabolism Half-life (days)	Parent	5.5	The 90th percentile
t½ from eight values for the parent and six values fore ach degradate
(MRIDs 454091 06/08/07/04/05).

	CCIM	2.2

CCIM-AM	13.6

CTCA	Stable

	Water column Half-life (days)

(Aerobic Aquatic Metabolism half-life)	Parent	16.4	The 90th percentile
t½ from four values for the parent (MRID 454091-10). For the
degradates: Considered stable as no significant hydrolysis at pH 7 as
per Guidance  (US EPA, 2002)

	CCIM	Stable

CCIM-AM

	CTCA

Benthic sediment Half-life (days) 

(Anaerobic Aquatic Metabolism half-life)	Parent	17.7	One half-life
value; 3x5.9=17.7 (MRID 454091-09)

	Both	Stable	No anaerobic metabolism data

Application Rate (Kg a.i./ha)	Refer to Table 3 (Efficiency= 0.99 for
ground spray)

Application Number (Method of application)	All; Refer to Table 4	Product
Label; with 14-day application intervals

Depth of Incorporation (cm)	All	5.08	CAM=4/soil application (Product
Label); degradate is expected to form, from parent in the top soil

Spray Drift (fraction)	All

6.4% default drift for Ground=G

Solubility (ppm)	All	0.107	MRID 454090-38

Koc (L Kg-1)	Parent	1,338	Parent: Average of eight values (MRID
454091-12). 

Degradates: Average of four values for each of degradates (MRID
454091-14). 

Koc model was determined to be appropriate.

	CCIM	753

CCIM-AM	2,397

CTCA	836

	Hydrolysis Half-life @ pH 7 (days)	Parent	11.9	Maximum value at pH 7
(MRID 454090-39) 

	CCIM	Stable	MRID 454091-01

	CCIM-AM

	CTCA

Direct Aqueous Photolysis Half-life(days)	Parent	0.02	Maximum dark
control corrected value (MRID 454091-02)

	CCIM	31.5

Degradates	Stable	No data



Results of PRZM/EXAMS modeling is summarized in Table 5 noting that an
87% was used for Percent Crop Area (PCA). 

Table 5 Summary of PRZM/EXAMS results (EDWCs in ppb)

Crop/Scenario	

Chemical	Peak	96 hr	21 Day	60 Day	90 Day	Yearly	All Years	Drift*

Carrots grown in CA (represented by CA 

Row

Crops) 	1st	

Parent	0.73428	0.53505	0.27927	0.18444	0.13311	0.03306	0.02697	29%

	2nd 	CCIM	1.65213	1.63908	1.58514	1.53207	1.49118	1.22583	1.07793	71%

CCIM-AM	0.41151	0.40803	0.40107	0.38715	0.37497	0.32451	0.27318

	CTCA	4.82589	4.82154	4.81284	4.80153	4.79544	4.76064	2.65437

3rd	CTCA	8.34678	8.27457	8.11623	7.94571	7.75692	6.4641	5.45664	26%

FL Carrots	1st	Parent	2.95017	1.9053	0.72123	0.38628	0.26796	0.06612
0.04176	6%

	2nd 	CCIM	1.49901	1.44159	1.29543	1.04052	0.85695	0.32451	0.21141	11%

CCIM-AM	0.42804	0.40542	0.35061	0.25926	0.22011	0.10179	0.07047

	CTCA	3.05457	2.90406	2.42991	1.86093	1.51032	0.67512	0.46632

3rd	CTCA	12.72549	12.09996	10.11984	7.74996	6.29358	2.81271	1.94445	5%

Carrots grown in TEXAS (represented by (South Texas Vegetables	1st
Parent	4.03767	2.55693	0.8265	0.35931	0.25752	0.06438	0.0348	9%

	2nd 	CCIM	1.61124	1.57818	1.4616	1.32501	1.2006	0.70992	0.4611	10%

CCIM-AM	0.55419	0.53157	0.44892	0.34017	0.28884	0.2001	0.14007

	CTCA	4.32651	4.22385	3.84888	3.21726	2.58303	1.57035	1.06836

3rd	CTCA	18.02466	17.60358	16.03845	13.40235	10.76103	6.54588	4.45266	5%

Maximums: 

Parent + CCIM + CCIM-AM	6.244	CTCA only	6.546	5.457

	* % of exposure resulting from drift (based on initial drift/peak
values from 1 in 10 years data. For degradates, % from drifted parent

For ground water, SCI-GROW program, a high exposure tier one model, was
used to arrive at the Estimated Drinking Water Concentration (EDWC) for
this chemical and its degradates from ground water sources.  Modeling
input/output values are summarized in Tables 6 and 7.

Table 6 Summary of inputs for SCI-GROW modeling for EDWCs from ground
water for cyazofamid/degradates

Parameter	Value* 	Reference (MRID Number)

Crop/ Seasonal No. of Applications	Soil Applied to Carrots	High Exposure
(maximum rate/number); Product label

Label Application Rate (lb a.i./acre)	1st Scenario: Parent	0.1561
Product label (lb a.i/A)

	2nd Scenario: CCIM	0.0659	

Calculated from molar ratios (lb a.i/A)

	CCIM-AM	0.0147

CTCA	0.0273

3rd Scenario: CTCA	0.1138

	Aerobic Soil Metabolism t½ (days)	Cyazofamid	4.7	Median of 8 values
(454091-06/08)

	CCIM	1.4	Median of 6 values (454091-07)

	CCIM-AM	8.3	Median of 6 values (454091-04)

	CTCA	10,000	Considered stable; half-life is >120 days (454091-05)

Koc (L Kg-1)	Cyazofamid	657	Lowest value (454091-12); variations >3 fold

	CCIM	690	

Median of 4 values for each degradate (454091-14)

	CCIM-AM	2,124

CTCA	708

	* Fate data values are as per Guidance for Selecting Input Parameters
in Modeling the Environmental Fate and Transport of Pesticides; Version
II February 28, 2002.

Table 7 Summary of outputs from SCI-GROW modeling for EDWCs from ground
water for cyazofamid/degradates (ppb).

Parameter	Value* 	Reference (MRID Number)

EDWC for ground water screening			1st Scenario: Parent	0.0029	Output for
one Model Run

	2nd Scenario: CCIM	0.0002	

Outputs for three Model Runs

	CCIM-AM	0.0007

CTCA	0.1310

3rd Scenario: CTCA	0.5450	Output for one Model Run

It is important to note that modeling for EDWCs from surface and ground
water is performed using maximum application rate/frequency and minimum
intervals which allow establishing first level values suitable for
screening purposes. They may be referred to as likely upper bound values
due to the use of the chemical at the maximum application rate and
additional refinements can be developed should they be needed. 

Uncertainties

EDWCs for cyazofamid and degradates were estimated for drinking water
based on half-lives calculated from supplemental aerobic soil and
aerobic/anaerobic water/sediment laboratory fate studies. In these
studies, suspected lack of extraction may have underestimated the
half-lives of cyazofamid and degradates possibly resulting in lower
model estimates for the EDWCs. In this respect, it is noted that major
identified degradates (CCIM, CCIM-AM and CTCA) may not constitute a
significant part of the late accumulated un-characterized bound residue
(due to the apparent adequate extraction of these degradates); however,
a degree of uncertainty exists in such estimates until new studies with
proven extraction procedures are submitted. No data were submitted by
the registrant suggested that attempts were made to extract or analyze
significant soil or sediment bound radioactivity. Complete
characterization of the fate of cyazofamid requires data to prove that
no parent or degradate was left as part of the bound residue and to
characterize various other components that may be present.  As a result,
EFED is requiring additional fate information/data be submitted to
assess the impact of these residues on the environment.

In this Memo, the acute values were obtained from summation of EECs of
three runs: Parent alone, CCIM degradate, and CCIM-AM degradate. This
means that resultant EDWCs are expected to be conservative because of
nearly double counting of the application rate (full rate for parent +
equivalent rates for CCIM and CCIM-AM). On the other hand, chronic
values were obtained from EECs for the terminal degradate which was
considered to be stable in all of its fate parameters.  Therefore, the
resultant EDWCs are expected to be highly conservative. 

Degradates CCTS, HTID, CDTS and p-Toluamide were found as major
degradates only in aqueous direct photolysis.  Significant amounts of
CCIM and CCTS form early (within a day), peak and show clear decline
while HTID, CDTS and p-Toluamide form/peak late (within days) and show
only slight or no decline under the conditions of the direct photolysis
experiment. Persistent degradates HTID, CDTS and p-Toluamide is
therefore not expected to be important components in natural aquatic
systems because of their late formation.  Previously, the Metabolism
Assessment Review Committee (MARC) determined that none of these
degradates will be more toxic than the parent.  In addition, based on
the use pattern, and the nature of parent, aqueous direct photolysis may
not be a major route of degradation in most natural environments.    SEQ
CHAPTER \h \r 1  Although the MARC recommended to exclude these
degradates from drinking water assessment, EFED will ask the
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