11

UNITED STATES ENVIRONMENTAL PROTECTION 

AGENCY

WASHINGTON D.C., 20460

OFFICE OF 

PREVENTION, PESTICIDES AND 

TOXIC SUBSTANCES

PC Code: 121301 

Chemical: Cyromazine 

DP Barcode: D358724 

July 6, 2009 

Drinking Water Assessment

SUBJECT: Drinking Water Assessment for New Use of Cyromazine (Trigard 75WP (75% 

ai)) on Succulent Beans. 

TO: Daniel Rosenblatt, Risk Manager, RM05 

 Susan Stanton, Risk Manager Reviewer 

Insecticide Branch 

 Registration Division (7505C) 

FROM: James K. Wolf, Environmental Scientist 

Environmental Risk Branch 3 

 Mark Corbin, Senior Scientist 

Environmental Risk Branch 3 

Dana Spatz, Branch Chief 

Environmental Risk Branch 3 

Environmental Fate and Effects Division (7507C) 

The Environmental Fate and Effects Division (EFED) was requested to prepare a drinking water 

assessment, as part of a Tolerance Petition (8E7470), for a new use of the insecticide 

cyromazine. The proposed new use [Labels [Supplemental 654A-S2-0508 and Technical SCP 

632-L (draft use)] is to control leafminers on succulent beans1

. Cyromazine is the active 

ingredient (ai) in Trigard® Insecticide (75 WP) [EPA Reg. No. 100-654]. The proposed 

maximum application rate for this use is 0.125 lb ai/acre, with a maximum number of 6 

applications per crop of succulent beans and a minimum reapplication interval of 7 days. The 

season total is 0.75 lb ai/acre. (Appendix 2, Table 1). 

 

1

 Includes only: Bean (Phaseolus spp.) succulent broad bean, green lima bean, runner bean, snap bean (green 

bean), and wax bean; and Bean (Vigna spp.) asparagus bean, black-eyed pea, Chinese longbean, cowpea, 

jackbean, moth bean, southern pea, and yardlong bean. 
2

The Supplemental Label for EPA Reg. No. 100-654 (SCP 654A-S2 0508) and the Technical 

Label 100-632 (SCP 632A-L (draft use) contain contradictory information. Page 2 of the 

Supplemental Label indicates that cowpeas are included in the new use, whereas Page 5 of the 

Technical Label excludes cowpeas. This discrepancy should be clarified. 

Previously, EFED prepared a Tier 1 Drinking Water Assessment for the use of cyromazine on 

potatoes (D324410 – Appendix 1).The EFED Tier 1 surface water (FIRST) and ground water 

(SCI-GROW) models were used. Two application rates were considered in that drinking water 

assessment, 6 applications @ 0.125 lb ai/acre and 3 applications @ 0.25 lb ai/acre, both with 7-

day reapplication intervals. Therefore, the rate proposed for succulent beans was previously 

assessed (Appendix 1). Three estimates (150, 178, and 450 days) of aerobic soil metabolism 

(ASM) rates were also previously used. It was shown previously that the half-live value selected 

for ASM had little effect on the EDWC estimated with the FIRST model (Appendix 1, Table 1). 

The recommended EDWCs were based upon the 450 days ASM half-life (assumed a single value 

times 3). Since the last drinking water assessment the submitted environmental fate studies have 

been reviewed to ensure that these data when used for model inputs following current EFED 

guidelines (USEPA, 2002). Additionally, aerobic and anaerobic soil metabolism studies, which 

are being reviewed, are also considered in this assessment. The values used for modeling inputs 

were adjusted (compare Tables 3 and Appendix 1, Table 3) to take into account addition 

information and updated guidance. 

The estimated drinking water concentrations (EDWCs) of cyromazine for the proposed succulent 

bean use (Table 1) is 47.1 and 15.8 μg/L, for the peak (acute) and annual (chronic and cancer), 

respectively. The EDWCs from the previous assessment (D324410) were 43.9 and 17.8 μg/L. 

Therefore, the EDWCs for the proposed new use are slightly higher for the acute exposure 

concentration and slightly less the chronic than those from the prior assessment. The increased 

acute concentration is due the use of a lower Kads value (i.e., lowest non sand). The lower chronic 

exposure concentration is due to a decrease in the aerobic soil metabolism half-life (T1⁄2 ~147.38 

days) and the addition of a default (2 times aerobic soil metabolism) value for the aerobic aquatic 

metabolism rate (T1⁄2 ~ 294.76 days) rather than assuming no aquatic metabolism. The primary 

degradation product of cyromazine is melamine. The Health Effects Division has determined that 

exposure to melamine derived from cyromazine does not exceed the Agencies Level of Concern 

(FR Vol. 64, No. 178, 09-15-99, 50043). 
3

Table 1. Estimated Drinking Water Concentrations (EDWC) of cyromazine residues for 

succulent beans using the Tier 1 FIRST applied as 6 applications at (0.125 lb ai/ac) rates, and 

a seasonal rate of 0.75 lb ai/acre. The concentrations have been adjusted with the Percent 

Crop Area (PCA) of 0.87 for a national assessment. 

 1-in-10 year Cyromazine Concentration 

Application rate/# number/interval 

(lbs ai/ac/#/days) 

Peak 

(μg/L) 

Annual Mean 

(μg/L) 

0.125/6/7/1 47.1 15.8 

It was previously noted that (D324410) the selection of an aerobic soil metabolism rate had a 

greater influence on the cyromazine concentrations in ground water as estimated by SCI-GROW. 

The estimated ground water concentration ranged from 5.35 to 26.6 μg/L (Appendix 1, Table 2), 

depending on half-life used. EFED had recommended that 6.9 μg/L be used as ground water 

concentration of cyromazine for human health risk assessment, which corresponded to the 178 

day half-life. 

EFED recommends that for this new use is that 1.1 μg/l (Table 2.) be used for acute and chronic 

exposure concentrations of cyromazine in ground water which considers the additional fate 

information (Koc = 99.6 mL/goc and mean ASM half-life of 104 days. The SCI-GROW runs are 

listed in the Appendix 3. 

Table 2. SCI-GROW estimates of cyromazine concentrations in ground water. 

Application rate/# number/interval 

(lbs ai/acre/number/days) 

Concentration 

(μg/L) 

0.125/6/7 1.1 

Physical/Chemical Properties

Several physical and chemical properties of cyromazine are given below. The chemical structure 

is shown in Figure 1. 

Chemical name: N-cyclopropyl-1,3,5-triazine-2,4,6-triamine 

Common name: Cyromazine 

CAS #: 66215-27-8 

Chemical Number: 121301 

Empirical Formula: C6H10N6

Molecular Weight: 166.19 

Solubility in Water: 11600 mg/L at 25°C 

Vapor Pressure: 1.13 x 10-9 mm Hg at 20°C 
4

Figure 1. Cyromazine Structure 

Environmental Fate and Transport Characterization

Based on previously submitted data, cyromazine is stable to hydrolysis and photolysis, and is 

persistent in aerobic soil (T1⁄2 > 60 days). This was confirmed in the field studies, where 

dissipation half-lives are as long as 250 days. Freundlich adsorption coefficients (Kads) for the 

mineral soils are less than 5 mL/g, and for the organic soil the Kads value was 17 mL/g. The Kads

values are not equal to Kd, because the slope (1/n) in the adsorption isotherm was less than 1 

(0.77 to 0.85). The logarithms (1.6 to 2.3) of the Koc values are generally less than 2, which falls 

into the “Mobile” category as described by the EFED Standardized Soil Mobility Classification 

Guidance (Bradbury, 2006). Cyromazine is also highly soluble (1.16 x 104 mg/L). These 

characteristics would suggest that cyromazine has the potential to leach through soils, especially 

sand, fine sands, and loamy sands, or to be transported in solution in runoff water. 

Melamine was identified as the primary cyromazine degradate. In aerobic metabolism studies the 

melamine levels ranged between 33 and 60 percent of the parent (as applied radioactivity). The 

persistence (T1⁄2), adsorption (Kd), and dissipation rate of melamine have not been specified, but 

in terrestrial field studies, melamine is shown to be more persistent and mobile than the parent, 

and may accumulate in soil with repeated uses. Two other degradates were also noted, but not 

identified. 

Modeling Inputs 

The FIRST and SCI-GROW models were used to estimate surface water and ground water 

drinking water concentrations, respectively. The aerobic soil [mineral soil] metabolism half-life 

(t1⁄2) was 142 days for a sandy loam and 107 days for a muck soil (157458, 479168-002), and 62 

days for a sandy loam (437679-01). Combining the half-life values by following EFED Input 

Guidance, the 90th percent upper bound on the mean aerobic soil metabolism (ASM) half-life for 

the three soils is 147.38 days. Because no aerobic aquatic metabolism half-life (AAqM) studies 

were submitted by the Registrant, the AAqM was estimated as 2 times the ASM half-life as 

recommended in EFED Input Guidance Document (USEPA, 2002). The lowest non-sand (2.37 

mL/g) was used for the mobility input value. Freundlich Kads for mineral soils were less (0.52 to 

3.87) than 5 mL/g, for a muck soil the Kads was 17 mL/g). The sorption for the organic soil 

(muck) was not considered because succulent beans are not generally grown on organic soils. 

The lowest non sand Kads (2.37 mL/g) was used for surface water (FIRST) and the mean Koc 
5

(99.6 mL/goc) was used for ground water (SCI-GROW), following EFED Model Input Parameter 

Guidance (USEPA, 2002).

Selected physical/chemical and environmental fate properties for cyromazine are summarized in 

Table 3. 

1

 The 90th percent upper bound of mean of 107, 142, and 62 days is 147.38 days. 2

 Aerobic Soil Metabolism half-life times 2, per EFED guidance (USEPA. 2002). 3

 Kads 0.52 (sand), 2.37 (sandy clay loam) and 3.87 (silt loam), (not included - organic soil Kads =17.0; Koc = 128) 4

 Koc model appears valid 

Table 3. Select Physical, Chemical, and Environment Properties and model input value for 

Cyromazine. 

Parameter Range Value Used Source 

Solubility in Water 1.16 x 104

 mg/L @ 25oC MRID 437679-01 

pKa (weak base) 5.22 @ 20oC Not used in FIRST or SCIGROW MRID 103148 

Hydrolysis T1/2 Stable at pH 5, 7, and 9 0 day MRID 103148 

Aquatic Photolysis T1/2 Stable in water at pH 7 0 day MRID 103149 

Aerobic Soil Metabolism 

(ASM) T1/2

142 days (sandy loam) 

104 days (sand-muck) 

62 days (sandy loam) 

147.381 days 

mean = 103.67, std = 40.10 

MRIDs 157458, 

470168-02, 

437679-01 (in review). 

Anaerobic Soil Metabolism 

T1/2

97.6 days Not used 437679-02 (in review). 

Aerobic Aquatic Metabolism 

(AAqM) T1/2

no data (estimated as 2 

times ASM) 

294.762

 days 

(147.38 x 2) 

USEPA, 2002 

Kads 0.52, 2.37, 3.873 mL/g lowest non sand = 2.37 MRIDs 103139, 103150, 

103165 

Koc 40, 73, 185 mL/g4 Lowest none sand = 73 

Mean = 99.6 mL/g 

MRIDs 103139, 103150, 

103165 
6

Citations: 

U.S. EPA. 2006. Drinking Water Assessment; New Use Rate for Trigard 75WP (75% ai) on 

potatoes. DP Barcode D324410 [Date: 06-20-06]. United States Environmental 

Protection Agency. Office of Pesticide Programs. Environmental Fate and Effects 

Division. Arlington, VA. 

U.S. EPA. 2002. Guidance for Selecting Input Parameters in Modeling the Environmental Fate 

and Transport of Pesticides. Version 2. U.S. Environmental Protection Agency. Office of 

Pesticide Programs. Environmental Fate and Effects Division, Arlington, VA. 

cc:/Rebecca Daiss,RRB4/HED, 7509P
7

Appendix 1. Previous Tier 1 Drinking Water Assessment for Potatoes (D324410)

Note: The CAS # 131860-33-8 was incorrect in the original document D324410, dated June 

20, 2006. The correct CAS # is 66215-27-8.

UNITED STATES ENVIRONMENTAL PROTECTION 

AGENCY

WASHINGTON D.C., 20460

OFFICE OF 

PREVENTION, PESTICIDES AND 

TOXIC SUBSTANCES

PC Code: 121301 

DP Barcode: D324410 

June 20, 2006 

Drinking Water Assessment

SUBJECT: New Use Rate for Trigard 75WP (75% ai) on potatoes. 

FROM: James K. Wolf, Environmental Scientist 

Environmental Risk Branch 3 

THRU: Mary Frankenberry, Senior Scientist 

Environmental Risk Branch 3 

Daniel Rieder, Branch Chief 

Environmental Risk Branch 3 

Environmental Fate and Effects Division (7507C) 

TO: George Larocca, RM13 

 Insecticide Branch 

 Registration Division (7505C) 

The Environmental Fate and Effects Division (EFED) has been requested to prepare a 

drinking water assessment for cyromazine for a new use rate of Trigard (75 WP) to control 

Colorado potato beetles (DP 324410) on potatoes. The EFED Tier 1 surface water (FIRST) and 

ground water (SCI-GROW) models were used in this assessment. The Registration Division also 

inquired whether additional ground water monitoring and mobility data were needed. 

 The registrant has requested, in this action (D324410), an alternative cyromazine 

(Trigard 75W) application schedule for the potato use. The proposed alternative is for a 
8

maximum of 3 applications per season at a rate of 0.25 lbs ai/acre per season to control the 

Colorado potato beetle. The reapplication interval is 7 to 14 days. Previously, EFED estimated 

drinking water concentrations (EDWCs) for a number of crops, including potatoes. Cyromazine 

was applied six times at maximum application rate of 0.125 lbs ai/acre, with a 7 day 

reapplication interval (D271623, D236191). The total for both rates is 0.75 lbs ai/acre. 

 The EDWCs for the potato use, with the proposed new application rate, is given in 

Table 1. The recommended peak concentration is 43.3 μg/L and the long term average is 17.8 

μg/L as this represent the most conservative concentrations for the peak concentration. The 

reduction in the number of applications (6 to 3) with the corresponding increased application rate 

(0.125 to 0.25 lbs ai/acre) had (Table 1) a limited influence on the initial concentration (peak). 

A range (150 to 450 days) of aerobic soil metabolism rate values was considered because 

there was some uncertainty associated with preparing the aerobic soil metabolism rate data as an 

input to the EFED screening models. This discussed in detail in the Environmental Fate 

Properties. The aerobic soil metabolism half-life had a small influenced on the peak cyromazine 

concentration. Aerobic soil metabolism has no effect on the estimated cyromazine 

concentrations once in the surface water (annual mean) body. The EDWCs for existing rate 

(0.125 lb ai/ac and 6 applications) are shown for comparison. The FIRST runs are provided in 

the Appendix. 

Table 1. Estimated Drinking Water Concentrations (EDWC) of cyromazine residues for 

potatoes using the Tier 1 FIRST model with three half-lives (150, 178, 450 day) and applied as 

3 applications (0.25 lbs ai/ac) or 6 applications at (0.125 lb ai/ac) rates, and a seasonal rate of 

0.75 lb ai/ac. The concentrations have been adjusted with the Percent Crop Area (PCA) of 

0.87 for a national assessment. The bold values represent the recommended EDWCs to be 

used in the drinking water assessment. 

 1-in-10 year Cyromazine Concentration 

Application rate/# number/interval/asm1

(lbs ai/ac/#/days/days) 

Peak 

(μg/L) 

Annual Mean 

(μg/L) 

0.250/3/7/150 42.8 17.3 

0.125/6/7/150 41.0 16.6 

0.250/3/7/178 43.1 17.4 

0.250/3/7/450 43.9 17.8 

0.125/6/7/450 43.3 17.5 1

 asm is aerobic soil metabolism half-life in days.

. 

 The selection of an aerobic soil metabolism rate had a greater influence on the 

cyromazine concentrations in ground water as estimated by SCI-GROW. The estimated ground 

water concentrations ranged from 5.35 to 26.6 μg/L (Table 2) for the 150 and 450 day half-life, 

respectively. Previous assessments used the 150 day half-life for ground water. EFED 

recommends that 6.9 μg/L be used as ground water concentration of cyromazine for human 

health risk assessment, which corresponds to the 178 day half-life. The SCI-GROW runs are 
9 

listed in the APPENDIX. 

Table 2. SCI-GROW estimates of cyromazine concentrations in ground water. 

Application rate/# number/interval/asm2

(lbs ai/acre/number/days/days) 

Concentration 

(μg/L) 

0.250/3/7/150 5.3 

0.0250/3/7/178 6.9 

0.125/6/7/450 26.6 

The bold value is the recommended EDWCs to be used in the drinking water assessment.

 

 

In addition to the preparing the water assessment for proposed new uses, the Registration 

Division (RD) included several specific (D324410) questions for EFED concerning monitoring 

and need for additional mobility data: 

1) Will additional ground water monitoring and ecological effects data be required to add 

potatoes to the label? Does the risk mitigation (label language) overcome the need for the 

ground water study? 

 

EFED recommends that the monitoring study (prospective ground water monitoring or ground 

water well monitoring or surface water monitoring) be placed in reserve. The concentrations 

necessary to reach HED’s level of concern are unlikely, for the currently registered crops. The 

label language about the potential to contaminate ground water should remain. 

There is no ecological effects data required at this time. 

2) The mobility data for the degradate melamine has not been submitted. Is it still needed? 

 It is also recommended that the requirement for the registrant to provide mobility data on 

melamine degradate be placed in reserved. This recommendation is made because toxicity is not 

a concern at this time. 

Environmental Fate and Transport Characterization 

Physical/Chemical Properties

Chemical name: N-cyclopropyl-1,3,5-triazine-2,4,6-triamine 

Common name: Cyromazine 

CAS #: 131860-33-8 

Empirical Formula: C6H10N6

Molecular Weight: 166.19 
10

Solubility in Water: 1100 mg/L at 20°C (pH 7.5) 

Vapor Pressure: 3.36 x 10-9 mm Hg at 20°C 

Chemical Number: 121301 

Environmental Fate Assessment

Based on previously submitted data, cyromazine is stable to hydrolysis and photolysis, and 

is quite persistent in aerobic soil (t1⁄2 ≈150 days or more). This was confirmed in the field studies, 

where dissipation half-lives were more than 250 days. Under anaerobic conditions cyromazine 

may be more persistent. Soil adsorption coefficients are generally low with Freundlich 

adsorption coefficients (Kf-ads) less than 20. Cyromazine is also highly soluble (1.36 x 105

mg/L). This would suggest that cyromazine has the potential to leach through soils, especially 

sand, fine sands, and loamy sands, or to be transported in solution in runoff water. Melamine 

was identified as the primary cyromazine degradate. The persistence (t1⁄2), adsorption (Kd), and 

dissipation rate of melamine have not been specified, but in terrestrial field studies, melamine is 

shown to be more persistent and mobile than the parent, and may accumulate in soil with 

repeated uses. Two other degradates were also noted, but not identified. 

Environmental Fate Properties

Selected physical/chemical and environmental fate properties for cyromazine are 

summarized in Table 3. Cyromazine is stable to hydrolysis and photolysis. 

Cyromazine is persistent in soil. The aerobic soil [mineral soil] metabolism half-life 

(t1⁄2) was 142 days for a sandy loam and 107 days for a muck soil (EFGWB #90679, 1990). It is 

unclear whether it is valid to combine results of a mineral soil (sandy loam) with an organic soil 

(muck). Combining the half-life values by following EFED Input Guidance, the 90th percent 

upper bound on the mean aerobic soil metabolism half-life for the two soils is 178.3 days. 

Earlier EFED assessments used the 150 day half-life, which was based upon information 

available at that time. When only one aerobic metabolism half-life is available, it should be 

multiplied by 3 [3 x 150 = 450 days; EFED Input Guidance]. The 178.3 day upper bound of the 

mean falls within the range of half-lives used in this assessment 150 to 450. For this assessment, 

the half-life of 450 days was used for to estimate cyromazine in surface water. Guidance for the 

SCI-GROW recommends using the average half-life value as an input parameter. EFED 

believes that the 178 day half-life value would be a better estimate of the mean than 450 days. 

Because the FIRST model simulates a rainfall event two days after the last application, 

thus, it is not very sensitive to a long half-life. The aerobic soil metabolism has essentially no 

influence on the estimated surface water concentrations when the half-life value is long. Under 

anaerobic conditions it may even be more persistent (Cargile, 1986). Field dissipation half-lives 

are variable, ranging from 75 days to more than 250 days. (Cargile, 1986; after CDPR, 1993). 

The half-life selected showed more of a difference in SCI-GROW (Table 2) as estimates 5.3 and 

26.6 μg/L when the half-life is 150 or 450 days, respectively. When the half-life is assumed to 

be 178 days, the estimated ground water concentration is 6.9 μg/L. 
11

 Soil adsorption coefficients are generally quite low, with Freundlich adsorption 

coefficients (Kads) less than 20. The Kads values are not equal to Kd, because the slope (1/n) in 

the adsorption isotherm was less than 1 (0.77 to 0.85). The logarithm of the Kocs are generally 

less than 2, which falls into the “Mobile” category as described by the EFED Standardized Soil 

Mobility Classification Guidance (Bradbury, 2006). 

1

 The 90th percent upper bound of mean of 107 and 142 days is 178.3 days. 2

 The 150 days represents half-life information previously used. 

3 The EFED Guidance recommends multiply a single aerobic soil metabolism half-life value by 3. 4

 Kads 0.52 (sand), 2.37 (sand), 3.87 (silt loam), 17 (clay loam) 

 

Melamine is identified as the primary cyromazine degradate. Aerobic metabolism 

studies indicated that melamine levels could be as much 33 percent of the parent. Two other 

degradates were also noted. 

Based on the above environmental fate information, EFED concluded that under certain 

conditions (e.g., sandy soils) cyromazine is both mobile and persistent, and has potential to move 

in soil or be transported off site in runoff water. 

Table 3. Select Physical, Chemical, and Environment Properties and model input value for 

Cyromazine. 

Parameter Range Value Used Source 

Solubility (water) 

(technical) 

1.36 x 105 mg/L 

1.16 x 104 mg/L 

1.36 x 105 mg/L @ 25° C EFED One-Liner 

Database (12/2/94) 

pKa (weak base) 5.22 

Hydrolysis t1/2 Stable at pH 5, 7, and 9 0 day EFED One-Liner 

Database (12/2/94) 

Aquatic Photolysis t1/2 Stable in water at pH 7 0 day EFED One-Liner 

Database (12/2/94) 

Aerobic Soil Metabolism 

t1/2 

~150 days 178.31 days 

1502

 days 

150 x 3 = 450 days3

(EFED Guidance) 

EFED One-Liner 

Database (12/2/94) 

Anaerobic Soil Metabolism 

t1/2 no data not considered 

Aerobic Aquatic 

Metabolism t1/2 no data not considered 

Kads 0.52 – 174 (5.94) mL/g see Koc values 

lowest non sand = 3.9 

EFED One-Liner 

Database (12/2/94) 

Koc 

Log(Koc) 

40 – 127 (106) mL/g 

[40, 73, 185, 127] 

106 mL/g ( Koc model 

appears valid) 

1.6 to 2.1 (2.06) 

1 to 2 = mobile in 

Standardized Soil 

Mobility 

Lowest none sand = 40 EFED One-Liner 

Database (12/2/94) 

Mobility Classification 

Guidance, April 18, 

2006 
12

GROUND WATER MONITORING DATA 

Prospective Ground Water Monitoring Study 

 The registrant conducted a small-scale prospective ground-water monitoring study on 

tomatoes in Florida (D178192, D199290). This study was conducted where leaching was 

unlikely due to a high water table and high evapotranspiration. There were no cyromazine 

residues detected in ground water during this study. Low levels of melamine were found in 

ground water, after irrigation was discontinued. The agronomic practices used at this study site 

resulted in applied irrigation water running off the treated field. The runoff water from the 

treated field was not assessed for cyromazine residues. The cyromazine degradate melamine was 

detected at levels ranging from 0.10 to 0.21 μg/L in shallow ground water at the study site in 

Florida. The overall study results and conclusions were limited, due to the fact that the study 

was conducted at one site and reflects only the conditions of the one site. 

 There were no reported detections of cyromazine residues in ground water at the time that 

the Pesticides in Ground Water Data Base was published, in 1992 (USEPA, 1992). This may be 

because very few ground-water samples have been analyzed for cyromazine (and melamine) 

residues in the United States and because it has limited usage areas and crops. Cyromazine and 

melamine were not included in the suite of analyses conducted in the USEPA's National Survey 

of Pesticides in Drinking Water Wells (USEPA, 1990, 1992). Cyromazine and melamine are 

also not included in the USGS NAQWA program. No surface water monitoring was located. 

Previous Recommendations 

Several specific recommendations were previously made (D199290) (two are cited below): 

 

1) The registrant should conduct one or more well-water monitoring surveys in a 

cyromazine use area, such as lettuce and celery rather than retrospective studies as previously 

stated in earlier reviews (memos C. Eiden, 7/26/89; Hutton, 1/4/90). The registrant could also 

consider conducting a prospective study in a use area in AZ, CA, or TX. 

2) The potential for surface water contamination should be addressed by the registrant 

through surface water monitoring 

3) The registrant should provide mobility data for the cyromazine degradate melamine. 

Status of Previous Recommendations 

 It is recommended that the above monitoring studies and the requirement for the 

registrant to provide mobility data on melamine degradate be reserved. This latter 

recommendation is made because toxicity is not currently a concern. The label language about 

the potential to contaminate ground water should remain. 
13

Citations 

Cargile, N. 1986. Aerobic and Anaerobic soil metabolism of CGA-72662 (cyromazine). 

CDPR, 1993. Cyromazine (Larvadex), Risk Characterization Document. Department of 

Pesticide Regulation, California Environmental Protection Agency. 3-24, 1993 

USEPA. 1989. National Survey of Pesticides in Drinking Water Wells (the National Pesticide 

Survey or NPS). Environmental Protection Agency, Washington D.C. 

USEPA. 1992. Pesticides in Ground Water Database. A compilation of monitoring studies: 

1971 -1991 National Summary. EPA 734-12-92-001. U. S. Environmental Protection Agency: 

Arlington, VA. 

USEPA. 1990, National survey of pesticides in drinking water wells: Phase 1 report. EPA 570/9-

90-015. U.S. Environmental Protection Agency. Washington, DC. 

USEPA, 1992. Another look: national survey of pesticides in drinking water wells - Phase 2 

report. EPA 570/9-91-020 

cc:/ Paula Deschamp/HED/REB3/7509C 

Demson Fuller SRRD/RRB1/ 7508C 
14

Appendix 2, Table 1. Calculation of application rates. 

Application Product AI (active 

ingredient) 

Max # Seasonal Total 

oz/acre lbs/acre1 % lbs ai/acre Appl. lbs ai/acre/season 

2.66 0.16625 75.0 0.1252 6 0.753

1

 oz/acre * 0.0625 lb/oz = lbs/acre 

2

 lbs ai/acre = lbs/acre * (75/100) 

3

 lbs ai/acre/season = lbs ai/acre * Max # Appl. 
15

Appendix 3. 

FIRST OUTPUTS

 RUN No. 1 FOR Cyromazine ON succulent * INPUT VALUES * 

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

 RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP 

 ONE(MULT) INTERVAL Kd (PPM ) (%DRIFT) AREA (IN) 

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

 .125( .692) 6 7 2.411600.0 AERIAL(16.0) 87.0 .0 

 FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) 

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

 METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED 

 (FIELD) RAIN/RUNOFF (RESERVOIR) (RES.-EFF) (RESER.) (RESER.) 

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

 147.38 2 N/A .00- .00 294.80 294.80 

 UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.0 JAN 1, 2007 

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

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC) 

 CONCENTRATION CONCENTRATION 

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

 47.100 15.745 

 RUN No. 2 FOR cyromazine ON succulent * INPUT VALUES * 

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

 RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP 

 ONE(MULT) INTERVAL Kd (PPM ) (%DRIFT) AREA (IN) 

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

 .125( .692) 6 7 2.411600.0 AERIAL(16.0) 87.0 .0 

 FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) 

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

 METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED 

 (FIELD) RAIN/RUNOFF (RESERVOIR) (RES.-EFF) (RESER.) (RESER.) 

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

 147.38 2 N/A .00- .00 .00 .00 

 UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.0 JAN 1, 2007 

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

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC) 

 CONCENTRATION CONCENTRATION 

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

 47.290 22.889 
16

SCI-GROW OUTPUT 

 SCIGROW 

 VERSION 2.3 

 ENVIRONMENTAL FATE AND EFFECTS DIVISION 

 OFFICE OF PESTICIDE PROGRAMS 

 U.S. ENVIRONMENTAL PROTECTION AGENCY 

 SCREENING MODEL 

 FOR AQUATIC PESTICIDE EXPOSURE 

 

 SciGrow version 2.3 

 chemical:cyromazine (new fate) 

 time is 7/ 1/2009 14:24:22 

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

 Application Number of Total Use Koc Soil Aerobic 

 rate (lb/acre) applications (lb/acre/yr) (ml/g) metabolism (days) 

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

 0.125 6.0 0.750 9.96E+01 103.7 

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

 groundwater screening cond (ppb) = 1.10E+00 

 ************************************************************************ 

 

 SciGrow version 2.3 

 chemical:cyromazine (new fate) 

 time is 7/ 1/2009 14:24:42 

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

 Application Number of Total Use Koc Soil Aerobic 

 rate (lb/acre) applications (lb/acre/yr) (ml/g) metabolism (days) 

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

 0.125 6.0 0.750 9.96E+01 147.4 

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

 groundwater screening cond (ppb) = 1.72E+00 

 ************************************************************************ 

 
17

Previous Assessment (D324410) 

FIRST 

SURFACE WATER 

RUN No. 1 FOR cyromazine ON potato * INPUT VALUES * 

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

 RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP 

 ONE(MULT) INTERVAL Kd (PPM ) (%DRIFT) AREA (IN) 

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

 .125( .730) 6 7 3.9 1.36e5 AERIAL(16.0) 87.0 .0 

 FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) 

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

 METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED 

 (FIELD) RAIN/RUNOFF (RESERVOIR) (RES.-EFF) (RESER.) (RESER.) 

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

 450.00 2 N/A .00- .00 .00 .00 

 UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.0 DEC 12, 2005 

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

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC) 

 CONCENTRATION CONCENTRATION 

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

 43.269 17.516 

 RUN No. 2 FOR cyromazine ON potato * INPUT VALUES * 

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

 RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP 

 ONE(MULT) INTERVAL Kd (PPM ) (%DRIFT) AREA (IN) 

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

 .250( .742) 3 7 3.9 1.36e5 AERIAL(16.0) 87.0 .0 

 FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) 

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

 METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED 

 (FIELD) RAIN/RUNOFF (RESERVOIR) (RES.-EFF) (RESER.) (RESER.) 

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

 450.00 2 N/A .00- .00 .00 .00 

 UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.0 DEC 12, 2005 

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

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC) 

 CONCENTRATION CONCENTRATION 

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

 43.903 17.765 
18

 RUN No. 1 FOR cyromazine ON potato * INPUT VALUES * 

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

 RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP 

 ONE(MULT) INTERVAL Kd (PPM ) (%DRIFT) AREA (IN) 

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

 .250( .726) 3 7 3.9******* AERIAL(16.0) 87.0 .0 

 FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) 

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

 METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED 

 (FIELD) RAIN/RUNOFF (RESERVOIR) (RES.-EFF) (RESER.) (RESER.) 

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

 150.00 2 N/A .00- .00 .00 .00 

 UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.0 DEC 12, 2005 

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

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC) 

 CONCENTRATION CONCENTRATION 

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

 42.825 17.342 

 RUN No. 2 FOR cyromazine ON potato * INPUT VALUES * 

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

 RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP 

 ONE(MULT) INTERVAL Kd (PPM ) (%DRIFT) AREA (IN) 

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

 .125( .693) 6 7 3.9******* AERIAL(16.0) 87.0 .0 

 FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) 

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

 METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED 

 (FIELD) RAIN/RUNOFF (RESERVOIR) (RES.-EFF) (RESER.) (RESER.) 

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

 150.00 2 N/A .00- .00 .00 .00 

 UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.0 DEC 12, 2005 

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

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC) 

 CONCENTRATION CONCENTRATION 

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

 41.031 16.639 

 
19

RUN No. 1 FOR cyromazine ON potato * INPUT VALUES * 

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

 RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP 

 ONE(MULT) INTERVAL Kd (PPM ) (%DRIFT) AREA (IN) 

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

 .250( .730) 3 7 3.9******* AERIAL(16.0) 87.0 .0 

 FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) 

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

 METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED 

 (FIELD) RAIN/RUNOFF (RESERVOIR) (RES.-EFF) (RESER.) (RESER.) 

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

 178.00 2 N/A .00- .00 .00 .00 

 UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.0 DEC 12, 2005 

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

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC) 

 CONCENTRATION CONCENTRATION 

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

 43.076 17.440