Basic Uncertainties

Numerous uncertainties in the aquatic modeling and ecological toxicity data may impact risk 

conclusions for listed and non-listed species. For example, registered labels for hydrogen 

cyanamide products include language requiring a 900 ft buffer between the site of application 

and “the mean high water mark for intertidal areas, surface waters, rivers, streams, or their 

flowing tributaries” to limit the potential for exposure of hydrogen cyanamide to aquatic 

environments. While aquatic estimated environmental concentrations (EECs) were modeled 

using a 900 ft buffer for spray drift, the Agency does not currently have a method for modeling 

the impact of a buffer on run-off. Therefore, EECs are primarily driven by the modeled run-off, 

which assumes no buffer between the site of application and the water body. Given the rapid 

degradation of hydrogen cyanamide in soil (aerobic soil half-life of 12 hours in sandy loam soil),

this is a major source of uncertainty in the aquatic exposure and subsequent risk assessment. 

Additionally, the aerobic aquatic metabolism half-life value of 5.28 days represents the 90th

percentile of the upper confidence bound for the mean of two available half-life values, one for 

ponded systems (3.2 days) and and for stream systems (1.2), and may be overly conservative for 

systems with flowing water. 

In addition, EPA is aware that a significant amount of research is available that demonstrates that 

a well maintained (e.g. non-channelized) vegetative buffer may significantly reduce pesticide 

runoff loads. As an example, the USDA’s “Conservation Buffers to Reduce Pesticide Losses” 

(USDA 2000) was specifically developed to address potential impact of vegetative buffers to 

reduce pesticide loading. In that analysis, the authors made no specific recommendations but 

suggest that in order to be effective, a buffer must be at least 100 feet wide to reduce dissolved 

pesticides and nutrients. In addition to the research described above, there are a number of 

available models for estimating runoff losses that have the ability to estimate the influence of 

buffers on these losses. EPA has begun preliminary evaluation of these models, and although 

none of these models have been implemented, they do show promise. EPA will continue to 

evaluate these tools. Taken together, this information suggests that the 900 foot buffer currently 

on product labels will reduce loading to aquatic resources below the levels estimated in this 

assessment provided that buffers are well maintinated (e.g. non-channelized). However, the 

extent and amount of reduction remains an uncertainty. While the approach used in this 

assessment is likely protective of more sensitive ponded systems, it may overestimate potential 

exposure in flow through systems such as rivers and, to a certain extent, coastal areas. As a 

result of these uncertainties, acute and chronic risks to aquatic organisms may be overestimated.

There is also uncertainty surrounding the potential for chronic risks to fish. Current data on the 

freshwater species, rainbow trout, are not adequate to derive a definitive no observed adverse 

effect concentration (NOAEC) because effects were noted at all test concentrations. This 

represents a substantial data gap in the analysis. Since the available lowest observed adverse 

effect concentration (LOAEC) is within one order of magnitude of the highest EEC, chronic risk

to freshwater fish cannot be precluded. However, the magnitude of biological effects observed at 

the lowest concentration level appears to be close to the limit of statistical and biological 

signifigance. In addition, as discussed previously, the aquatic EECs do not take into 

consideration the impacts of the required 900 ft buffer on run-off. Therefore, the benefits of 

receiving another fish early life stage study to define a NOAEC may not be substantial. For 

estuarine/marine fish, chronic toxicity data was not available. It is not possible to calculate an 
acute-to-chronic ratio (ACR) because, as discussed above, only a non-definitive NOAEC is 

available for the freshwater fish. This represents a substantial data gap in the analysis. 

Another area of uncertainty surrounds the potential for chronic risks to estuarine/marine 

invertebrates because toxicity data for this taxa is not available. While there is uncertainty 

associated with applying an acute to chronic ratio (ACR) for the daphnid (most sensitive 

freshwater invertebrate) to the mollusk (most sensitive estuarine/marine invertebrate) because of 

the differences in life history, applying the ACR to the mollusk and the less sensitive Mysid 

shrimp can be used to bracket the potential risks to estuarine/marine invertebrates. When the 

ACR was used to estimate chronic toxicity to the eastern oyster, RQs ranged from 0.09 to 1.0, 

indicating potential for risks to estuarine/marine mollusks from chronic exposure from hydrogen 

cyanamide use on cherries. Additionally, when the ACR for the daphnid was applied to the acute 

toxicity value available for the pink shrimp (LC50 = 6300 ppb), RQs ranged from 0.03 to 0.36, 

suggesting that the potential for chronic risk to crustaceans is low. With this information chronic 

risks to estuarine/marine invertebrates can not be precluded, but risks to crustaceans are likely 

low. 

Additionally, the Agency has only received data for two species of non-vascular aquatic plants, 

instead of the four species typically required. Without this data risks to these taxa of aquatic 

plants may be underestimated.

Potential for chronic risk to birds is also uncertain because current data on mallard duck are 

inadequate to derive a definitive NOAEC or make a definitive determination of risk (effects were 

noted at all test concentrations). While a second avian reproduction study on mallard duck that 

results in derivation of a NOAEC would reduce uncertainty, chronic risks are already identified 

for birds based on the available bobwhite quail data. Therefore, additional data on the mallard 

duck is not necessary at this time. In addition, acute toxicity data is not available for a passerine 

species; however, given the magnitude of difference needed to reduce application rates such that 

risk would be below the level of concern, this data is unlikely to change the risk assessment.

There are considerable uncertainties associated with the available plant toxicity data. For 

seedling emergence, definitive EC25 and NOAEC values were not calculable for the most 

sensitive dicot species (lettuce) in the available study. As a result, risks to non-listed plant 

species could not be calculated and RQs for listed species were calculated based on the available 

LOAEC (0.056 lbs a.i./A). RQs may underestimate the magnitude of risk to listed species 

exposed to hydrogen cyanamide via run-off and spray drift. In addition, phytotoxicity observed 

in the control group was greater than 25% for one species (oat) in the vegetative vigor study. 

This suggests that growing conditions may not have been optimal for this species or cross 

contamination may have occurred. As a result, this data could not be used in the AgDrift analysis 

to calculate buffer distances. Risks may be underestimated for plants with similar toxicity to 

hydrogen cyanamide as oat. In addition, the EC25 value for the most sensitive dicot species

(tomato) should be interpreted with caution because it is not bracketed by the test concentrations.
Table 1. Risk Resulting from Hydrogen Cyanamide Exposure Presented by Taxon

Use Birds

(surrogate for 

reptiles and 

terrestrial-phase 

amphibians)*

Mammals* Plants Terrestrial Inverts Fish

(surrogate for 

aquatic-phase 

amphibians)**

Aquatic 

Invertebreates

Nectarines;

Peaches

Acute risk: 

Yes1

(except medium and 

large granivores)

Chronic risk:

Yes1

(except birds that eat 

fruits/pods/seeds)

Acute risk: 

Yes1

(except large 

mammals that eat 

fruits/pods/seeds)

Chronic risk: 

Yes1,2

Terrestrial: 

Yes1

Aquatic: 

Not expected

Non-listed and 

Listed: 

Uncertain3

Acute risk:

Not expected

Chronic risk: 

Uncertain4

Acute risk:

Not expected

Chronic risk: 

Uncertain4

Blackberries;

Blueberries

Acute risk: 

Yes1

(except large 

granivores)

Chronic risk:

Yes1,2

Acute risk: 

Yes1

Chronic risk: 

Yes1,2

Terrestrial: 

Yes1

Aquatic:

Not expected

Non-listed and 

Listed: 

Uncertain3

Acute risk:

Not expected

Chronic risk: 

Uncertain4

Acute risk:

Not expected

Chronic risk: 

Uncertain4

Apples;

Cherries;

California figs;

Grapes;

Kiwi fruits

Acute risk: 

Yes1

(except large 

granivores)

Chronic risk: 

Yes1,2

Acute risk: 

Yes1

Chronic risk: 

Yes1,2

Terrestrial: 

Yes1

Aquatic:

Uncertain4

(non-vascular 

plants)

Non-listed and 

Listed: 

Uncertain3

Acute risk:

Not expected

Chronic risk: 

Uncertain4

Acute risk:

Not expected

Chronic risk: 

Uncertain4

1 “Yes” indicates risk concerns for both listed and non-listed taxa. 2 Risk may be mediated by the rapid degradation of hydrogen cyanamide in the environment.

3 Risk is uncertain because the limit dose was not high enough to preclude risks given the high application rate of hydrogen cyanamide. 4 Risk is uncertain due to: the absence of acceptable data describing the toxicity of hydrogen cyanamide to the taxa of interest, uncertainties in EECs given the 

labeled 900 ft buffer, and uncertainties in the duration of exposure given the rapid degradation of hydrogen cyanamide in soil and water (aerobic soil half-life of 

12 hours in sandy loam soil, aerobic aquatic half-life of 3.2 days in a pond system, and aerobic aquatic half-life of 1.2 days in a river system).
Additional Considerations for Listed Species

Based on this screening-level assessment, there are potential risks of direct effects to listed and 

non-listed mammals, birds (birds are surrogates for terrestrial phase reptiles and amphibians), 

and terrestrial plants from the uses of hydrogen cyanamide. The potential direct effects to listed 

and non-listed freshwater and estuarine/marine fish and invertebrates and terrestrial invertebrates 

are uncertain given limitations in the available toxicity data. Listed species of freshwater and 

estuarine/marine invertebrates, mammals, birds, and terrestrial invertebrates may also be affected 

through indirect effects because of the potential direct effects on listed and non-listed species. 

Potential direct effects on listed and non-listed freshwater and estuarine/marine invertebrates, 

birds, and terrestrial invertebrates from the use of hydrogen cyanamide may be associated with 

modification of Primary Constituent Elements (PCEs) of designated critical habitats, where such 

designations have been made. However, at this current stage of the Registration Review process, 

it is premature to make effects determinations for listed species until further scientific analysis 

and refinements are conducted, based on recommendations received from the National Academy 

of Sciences’ (NAS) National Research Council (NRC) April 2013 report, available at

http://www.nap.edu/catalog.php?record_id=18344. The NAS report outlines recommendations 

on specific scientific and technical issues related to the development of pesticide risk 

assessments that are compliant with the Endangered Species Act (ESA) and the Federal 

Insecticide, Fungicide, and Rodenticide Act (FIFRA).

The EPA along with the U.S. Fish & Wildlife Service (USFWS), the National Marine Fisheries 

Service (NMFS) (collectively, the Services), and the U.S. Department of Agriculture (USDA), 

released a summary of their implementation plan for assessing risks of pesticides to listed species 

ahead of the stakeholder workshop held on November 15, 2013. This plan was developed in 

response to the NAS’ recommendations, including a common approach to risk assessment as a 

way of addressing scientific differences between EPA and the Services. During the workshop, 

the agencies received feedback from the public on the interim scientific approaches that were 

developed as part of the initial implementation of the NAS recommendations. These approaches 

will be jointly implemented and vetted as part of a phased iterative process. Once fully vetted, 

EPA will further refine the listed species effects determination portion of this risk assessment. 

To make effects determinations for individual listed species, useful refinements may include, but 

are not limited to, analyses of: 1) more detailed, species-specific ecological and biological data; 

2) more detailed and accurate information on hydrogen cyanamide use patterns; and 3) subcounty level spatial proximity data for the co-occurrence of potential effects areas and listed 

species and any designated critical habitat. Examples of such refinements are described below.

EFED is currently developing tools that are expected to further refine the assessment and are 

designed to support effects determinations for individual federally listed species and their 

designated critical habitats (where applicable). Scientific information obtained from the 

Services, and other reliable sources is being collated by EFED to address all currently listed 

species. This information is being stored in an Office of Pesticide Programs (OPP) Pesticide 

Registration Information SysteM (PRISM) listed species knowledgebase. The listed species 

knowledgebase consists of an information repository that houses biological and behavioral 

information relevant to individual species (e.g., habitat, diet, and life history, including specific 
temporal and spatial associations) and a document repository that contains supporting documents 

(e.g., USFWS recovery plans) and electronic information (e.g., GIS data files). For terrestrial 

taxa, biological information relevant to the assessment (e.g., diet and body weight) will be used 

to parameterize exposure estimates using a method consistent with currently used methods in the 

T-REX and T-HERPS models. 

Refinements will also include more detailed analyses of the registered uses and specific use 

patterns that result in either “Likely to Adversely Affect” (LAA) or “Not Likely to Adversely 

Affect” (NLAA) determinations for federally listed species. The analyses may include more 

information on where, when, and how hydrogen cyanamide is used on all use sites. Actual usage 

data (when available) and national land-cover datasets that indicate potential use sites [e.g., 

National Land Cover Dataset (NLCD), Cropland Data Layer (CDL)] may be used to support a 

more refined analysis of where hydrogen cyanamide is reasonably expected to be used. 

Similarly, refinements on the timing of applications and a more in-depth exploration of 

agronomic practices for hydrogen cyanamide may be included as part of the refinement.

The refinements based on individual species data; additional, detailed usage information, when 

available; and recommendations from the NRC report are expected to help to more accurately 

identify potential areas of effect and to better inform effects and habitat determinations for listed 

species and any designated critical habitats.
Environmental Fate and Ecological Risk Assessment 

for the Reregistration of Hydrogen Cyanamide

CH

2

N

2

CAS Registry Number 420-04-2 

PC Code 014002

Prepared by:

Elizabeth Riley, Biologist

Ibrahim Abdel-Saheb, Ph.D, Environmental Scientist

U. S. Environmental Protection Agency

Office of Pesticide Programs

Environmental Fate and Effects Division

Environmental Risk Branch IV

1200 Pennsylvania Ave., NW

Mail Code 7507P

Washington DC 20460

Reviewed by:

Michael Wagman, Biologist ERB VI

Andrew Shelby, Fate Scientist, ERB VI

Mark Corbin, Branch Chief, ERB VI

Date: February 27, 2014
-Page 2 of 115-

Table of Contents

1.1. Nature of Chemical Stressor....................................................................................................................4

1.2. Potential Risks to Non-target Organisms...............................................................................................4

1.3. Conclusions - Exposure Characterization ..............................................................................................6

1.4. Conclusions - Effects and Risk Characterization ..................................................................................7

2. Problem Formulation ........................................................................................................... 9

2.1. Nature of Regulatory Action..................................................................................................................10

2.2. Stressor Source and Distribution ..........................................................................................................10

2.2.1. Nature of Chemical Stressor..............................................................................................................10

2.2.2. Overview of Pesticide Usage.............................................................................................................11

2.3. Receptors.................................................................................................................................................11

2.3.1. Aquatic and Terrestrial Effects..........................................................................................................11

2.3.2. Ecosystems Potentially at Risk..........................................................................................................12

2.4. Assessment Endpoints............................................................................................................................12

2.5. Conceptual Model ...................................................................................................................................13

2.5.1. Risk Hypotheses................................................................................................................................13

2.5.2. Conceptual Diagram..........................................................................................................................13

2.6. Analysis Plan ...........................................................................................................................................15

2.6.1. Residues of Concern..........................................................................................................................15

2.6.2. Preliminary Identification of Data Gaps and Uncertainties...............................................................15

2.6.3. Evaluation of Multiple Active Ingredients and Mixtures..................................................................16

2.6.4. Measures of Exposure .......................................................................................................................16

2.6.5. Measures of Effect.............................................................................................................................17

2.6.6. Integration of Exposure and Effects..................................................................................................19

3. Analysis............................................................................................................................. 20

3.1. Use Characterization..............................................................................................................................20

3.2. Exposure Characterization....................................................................................................................21

3.2.1. Environmental Fate and Transport Characterization .........................................................................21

3.2.2. Measures of Aquatic Exposure..........................................................................................................25

3.2.3. Measures of Terrestrial Exposure......................................................................................................28

3.3. Ecological Effects Characterization......................................................................................................30

3.3.1. Aquatic Toxicity Assessment ............................................................................................................31

3.3.2 Terrestrial Effects Characterization...................................................................................................35

4. Risk Characterization......................................................................................................... 39

4.1. Risk Estimation.......................................................................................................................................39

4.1.1. Aquatic Organisms............................................................................................................................39

4.1.2. Terrestrial Organisms........................................................................................................................41

4.2. Incident Database Review .............................................................................................................................50

4.3. Risk Description......................................................................................................................................50

4.3.4. Risks to Mammals.............................................................................................................................53

4.3.5. Risk to Birds......................................................................................................................................54

4.3.6. Potential Effects on Terrestrial Invertebrates....................................................................................55

4.3.7. Risk to Terrestrial Non-target Plants.................................................................................................55

4.4. Uncertainties and Data Gaps.................................................................................................................57

4.4.1. Fate and Transport.............................................................................................................................57

4.4.2. Aquatic Exposure ..............................................................................................................................58

4.4.3. Effects Uncertainties .........................................................................................................................58

5. Federally Threatened and Endangered (Listed) Species Concerns............................... 59

5.1. Action Area .............................................................................................................................................60

5.2. Taxonomic Groups Potentially at Risk.................................................................................................60

5.2.1. Probit Dose-Response Analysis ......................................................................................................63

6. References............................................................................................................................ 65
-Page 3 of 115-

6.1. Submitted Product Chemistry and Environmental Fate Studies.......................................................66

161-1 Hydrolysis – 014002 Cyanamide Fate ....................................................................................66

161-2 Photodegradation-water............................................................................................................66

162-1 Aerobic soil metabolism............................................................................................................66

162-2 Anaerobic soil metabolism .......................................................................................................67

162-4 Aerobic aquatic metab...............................................................................................................68

163-1 Leach/adsorp/desorption ..........................................................................................................68

164-1 Terrestrial field dissipation.......................................................................................................68

165-1 Confined rotational crop ...........................................................................................................69

6.2. Submitted Ecotoxicity Studies...............................................................................................................69

71-1 Avian Single Dose Oral Toxicity – 014002 Cyanamide Eco................................................69

71-2 Avian Dietary Toxicity ..................................................................................................................70

71-4 Avian Reproduction......................................................................................................................70

72-1 Acute Toxicity to Freshwater Fish ............................................................................................70

72-2 Acute Toxicity to Freshwater Invertebrates............................................................................71

72-3 Acute Toxicity to Estuarine/Marine Organisms.....................................................................71

72-4 Fish Early Life Stage/Aquatic Invertebrate Life Cycle Study .............................................71

122-1 Seed Germination/Seedline Emergence and Vegetable Vigor ........................................72

122-2 Aquatic plant growth..................................................................................................................72

141-1 Honey bee acute contact...........................................................................................................73

Appendix A. Submitted Ecological Effects Data for Hydrogen Cyanamide........................ 74

Appendix B. Catalogue of Submitted Environmental Fate Studies for Hydrogen 

cyanamide. ................................................................................................................................... 77

Appendix C. PE5 Output File .................................................................................................... 81

Appendix D. Example Terrestrial Exposure Model Inputs/Outputs................................... 100

Appendix E. Reported Hydrogen Cyanamide Ecological Incident Summaries in the EIIS 

Database..................................................................................................................................... 108
-Page 4 of 115-

1. Executive Summary

1.1. Nature of Chemical Stressor

Under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and in order to ensure 

that registered pesticides meet current scientific and regulatory standards, EPA is initiating the 

re-registration of hydrogen cyanamide (CH2N

2

; CAS#: 420-04-2; PC code: 014002). Hydrogen 

cyanamide is a restricted use plant growth regulator currently registered (under Section 3 of 

FIFRA) for use on various crops. It is applied to the plant buds approximately 30 days before 

bud break to synchronize blossoming and/or produce a more uniform bud break in plants that 

have received less than their full chill hour requirement.

There is no clear understanding of the physiological and biochemical mode of action of hydrogen 

cyanamide and other chemicals used in dormancy- breaking. However, in a recent report by 

Perez and Vergara (2009) it is suggested that hydrogen cyanamide and other dormancy-breaking 

compounds act by transiently inhibiting respiration, thereby triggering processes leading to shoot 

growth and flowering.

This assessment is for a national registration request for the following uses: apples, blueberries, 

cherries, grapes (wine and raisin; desert; non-desert), kiwi fruit (California only), peaches and 

nectarines. It is registered under FIFRA section 24(c) on the following crops: blackberries in 

Georgia (GA03000600), figs in California (CA04000200) and grapes in Hawaii (HI03000300).

Maximum single application rates range from 6.6 to 17.6 lbs a.i./A-yr. This assessment is based 

on proposed maximum application rates for all uses. 

Hydrogen cyanamide and its degradates are potentially mobile in soil since they are soluble in 

water and were primarily associated with the aqueous phase in both the anaerobic soil 

metabolism and batch equilibrium studies in this review. However, the use of hydrogen 

cyanamide should not pose a significant additional ground water threat. This is due to the fact 

that the parent compound is not persistent, and the degradates are short-1ived, ubiquitous, low 

molecular weight organic nitrogen compounds that can be readily incorporated into the 

metabolism of microbes and higher plants.

1.2. Potential Risks to Non-target Organisms

The results of this screening-level assessment on the proposed hydrogen cyanamide uses indicate 

that risk from acute and chronic exposure is expected for birds, reptiles, terrestrial-phase 

amphibians, and mammals. Risk is also expected for plants, especially during the most sensitive 

life-stage of seedling emergence. Potential acute risk to listed mollusks is indicated based on 

marginal exceedance of the LOC. In addition, chronic risk to freshwater and estuarine/marine 

fish can not be precluded. Table 1.1 describes the potential for direct effects to listed species by 

taxa from the registered uses of hydrogen cyanamide. 
-Page 5 of 115-

Table 11. Potential Effects to Federally Listed Taxa Associated with Direct Effects from 

the Registered Uses of Hydrogen Cyanamide.

Listed Plant Taxon Potential Direct Effects

Terrestrial and semi-aquatic 

plants – monocots and dicots Yes

Aquatic nonvascular plants Uncertain7,8

Aquatic vascular plants No

Listed Animal Taxon Potential Direct Effects

Acute Chronic

Terrestrial invertebrates Uncertain1 ND

Mammals Yes2,3,5 Yes3,5

Birds Yes2,4,5 Yes4,5

Reptiles Yes2,4,5 Yes

Amphibians No effect6 Uncertain7,9

Freshwater fish No effect6 Uncertain7,9

Freshwater invertebrates No effect6 No effect10

Mollusks No effect6 ND

Estuarine/marine fish No effect6 Uncertain7,11

Estuarine/marine invertebrates No effect6 Uncertain7,12

ND Not determined. 1 Although no effects were seen in the acute contact toxicity tests with honey bees, the limit dose (36.2 μg a.i./bee) was not high 

enough to preclude risk at the listed species LOC, based on the relatively high hydrogen cyanamide EECs for registered uses.

2 Risks to terrestrial animals from exposure to hydrogen cyanamide are extensive as a result of the high application rates currently 

registered for use. 

3 Based on its reported toxicity to mammals, the maximum application rate that would not result in acute or chronic risk concerns 

is 0.65 lb a.i./A or 0.005 lb a.i./A, respectively. Chance of individual effect for listed species is 1 in 1 at derived RQ. 4 Based on its reported toxicity to birds, the maximum application rate that would not result in acute risks is 0.32 lb a.i./A, while 

the application rate that would not result in chronic risks is 0.64 lb a.i./A. Chance of individual effect for listed species is 1 in 1 at 

derived RQ.

5 Risk may be limited by geographic and temporal use patterns of hydrogen cyanamide (i.e., it is only for use on a nectarines, 

peaches, blackberries, blueberries, figs, apples, cherries, grapes, and kiwi fruits; it is subject to several geographic use 

restrictions; and is only applied December through March). 

6 Risk of direct effects from acute aquatic exposure to formulated hydrogen cyanamide is expected to be below the LOC. 

7 EECs are primarily driven by the modeled run-off, which assumes no buffer between the site of application and the water body. 

Hydrogen cyanamide degrades rapidly in soil (aerobic soil half-life of 12 hours in sandy loam soil), and the aerobic aquatic 

metabolism half-life value of 5.28 days represents the 90th percentile of the upper confidence bound for the mean of the two 

available half-life values (3.2 days in a pond system and 1.2 days in a stream system). Therefore chronic risks to aquatic 

organisms may be overestimated. 

8 The acute listed species RQ is equal to the LOC for non-vascular plants exposed to hydrogen cyanamide from the cherry use 

only. EECs would only need to drop ~1% to result in RQs below the level of concern.

9 Current data on the freshwater species, rainbow trout, are not adequate to derive a definitive NOAEC because effects were 

noted at all test concentrations. Since the available LOAEC is within one order of magnitude of the highest EEC, chronic risk to 

listed freshwater fish cannot be precluded. However, the magnitude of biological effects observed at the lowest concentration

level appears to be close to the limit of statistical and biological significance. 10 Risk of direct effects from chronic aquatic exposure to formulated hydrogen cyanamide is expected to be below the LOC. 11 Chronic toxicity data was not available for estuarine/marine fish. It is not possible to calculate an acute-to-chronic ratio (ACR) 

because only a non-definitive NOAEC is available for the freshwater fish. This represents a substantial data gap in the analysis. 

Based on the available acute toxicity data, estuarine/marine fish exhibit similar toxicity as freshwater fish so it is likely that they 

exhibit similar toxicity on a chronic exposure basis.

12 Chronic toxicity data is not available for estuarine/marine invertebrates, RQs calculated based on an ACR for the daphnid 

range from well below the listed species LOC to just exceeding the listed species LOC.

Risks to aquatic organisms may be mitigated by the 900 ft buffer required on all hydrogen 

cyanamide labels between the site of application and “the mean high water mark for intertidal 

areas, surface waters, rivers, streams, or their flowing tributaries” to limit the potential for 

exposure of hydrogen cyanamide to aquatic environments. While aquatic EECs were modeled 
-Page 6 of 115-

using a 900 ft buffer for drift, the Agency does not currently have a method for modeling the 

impact of a buffer on run-off. Therefore, EECs are primarily driven by the modeled run-off, 

which assumes no buffer between the site of application and the water body. Given the rapid 

degradation of hydrogen cyanamide in soil, this is a major source of uncertainty in the aquatic 

exposure and subsequent risk assessment. As a result of this limitation risks to aquatic organisms 

may be overestimated.

Risks to terrestrial organisms from exposure to hydrogen cyanamide are extensive because of the 

high application rates currently registered for use. Based on derived RQs, the chance of an 

idividual effect to a listed bird or mammal is 1 in 1 after exposure to hydrogen cyanamide. In 

fact, based on its reported toxicity to mammals, the maximum application rate of hydrogen 

cyanamide that would not result in acute or chronic risk concerns is 0.65 lb a.i./A or 0.005 lb 

a.i./A, respectively. For birds, the maximum application rate that would not result in acute risks 

is 0.32 lb a.i./A, while the application rate that would not result in chronic risks is 0.64 lb a.i./A. 

However, these risks may be mitigated by the geographic and temporal limitations of the 

chemical. Hydrogen cyanamide is only registered for use on a limited number of fruit bearing 

trees and ground fruit, including: nectarines, peaches, blackberries, blueberries, figs, apples, 

cherries, grapes, and kiwi fruits. Further, geographic restrictions outlined on the labels limit the 

use of hydrogen cyanamide on certain crops and in certain regions. For example, use on 

blueberries is limited to Florida and use on grapes is limited to California and Arizona (see 

Table 3.1 for more information). These limited use patterns for hydrogen cyanamide may result 

in substantially less overlap with endangered species habitat than a chemical with a ubiquitous 

use pattern (e.g., corn). In addition to these geographic boundaries, labels state that hydrogen 

cyanamide is to be applied 30 days prior to normal bud break. For the assessed uses this means 

that application occurs between December and March (see Table 3.6 for more information). The 

temporal and geographic limitations suggest that potential for acute risks are limited to those 

species that are active in late winter, especially in temperate regions of the country. The 

exception may be for uses of hydrogen cyanmide in areas with winters mild enough that birds 

and mammals remain active and plants do not senesce (e.g., California, Hawaii, and Florida). In 

addition, the chemical properties and available residue data suggest that hydrogen cyanamide 

degrades rapidly in the environment. Without prolonged exposure, chronic risks to terrestrial 

animals may be overestimated.

For terrestrial plants, AgDRIFT was used to refine potential exposure to vegetatively active 

plants from drift of hydrogen cyanamide off of the field. Based on this analysis, airblast 

applications for the orchard uses and ground spray for the other uses limit the potential for 

exposure from drift such that most of the assessed species would not be expected to be at risk 

beyond the edge of the field. Exposure through run-off may still be a concern; however, risks 

from run-off may be over estimated given the rapid degradation of hydrogen cyanamide in soil

as discussed previously.

1.3. Conclusions - Exposure Characterization 

Hydrogen cyanamide is expected to dissipate quickly in both terrestrial and aquatic environments 
-Page 7 of 115-

under aerobic and anaerobic conditions (aerobic soil metabolism t1/2 of 12 hours; and t1/2 1.2- 3.2 

day under aerobic aquatic conditions), and is considered highly mobile and nonvolatile. Aerobic 

metabolism is considered the major route of degradation. Abiotic degradation processes 

(hydrolysis and photolysis) are not important, as metabolism is much quicker. Cyanamide is 

completely soluble in water. Hydrogen cyanamide is considered highly mobile. There is no 

evidence of degradation via hydrolysis, which was studied across environmental pHs. Hydrogen 

cyanamide does not bioconcentrate in aquatic organisms (Log Kow -0.82). The use of hydrogen 

cyanamide should not pose a significant additional ground water threat since the parent 

compound is not persistent, and the degradates are short-1ived, ubiquitous, low molecular weight 

organic nitrogen compounds that can be readily incorporated into the metabolism of microbes 

and higher plants.

Aquatic exposure estimates are based on the exposure of the parent compound hydrogen 

cyanamide only. Degradates are short-1ived, ubiquitous, low molecular weight organic nitrogen 

compounds that can be readily incorporated into the metabolism of microbes and higher plants.

The conservative aquatic exposure estimates (for all uses modeled) result in the high-end 

exposure for each type of application method. The range of uses is listed in Table 3.1. 

Acute 1-in-10 year estimated environmental concentrations (EECs) in surface water for all 

modeled uses of hydrogen cyanamide ranged from 9.35 μg/L to 92.0 μg/L with the addition of a 

900 ft buffer as required on product labels. 

In addition, registered labels for hydrogen cyanamide products include a language requiring a 

900 ft buffer between the site of application and “the mean high water mark for intertidal areas, 

surface waters, rivers, streams, or their flowing tributaries” to limit the potential for exposure of 

hydrogen cyanamide to aquatic environments. While aquatic EECs were modeled using a 900 ft 

buffer for drift, the Agency does not currently have a method for modeling the impact of a buffer 

on run-off. Therefore, EECs are primarily driven by the modeled run-off, which assumes no 

buffer between the site of application and the water body. Given the rapid degradation of 

hydrogen cyanamide in soil, this is a major source of uncertainty in the aquatic exposure and 

subsequent risk assessment. As a result of this limitation risks to aquatic organisms may be 

overestimated, except in areas where channelized flow occurs. 

1.4. Conclusions - Effects and Risk Characterization 

Aquatic Organisms

Results of acute toxicity studies indicate that hydrogen cyanamide is “slightly toxic” to 

freshwater and estuarine/marine fish and “moderately toxic” to freshwater and estuarine/marine 

invertebrates on an acute exposure basis. Toxicological sings oberseved in fish included 

quiescence, ceased swimming, dark discoloration, hyperexcitability, and erratic swimming. 

Acute risks to fish and aquatic invertebrates are not expected. 
-Page 8 of 115-

Available chronic toxicity data for freshwater fish reported a NOAEC value for reproductive

endpoints (i.e., days to hatch, days to swimup, and hatch survival) as 2.03 ppm with an

associated LOAEC of 4.03 ppm. However, effects on growth endpoints (i.e., length and wet 

weight) were observed at all treatment levels; therefore, the NOAEC for this study was <0.507 

and the LOAEC was 0.507. While risk quotients could not be calculated for freshwater fish on a 

chronic exposure basis because of the non-definitive NOAEC, the magnitude of biological 

effects observed at the lowest concentration tested appear to be close to the limit of statistical 

and biological significance. This information, combined with the likely overestimation of 

EECs as a result of the run-off modeling discussed above, suggest that while chronic risks to 

freshwater fish can not be precluded they are likely low. 

Chronic data was not available for estuarine/marine fish. Based on the available acute toxicity 

data, estuarine/marine fish exhibit similar toxicity as freshwater fish so it is likely that they 

exhibit similar toxicity on a chronic exposure basis. In addition, available aerobic aquatic 

metabolism data (1.2 days in a stream system) suggests that hydrogen cyanamide degrades faster 

under flowing conditions, such as may be found in some estuarine/marine systems. As a result of 

this shorter half-life, while chronic risks can not be precluded, those estuarine/marine fish that 

reside in flowing waters may be low. 

Chronic risk to freshwater invertebrates is expected to be low based on chronic toxicity data 

submitted for the daphnid, with RQs ranging from 0.06 to 0.69. Chronic toxicity data is not 

available for estuarine/marine invertebrates. The acute to chronic ratio (ACR) for the daphnid 

(most sensitive freshwater invertebrate) was applied to the available acute mollusk (the most 

sensitive estuarine/marine invertebrate) and acute Mysid shrimp data in order to bracket the 

potential for chronic effects to estuarine/marine invertebrates. Uncertainties associated with this 

approach are discussed further in the uncertainties section. When the ACR was used to estimate 

chronic toxicity to the eastern oyster, RQs ranged from 0.09 to 1.0, indicating potential for risks 

to estuarine/marine mollusks from chronic exposure from hydrogen cyanamide use on cherries. 

Additionally, when the ACR for the daphnid were applied to the acute toxicity value available 

for the pink shrimp (LC50 = 6300 ppb), RQs ranged from 0.03 to 0.36, suggesting that the 

potential for chronic risk to crustaceans is low. With this information chronic risks to mollusks 

can not be precluded but risks to crustaceans are likely low. 

Although hydrogen cyanamide does exhibit effects on both Lemna gibba and Anabaena flosaquae, these effects are at much higher concentrations than those estimated for the majority of 

the hydrogen cyanamide uses. However, the acute listed species RQ is equal to the LOC for 

non-vascular plants exposed to hydrogen cyanamide from the cherry use, which indicates that 

risks to listed and non-listed aquatic non-vascular plants may occur. However, EECs are

primarily driven by the modeled run-off, which assumes no buffer between the site of application 

and the water body. Given the 900 ft buffer required between the site of application and any 

waterbody and the rapid degradation of hydrogen cyanamide in soil, exposure to aquatic 

environments may be over estimated. As a result of this limitation risks to aquatic non-vascular 

plants may be overestimated. In fact, EECs for use of hydrogen cyanamide on cherries would 

only need to drop ~1% to result in RQs below the level of concern. In addition, risk to aquatic 

nonvascular species is typically evaluated with not only the cyanobacteria species that was 
-Page 9 of 115-

submitted, but also with a green algae, a centric diatom and a pinnate diatom. Acceptable studies 

with these species have not been submitted and are an appreciable source of uncertainty in the 

risk assessment. These planktonic taxa form the basis of the aquatic food web and are frequently 

more sensitive to pesticides than cyanobacteria. Without data on these additional species, and 

considering the listed species RQ is equal to the LOC for the highest use pattern, risks to aquatic 

plants can not be precluded. 

Terrestrial Organisms

Results of toxicity studies indicate that hydrogen cynamide is “moderately toxic” to mammals on 

an acute exposure basis. Acute risk concerns were triggered for all assessed uses of hydrogen 

cyanamide. Results of the screening model SIP also indicate that drinking water exposure is a 

potential concern for mammals based on acute and chronic exposure. 

Results of toxicity studies indicate that hydrogen cynamide is “moderately toxic” to birds on an 

acute dose-based exposure basis, while it is “practically non-toxic” on an acute dietary-based 

exposure basis. Acute dose-based risk concerns were triggered for all assessed uses of hydrogen 

cyanamide. Results of the screening models SIP and STIR indicate that drinking water and 

inhalation exposure are also of potential concern for birds based on acute and chronic exposure. 

An acute contact toxicity study (MRID 438669- 02) showed that cyanamide is essentially 

non-toxic to the honey bee (LD50 >36.2 mg a.i./bee, and NOEL approximately 12 mg 

a.i./bee). However, the high application rates used may pose risks to bees as a result of high field 

residues (max EECs are over 1600 ppm a.i.). A foliar dissipation study would reduce 

uncertainties associated with risks to beneficial insects. 

For hydrogen cyanamide, seedling emergence is a much more sensitive life stage than vegetative 

vigor. Though there are substantial uncertanites associated with the risk picture for plants as a 

result of the quality of the available seedling emergence data (discussed in section 3.3.2.4), 

observable effects on plants at rates considerably lower than labeled rates trigger concerns for

listed and non-listed plants.

2. Problem Formulation

The purpose of problem formulation is to provide the foundation for the environmental fate and 

ecological risk assessment for the registration review risk assessment for the growth regulator

hydrogen cyanamide, (CH

2

N

2

; CAS#: 420-04-2; PC code: 014002). The problem formulation 

sets the objectives for the risk assessment, establishes a risk hypothesis and conceptual model 

depicting potential risk, and provides a plan for analyzing the data and characterizing the risk 

associated with the proposed use of hydrogen cyanamide (USEPA, 1998). 
-Page 10 of 115-

2.1. Nature of Regulatory Action

The U.S. Environmental Protection Agency (EPA or the Agency) is required under the Federal 

Insecticide, Fungicide, and Rodenticide Act (FIFRA) to ensure that the currently registered 

pesticides, including hydrogen cyanamide, remain eligible for reregistrtion and do not result in 

unreasonable adverse effects to the environment. In addition to non-target animals and plants, 

potential effects to listed species (i.e., species on the Federal list of endangered and threatened 

wildlife and plants) and their designated critical habitat are also considered under the 

Endangered Species Act (ESA) in order to ensure that the continued registration of hydrogen 

cyanamide is not likely to jeopardize the continued existence of listed species or adversely 

modify their critical habitat. In order to meet the requirements of FIFRA and the ESA, this 

assessment follows EPA guidance on conducting ecological risk assessments (USEPA, 1998) 

and Office of Pesticide Program’s Overview Document, which contains guidance for assessing 

pesticide risks to non-target and listed organisms (USEPA, 2004).

The end result of the EPA pesticide registration process (i.e., the FIFRA regulatory action) is an 

approved (or disapproved) product label. The label is a legal document that stipulates how and 

where a given pesticide may be used. Product labels (also known as end-use labels) describe the 

formulation type (e.g., liquid or granular), acceptable methods of application, approved use sites, 

and any restrictions on how applications may be conducted. Therefore, the use, or potential use, 

described by the pesticide’s labels is considered “the action” being assessed. This assessment 

was prepared to support evaluation of the reregistration of hydrogen cyanamide. 

2.2. Stressor Source and Distribution

2.2.1. Nature of Chemical Stressor

Hydrogen cyanamide is a plant growth regulator used to promote uniform bud break in fruit trees 

and vines. Based on the rapid metabolism of this chemical, residues are not expected at harvest. 

All registered uses can be considered non-food uses. Hydrogen cyanamide is currently 

registered for use under FIFRA Section 3 on the following bearing fruit trees and vines prior to 

bud-break: apples, blueberries, cherries, grapes (wine and raisin; kiwi fruit (California only), 

peaches, and nectarines. Hydrogen cyanamide is formulated as a soluble concentrate and may be 

applied using airblast or backpack sprayers. Hydrogen cyanamide is not registered for residential 

use. 

The mode of action is poorly understood (Or et al. 2000, 2002; Perez and Burgos 2004). It was 

suggested that hydrogen cyanamide and other dormancy-breaking compounds act by transiently 

inhibiting respiration, thereby triggering processes leading to shoot growth and flowering (Perez 

et al., 2008). The stresser of concern is the paerent only. Degradates are short-1ived, ubiquitous, 

low molecular weight organic nitrogen compounds that can be readily incorporated into the 

metabolism of microbes and higher plants.
-Page 11 of 115-

2.2.2. Overview of Pesticide Usage

The Biological and Economic Analysis Division’s (BEAD) Screening Level Usage Analysis 

(SLUA; USEPA 2012) shows that an average of 263,000 lbs of hydrogen cyanamide is applied 

annually on various crops (Table 2.1). The SLUA also reports that grapes and cherrries were the 

top crops treated with hydrogen cyanamide. 

Table 2.1. Screening Level Estimates of Agricultural Uses of Cyanamide (014002)

Sorted Alphabetically

Crop Lbs. A.I.

Percent Crop Ttd.

Avg. Max.

1 Apples 5,000 <1 <2.5

2 Blueberries 2,000 <2.5 <2.5

3 Cherries 100,000 5 10

4 Figs * 2,000 ND ND

5 Grapes 140,000 10 20

6 Kiwifruit * 14,000 ND ND

All numbers rounded.

<2.5 Less than 2.5 percent of crop treated

<1 Less than 1 percent of crop treated

ND No data

* Based on CA DPR data only (valid because 95% or more of U.S. acres grown are in California)

2.3. Receptors

2.3.1. Aquatic and Terrestrial Effects

In ecological risk assessment, a receptor is a biological entity that is exposed to a stressor 

(USEPA, 1998). Consistent with the process described in the Overview Document (USEPA, 

2004), this risk assessment uses a surrogate species approach in its evaluation of hydrogen 

cyanamide. Toxicity data generated using surrogate test species, which are intended to be 

representative of broad taxonomic groups, are used to infer potential effects on a variety of 

species (receptors) included under these broader taxonomic groupings. Table 2.2 provides the 

general taxonomic groups and surrogate species tested to evaluate potential ecological effects of 

hydrogen cyanamide to broad classes of non-target organisms. Within each of these taxonomic 

groups, a measure of effect is selected from among the available test data. 

Table 2.2. Taxonomic Groups and Test Species Evaluated for Assessing Potential 

Ecological Effects of Hydrogen cyanamide.

Taxonomic Group Typical Species

Birds1 Mallard duck (Anas platyrhynchos)

Bobwhite quail (Colinus virginianus)

Mammals Norway rat (Ratus norvegicus)

Invertebrates Honey bee (Apis mellifera L.)
-Page 12 of 115-

Table 2.2. Taxonomic Groups and Test Species Evaluated for Assessing Potential 

Ecological Effects of Hydrogen cyanamide.

Taxonomic Group Typical Species

Freshwater fish2 Bluegill sunfish (Lepomis macrochirus)

Rainbow trout (Oncorhynchus mykiss)

Fathead minnow (Pimephales promelas)

Freshwater invertebrates Water flea (Daphnia magna)

Midge (Chironomus riparius)

Estuarine/marine fish Sheepshead minnow (Cyprinodon variegatus)

Estuarine/marine invertebrates Mysid (Americamysis bahia)

Eastern oyster (Crassostrea virginica)

Terrestrial plants3 Monocots – # Crop species, such as corn (Zea mays)

Dicots – # Crop Species, such as soybean (Glycine max)

Aquatic plants and algae Duckweed (Lemna gibba) 

Freshwater Algae (Pseudokirchneriella subcapitata and 

Anabaena flos-aquae) 1 Birds represent surrogates for terrestrial-phase amphibians and reptiles. 2 Freshwater fish may be surrogates for aquatic-phase amphibians. 3 Four species of two families of monocots, of which one is corn; six species of at least four dicot families, of which one is soybeans.

2.3.2. Ecosystems Potentially at Risk 

The ecosystems potentially at risk are often extensive in scope; therefore, it may not be possible 

to identify specific ecosystems during the development of a nation-wide ecological risk 

assessment. However, in general terms, terrestrial ecosystems potentially at risk could include 

the treated field and immediately adjacent areas that may receive drift or runoff. Areas adjacent 

to the treated field could include cultivated fields, fencerows and hedgerows, meadows, fallow 

fields or grasslands, woodlands, riparian habitats, and other uncultivated areas. 

Aquatic ecosystems potentially at risk include water bodies adjacent to or downstream from use 

sites, and might include impounded bodies such as ponds, lakes and reservoirs, or flowing 

waterways such as streams or rivers including all adjacent off-channel habitats that are 

permanently or intermittently connected to flowing waters. For uses in coastal areas, aquatic 

habitat also includes marine ecosystems, including estuaries, embayments, and near-shore 

environments such as tidal marshes.

2.4. Assessment Endpoints

Assessment endpoints represent the actual environmental value that is to be protected, defined by 

an ecological entity (species, community, or other entity) and its attribute or characteristics 

(USEPA, 1998). For hydrogen cyanamide, ecological entities of potential concern include the 

following: birds, amphibians, reptiles, mammals, freshwater fish and invertebrates, 

estuarine/marine fish and invertebrates, non-target terrestrial plants, terrestrial invertebrates, and 

aquatic vascular and non-vascular plants. The attributes for each of these entities may include 

growth, survival, and reproduction (Table 2.3 in Section 2.6.4).
-Page 13 of 115-

2.5. Conceptual Model

For a pesticide to pose an ecological risk, it must reach ecological receptors in biologically 

significant concentrations. An exposure pathway is the means by which a pesticide moves in the 

environment from a source to an ecological receptor. For an ecological pathway to be complete, 

it must have a source, a release mechanism, an environmental transport mechanism, and a 

feasible route of exposure.

The conceptual model is intended to provide a written description and visual representation of 

anticipated relationships between hydrogen cyanamide, potential routes of exposure, and the 

predicted effects for the assessment endpoints. The conceptual model consists of two major 

components: risk hypotheses and a conceptual diagram (USEPA, 1998).

2.5.1. Risk Hypotheses

Risk hypotheses are specific assumptions about potential adverse effects (i.e., changes in 

assessment endpoints) and may be based on theory and logic, empirical data, mathematical 

models, or probability models (USEPA, 1998). For this assessment, the risk is stressor-linked, 

where the stressor is the release of hydrogen cyanamide to the environment. The following risk 

hypotheses are presumed in this assessment:

Hydrogen cyanamide, when used outdoors in accordance with registered labels, will 

likely lead to off-site movement of the compound via agricultural runoff and spray drift 

leading to exposure of nontarget plants and animals. Based on information on the 

environmental fate, mode of action, direct toxicity and potential indirect effects, EFED 

assumes that registered uses of hydrogen cyanamide have the potential to cause reduced 

survival, growth, and reproduction to non-target terrestrial and/ or aquatic animals and 

plants.

 2.5.2. Conceptual Diagram

The conceptual model is a graphical representation of predicted relationships between ecological 

receptors, both listed (threatened and endangered) and non-listed, and the stressors to which they 

may be exposed. A conceptual model specifies potential routes of exposure, biological receptor 

types, and effects endpoints of potential concern. 

Hydrogen cyanamide is expected to dissipate quickly in both terrestrial and aquatic environments 

under aerobic and anaerobic conditions (aerobic soil metabolism t1/2 of 12 hours; and t1/2 1.2 and 

3.2 day under aerobic aquatic conditions), and is considered highly mobile and nonvolatile. 

Aerobic metabolism is considered the major route of degradation. Abiotic degradation processes 

(hydrolysis and photolysis) are not important, as metabolism is much quicker. Cyanamide is 

completely soluble in water, and in batch equilibrium experiments less than 2% of the mass 

adsorbed to sandy and silt loam soil. Thus, it is expected to be very mobile in soil-water systems. 

The degradates of cyanamide include simple nitrogen compounds (dicyanodiamide, guanylurea, 
-Page 14 of 115-

guanidine, and urea) which are readily utilized as plant nutrients.

The use of hydrogen cyanamide should not pose a significant additional ground water threat 

since the parent compound is not persistent, and the degradates are short-1ived, ubiquitous, low 

molecular weight organic nitrogen compounds that can be readily incorporated into the 

metabolism of microbes and higher plants.

Hydrogen cyanamide is applied as a spray 30 days before bud break. Figure 2.1 depicts the 

stressors, exposure pathways, and potential effects to terrestrial organisms from proposed uses of 

hydrogen cyanamide. Figure 2.2 depicts the stressors, exposure pathways, and potential effects 

to aquatic organisms from proposed uses of hydrogen cyanamide. For both figures, dotted lines 

indicate exposure pathways that are expected to have a low likelihood of contributing to 

ecological risk. 

 

 

 Figure 2.1. Conceptual model for hydrogen cyanamide effects on aquatic and terrestrial organisms.
-Page 15 of 115-

2.6. Analysis Plan

2.6.1. Residues of Concern

In this assessment, the parent (hydrogen cyanamide) is the only residue of concern. There is no 

concern for the degradates. The degradates of cyanamide include simple nitrogen compounds 

(dicyanodiamide, guanylurea, guanidine, and urea) which are readily utilized as plant nutrients. 

Chemical names, chemical structures, and data on the formation of these degradates are provided 

in Table 3.4. 

2.6.2. Preliminary Identification of Data Gaps and Uncertainties 

For the purposes of this assessment, data gaps refer to the absence of necessary data for a 

complete risk assessment. A catalogue of submitted ecological effects data for hydrogen 

cyanamide is available in Appendix A. Without eco-toxicity data or evidence to demonstrate 

otherwise, risk to non-listed and listed species of a taxon is presumed. An area of considerable 

uncertainty for this assessment surrounds potential chronic risk to birds. Current data on mallard 

duck are inadequate to derive a definitive NOAEC or make a definitive determination of risk 

(effects were noted at all test concentrations). While chronic risk was identified for birds based 

on the available bobwhite quail study, a second avian reproduction study on mallard duck that 

results in derivation of a NOAEC would reduce uncertainty.

Acute oral toxicity data is not available for a passerine species, resulting in another area of 

substantial uncertainty. In the absence of this data, risk will be presumed for passerine species. In 

addition, the avoidance behavior observed in the sub-acute dietary study with the mallard duck 

(as indicated by reduced feed consumption and weight loss at all treatment levels) suggests 

potential for adverse effects to passerines from advoidance or regurgitation behavior as well. An 

acute oral toxicity study with a passerine species, or a sub-acute dietary study if regurgitation is 

observed, would reduce this uncertainty. 

Another area of uncertainty surrounds the potential for chronic risks to aquatic animals. Current 

data on the freshwater species, rainbow trout, are not adequate to derive a definitive NOAEC 

because effects were noted at all test concentrations. Chronic data are not available for an 

estuarine/marine fish or invertebrate species, introducing additional uncertainties. Acute to 

chronic ratios (ACRs) were not appropriate for use in lieu of actual data because 1) the chronic 

freshwater fish study did not have a definitive NOAEC value and 2) the most sensitive 

estuarine/marine invertebrate, the eastern oyster, does not have a similar life history to the 

available freshwater species, the daphnid. Additionally, the Agency has only received data for 

two species of non-vascular aquatic plants, instead of the four species typically required. Without 

this data risks to this taxa of aquatic plants may be underestimated. 

There are additional uncertainties associated with the available plant toxicity data. Though tier II 

terrestrial plant toxicity data are available for hydrogen cyanamide, considerable variability in 

the available data for certain species, most notably variability in plant height for the most 

sensitive species in the seedling emergence study, increases the uncertainty associated with the 
-Page 16 of 115-

plant toxicity data. For example, definitive EC25 and NOAEC values were not determined for the 

most sensitive dicot (lettuce emergence) due to high variability in the available data. The 

NOAEC for lettuce is therefore less than 0.056, the lowest dose tested. The next most sensitive 

dicot species was carrot based on dry weight, with NOAEC and EC25 values of 0.22 and 0.60 lb 

a.i./A, respectively. This indicates that hydrogen cyanamide may affect seedling emergence at 

rates up two orders of magnitude below the currently registered application rates. For the 

purposes of this risk assessment, the LOAEC value for lettuce of 0.056 lbs a.i./Awas used to 

characterize the lower bounds of risk from exposure to terrestrial plants to hydrogen cyanamide. 

For the purposes of risk assessment the submitted environmental fate data are adequate. The 

quality of the submitted data is adequate. A catalog of submitted environmental fate studies for 

hydrogen cyanamide and its degradates, along with justified review classifications, can be found 

in Appendix B. 

2.6.3. Evaluation of Multiple Active Ingredients and Mixtures 

The Agency does not routinely include in its risk assessments an evaluation of mixtures of active 

ingredients, either those mixtures of multiple active ingredients in product formulations or those 

in the applicator’s tank. In the case of the product formulations of active ingredients (that is, a 

registered product containing more than one active ingredient), each active ingredient is subject 

to an individual risk assessment for regulatory decision regarding the active ingredient on a 

particular use site. If effects data are available for a formulated product containing more than 

one active ingredient, they may be used qualitatively or quantitatively in accordance with the 

Agency’s Overview Document and the Services’ Evaluation Memorandum (U.S. EPA 2004; 

U.S. FWS/NMFS 2004). 

Current registered labels of hydrogen cyanamide do not specify the use of other active 

ingredients in tank mixtures. However, language does indicate that hydrogen cyanamide should 

not be applied within 14 days of dormant sprays containing oil or within 30 days of dormant 

sprays containing copper as this may lead to crop damage or reduced insect/disease control. 

2.6.4. Measures of Exposure 

Measures of exposure are based on aquatic and terrestrial models that estimate environmental 

concentrations of hydrogen cyanamide using labeled application rates and methods. For aquatic 

exposure the Tier II model Pesticide Root Zone Model (PRZM v3.12.2; May 12, 2005) linked 

with EXposure Analysis Modeling System (EXAMS v2.98.4.6; Apr. 25, 2005) via the 

PRZM/EXAMS model shell (PE v5.0, Nov. 15, 2006), i.e., PRZM/EXAMS) was used to 

estimate screening-level exposure concentrations in aquatic environments. The measure of 

exposure for aquatic species in surface water bodies receiving runoff and/or spray drift is a return 

frequency of 1-in-10 years of the estimated environmental concentrations (EEC), based on 30-

year simulations. The maximum 1-in-10 year return frequency concentration is used for 

estimating acute exposures to aquatic organisms (plants and animals); the 1-in-10 year 21-day 

mean concentration is used for assessing aquatic invertebrate chronic exposure; and the 1-in-10 
-Page 17 of 115-

year 60-day mean concentration is used for assessing chronic exposure for fish (and aquaticphase amphibians for which fish serve as surrogates). 

Terrestrial exposure estimates for avian and mammalian risk assessments were derived using the 

T-REX model (version 1.5,3/22/2012). T-REX is used to calculate dietary and dose-based 

EECs of hydrogen cyanamide for birds (and surrogates) and mammals inhabiting terrestrial 

areas. T-REX simulates a 1-year time period. The default foliar dissipation half life of 35 days 

(Willis and McDowell 1987) is used as input to T-REX. Use-specific input values, including 

number of applications, application rate and application interval are also inputs. 

Exposure for terrestrial plants inhabiting dry and semi-aquatic areas (e.g., low-lying wet areas 

that may dry up at times throughout the year), using TerrPlant v 1.2.1, is based on the following:

(1) the pesticide's water solubility and the amount of pesticide present on the soil surface 

and its top one centimeter,

(2) potential "sheet runoff" (one treated acre to an adjacent acre) for dry areas,

(3) potential "channel runoff" (10 acres to a distant low-lying acre) for semi-aquatic or 

wetland areas,

(4) fractional runoff values of 0.01, 0.02, and 0.05 for pesticide water solubilities of <10, 

10-100, and <100 ppm, respectively

(5) drift assumption of 1% for ground and 5% for aerial application

AgDRIFT (v 2.1.1) is used to refine drift exposure to terrestrial plants and to refine buffers for 

aquatic assessments, providing an estimate of the area of concern for these taxa surrounding the 

area of application.

The Screening Imbibition Program (SIP v.1.0) was used to calculate an upper bound estimate of 

wildlife exposure via drinking water using hydrogen cyanamide’s solubility avian and 

mammalian toxicity endpoints. 

The Screening Tool for Inhalation Risk (STIR v.1.0) was used to calculate an upper bound 

estimate of wildlife exposure via both vapor phase and spray droplet inhalation using hydrogen 

cyanamide’s vapor pressure and avian and mammalian toxicity endpoints. 

2.6.5. Measures of Effect 

Measures of effect are obtained from a suite of registrant-submitted guideline studies that were 

conducted with a limited number of surrogate test species (Table 2.1). No additional ecotoxicity 

data on hydrogen cyanamide were located, based on an August 2011 query of the open literature 

in the publically available version of the ECOTOX database (http://cfpub.epa.gov/ecotox/).

The acute measures of effect used in this baseline assessment are the LD50 (median Lethal Dose), 

LC50 (median Lethal Concentration) or EC50 (median Effects Concentration). These are 

measures of acute toxicity which result in 50% of the respective effect in tested organisms. The 

endpoints for chronic measures of exposure are the no observed adverse effect concentration 

(NOAEC) and the no observed adverse effect level (NOAEL). Toxicity studies were submitted 
-Page 18 of 115-

for freshwater fish and invertebrates, estuarine/marine fish and invertebrates, aquatic plants, 

birds, mammals, bees, and other terrestrial invertebrates. The endpoints used for risk 

characterization are derived from studies which underwent review and were classified as 

“acceptable” (conducted under guideline conditions and considered to be scientifically valid) or 

“supplemental” (conditions deviated from guidelines but the results are considered to be 

scientifically valid). 

Table 2.3 lists the measures of environmental exposure and ecological effects used to assess the 

potential risks of hydrogen cyanamide to non-target organisms. The methods used to assess the 

risk are consistent with those outlined in the document “Overview of the Ecological Risk 

Assessment Process in the Office of Pesticide Programs” (USEPA, 2004).

Table 2.3. Measures of Exposure and Measures of Effect Used in Assessing Potential Risks 

Associated with the Proposed Uses of Hydrogen cyanamide.

Assessment Endpoint Surrogate Species and Measures of 

Ecological Effect1 Measures of Exposure

Birds2

Survival

Lowest acute LD50 (single oral dose 

test) and LC50 (subacute dietary test)

Upper-bound residues on 

food items

Reproduction 

and Growth

Lowest NOAEC

(21-week reproduction test)

Mammals

Survival

Lowest acute LD50 (single oral dose 

test)

Reproduction 

and Growth

Lowest NOAEC 

(2-generation reproduction test)

Aquatic Animals (Fish and 

invertebrates)3

Survival Lowest tested LC50 or EC50

(acute toxicity test)

Peak EECs4

Reproduction 

and Growth

Lowest NOAEC (early life-stage or full 

life-cycle tests)

21-day EECs for invertebrates 

and 60-day EECs for fish4

Terrestrial plants5 Survival and 

growth

Lowest EC25 (for non-listed plants) and 

corresponding NOAEC (for listed 

plants)

(endpoints derived for monocots and 

dicots from seedling emergence and 

vegetative vigor studies)

Estimates of runoff and spray 

drift to non-target areas

Insects6 Survival (not 

quantitatively 

assessed)

Lowest honeybee LD50 (acute contact 

test)

Lowest Earthworm LC50

Maximum application rate for 

honeybees and estimates of 

soil concentrations for 

earthworms 

Aquatic plants (vascular 

and non-vascular)

Survival and 

growth

Lowest EC50 (for non-listed plants) and 

corresponding NOAEC or EC05 (for 

listed plants)

Peak EECs4

1 The most sensitive species tested within taxonomic groups is used for screening-level risk assessments. 2 Birds represent surrogates for terrestrial-phase amphibians and reptiles. 3 Freshwater fish represent surrogates for aquatic-phase amphibians. 4 Aquatic EECs are based on modeling described in Section 3.2.2.1. 5 Four species of two families of monocots - one is corn, six species of at least four dicot families, of which one is soybeans. 6 Risk to terrestrial invertebrates from hydrogen cyanamide use is not evaluated, rather the potential hazard to honey bees and earthworms (i.e. the 

available data) are qualitatively assessed. 
-Page 19 of 115-

2.6.6. Integration of Exposure and Effects

Exposure and toxicity data are integrated in order to evaluate the risks of adverse ecological 

effects on non-target species. For the screening-level risk assessment of hydrogen cyanamide, 

the deterministic risk quotient (RQ) method is used to compare estimated exposure 

concentrations with measured toxicity values. The RQ method involves dividing point estimates 

of environmental concentrations by acute and chronic toxicity values. The resulting unitless RQs 

are then compared to the Agency’s Levels of Concern (LOC) (USEPA, 2004) (Table 2.4). 

These criteria are used to indicate when applications of hydrogen cyanamide, as directed on the 

proposed labels, have the potential to cause adverse effects to listed and non-listed non-target 

organisms.

Table 2.4. Agency Risk Quotient (RQ) Metrics and Levels of Concern (LOC) Per Risk 

Class.

RISK CLASS RISK DESCRIPTION RQ LOC

Aquatic Animals (fish and invertebrates)

Acute Potential for effects to non-listed animals from acute 

exposures

Peak EEC/LC501 0.5

Acute 

Restricted Use

Potential for effects to animals from acute exposures

Risks may be mitigated through restricted use classification Peak EEC/LC501 0.1

Acute Listed 

Species

Listed species may be potentially affected by acute 

exposures

Peak EEC/LC501 0.05

Chronic Potential for effects to non-listed and listed animals from 

chronic exposures

60-day EEC/NOAEC 

(fish) 1

21-day EEC/NOAEC 

(invertebrates)

Aquatic Plants

Non-Listed Potential for effects to non-listed plants from exposures Peak EEC/LC501 1

Listed Potential for effects to listed plants from exposures Peak EEC/NOAEC 1

Terrestrial Animals (mammals and birds)

Acute Potential for effects to non-listed animals from acute 

exposures

EEC2/LC50 (Dietary) 0.5

EEC/LD50 (Dose)

Acute 

Restricted Use

Potential for effects to animals from acute exposures

Risks may be mitigated through restricted use classification

EEC2/LC50 (Dietary) 0.2

EEC/LD50 (Dose)

Acute Listed 

Species

Listed species may be potentially affected by acute 

exposures

EEC2/LC50 (Dietary) 0.1

EEC/LD50 (Dose)

Chronic Potential for effects to non-listed and listed animals from 

chronic exposures EEC 2

/NOAEC 1

Terrestrial and Semi-Aquatic Plants

Non-Listed Potential for effects to non-target, non-listed plants from 

exposures

EEC/ EC25 1

Listed Plant Potential for effects to non-target, listed plants from 

exposures

EEC/ NOAEC

1

EEC/ EC05

1 LC50 or EC50. 2 Based on upper bound seeding rates.
-Page 20 of 115-

3. Analysis

3.1. Use Characterization

Hydrogen cyanamide, (Dormex, EPA Reg. No. 54555-2) is a restricted use plant growth regulator 

currently registered (under Section 3 of FIFRA) for use on apples, blueberries, cherries, grapes 

(wine and raisin; desert; non-desert) kiwi fruit (California only), peaches and nectarines. It is 

registered under FIFRA section 24(c) on the following crops: blackberries in Georgia 

(GA03000600), figs in California (CA04000200) and grapes in Hawaii (HI03000300). Hydrogen 

cyanamide is applied as a single airblast or backpack spray to the plant buds approximately 30 

days before bud break to synchronize blossoming and/or produce a more uniform bud break in 

plants that have received less than their full chill hour requirement. Aerial application of 

Dormex is prohibited. Hydrogen cyanamide cannot be applied through any type of irrigation 

system, and is not to be used as a blossom thinner under any conditions. As a result of label 

language requiring complete dormancy of deciduous crops to avoid crop damage, this 

assessment assumes a single application per year. All use patterns for hydrogen cyanamide are 

presented in Table 3.1.

Table 3.1. Summary of Agrlicultural Use for Hydrogen Cyanamide

Use Site

Maximum

Application

Rate

(lb a.i./A)

Maximum 

Number of

Applications

*

Application 

Interval

(days)*

Maximum 

Yearly 

Application

(lb a.i./A)

Geographic

Restrictions

Apple 17.6 NS N/A NS No Restrictions

Blackberry 13.2 NS N/A NS No Restrictions

Blueberry 13.2 NS N/A NS Use only in FL

Cherry 17.6 NS N/A NS No Restrictions

Fig 17.6 1 N/A NS

Grapes 17.6 1 N/A NS

To use on desert 

grown grapes in CA 

and AZ

Kiwi Fruit 17.6 1 N/A NS Use only in CA

Nectarine 6.6 NS N/A NS No use in CA

Peach 6.6 NS N/A NS No use in CA

*The assessment assumed a single application where the maximum number of applications was not specified on the 

label because of label language requiring complete dormancy of deciduous crops to avoid crop damage. 

NS = Not specified on labels

N/A = Not available
-Page 21 of 115-

3.2. Exposure Characterization

3.2.1. Environmental Fate and Transport Characterization

The general physical/chemical properties of hydrogen cyanamide are summarized in Table 3.2. 

Environmental fate and transport properties of hydrogen cyanamide are characterized in further 

detail in the following sections. The Agency’s understanding of these properties is limited by the 

available dataset. Additional detail on each study is provided in below.

Table 3.2 General Physical and Chemical Properties of hydrogen cyanamide

Property Value Reference

Chemical Name (IUPAC) Hydrogen cyanamide Foot Print Pesticide Properties 

Database. Accessed on September 

20, 2012

CAS Registry Number

420-04-2

Foot Print Pesticide Properties 

Database. Accessed on September 

20, 2012

Molecular Formula CH

2

N

2 Foot Print Pesticide Properties 

Database. Accessed on September 

20, 2012

Mol. Wt (g/mol) 42.04 Lide (2007)

Physical State Colourless solid Foot Print Pesticide Properties 

Database. Accessed on September 

20, 2012

Melting Point, oC 46.1 Foot Print Pesticide Properties 

Database. Accessed on September 

20, 2012

Boiling Point, oC 275.4 @ 760 mmHg Foot Print Pesticide Properties 

Database. Accessed on September 

20, 2012

Vapor Pressure, mmHg @ 20 

oC

0.00375 EPIWEB 4.1

Solubility in Water @ 20 oC 

(mg/L)

780000 Tomlin (2003)

Octanol-Water Partition 

Coefficient (Log Kow) (20 oC)

-0.82 Tomlin (2004)

Henry’s Law constant ( atm

m3/ mol)

2.68 X 10-10 Calculated using solubility and 

vapor pressure
-Page 22 of 115-

The available environmental fate data for hydrogen cyanamide indicate that it is not persistent in soil 

or water. With the exception of except spray drift at the time of application, hydrogen cyanamide is 

not expected to partition into air (based on its Henry's Law constant, and and water solubility. This 

Henry's Law constant indicates that cyanamide is expected to be essentially nonvolatile from 

water surfaces. Cyanamide's Henry's Law constant indicates that volatilization from moist soil 

surfaces is not expected to occur. Abiotic degradation processes (hydrolysis and photolysis) are not 

important, as metabolism is much quicker. Cyanamide is completely miscible with water, and in 

batch equilibrium experiments less than 2% of the mass adsorbed to sandy and silt loam soil. Thus, it 

is expected to be very mobile in soil systems. 

A summary of the submitted environmental fate and transport data is summarized below in 

Table 3.3.

Table 3.3 Environmental Fate Data Summary for hydrogen cyanamide 

Input Parameter Value Source/comment

Hydrolysis half-life pH 5: 237 days 

pH 7: 66 years 

pH 9: 105 days 

MRID 00150354

Aqueous Photolysis half-life 29 days in pH 5 and 38.5 days

in pH 7 buffers at 25oC 

MRID 42178409 

Aerobic Soil metabolism half-life 12 hours in sandy loam soil MRID 42178410 

Anaerobic Soil metabolism halflife

35-day half life in sandy loam 

soil 

MRID 42178412 

Aerobic Aquatic metabolism 

half-life

1.2 and 3.2 days in the river 

and pond systems 

MRID# 42382202

Anaerobic aquatic metabolism 

half-life

Not available Waived; was not requested because no 

useful results would be obtained based 

on the rapid aerobic soil degradation 

(MRID 42178410) Also, rapid 

degradation in the Aerobic aquatic 

metabolism study (MRID# 42382202).

Terrestrial Field Dissipation Not available Waived; was not requested because no 

useful results would be obtained based 

on the rapid aerobic soil degradation 

(MRID 42178410) Also, rapid 

degradation in the Aerobic aquatic 

metabolism study (MRID# 42382202).

Organic carbon normalized soil 

partition coefficient Koc

7.3 EPIWEB 4.1.

In lab studies, only <2% adsorption in 

sandy, sandy loam, and silt loam 

soilsMRID 42178415, 42178414 
-Page 23 of 115-

3.2.1.1. Transport and Mobility

Data from an unaged batch equibrium study showed that no more than 2 % of the applied 

hydrogen cyanamide was adsorbed at all intervals to sandy, sandy loam, and silt loam soils. The 

batch equilibrium study demonstrates a lack of adsorption to soil particles. Adsorption of 

hydrogen cyanamide was so limited that Freundlich-values would not accurately quantify the 

mobility of hydrogen cyanamide.

The unaged soil column leaching study demonstrates the mobility of hydrogen cyanamide in soil. 

Hydrogen cyanamide was detected at 0.08-2.9% of the applied amount in the leachate, from 

columns of sand, loamy sand, and sandy loam soil that were leached with 20 cm {7.87 inches} of 

water (MRID 42178415, 42178414).

3.2.1.2. Degradation

Hydrogen cyananide is stable to hydrolysis at pH's 5, 7 and 9 (MRID 00150354). Hydrogen 

cyanamide degraded with a half-ife of approximately 12 hours in sandy loam soil that was 

incubated in darkness at 23-25 OC and 70-75% of field moisture capacity. CO2 was the major 

degradate, and dicyanodiamide was the only minor degradate, with a half-1ife of 4.1 days 

(MRID# 42178410). Under aerobic aquatic conditions, hydrogen cyanamide degrades rapidly 

with a half-life of 1.2 and 3.2 days in the river and pond systems, respectively (MRID# 

42382202). Hydrogen cyanamide degraded under anaerobic soil conditions with half-life of 35 

days (MRID# 42178412); and via photolytic degradation with half-life 29 days (MRID 

42178409).

3.2.1.3. Field Studies

There are no acceptable Terrestrial field dissipation (TFD) studies submitted. A compilatlon of 

literature articles and submitted laboratory studies demonstrate that hydrogen cyanamide 

degrades rapidly (T1/2 =0.5 day) in soils to to dicyanodiamide, urea and ammonia. Hydrogen 

cyanamide and its degradates are mobile in soi1. However, the degradation and metabolism of 

hydrogencyanamide and its degradates should exceed the potential of leaching under most 

environmental conditions.
-Page 24 of 115-

3.2.1.4. Bioconcentration

The Log Kow of hydrogen cyanamide (-0.82) is low and indicating the compound has a low 

potential to bioaccumulate.

3.2.1.5. Environmental Degradates

Aerobic soil metabolism and aerobic aquatic metabolism are the major mean of degradation of 

hydrogen cyanamide. Hydrogen cyanamide rapidly (12 hrs) degrades in aerobic soil to the 

degradates CO2, and dicyanodiamide. Dicyanodiamide degraded with a half-life of 4 days to the 

common1y-applied fertilizer degradates urea and ammonia. Under aerobic aquatic conditions, 

hydrogen cyanamide degraded with half-lives range from 1.2 to 3.2 days.

Hydrogen cyanamide and its degradates are potentially mobile in soil since they are completely 

soluble in water and were primarily associated with the aqueous phase in both the anaerobic soil 

metabolism and batch equilibrium studies in this review. However, the use of hydrogen 

cyanamide should not pose a significant, additional ground water threat since the parent 

compound is not persistent, and the degradates are short-1ived, ubiquitous, low molecular weight 

organic nitrogen compounds that can be readily incorporated into the metabolism of microbes 

and higher plants.

The degradates of cyanamide (Table 3.4) include simple nitrogen compounds (dicyanodiamide, 

guanylurea, guanidine, and urea) which are readily utilized as plant nutrients.

Table 3.4 Summary of degradates distribution based on laboratory fate studies

Degradate

Max. Degradate % of Applied (Time of Peak)

Hydroly

sis

Aqueous 

Photolysis Aerobic Soil

Anaerobic 

Soil Aerobic Aquatic

Urea Not 

observed

42.4% (pH 5;30 d)

12.2% (pH 7, 30 d)

1.39 (<60 d) 6.7% (2 d)

13.4% (1 d)

CO2 Not 

observed

97.1% (14 d) 48.6 (15 d) 86.1% (28 d)

83.6% (28 d)

Dicyanodiamide Not 

observed

5.38% (0.33 d) 5.72 (<60 d) 0.3% (6 d)
-Page 25 of 115-

3.2.2. Measures of Aquatic Exposure

3.2.2.1. Surface Water Exposure

The Tier II model Pesticide Root Zone Model (PRZM v3.12.2; May 12, 2005; Carousel et al., 

undated) linked with EXposure Analysis Modeling System (EXAMS v2.98.4.6; Apr. 25, 2005; 

Burns, 2004) via the PRZM/EXAMS model shell (PE v5.0, Nov. 15, 2006), i.e., 

PRZM/EXAMS) were used to estimate screening-level exposure concentrations in aquatic 

environments. The PRZM model simulates pesticide movement and transformation on and 

across the agricultural field resulting from crop applications. The EXAMS model simulates 

pesticide concentrations in water due to loading via runoff, erosion, and spray drift, assuming a 

standard 1-ha pond, 2-m deep (20,000 m3) with no outlet that borders a 10-ha treated field. 

Simulations are for multiple (usually 30) years, from which the Agency estimates peak values 

that are expected to recur on average once every ten years, based on time series of daily 

estimated concentrations. The coupled PRZM and EXAMS models and user’s manuals are 

available from the U.S. Environmental Protection Agency Water Models web-page (USEPA, 

2011b).

Exposure estimates generated using the standard pond are intended as surrogates for potential 

concentrations in a wide variety of vulnerable water bodies, including prairie potholes, playa 

lakes, vernal pools, other wetlands, man-made and natural ponds, and ephemeral and first-order 

streams. Innumerable site-specific factors will tend to make such water bodies more or less 

vulnerable than the standard pond. Static water bodies that have larger ratios of pesticide-treated 

drainage area to water body volume are generally expected to have higher peak concentrations 

than the standard pond’s EECs. Such water bodies may be smaller in size, and/or have larger 

drainage areas. However such water bodies may be more likely to overflow and discharge 

pesticide in their effluent, whereas the standard pond has no discharge. As watershed size 

increases, it becomes increasingly unlikely that the entire watershed is planted with a single crop 

that is all treated simultaneously with a pesticide. Headwater streams may have peak 

concentrations that are higher than those predicted for the standard pond, but such concentrations 

will likely persist for only short periods of time or distance, as they are carried downstream and 

diluted with water originating elsewhere.

The general chemical and environmental fate data for hydrogen cyanamide listed in Table 3.2-

3.3 were used for generating model input parameters for PRZM and EXAMS (listed in Table 

3.5). Chemical specific and model input values were chosen in accordance with current 

divisional guidance (USEPA, 2009). 

Table 3.5. PRZM and EXAMS Surface Water Chemical Input Parameters for 

Hydrogen cyanamide. 

PARAMETER (units) VALUE (S) SOURCE COMMENT

Mol. Wt (g/mol) 42.04 Lide, D.R. 2007

Solubility (mg/L) 7.8E+5 EPIWEB 4.1 Tomlin (2003) as cited in EPISuite

Henry’s Law Constant 

(atm-m3/mol)

2.68 X 10-10 EPIWEB 4.1 Value calculated from literature 

values for vapor pressure and 

solubility cited in EPISuite

Vap. Pressure (Torr) 0.00375 EPIWEB 4.1 Tomlin (2003) as cited in EPiSuite
-Page 26 of 115-

Application Rate (lb a.i. 

/A)

See Table 3.6

Number of Applications 1 EPA Reg. No. 54555-2

Interval between 

Applications (days)

N/A EPA Reg. No. 54555-2

spray drift fraction 0.001 AgDrift modeling using a 

required 900 ft buffer zone

EPA Reg. No. 54555-2

Soil Partition Coefficient

KOC, (mL/g)

7.3 EPIWEB 4.1 Data in MRID 42178415 could not 

be used to determine coefficient.

Aerobic Soil Metabolism 

Half-life

(days)

1.5 MRID 42178410 Single half-life is available; 

multiplied by 3; Guidance for 

Selecting Input Parameters in

Modeling the Environmental Fate 

and

Transport of Pesticides

Version 2.1 (2009)

Wetted in? No EPA Reg. No. 54555-2

Depth of Incorporation

(inches )

0 EPA Reg. No. 54555-2

Method of Application Ground

Airblast

EPA Reg. No. 54555-2

Hydrolysis Half-life @ pH 

7 (days)

stable Literature Review EFED Review of Data, 1993.

Aerobic Aquatic 

Metabolism

Half-life (days)

5.28 MRID# 45382202 Represents the 90th percentile of the 

upper confidence bound on the mean 

of 2 half-life values: 1.2, and 3.2; 

mean 2.2, std. dev, 1.41 . Guidance 

for Selecting Input Parameters in

Modeling the Environmental Fate 

and

Transport of Pesticides

Version 2.1 (2009)

Anaerobic Aquatic 

Metabolism

Half-life (days)

210 MRID#42178412 Anaerobic soil met. half-life (35 

days) multiplied by 3 for a single 

half-life available (105 days) x2; 

Guidance for Selecting Input 

Parameters in

Modeling the Environmental Fate 

and Transport of Pesticides

Aquatic Photolysis Halflife @ pH 7 (days)38 MRID# 42178409 Guidance for Selecting Input 

Parameters in Modeling the 

Environmental Fate and

Transport of Pesticides

Version 2.1 (2009)

*: D1=D2*√MW2/MW1; D1: unknown air diffusion, D2: known air diffusion =14688 (for Methanol; Thoma et al., 1992); MW2 for known = 

32.04 (Methanol).

The initial application date was selected in order to simulate 30 or more days before normal 

budbreak. Application dates for modeling purposes were selected in accordance with the 

proposed labels to generate the most conservative estimates of aquatic exposure and based on 

information from the Cooperative Extension offices or the references provided in Table 3.6.
-Page 27 of 115-

Table 3.6. Modeling Scenarios used for hydrogen cycnamide applied to various crops.

Crop

Maximum 

Application rate

(lb ai/acre)

PRZM Scenario Application 

timing

Data source/

Comments

Apple

17.6

ORapples February 4 Univ. of Oregon extension office

PAapples February 20 www.boyernurseries.com

NCapples February 4 North Carolina S. Univ. extension office

Blackberry, 

Blueberry

13.2 GAPeaches December 1

2007 CENSUS OF AGRICULTURE, USDA, 

National Agricultural Statistics Service; Personal 

communication with Dr. G. Williamson @ U. FL.

Cherry

17.6

MIcherries March 24

Northwest Michigan Horticultural Research Center @ 

http://www.leelanaunews.com/news/OldArchive/Spec

ial_Interests/Cherry_blossom_blooms_earliest_in_yea

rs.html.

Grapes

17.6

NYgrapes March 25

cornell.edu@ 

http://flg.cce.cornell.edu/2012/03/15/early-budbreakin-2012/

CAgrapes February 9 UCDAVIS.edu@http://www.ipm.ucdavis.edu/PMG/C

302/mt302yi01.html#BREAK

Nectarine

Peaches

6.6

GApeaches February 14 Univ. of Georgia (personal contact @ 478-987-2028).

Kiwi fruit

Fig

17.6

CAfruits March 1st The California Minor Crops Council. 2003

Based on its use pattern, one application of hydrogen cyanamide is used in this assessment. 

The label (EPA Registration Number 54555-2) did not specify the number of applications 

allowable per season. The label should reflect this for future actions.

The modeled aquatic EECs resulting from the proposed hydrogen cyanamide uses (listed in 

Table 3.7) were used for risk estimation in this screening-level assessment. The model input and 

output filenames supporting these values are listed in Appendix C.
-Page 28 of 115-

Table 3.7. Modeled Aquatic Surface Water 1-in-10-year EECs for Registered Uses of hydrogen 

cyanamide on various crops.

Crop PRZM Scenario

1-in-10 year 

peak daily, 

ppb

1-in-10 year, 

peak 21-day 

average, ppb

1-in-10 year, 

peak 60-day 

average, ppb

Apples

ORapplesSTD.txt 31.8 23.1 13.0

PAapplesSTD.txt 15.5 12.0 7.41

NCapplesSTD.txt 11.0 8.09 4.83

Blackberry/Blueberry GApeachesSTD.txt 9.35 6.42 3.00

Cherry MIcherriesSTD.txt 92.0 69.0 37.5

Grapes

CAgrapes_WirrigSTD.txt 83.6 56.4 30.0

NYgrapesSTD.txt 21.2 14.6 7.85

Kiwifruit/Fig CAfruit_WirrigSTD.txt 77.5 44.7 21.6

Peaches/Nectarines GApeachesSTD.txt 28.6 18.8 9.55

3.2.3. Measures of Terrestrial Exposure

3.2.3.1. Terrestrial Wildlife

Exposure estimates for terrestrial organisms assumed to be in the target area or in an area 

exposed to off-site deposition are derived using the T-REX model (version 1.4.1, 10/09/2008). 

This model incorporates the Kenaga nomograph, as modified by Fletcher et al. (1994), which is 

based on a large set of field residue data. The upper limit values from the nomograph represent 

the upper bound of residue values from actual field measurements (Hoerger and Kenaga 1972). 

The Fletcher et al. (1994) modifications to the Kenaga nomograph are based on measured field 

residues from 249 published research papers, including information on 118 species of plants, 121 

pesticides, and 17 chemical classes. Based on these data, T-REX assumes a 35-day foliar 

dissipation half-life in the absence of other data. However, in an available residue study where

hydrogen cyanamide was applied to table grapes at a rate of up to 8 lbs a.i./A, residues 1 hour 

after application were < 3.49 ppm and dropped below the limits of detection (0.05 ppm) after 14 

days (MRID # 40329902). Though there were uncertainties identified with the analytical 

methods used to extract and identify residues, these data do suggest that the foliar dissipation 

half-life for hydrogen cyanamide is less than the 35 days assumed by T-REX. This will be 

discussed further in the risk characterization section. 

In order to determine if more data are necessary, the Screening Tool for Inhalation Risk (STIR 

v.1.0) was used to calculate an upper bound estimate of exposure using hydrogen cyanamide’s 

vapor pressure (3.75 x10-3) and molecular weight (42.04) for vapor phase exposure as well as the 
-Page 29 of 115-

maximum application rate and method of application for spray drift. STIR incorporates results 

from several toxicity studies including acute oral (>2.0 mg ai/kg-bw, MRID# 47469103) and 

inhalation (300 mg ai/L) rat toxicity endpoints obtained from the “six-pack” of core studies, 

which are a series of six guideline studies that are submitted to the Registration Division of the 

Office of Pesticide Programs for technical and formulated products of a pesticide as well as the 

most sensitive acute oral avian (173 mg ai/kg-bw) toxicity endpoint. Based on the results of the 

STIR model, inhalation exposure alone was not determined to be a potential pathway of concern 

for mammalian species on an acute exposure basis; however, acute inhalation exposure may be a 

potential pathway of concern for avian species. Please see Appendix D for sample output 

generated by STIR v.1.0. Detailed information about STIR v.1.0, as well as the tool, can be 

found on the EPA’s website at:http://www.epa.gov/pesticides/science/models_pg.htm#terrestrial.

The Screening Imbibition Program (SIP v.1.0) was used to calculate an upper bound estimate of 

exposure using an estimate of hydrogen cyanamide’s solubility (7.8x105 ppm), as well as the 

most sensitive acute and chronic avian and mammalian toxicity endpoints. As a result of 

hydrogen cyanamide’s high solubility, drinking water exposure was determined to be a potential 

pathway of concern for both avian (and surrogates) and mammalian species on an acute and 

chronic exposure basis. More information on residues of hydrogen cyanamide on the field, in 

run-off, and puddle water would help to alleviate uncertainties associated with this concern. 

Without this information risks to mammals and birds from drinking water will remain an 

unquantifiable concern. . For a sample of the output generated by SIP v.1.0, please see Appendix 

D. Detailed information about the SIP v.1.0, as well as the tool, can be found on the EPA’s 

website at http://www.epa.gov/pesticides/science/models_pg.htm#terrestrial.

EECs for terrestrial plants are derived using TerrPlant (v.1.2.2). This model uses estimates of 

pesticides in runoff and in spray drift to calculate EECs. EECs are based upon solubility, 

application rate and minimum incorporation depth. 

3.2.3.2. Terrestrial Plants

Exposure of naturally-occurring terrestrial and semi-aquatic (wetland) plant species is typically 

estimated using OPP’s TerrPlant (v1.2.2; USEPA, 2006b) model and is assumed to encompass 

areas outside the immediate use site. The TerrPlant model is used to derive EECs in runoff and 

drift for terrestrial and semi-aquatic plants near areas where hydrogen cyanamide has been 

applied. Runoff exposure is assessed in two scenarios: sheet and channel runoff. In the sheet 

runoff scenario, the treated area generating runoff is assumed to drain into an area with equal 

size containing seedlings, resulting in 1, 2, or 5% of the amount applied being deposited. In the 

channel runoff scenario, a ten-to-one ratio of treatment area to receiving area results in 10, 20, or 

50% of the amount applied being deposited on soil with emerging or emerged seedlings. Spray 

drift is also a source of pesticide loading to non-target areas. TerrPlant estimates EECs based on 

application rate, application method, chemical solubility in water, type of runoff and default 

assumptions of drift. Detailed information about TerrPlant, as well as the tool, can be found on 

the EPA’s website at http://www.epa.gov/pesticides/science/models_pg.htm#terrestrial.
-Page 30 of 115-

The AgDRIFT (v 2.01; May 2001) spray drift model is used to assess exposures of terrestrial 

plants to hydrogen cyanamide deposited on terrestrial or aquatic habitats by spray drift at a given 

distance from the application area. 

3.3. Ecological Effects Characterization 

In screening-level ecological risk assessments, effects characterization describes the types of 

effects a pesticide can have on aquatic and terrestrial organisms. To date, toxicity tests for 

amphibians or reptiles are not required; birds are used as surrogates for reptiles and terrestrialphase amphibians and freshwater fish are used as surrogates for aquatic-phase amphibians. This 

characterization is based on the registrant-submitted toxicity data for birds, mammals, fish, 

invertebrates, and plants for hydrogen cyanamide. 

This assessment evaluates the potential for hydrogen cyanamide to directly or indirectly affect 

listed species or modify designated critical habitat. As previously discussed in Section 2.7, 

assessment endpoints include direct toxic effects on the survival, reproduction, and growth of 

listed entities, as well as indirect effects, such as reduction of the prey base or modification of 

habitat. In addition, potential modification of critical habitat is assessed by evaluating effects to 

the PCEs, which are components of the critical habitat areas that provide essential life cycle 

needs of listed entities. 

As described in the Agency’s Overview Document (USEPA 2004), the most sensitive endpoint 

for each taxon is used for risk estimation. For this assessment, evaluated taxa include aquaticphase amphibians, freshwater fish, freshwater invertebrates, aquatic plants, birds (surrogate for 

terrestrial-phase amphibians), mammals, terrestrial invertebrates, and terrestrial plants. 

Toxicity endpoints are established based on data generated from guideline studies submitted by 

the registrant, and from open literature studies that meet the criteria for inclusion into the 

ECOTOX database maintained by EPA/Office of Research and Development (ORD) (U.S. EPA, 

2004). Open literature data presented in this assessment were obtained from ECOTOX 

information obtained in December 2007. In order to be included in the ECOTOX database, 

papers must meet the following minimum criteria:

(1) the toxic effects are related to single chemical exposure;

(2) the toxic effects are on an aquatic or terrestrial plant or animal species;

(3) there is a biological effect on live, whole organisms;

(4) a concurrent environmental chemical concentration/dose or application rate is 

reported; and

(5) there is an explicit duration of exposure.

Data that pass the ECOTOX screen are evaluated along with the registrant-submitted data, and 

may be incorporated qualitatively or quantitatively into this endangered species assessment. In 

general, effects data in the open literature that are more conservative than the registrantsubmitted data are considered. The degree to which open literature data are quantitatively or 

qualitatively characterized is dependent on whether the information is relevant to the assessment 
-Page 31 of 115-

endpoints (i.e., maintenance of survival, reproduction, and growth) identified in Section 2.8. For 

example, endpoints such as behavior modifications are likely to be qualitatively evaluated, 

because quantitative relationships between modifications and reduction in species survival, 

reproduction, and/or growth are not available. 

In addition to registrant-submitted and open literature toxicity information, other sources of 

information, including use of the acute probit dose-response relationship to establish the 

probability of an individual effect and reviews of the Ecological Incident Information System 

(EIIS), are conducted to further refine the characterization of potential ecological effects 

associated with exposure to hydrogen cyanamide. A summary of the available aquatic and 

terrestrial ecotoxicity information, use of the probit dose-response relationship, and the incident 

information for hydrogen cyanamide are provided in Sections 4.1 through 4.4, respectively.

Data identified in ECOTOX were not used in this assessment because they did not represent the 

most senstitive endpoints. No data are available on the toxicity of the major degradates of 

hydrogen cyanamide.

No toxicity data were available on hydrogen cyanamide mixtures with other pesticides; no multia.i. products are registered for hydrogen cyanamide.

3.3.1. Aquatic Toxicity Assessment

The most sensitive acute and chronic effects measurement endpoints associated with hydrogen 

cyanamide exposure to freshwater and estuarine/marine species are summarized in Table 3.8. 

All acceptable and supplemental studies available for hydrogen cyanamide are described below. 
-Page 32 of 115-

Table 3.8. Most Sensitive Acute and Chronic Toxicity Data for Aquatic Organisms 

Exposed to Hydrogen cyanamide Technical 

Exposure 

Scenario Species

Affected 

Endpoint Toxicity Measurement

Toxicity 

Classification

MRID

(Classification)

Freshwater Fish

Acute Rainbow trout

(Oncorhynchus 

mykiss)

Mortality 96-hr LC50 = 46 mg a.i./L

Slope: 8.65

Slighty toxic MRID 00148043

(Acceptable)

Chronic Rainbow trout

(Oncorhynchus 

mykiss)

Adult 

growth

NOAEC <0.507 mg a.i./L -- MRID 44076701

(Supplemental)

Freshwater Invertebrates

Acute Water flea

(Daphnia spp.)

Immobility 48-hr EC50 = 3.3 mg a.i./L

Slope: 7.70

Moderately 

toxic

MRID 00148046

(Acceptable)

Chronic Water flea

(Daphnia spp.)

Adult 21-

day length

NOAEC = 100 μg a.i./L -- MRID 44076702

(Acceptable)

Estuarine/Marine Fish

Acute Sheepshead 

minnow

(Cyprinodon 

variegatus)

Mortality 96-hr LC50= 58 mg a.i./L

Slope: 15

Slightly toxic MRID 44804702

(Acceptable)

Chronic No data available

Estuarine/Marine Invertebrates

Acute Eastern oyster

(Crassostrea 

virginica)

Shell 

deposition

96-hr EC50 = 2.3 mg a.i./L

Slope: NA

M oderately 

toxic

MRID 44804704

(Acceptable)

Chronic No data available. 

Aquatic Plants

7-day 

exposure

Duckweed

(Lemna gibba)

Frond 

count

EC50 = 3.0 mg a.i./L

NOAEC = 0.31 mg a.i./L

-- MRID 45406602 

(Acceptable)

72-hour 

exposure

Anabaena flosaquaeNone EC50 = 0.37 mg a.i./L

NOAEC = 0.09 mg a.i./L

-- MRID 45382201

(Supplemental)

3.3.1.1 Toxicity to Freshwater Fish

Acute Effects

In the acute toxicity study with a warmwater species, bluegill sunfish were exposed to 49% 

aqueous hydrogen cyanamide for 96 hours. The resulting 96-hour LC50 was determined to be 88 

ppm a.i. (EPA Acc. No. 073728, MRID 00153786; acceptable). For the coldwater species, 

rainbow trout (coldwater freshwater fish) were exposed to 49% aqueous hydrogen cyanamide for 

96 hours. The resulting 96-hour LC50 was 46 ppm a.i. (EPA Acc. No. 073728, MRID 00148043; 

acceptable). Toxicological signs observed included: quiescence, ceased swimming, dark 

discoloration, hyperexcitability at the lower concentrations, and erratic swimming. These results 

classify cyanamide as slightly toxic to fish.

Chronic Effects
-Page 33 of 115-

In the chronic toxicity study, rainbow trout were exposed to 50% aqueous hydrogen cyanamide 

(MRID 44076701; supplemental). The reported NOAEC for reproduction endpoints (i.e., days to 

hatch, days to swimup, and hatch survival) was 2.03 ppm and the associated LOAEC was 4.03 

ppm. However, effects on growth endpoints (i.e., length and wet weight) were observed at all 

treatment levels; therefore, the NOAEC for this study was <0.507 and the LOAEC was 0.507. 

While effects were observed at all treatment levels, the minimum difference from the control for 

the endpoints of interest (i.e, length and weight) to be significant is based on a relatively small 

percent difference (2.7% and 7.4% for length and weight, respectively). For example, in the 

lowest treatment concentration, mean length was 3% different from the control and mean wet 

weight was 8.7% different from the control. It is uncertain whether these values represent 

biologically relevant differences. In addition, further examination of the available raw data 

suggests that the differences observed in the growth endpoints were based on the poor 

performance of 3 fish (1 fish for length and 2 fish for weight) out of 59 total fish within the 

treatment level. Measurements for these few fish were sufficiently reduced such that they 

reduced the overall mean for the entire treatment level. If those fish had preformed as well as the 

remaining fish in the treatment level, there would no longer be significant differences from the 

controls. For example, removing the one poorly performing fish for length (25 mm vs 45.4 mm 

for the treatment group) would increase the treatment level mean from 45.4 to 45.7, resulting in a 

2.4% difference from the control. Since a definitive NOAEC was not determined for the most 

sensitive endpoints, this study is classified as supplemental. 

3.3.1.2. Toxicity to Freshwater Invertebrates

Acute Effects

The 48-hour acute toxicity of hydrogen cyanamide TEP (Dormex, 49% a.i.) to the freshwater 

invertebrate Daphnia magna is 3.3 ppm a.i., which classifies it as highly toxic (EPA Acc. No. 

073728; acceptable). Sublethal effects were not reported in the study. 

Chronic Effects

In the chronic toxicity study, Daphnia magna were exposed to 50% aqueous hydrogen 

cyanamide (MRID 44076702; acceptable). Data indicate that hydrogen cyanamide is highly 

toxic to daphnid growth and reproduction of young. The most sensitive endpoint was adult 

length after 21 days exposure (LOEC=210 ppb a.i. and NOEC = 100 ppb a.i.). Numbers of 

young produced per female per reproduction day were also affected at a concentration of 410 

ppb a.i.

3.3.1.3. Toxicity to Estuarine/Marine Fish

Acute Effects
-Page 34 of 115-

In the acute toxicity study, sheepshead minnow were exposed to 50.8% aqueous hydrogen 

cyanamide for 96 hours. The resulting 96-hour LC50 was determined to be 58 ppm a.i. which 

classifies hydrogen cyanamide as slightly toxic (MRID 44804702; acceptable). Signs of toxicity 

observed in the two highest concentrations included surfacing, lethargy, loss of equilibrium, and 

quiescence. 

Chronic Effects

No chronic toxicity tests in estuarine/marine fish with the TGAI, formulations, or degradates 

were submitted.

3.3.1.4. Toxicity to Estuarine/Marine Invertebrates

Acute Effects

In a shell deposition test, Eastern oysters (Crassostrea virginica) were exposed to 50.8% 

aqueous hydrogen cyanamide for 96 hours (MRID 44804704, acceptable). The resulting data 

indicated a 96-hour EC50 of 2.3 ppm a.i., classifying hydrogen cyanamide as moderately toxic to 

the Eastern oyster. 

In an additional acute toxicity study, mysid shrimp (Mysidopsis bahia) were exposed to 50.8% 

aqueous hydrogen cyanamide for 96 hours. The resulting 96-hour LC50 for mysids was 6.3 ppm 

a.i., which classifies this compound as moderately toxic to Mysidopsis bahia (MRID 44804703; 

acceptable). Toxicological signs oberseved at the two highest concentrations included erratic 

swimming and lethargy. 

Chronic Effects

No chronic toxicity tests in estuarine/marine invertebrates with the TGAI, formulations, or 

degradates were submitted

3.3.1.5. Toxicity to Aquatic Plants

In a registrant submitted non-vascular plant study using Anabaena flos-aquae the 72-hour EC50

and NOAEC values for cell density were 0.37 ppm a.i. and 0.09 ppm a.i., respectively (MRID 

45382201, supplemental). In an additional study using Pseudokirchneriella subcapitata the 72-

hour EC50 and NOAEC values for cell density were and 12 ppm a.i. and 4.26 ppm a.i., 

respectively (MRID 45406601, supplemental). These studies were classified as supplemental 

because the exposure window was 72 hours, while the typical guideline study exposes nonvascular plants for 96 hours. 

In a registrant submitted vascular aquatic plant study with Lemna gibba the 7-day EC50 and 

NOAEC values for frond count were 3.0 ppm a.i. and 0.31 ppm a.i., respectively (MRID 

45406602, acceptable).
-Page 35 of 115-

3.3.2 Terrestrial Effects Characterization

The most sensitive acute and chronic toxicity reference values associated with hydrogen 

cyanamide exposure to mammals, birds, and terrestrial invertebrates are summarized in Table 

3.9. The most sensitive measurement endpoints for terrestrial plants are presented in Table 3.10. 

Table 3.9. Hydrogen cyanamide Technical Grade Toxicity Measurement Endpoints for 

Terrestrial Animals.

Exposure 

Scenario

Species Exposure 

Duration

Toxicity 

Reference Value

Toxicity 

Classificaiton

MRID 

(Classification)

Mammals

Acute

(Dose-based)

Laboratory 

rat (Rattus 

norvegicus)

Single oral 

dose

LD50 = 300 mg 

a.i./kg bw

Moderately 

toxic

Acc. No. 073726

Acceptable

Chronic

(Dietary-based)

Laboratory 

rat

TwogenerationNOAEL = 1.25 mg 

a.i./kg/day 

Endpoints based on 

decreased maternal 

weight gain, 

decreased food 

consumption

-- MRID 41566504

Acceptable

Birds

Acute 

(Dose-based)

Bobwhite 

quail 

Colinus 

virginianus

14-day single 

oral dose

LD50 = 173 mg 

a.i./kg bw

Slope: NA

Moderately 

toxic

MRID 00153783

(Acceptable)

Acute 

(Dietary-based)

Bobwhite 

quail 

Colinus 

virginianus

8-day dietary LC50: >5000 mg 

ai/kg diet 

NOAEC: 625 mg 

ai/kg diet

(based on behavior 

effects)

Practically nontoxicMRID 42178402

(Acceptable)

Mallard duck

Anas 

platyrhynchos

8-day dietary LC50: >5000 mg 

ai/kg diet

NOAEC: 312.5 mg 

ai/kg diet (based on 

behavior effects)

Practically 

non-toxic

MRID 42178401

(Acceptable)

Chronic 

(Dietary-based)

Mallard duck

Anas 

platyrhynchos

No data available.
-Page 36 of 115-

Table 3.9. Hydrogen cyanamide Technical Grade Toxicity Measurement Endpoints for 

Terrestrial Animals.

Exposure 

Scenario

Species Exposure 

Duration

Toxicity 

Reference Value

Toxicity 

Classificaiton

MRID 

(Classification)

Bobwhite 

quail 

Colinus 

virginianus

ca. 21 week 

avian 

reproduction 

study

LOAEC: 526 mg 

ai/kg diet

NOAEC: 153 mg 

ai/kg diet 

(Based on 14-day 

survivor weight and 

mean food 

consumption)

-- MRID 45797201

(Supplemental)

Terrestrial Invertebrates

Acute

(Contact)

Honeybee 48-hour LD50 >36.2 μg 

a.i./bee

NOAEL = 12 μg 

ai/bee

Practically nontoxicMRID 43866902

(Acceptable)

Table 3.10. Hydrogen Cyanamide Toxicity Measurement Endpoints for Terrestrial Plants.

Exposure 

Scenario

Formulation Species Exposure 

Duration

Toxicity Reference 

Value

Reference

(Classification)

Seedling 

Emergence

Cyanamide L 

500

Onion

(Allium cepa)

21-day test 

-single 

application 

EC25 = 0.44 lbs a.i./A 

NOAEC1 = 0.041 lbs a.i./A 

MRID 48404301

(Supplemental)

Lettuce

(Lactuca 

sativa)

EC25 = not calculable

NOAEC < 0.056 lbs a.i./A 

Vegetative 

Vigor

Cyanamide L 

500

Corn

(Zea mays)

21-day test 

- single 

application

EC25 = 7.9 lbs a.i./A 

NOAEC = 7.2 lbs a.i./A 

MRID 48404302

(Supplemental)

Tomato

(Lycopersicon 

esculentum)

EC25 = 0.89 lbs a.i./A 

NOAEC = 0.096 lbs a.i./A

1 The EC05 is used in lieu of the NOAEC. 

3.3.2.1. Toxicity to Mammals

Acute Effects

The acute oral LD50 for the laboratory rat is 300 mg a.i./kg (EPA Acc. No. 073726), which 

classifies hydrogen cyanamide as moderately toxic. An acute dietary study is not available for 

hydrogen cyanamide. This represents a data gap. 

Chronic Effects

A two-generation reproduction study established a NOAEL of 25 ppm a.i. or 1.25 mg a.i./kg/day. 

The endpoints affected were decreased maternal body weight gain and decreased food 

consumption.
-Page 37 of 115-

3.3.2.2. Toxicity to Birds

Acute and Subacute Dietary

Acute 

In the available acute oral toxicity study the oral LD50 for the bobwhite quail was 173 mg a.i./kg 

(EPA Acc. No. 073728), classifying hydrogen cyanamide as moderately toxic to birds on an 

acute basis. At the 250 mg/kg dosage one male mortality was observed on day one. Seven 

mortalities occurred on day one at the 500 mg/kg level followed by two more mortalities by the 

48-hour point. Only one bird survived at this test level. Total mortality occurred within 4 hours at 

the 1000 and 2000 mg/kg dosage level. All mortalities were preceded by hypoactivity and 

prostration. All birds surviving after this 48-hour period returned to normal behavior. 

No data is available for a passerine species. 

Subacute

The 8-day dietary LC50 for both mallard duck and bobwhite quail was determined to be greater 

than 5000 ppm (MRID 42178401,42178402), which categorizes cyanamide as practically nontoxic on a sub-acute dietary basis. However, behavioral modification, including decreased food 

consumption and signs of stress, occurred in both studies and treatment-related effects on adult 

body weights were reported for the mallard duck. 

For the mallard duck (MRID 42178401), there were no mortalities in the control groups or in the 

treatment groups (312.5, 625, 1250, 2500, 5000 ppm a.i.). During exposure and up to day 6 (1 

day after exposure) abnormal behavioral signs were noted in test concentrations ≥ 625ppm a.i. 

(nominal). These included lethargy, ruffled appearance and reduced reactions to sound and 

movement stimuli. There were significant effects on body weight gain or loss at all concentration 

levels. A corresponding reduction in feed consumption was also observed, thus indicating an 

aversion to consumption of the hydrogen cyanamide dosed food. The NOAEC based on 

behavioral modifications is < 312.5 ppm a.i. 

For the bobwhite quail (MRID 42178402), there were no mortalities in the control groups or test 

concentration groups (312.5, 625, 1250, 2500, and 5000 ppm). During exposure and up to day 6 

(1 day after exposure) abnormal behavioral signs were noted in test concentrations ≥ 1250, ppm 

a.i. (nominal). These included lethargy, ruffled appearance and reduced reactions to sound and 

movement stimuli. By day 7 all birds appeared to return to normal appearance and behavior. No 

effects on body weight or food consumption were noted at any concentration level. The NOAEC 

based on behavioral modifications is 625 ppm a.i. with a LOAEC of 1250 ppm a.i.

Chronic

A supplemental one-generation avian reproduction study is available for the formulation 

Cyanamide L 500, which is an aqueous formulation containing 50.6% active ingredient, for the 
-Page 38 of 115-

bobwhite quail (MRID 45797201). 

The body weights of surviving 14-day old chicks were statistically-reduced compared to the 

control group at 1040 ppm formulation (526 ppm a.i.). Therefore the LOAEC is 526 ppm a.i. 

and the NOAEC is 153 ppm a.i. This study was classified as supplemental because of its use of a 

formulation rather than the technical grade active ingredient. 

3.3.2.3. Toxicity to Terrestrial Invertebrates

Acute Effects

Honey bee

In the acute contact toxicity study (MRID 438669- 02), honey bees were exposed to Dormex 4.0 

SL (50% hydrogen cyanamide) formulated as 10% dust. Data showed that cyanamide is 

essentially non-toxic to the honey bee (LD50 >36.2 mg a.i./bee, and NOAEL approximately 12 

mg a.i./bee).

3.3.2.4. Toxicity to Terrestrial Plants

Terrestrial plant toxicity data are available for the formulation Cyanamide L 500 (50.6% 

cyanamide). In the tier II seedling emergence study (MRID 48404301, supplemental) inhibitions 

in emergence/survival for the most sensitive species, onion and lettuce, were 95% and 80%, 

respectively. Additionally, onion experienced a 76% inhibition in plant length while lettuce 

experienced a 46% inhibition in dry weight. Therefore, the most sensitive monocot species was 

onion based on emergence and survival, with EC05 and EC25 values of 0.041 and 0.44 lb ai/A, 

respectively. Definitive EC25 and NOAEC values were not determined for the most sensitive 

dicot endpoint (lettuce emergence) as a result of high variability within treatment levels, wide 

confidence intervals, and fluctuations in inhibitions as the dose increased. Poor control 

emergence (77%) may have also been a factor. The next most sensitive dicot species was carrot 

based on dry weight, with NOAEC and EC25 values of 0.22 and 0.60 lb a.i./A. This indicates that 

hydrogen cyanamide may affect seedling emergence at rates up to two orders of magnitude 

below the currently registered application rates. 

However, evidence of a low-dose response may be indicative of the heightened species 

sensitivity for lettuce, therefore, the LOAEC value for this species is the lowest concentration 

tested, 0.056 lb a.i./A. For the purposes of this risk assessment, the LOAEC value for lettuce of 

0.056 lb a.i/A will be used to characterize the lower bounds of risk from exposure to terrestrial 

plants to hydrogen cyanamide. Submission of a seedling emergence study that provides 

definitive EC25 and NOAEC values for all ten species would greatly reduce the uncertainty 

associated with these values.

In the vegetative vigor study (MRID 48404302, supplemental) the most sensitive monocot 

species was corn based on dry weight, with NOAEC and EC25 values of 7.2 and 7.9 lb ai/A, 
-Page 39 of 115-

respectively. The most sensitive dicot species was tomato based on dry weight, with NOAEC 

and EC25 values of 0.096 and 0.89 lb ai/A, respectively. However, the EC25 value for tomato 

should be interpreted with caution, as it is not bracketed by the test concentrations.

4. Risk Characterization

4.1. Risk Estimation

Toxicity data and exposure estimates are used to evaluate the potential for adverse ecological 

effects on non-target species. This screening-level assessment for hydrogen cyanamide relies on 

the deterministic RQ method to provide a metric of potential risks. The RQ provides a 

comparison of exposure estimates to toxicity endpoints (i.e., the estimated exposure 

concentrations are divided by acute and chronic toxicity values). The resulting unitless RQs are 

compared to the Agency’s LOCs, as shown in Table 2.3. LOCs are used by the Agency to 

indicate when the use of a pesticide, as directed by the label, has the potential to cause adverse 

effects to non-target organisms.

4.1.1. Aquatic Organisms 

The highest screening-level aquatic EECs based on the maximum application rates for each 

proposed use pattern were used to derive RQs. These exposure estimates represent 

concentrations in surface water (Table 3.7). Peak EECs are used to represent acute exposure to 

fish, aquatic invertebrates, and aquatic plants, and the highest 21-day and 60-day average EECs 

represent chronic exposure to aquatic invertebrates and fish, respectively. 

4.1.1.1. Fish and Invertebrates

Fish

Results of acute toxicity studies in freshwater and estuarine/marine fish (Table 3.9) indicate that 

hydrogen cyanamide is “slightly toxic” to freshwater and estuarine/marine fish on an acute 

exposure basis. For both freshwater and estuarine/marine fish, all acute RQs for the uses of 

hydrogen cyanamide fall well below the Agency’s acute risk to listed species LOC (0.05), as 

well as the Agency’s acute risk to non-listed species LOC of 0.5. RQs range from <0.01 to 0.01 

for freshwater and estuarine/marine invertebrates. 

RQs for chronic exposures to freshwater fish could not be calculated because a definitive 

NOAEC was not available. There are no chronic toxicity data available for estuarine/marine fish. 

Aquatic Invertebrates

Based on all available acute studies, hydrogen cyanamide is categorized as “moderately toxic” to 

aquatic invertebrates on an acute exposure basis. However, RQs for the uses of hydrogen 
-Page 40 of 115-

cyanamide fall below the Agency’s acute risk to listed species and non-listed speices LOCs (0.05 

and 0.5, respectively). RQs range from <0.01 to 0.03 for freshwater invertebrates and from <0.01 

to 0.04 for estuarine/marine invertebrates.

RQs for chronic exposure to freshwater invertebrates fell below the Agency’s chronic risk to 

listed and non-listed species LOC (1.0). RQs for freshwater invertebrates range from 0.06 to 

0.69. Chronic toxicity data for estuarine/marine invertebrates is not available so RQs could not 

be calculated. This will be discussed further in risk characterization. 

4.1.1.2. Aquatic Plants

Table 4.1 lists acute RQs for aquatic vascular and non-vascular plants exposed to hydrogen 

cyanamide. Although hydrogen cyanamide does exhibit effects on both Lemna gibba and 

Anabaena flos-aquae, these effects are at much higher concentrations than those estimated for 

the majority of the hydrogen cyanamide uses. However, the acute listed species LOC (1.0) is 

equal to the LOC for non-vascular plants exposed to hydrogen cynamide from use on cherries. 

Table 4.1. Acute RQs for Aquatic Vascular and Non-vascular Plants Exposed to Hydrogen 

Cyanamide.

Use

(App. Method)

Application 

Rate

lbs a.i./A

(#app)

PRZM Scenario

Peak

EECs

(ppb)

Vascular Aquatic 

Plant RQs

EC50 = 3000 ppb

NOAEC = 370 ppb

Non-vascular Plant RQs

EC50 = 310 ppb

NOAEC = 90 ppb

Acute 

Nonlisted 

Species

Acute 

Listed 

Species

Non-listed 

Species

Listed 

Species

Apples

(airblast) 17.6 (1)

ORapples 31.8 0.01 0.09 0.10 0.35

PAapples 15.5 0.01 0.04 0.05 0.17

NCapples 11.0 <0.01 0.03 0.04 0.12

Blackberry, 

Blueberry 13.2 (1) GApeaches 9.35 <0.01 0.03 0.03 0.10

Cherry 17.6 (1) MIcherries 92.0 0.03 0.24 0.30 1.0*

Grapes 17.6 (1) CAgrapes_Wirri

g

83.6 0.03 0.23 0.30 0.92
-Page 41 of 115-

NYgrapes 21.2 0.01 0.06 0.07 0.24

Kiwifruit,

Fig 17.6 (1) CAfruit_Wirrig 77.5 0.03 0.212 0.25 0.86

Peaches,

Nectarines 6.8 (1) GAPeaches 28.6 0.01 0.08 0.09 0.32

*Bold values indicate acute risk to listed and non-listed aquatic plants LOC (1.0) is exceeded. 

4.1.2. Terrestrial Organisms 

4.1.2.1. Mammals

There are acute dose-based exceedances of the LOC for mammals from exposure to hydrogen 

cyanamide (Table 4.2). The non-listed species LOC is exceeded for all assessed mammalian

size classes foraging on short grass, tall grass, broadleaf plants and small and large arthropods

for all assessed uses. For mammals foraging on fruits/pods/seeds, the non-listed species LOC is 

exceeded for all assessed size classes, except for large mammals (1000 g) exposed to hydrogen 

cyanamide from use on nectarines and peaches. No LOCs were exceeded for granivorous 

mammals. Subacute dietary toxicity data is not available for hydrogen cyanamide. Potential risks 

to mammals from dietary exposure will be discussed in more detail in the Risk Description.

Based on the proposed maximum application rates, there are chronic dose-based exposure 

concerns for mammals of all size classes for all use patterns for all modeled scenarios. RQ

values range from 3.50 to1466. Uncertainties and assumptions will be discussed further in the 

risk characterization section. Table 4.3 lists maximum chronic EECs and RQs for all of the 

proposed use rates based on the upper 90th percentile Kenaga values. Additionally, there are 

exceedances for dietary-based exposure (Table 4.4). There are exceedances for mammals of all 

size class, use patterns and modeled scenarios. RQ values range from 3.96 to 169. 
-Page 42 of 115-

Table 4.2. Acute Dosed-based Mammalian RQs for the Uses of Hydrogen Cyanamide. 

Rate

(# apps; 

interval)

Size 

Class

(grams)

Adjusted 

NOAEL

EECs and RQs

Short Grass Tall Grass Broadleaf 

Plants

Fruits/Pods/

Seeds Arthropods Granivore

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

6.6 (1)1

15 659.35 1510 2.29** 692 1.05** 850 1.29** 94.4 0.14* 592 0.90** 21.0 0.03

35 533.48 1044 1.96** 478 0.90** 587 1.10** 65.2 0.12* 409 0.77** 14.5 0.03

1000 230.75 242 1.05** 111 0.48* 136 0.59** 15.1 0.07 94.8 0.41* 3.36 0.01

13.2 (1)2

15 659.35 3020 4.58** 1384 2.10** 1699 2.58** 189 0.29* 1183 1.79** 42.0 0.06

35 533.48 2088 3.91** 957 1.79** 1174 2.20** 130 0.24* 818 1.53** 29.0 0.05

1000 230.75 484 2.10** 222 0.96** 272 1.18** 30.3 0.13* 190 0.82** 6.72 0.02

17.6 (1)3

15 659.35 4027 6.11** 1846 2.80** 2265 3.44** 252 0.38* 1577 2.39** 55.9 0.08

35 533.48 2783 5.22** 1276 2.39** 1566 2.93** 174 0.33* 1090 2.04** 38.7 0.07

1000 230.75 645 2.80** 296 1.28** 363 1.57** 40.3 0.17* 253 1.10** 8.96 0.03 1

nectarines and peaches

2

blackberries and blueberries

3

California figs, apples, cherries, grapes, and kiwi fruits

*Bold indicates exceedance of the listed species acute-based LOC (0.1).

** Bold indicates exceedance of the non-listed species acute-based LOC (0.5).
-Page 43 of 115-

Table 4.3. Chronic Dosed-based Mammalian RQs for the Uses of Hydrogen Cyanamide. 

Rate

(# apps; 

interval)

Size 

Class

(grams)

Adjusted 

NOAEL

EECs and RQs

Short Grass Tall Grass Broadleaf 

Plants

Fruits/Pods/

Seeds Arthropods Granivore

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

6.6 (1)1

15 2.75 1510 550 692 252 850 309 94.4 34.4 592 215 21.0 7.63

35 2.22 1044 470 478 215 587 264 65.2 29.4 409 184 14.5 6.52

1000 0.96 242 252 111 115 136 142 15.1 15.7 94.8 98.6 3.36 3.50

13.2 (1)2

15 2.75 3020 1099 1384 504 1699 618 189 68.7 1183 431 42.0 15.3

35 2.22 2088 939 957 430 1174 528 130 58.7 818 368 29.0 13.0

1000 0.96 484 503 222 231 272 283 30.3 31.5 190 197 6.72 6.99

17.6 (1)3

15 2.75 4027 1466 1846 672 2265 825 252 91.6 1577 574 55.9 20.36

35 2.22 2783 1252 1276 574 1566 704 174 78.3 1090 490 38.7 17.39

1000 0.96 645 671 296 308 363 378 40.3 42.0 253 263 8.96 9.32 1

nectarines and peaches

2

blackberries and blueberries

3

California figs, apples, cherries, grapes, and kiwi fruits

Bold indicates exceedance of the listed and non-listed species chronic LOC (1.0)
-Page 44 of 115-

Table 4.4. Chronic Dietary-based Mammalian RQs for the Uses of Hydrogen 

Cyanamide. 

Rate

(# apps; 

interval)

NOAE

C 

(ppm)

EECs and RQs

Short Grass Tall Grass Broadleaf 

Plants

Fruits/Pods/

Seeds Arthrpods

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

6.6 (1)1

25

1584 63.4 726 29.0 891 35.6 99.0 3.96 620 24.8

13.2 (1)2 3168 127 1452 58.1 1782 71.3 198 7.92 1240 49.6

17.6 (1)3 4224 169 1936 77.4 2376 95.0 264 10.6 1654 66.2 1

nectarines and peaches 2

blackberries and blueberries

3

California figs, apples, cherries, grapes, and kiwi fruits

Bold indicates exceedance of the listed and non-listed species chronic LOC (1.0)
-Page 45 of 115-

4.1.2.2. Birds

There are acute dose-based exceedances of the LOC for birds from exposure to hydrogen 

cyanamide. The non-listed species LOC is exceeded for all assessed avian size classes foraging 

on short grass, tall grass, broadleaf plants, and arthropods for all assessed uses. For uses on 

blackberries, blueberries, California figs, apples, cherries, grapes, and kiwi fruits, small and 

medium bird (20 g and 100 g, respectively) foraging on fruits/pods/seeds exceed the non-listed 

species LOC, while large birds exceed the listed species LOC only. For uses on nectarines and 

peaches, small birds foraging on fruits/pods/seed exceed the non-listed species LOC, while 

medium and large birds exceed the listed species LOC only. For granivorous birds, RQs exceed 

the non-listed species LOC for small birds from use of hydrogen cyanamide on California fig, 

apples, cherries, grapes, and kiwi fruits. In addition, the listed speices LOC is exceeded for small 

birds from uses on peaches and nectarines, small and medium birds from uses on blackberries 

and blueberries, and medium birds from uses on California figs, apples, cherries, grapes, and 

kiwi fruits. RQs ranged from 0.03 to 38.6 (Table 4.5). 

Based on the available acute dietary toxicity data, no mortality was observed in any of the avian 

studies conducted on hydrogen cyanamide at the highest concentrations; as such, hydrogen 

cyanamide is categorized “practically nontoxic” to birds on an acute-dietary exposure basis. 

However, sublethal effects, including lethargy, ruffled appearance, reduced reactions to sound 

and movement stimuli, effects on body weight gain or loss, and reduction in feed consumption 

was also observed, indicating potential toxicity. Though the acute dietary endpoint available for 

birds is a non-definitive value (>5000 ppm), it was used to calculate the upper bounds of 

potential risk. Based on the registered maximum application rates, the subacute dietary-based 

LOC may be exceeded for non-listed species feeding on short grass exposed to 13.2 or 17.6 lbs 

of hydrogen cyanamide per acre. In addition, the LOC may be exceeded for listed species 

feeding on short grass, tall grass, broadleaf plants, and anthropods from all uses of hydrogen 

cyanamide (Table 4.6). The RQs, ranging from 0.02 to 0.84, represent the upper bounds of 

potential risk. 

 

Based on the registered maximum application rates, the chronic dietary-based LOC is exceeded 

for all modeled scenarios except for birds foraging on fruits/pods/seeds exposed to hydrogen 

cyanamide from uses on nectarines and peaches (i.e., the lowest application rate). RQs ranged

from 0.65 to 27.6 (Table 4.7). 
-Page 46 of 115-

Table 4.5. Acute Dose-based Avian RQ for the Uses of Hydrogen Cyanamide.

Rate

(# apps; 

interval)

Size 

Class

(grams)

Adjusted

LD50

EECs and RQs

Short Grass Tall Grass Broadleaf 

Plants

Fruits/Pods/

Seeds Arthropods Granivore

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

6.6 (1)1

20 124.63 1804 14.5** 827 6.63** 1015 8.14** 113 0.90** 707 5.67** 25.1 0.20*

100 158.67 1029 6.48** 472 2.97** 579 3.65** 64.3 0.41* 403 2.54** 14.3 0.09

1000 224.12 461 2.06** 211 0.94** 259 1.16** 28.8 0.13* 180 0.80** 6.40 0.03

13.2 (1)2

20 124.63 3608 29.0** 1654 13.3** 2030 16.3** 226 1.81** 1413 11.34** 50.1 0.41*

100 158.67 2057 13.0** 943 5.94** 1157 7.29** 129 0.81** 806 5.08** 28.6 0.18*

1000 224.12 921 4.11** 422 1.88** 518 2.31** 57.6 0.26* 361 1.61** 12.8 0.06

17.6 (1)3

20 124.63 4811 38.6** 2205 17.7** 2706 21.7** 301 2.41** 1884 15.1** 66.8 0.54**

100 158.67 2743 17.3** 1257 7.92** 1543 9.73** 171 1.08** 1074 6.77** 38.1 0.24*

1000 224.12 1228 5.48** 563 2.51** 691 3.08** 76.8 0.34* 481 2.15** 17.1 0.08 1

nectarines and peaches

2

blackberries and blueberries

3

California figs, apples, cherries, grapes, and kiwi fruits

*Bold indicates exceedance of the listed species acute-based LOC (0.1).

** Bold indicates exceedance of the non-listed species acute-based LOC (0.5).
-Page 47 of 115-

Table 4.6. Subacute Dietary-based Avian RQ for the Uses of Hydrogen Cyanamide.

Rate

(# apps; 

interval)

LC50

(ppm)

EECs and RQs

Short Grass Tall Grass Broadleaf 

Plants

Fruits/Pods/

Seeds Arthropods

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

6.6 (1)1

>5000

1584

<0.32

* 726

<0.15

* 891

<0.18

* 99.0 <0.02 620

<0.12

*

13.2 (1)2

3168

<0.63

** 1452

<0.29

* 1782

<0.36

* 198 <0.04 1240

<0.25

*

17.6 (1)3

4224

<0.84

** 1936

<0.39

* 2376

<0.48

* 264 <0.05 1654

<0.33

* 1

nectarines and peaches

2

blackberries and blueberries 3

California figs, apples, cherries, grapes, and kiwi fruits

*Bold indicates exceedance of the listed species acute-based LOC (0.1).

** Bold indicates exceedance of the non-listed species acute-based LOC (0.5).

Table 4.7. Chronic Dietary-based Avian RQ for the Uses of Hydrogen Cyanamide.

Rate

(# apps; 

interval)

NOAEC 

(ppm)

EECs and RQs

Short Grass Tall Grass Broadleaf 

Plants

Fruits/Pods/

Seeds Arthropods

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

6.6 (1)

1

153

1584 10.4 726 4.75 891 5.82 99.0 0.65 620 4.05

13.2 (1)2

3168 20.7 1452 9.49 1782 11.7 198 1.29 1240 8.11

17.6 (1)3

4224 27.6 1936 12.7 2376 15.5 264 1.73 1654 10.8 1

nectarines and peaches

2

blackberries and blueberries

3

California figs, apples, cherries, grapes, and kiwi fruits

Bold indicates exceedance of the listed and non-listed species chronic LOC (1.0)

4.1.2.3. Terrestrial Invertebrates 

In order to assess the risks of hydrogen cyanamide to terrestrial invertebrates, the honey bee 

(acute contact LD50 of > 36.2 μg a.i./bee; MRID 43866902) is used as a surrogate for terrestrial 

invertebrates. The toxicity value for terrestrial invertebrates is calculated by multiplying the 

lowest available acute contact LD50 of >36.2 μg a.i./bee by 1 bee/0.128g, which is based on the 

weight of an adult honey bee. EECs (μg a.i./g of bee) calculated by T-REX for arthropods are 

divided by the calculated toxicity value for terrestrial invertebrates, which is >4.63 μg a.i./g of 
-Page 48 of 115-

bee (Table 4.8). Based on this analysis RQs for terrestrial invertebrates exceed the LOC (0.05) 

for all assessed uses of hydrogen cyanamide. These RQs represent the upper bound of the 

potential risk. Without a definitive toxicity endpoint it is not possible to determine the magnitude 

of the risk. RQs range from 134 to 357. 

Table 4.8. Terrestrial Invertebrate RQs for Hydrogen Cyanamide.

Rate

(# apps; 

interval)

LC50

(μg a.i./g bee)

EECs and RQs

Arthropods

EEC RQ

6.6 (1)1

>4.63

620 <134

13.2 (1)2

1240 <268

17.6 (1)3

1654 <357 1

nectarines and peaches

2

blackberries and blueberries

3

California figs, apples, cherries, grapes, and kiwi fruits

Bold indicates exceedance of the LOC (0.05)

4.1.2.4. Non-target Terrestrial Plants

Potential effects to riparian and upland vegetation are assessed deriving RQs from terrestrial 

plant seedling emergence and vegetative vigor EC25 and NOAEC endpoints. As discussed in 

Section 3.3.2.4, a non-definitive NOAEC value (<0.056 lb a.i./A) for the most sensitive dicot 

species from the seedling emergence study was used in risk calculation. Therefore, RQs based on 

this value (i.e., dicot listed species in dry and semi-aquatic areas) appear as greater than values in 

Tables 4.9 and 4.10. The magnitude of these RQs is unknown. In addition, a corresponding EC25

value was not available for the most sensitive dicot species from the seedling emergence study. 

As a result, RQs for non-listed species could not be calculated for dicots in dry and semi-aquatic 

areas. However, RQs for dicots in these areas that were calculable exceed the LOC for listed 

species for all modeled exposures. In addition, RQs for monocots in dry and semi-aquatic areas 

exceed the LOC for listed and non-listed species for all modeled exposures. For plants exposed 

through spray drift, RQs exceed the LOC for listed monocots and dicots for all modeled 

exposures, while RQs exceed the LOC for non-listed monocots for airblast applications to 

blueberries, blackberries, California figs, apples, cherries, grapes, and kiwi fruits and for nonlisted dicots for airblast applications to apples, cherries, grapes, and kiwi fruits. 
-Page 49 of 115-

Table 4.9. RQs for Terrestrial Plants Inhabiting Dry and Semi-aquatic Areas Exposed to 

Hydrogen Cyanamide via Runoff and/or Spray Drift from Airblast Applications.

Application 

Rate

lbs ai/A Plant Type

Listed 

Status Dry Semi-Aquatic Spray Drift

6.62

Monocot non-listed 1.55 8.50 0.77

Monocot listed 16.59 91.11 8.29

Dicot1 non-listed -- -- 0.38 

Dicot1 listed >12.14 >66.79 6.07

13.23

Monocot non-listed 3.00 16.50 1.50 

Monocot listed 32.20 177.07 16.10

Dicot1 non-listed -- -- 0.74 

Dicot1 listed >23.57 >129.64 11.79

17.64

Monocot non-listed 4.00 22.00 2.00 

Monocot listed 42.93 236.10 21.46

Dicot1 non-listed -- -- 0.99 

Dicot1 listed >31.43 >172.86 15.71 1

definitive NOAEC and EC25 values were not calculable for the most sensitive species in the seedling emergence study. For 

calcluations that rely on this information (i.e., plants exposure via run-off), the LOAEC of 0.056 lb a.i./A is used in place of a 

NOAEC to represent the lower bound of risk exposure. 2

nectarines and peaches

3

blackberries and blueberries

4

California figs, apples, cherries, grapes, and kiwi fruits

Bolded values exceed LOC for plants (RQ>1.0)

Table 4.10. RQs for Terrestrial Plants Inhabiting Dry and Semi-aquatic Areas Exposed to 

Hydrogen Cyanamide via Runoff and/or Spray Drift from Ground Spray Applications.

Application 

Rate

lbs ai/A Plant Type

Listed 

Status Dry Semi-Aquatic Spray Drift

6.62

Monocot non-listed 0.93 7.88 0.15 

Monocot listed 9.95 84.59 1.66

Dicot1 non-listed -- -- <0.1 

Dicot1 listed >7.29 >61.93 1.21

13.23

Monocot non-listed 1.80 15.30 0.30 

Monocot listed 19.32 164.20 3.22

Dicot1 non-listed -- -- 0.15 

Dicot1 listed >14.14 >120.21 2.36

17.64

Monocot non-listed 2.40 20.40 0.40 

Monocot listed 25.76 218.93 4.29

Dicot1 non-listed -- -- 0.20 

Dicot1 listed >18.86 >160.29 3.14 1

definitive NOAEC and EC25 values were not calculable for the most sensitive species in the seedling emergence study. For 

calcluations that rely on this information (i.e., plants exposure via run-off), the LOAEC of 0.056 lb a.i./A is used to represent the 

lower bound of risk exposure. 2

nectarines and peaches

3

blackberries and blueberries

4

California figs, apples, cherries, grapes, and kiwi fruits

Bolded values exceed LOC for plants (RQ>1.0)
-Page 50 of 115-

4.2. Incident Database Review

A review of the Ecological Incident InformationSystem (EIIS) database for incidents involving 

hydrogen cyanamide was conducted on February 27th, 2014. Two incidents for hydrogen 

cyanamide are reported in the database (Appendix E). The first incident, I000423-001, was 

classified as probable and resulted from an accidental misuse of hydrogen cyanamide on grape 

vineyards. The incident report indicates that hydrogen cyanamide applied during stormy weather 

using a high pressure sprayer resulted in defoliation of several groves of nearby lemon trees. 

Label language requires use of a low pressure sprayer and application only when weather 

conditions do not favor drift. In the second incident, I016036-022, the California Department of 

Pesticide Regulations reported 380 acres of kiwifruits were damaged after hydrogen cyanamide 

application. This incident is classified as possible and resulted from a registered use of hydrogen 

cyanamide. 

Similarly, a search of the Avian Incident Monitoring System (AIMS; 

http://www.abcbirds.org/abcprograms/policy/toxins/aims/aims/index.cfm) was conducted on 

February 27th, 2014. AIMS is a database administered by the American Bird Conservancy that 

contains publicly available data on reported avian incidents involving pesticides. No incidents

involving hydrogen cyanamide were found. 

Pesticide registrants report certain types of incidents to the Agency as aggregate counts of 

incidents occurring per product per quarter. Aggregate incident data is not available for 

hydrogen cyanamide. 

The number of reports listed in the EIIS database is believed to be only a small fraction of the 

total incidents involving organism mortality and damage caused by pesticides. Few resources are 

assigned to incident reporting. Reporting by states is only voluntary, and individuals discovering 

incidents may not be informed on the procedure of reporting these occurrences. Additionally, 

much of the database is generated from registrant-submitted incident reports. In addition, 

incident reports for non-target organisms typically provide information only on mortality events 

and plant damage incidents. Impacts to non-commercial beneficial insects and other invertebrates 

are not likely to be reported. Except for phytotoxic effects in terrestrial plants, sublethal effects 

for organisms such as reduced growth or impaired reproduction are rarely reported. Because of 

these logistical difficulties, EIIS is most likely a minimal representation of all pesticide-related 

ecological incidents.

Therefore, the weight of evidence based on the currently available data suggests that direct 

effects to terrestrial plant species are expected from the currently registered use of hydrogen 

cyanamide. 

4.3. Risk Description

The results of risk estimation indicate that uses of hydrogen cyanamide are unlikely to adversely 

affect fish, aquatic invertebrates or aquatic plants on either an acute or chronic exposure basis. 

However, acute and chronic risks to terrestrial animals (i.e., mammals, birds, and their 
-Page 51 of 115-

surrogates) are very likely. Similarly, terrestiral plant risks are well above the Agency’s levels of 

concern. Therefore, the risk hypothesis for this risk assessment is partially supported (risk to 

terrestrial organisms but not for aquatic organisms).

4.3.1 Exposure to Aquatic Organisms

The Tier II model Pesticide Root Zone Model (PRZM v3.12.2; May 12, 2005; Carousel et al., 

undated) linked with EXposure Analysis Modeling System (EXAMS v2.98.4.6; Apr. 25, 2005; 

Burns, 2004) via the PRZM/EXAMS model shell (PE v5.0, Nov. 15, 2006), i.e., 

PRZM/EXAMS) were used to estimate screening-level exposure concentrations in aquatic 

environments. The PRZM model simulates pesticide movement and transformation on and 

across the agricultural field resulting from crop applications. The EXAMS model simulates 

pesticide concentrations in water due to loading via runoff, erosion, and spray drift, assuming a 

standard 1-ha pond, 2-m deep (20,000 m3

) with no outlet that borders a 10-ha treated field. 

Simulations are for multiple (usually 30) years, from which the Agency estimates peak values 

that are expected to recur on average once every ten years, based on time series of daily 

estimated concentrations. The coupled PRZM and EXAMS models and user’s manuals are 

available from the U.S. Environmental Protection Agency Water Models web-page (USEPA, 

2011b).

Aquatic exposure was modeled with a 900 foot buffer for drift but not run-off. Current label 

language requires a 900 foot buffer between the field of application and “the mean high water 

mark for intertidal areas, surface waters, rivers, streams, or their flowing tributaries” to reduce 

potential exposures to nearby waterbodies.

The initial application date was selected in consulation with experts in order to simulate 30 or 

more days before normal budbreak. Application dates for modeling purposes were selected in 

accordance with the proposed labels to generate the most conservative estimates of aquatic 

exposure and based on information from the Cooperative Extension offices or from the World 

Wide Web.

Model uncertainties are discussed in greater detail in Section 4.4.

4.3.2 Risks to Aquatic Animals

Although hydrogen cyanamide does exhibit topxic effects on freshwater and estuarine/marine 

fish and invertebrates on an acute exposure basis, RQs are all well below the Agency’s levels of 

concern for all of the modeled scenarios. 

Risk quotients could not be calculated for freshwater fish on a chronic exposure basis because 

the available study provides a non-definintive NOAEC value of < 507 ppb, the lowest 

concentration tested. Lack of a definitive NOAEC value, and a LOAEC value within one order 
-Page 52 of 115-

of magnitude of the highest exposure scenario, suggest that risk to freshwater fish from chronic 

exposure to hydrogen cyanamide can not be precluded. However, as discussed previously, the 

magnitude of biological effects observed at the lowest concentration tested appear to be close 

to the limit of statistical and biological significance. This information, combined with the 

evidence of a dose response in the higher treatment concentrations, make it unlikely that 

another early life stage test with the rainbow trout will provide a NOAEC value that is 

substantially lower than the lowest concentration tested in the available study.

Chronic toxicity data was not avaible for estuarine/marine fish. It is not possible to calculate an 

acute-to-chronic ratio (ACR) because only a non-definitive NOAEC is available for the 

freshwater fish. Based on the available acute toxicity data, estuarine/marine fish exhibit similar 

toxicity as freshwater fish so it is likely that they exhibit similar toxicity on a chronic exposure 

basis. Chronic risk to estuarine/marine fish cannot be precluded. In addition, available aerobic 

aquatic metabolism data suggests that hydrogen cyanamide degrades faster under flowing 

conditions (1.2 days in a stream system versus 3.2 days in a pond system), such as may be found 

in some estuarine/marine systems. As a result of this shorter half-life, chronic risks to 

estuarine/marine fish that reside in flowing waters may be low. 

Chronic risk to freshwater invertebrates is expected to be low based on chronic toxicity data 

submitted for the daphnid, with RQs ranging from 0.06 to 0.69. Chronic toxicity data is not 

available for estuarine/marine invertebrates. The acute to chronic ratio (ACR) of 33 for the 

daphnid (most sensitive freshwater invertebrate) was applied to the available acute mollusk (the 

most sensitive estuarine/marine invertebrate) and acute Mysid shrimp data in order to bracket the 

potential for chronic effects to estuarine/marine invertebrates. Uncertainties associated with this 

approach are discussed further in the uncertainties section. When the ACR was used to estimate 

chronic toxicity to the eastern oyster, RQs ranged from 0.09 to 1.0, indicating potential for risks

to estuarine/marine mollusks from chronic exposure from hydrogen cyanamide use on cherries. 

Additionally, when the ACR for the daphnid was applied to the acute toxicity value available for 

the pink shrimp (LC50 = 6300 ppb), RQs ranged from 0.03 to 0.36, suggesting that the potential 

for chronic risk to crustaceans is low. With this information chronic risks to mollusks can not be 

precluded but risks to crustaceans are not likely. 

4.3.3 Risks to Aquatic Plants

Although hydrogen cyanamide does exhibit effects on both Lemna gibba and Anabaena flosaquae, these effects are at much higher concentrations than those estimated for the majority of 

the hydrogen cyanamide uses. However, the acute listed species RQ is equal to the LOC for 

non-vascular plants exposed to hydrogen cyanamide from the cherry use, which indicates that 

risks to listed aquatic non-vascular plants may occur. However, as discussed previously EECs 

are primarily driven by the modeled run-off, which assumes no buffer between the site of 

application and the water body. Given the 900 ft buffer required between the site of application 

and any waterbody and the rapid degradation of hydrogen cyanamide in soil, exposure to aquatic 

environments may be over estimated. As a result of this limitation risks to aquatic non-vascular 
-Page 53 of 115-

plants may be overestimated. In fact, EECs for use of hydrogen cyanamide on cherries would 

only need to drop ~1% to result in RQs below the level of concern. 

In addition, risk to aquatic nonvascular species is typically evaluated with not only the 

cyanobacteria species that was submitted, but also with a green algae, a centric diatom and a 

pinnate diatom. Acceptable studies with these species have not been submitted and are an 

appreciable source of uncertainty in the risk assessment. These planktonic taxa form the basis of 

the aquatic food web and are frequently more sensitive to pesticides than cyanobacteria. While 

uncertainties associated with EECs discussed above likely result in an over estimation of 

exposure to aquatic environments, risks to aquatic non-vascular plants cannot be precluded 

without data on the additional algal species. 

4.3.4. Risks to Mammals

Results of toxicity studies indicate that hydrogen cynamide is “moderately toxic” to mammals on 

an acute exposure basis. Acute risk concerns were triggered for all assessed mammalian size 

classes foraging on short grass, tall grass, and broadleaf plants, and arthropods for all assessed 

uses. For mammals foraging on fruits/pods/seeds, acute risk concerns were triggered for all 

assessed size classes, except for large mammals (1000 g) exposed to hydrogen cyanamide from 

use on nectarines and peaches. Acute risk is not expected for granivorous mammals. Acute dosebased RQs range from 0.02 for large granivorous mammals to 6.11 for small mammals feeding 

on short grass. Based on its reported toxicity to mammals, the maximum application rate of 

hydrogen cyanamide that would not result in acute risk concerns is 0.65 lbs a.i./A.

In addition to the acute risk concerns identified, chronic dose-based and dietary-based risk 

concerns are triggered for mammals of all size class for all use patterns for all modeled 

scenarios. RQs for chronic dose-based exposure range from 3.60 to 1466 and RQs from chronic 

dietary-based exposure range from 26.5 to 169. Based on these conservative RQs, the maximum 

application rate of hydgrogen cyanamide that would not result in chronic dose-based or chronic 

dietary-based concerns is 0.005 lbs a.i./A. However, the chemical properties and available 

residue data discussed previously suggest that hydrogen cyanamide degrades rapidly in the 

environment. Without prolonged exposure, chronic risks to mammals may be considerably 

reduced. However, if the foliar half-life for hydrogen cyanamide is 1 day, risks to mammals from 

chronic exposure would likely not occur given that the chemical is only applied once per season. 

A foliar dissipation study would reduce the uncertainty associated with chronic risk to mammals.

Results of the screening model SIP also indicate that drinking water exposure is a potential 

concern for mammals based on acute and chronic exposure. Hydrogen cyanamide has a very 

high solubility in water (780,000 mg/L), which is the only parameter used in estimating potential 

exposure, and mammals are particularly sensitive to hydrogen cyanamide on an acute and

chronic basis.

Risks may be mitigated by the geographic and temporal limitations of the chemical. Hydrogen 

cyanamide is only registered for use on a limited number of fruit bearing trees and ground fruit, 
-Page 54 of 115-

including: nectarines, peaches, blackberries, blueberries, figs, apples, cherries, grapes, and kiwi 

fruits. Further, geographic restrictions outlined on the labels limit the use of hydrogen cyanamide 

on certain crops and in certain regions (see Table 3.1 for more information). Thes limited use 

patterns for hydrogen cyanamide may result in substantially less overlap with endangered species 

habitat than a chemical with a ubiquitous use pattern (e.g., corn). In addition to these geographic 

boundaries, labels state that hydrogen cyanamide is to be applied 30 days prior to normal bud 

break. For the assessed uses this means that application occurs between December and March

(see Table 3.6 for more information). The temporal and geographic limitations suggest that 

potential for acute risks are limited to those species that are active in late winter, especially in 

temperate regions of the country. The exception may be for uses of hydrogen cyanmide in areas 

with winters mild enough that mammals remain active and plants do not senesce (e.g.,

California, Hawaii, and Florida).

4.3.5. Risk to Birds

Results of toxicity studies indicate that hydrogen cynamide is “moderately toxic” to birds on an 

acute dose-based exposure basis. Combined with the high application rates, acute dose-based risk 

concerns were triggered for all assessed avian size classes foraging on short grass, tall grass, 

broadleaf plants, and arthropods for all assessed uses. For uses on blackberries, blueberries, 

California figs, apples, cherries, grapes, and kiwi fruits, small and medium birds (20 g and 100 g, 

respectively) foraging on fruits/pods/seeds are at risk, while only listed species of large birds 

may be at risk. For uses on nectarines and peaches, small birds foraging on fruits/pods/seed are 

at risk, while only listed species of medium and large birds are at risk. For granivorous birds, 

small birds are at risk from use of hydrogen cyanamide on California fig, apples, cherries, 

grapes, and kiwi fruits. In addition, listed species of small birds may be at risk from uses on 

peaches and nectarines, listed small and medium birds from uses on blackberries and blueberries, 

and listed medium birds from uses on California figs, apples, cherries, grapes, and kiwi fruits. 

The maximum application rate of hydgrogen cyanamide that would not result in acute dosebased concerns to non-listed species is 0.32 lbs a.i./A. 

Results of the acute dietary studies classify hydrogen cyanamide as “practically non-toxic”. 

However, application rates for the assessed uses were sufficient to trigger risk concerns for birds 

from dietary exposure to hydrogen cyanamide. In addition, sublethal effects including lethargy, 

ruffled appearance, reduced reactions to sound and movement stimuli, effects on body weight 

gain or loss, and reduction in feed consumption observed during the studis indicate that hydrogen 

cyanmide is potentially toxicity or unpalatable to upland and game bird species. These 

behavioral modifications, especially the food avoidance behavior, may result in even greater 

dietary risks to passerine species, which exhibit regurgitation behavior when they come in 

contact with unpalatable or toxic substances. Acute dose-based and dietary-based risks to 

passerine species respresent a substantial uncertainty in this analysis. 

In addition to the acute risks identified, chronic dietary-based concerns are triggered for all 

modeled scenarios except for birds foraging on fruits/pods/seeds exposed to hydrogen cyanamide 
-Page 55 of 115-

from uses on nectarines and peaches (i.e., the lowest application rate). The maximum 

application rate of hydrogen cyanamide that would not result in chronic dietary-based concerns 

to listed or non-listed species is 0.64 lbs a.i./A. However, the chemical properties and available 

residue data discussed previously suggest that hydrogen cyanamide degrades rapidly in the 

environment. Without prolonged exposure, chronic risks to birds may be considerably reduced.

However, if the foliar half-life for hydrogen cyanamide is 1 day, risks to birds from chronic 

exposure would likely not occur, especially given hydrogen cyanamide’s single application per 

season use. A foliar dissipation study would reduce the uncertainty associated with chronic risk 

to birds. 

Results of the screening models SIP and STIR indicate that drinking water and inhalation 

exposure are of potential concern for birds based on acute and chronic exposure. Hydrogen 

cyanamide has a very high solubility in water (780,000 mg/L) and relatively volatile (0.00375 

mmHg), which are the only parameters used in estimating potential exposure for SIP and STIR, 

respectively. In addition birds are relatively sensitive to hydrogen cyanamide on an acute and 

chronic basis.

As discussed in the previous section, risks to birds may be mitigated by the geographic and 

temporal limitations of hydrogen cyanamide use.

4.3.6. Potential Effects on Terrestrial Invertebrates

An acute contact toxicity study (MRID 43866902) showed that cyanamide is essentially nontoxic to the honey bee (LD50 >36.2 mg a.i./bee, and NOEL approximately 12 mg a.i./bee). 

Screening-level risk assessments do not typically evaluate risks to terrestrial invertebrates; 

however, toxicity information for beneficial insects is used to develop precautionary label 

language where necessary. While hydrogen cyanamide is “practically non-toxic” to honey bees, 

the high application rates used may pose risks to bees as a result of high field residues (max 

EECs are over 1600 ppm a.i.). A foliar dissipation study would reduce uncertainties associated 

with risks to beneficial insects.

4.3.7. Risk to Terrestrial Non-target Plants

As discussed in Section 3.3.2.4, there are considerable uncertainties associated with the available 

terrestrial plant data, including the use of a non-definitive NOAEC value (<0.056 lb a.i/A) for the 

most sensitive dicot species from the seedling emergence study to calculate risk. As a result, RQs 

based on this value (i.e., dicot listed species in dry and semi-aquatic areas) appear as greater than 

values and yhe magnitude of risk is unknown. In addition, due to uncertainties in the available 

data set, risk could not be estimated for non-listed dicots in dry and semi-aquatic areas (i.e., risk 

from exposure through run off). However, risk is expected for listed terrestrial plants (dicot and 

monocot) in dry and semi-aquatic areas for all modeled exposures. In addition, two incidencts 

have been reported for hydrogen cyanamide; however, both incidents reported damage to crops 

after potential misuse (I000423-001 and I016036-022). 
-Page 56 of 115-

The Agency does not currently have guidance to refine the risk posed by runoff, but the risk from 

spray drift alone can be refined using AgDRIFT. AgDRIFT was used to determine the distance 

from the edge of field where the RQ falls below the LOC for each of the species (Tables 4.8-4.9) 

for airblast applications for for the most common and highest application rate (17.6 lbs ai/A for 

use on California fig, apples, cherries, grapes, and kiwi fruit) and the lowest application rate (6.6 

lbs ai/A for use on nectarines and peaches). Model defaults for each scenario were used.

Uncertainties and gaps in the available terrestrial plant data (e.g., EC25 values are not available 

for all species) limit the accuracy of this information. 

Table 4.10 Distance (feet) from the edge of field where the RQ falls below the risk 

to terrestrial plant LOC for vegetative vigor and seedling emergence endpoints for 

airblast application, based on AgDRIFT EECs for the aerial application at 6.6 lbs 

ai/A.

Plant 

Species

Vegetative Vigor

EC25 NOAEC Nonlisted Listed

Corn 7.9 7.2 0 0

Oat -

a

- -- a -- a -- a

Ryegrass >20 20 0 0

Onion 13 7.2 0 0

Lettuce 4.5 3.6 0 0

Cabbage >14 1.8 0 0

Tomato 0.89 0.096 0 0

Carrot >20 20 0 0

Cucumber 4.2 0.73 0 0

Soybean 9.6 7.2 0 0

a Phytotoxic effects >25% were observed in the control group, indicating poor husbandry. The vegetative vigor 

endpoints for this species were invalidated; therefore, buffer distances could not be calculated. 

Table 4.11 Distance (feet) from the edge of field where the RQ falls below the risk to 

terrestrial plant LOC for vegetative vigor and seedling emergence endpoints for 

airblast application, based on AgDRIFT EECs for the aerial application at 17.6 lbs 

ai/A.

Vegetative Vigor
-Page 57 of 115-

Plant Species EC25 NOAEC Nonlisted Listed

Corn 7.9 7.2 0 0

Oat -- a -- a -- a -- a

Ryegrass >20 20 0 0

Onion 13 7.2 0 0

Lettuce 4.5 3.6 0 0

Cabbage >14 1.8 0 0

Tomato 0.89 0.096 0 7

Carrot >20 20 0 0

Cucumber 4.2 0.73 0 0

Soybean 9.6 7.2 0 0

a Phytotoxic effects >25% were observed in the control group, indicating poor husbandry. The vegetative vigor 

endpoints for this species were invalidated, therefore buffer distances could not be calculated. 

Airblast applications result in more drift than ground sprays, therefore, impacts from airblast 

applications are expected farther from the field edge for ground applications. Application rate is 

a key variable in determining the distance effective drift is expected to travel, so airblast 

applications of 17.6 lbs ai/A will have an impact at greater distance from the application area 

than the 6.6 lbs ai/A rate. For nonlisted and listed plants, assessed species are not expected to be 

at risk beyond the edge of the application area. In addition, hydrogen cyanamide labels attempt

to account for possible risks to endangered species from drift by restricting the use of hydrogen 

cyanamide products in areas with endangered species; however, labels do not mention specific 

buffer distances. 

4.4. Uncertainties and Data Gaps

4.4.1. Fate and Transport

For the purposes of risk assessment the submitted environmental fate data are adequate. The 

quality of the submitted data is generally adequate. The acceptable batchequilibrium study 

(MIID 42178414) demonstrates a lack of adsorption to soil particles. Adsorption of hydrogen 

cyanamide was so limited that Freundlick coefficient-values would not accurately quantify the 

mobility of hydrogen cyanamide. Although a single acceptable aerobic study was reviewed, a 

conservative approach was used when evaluating aquatic exposure by multiplying the single 
-Page 58 of 115-

value by 3 (Table 3.5).

4.4.2. Aquatic Exposure

There is uncertainty associated with the ability of the aquatic exposure modeling to simulate 

aquatic exposures as well as with the selection of input parameters. In this regard, one of the 

potentially important parameters that can impact concentration estimates is the selection of 

appropriate application dates. Although the pesticide application dates were selected to be most 

appropriate with considerations for labeled application recommendations (e.g., 30 days before 

bud break) model simulated cropping dates, and label restrictions, variability nevertheless results 

because the time span that a pesticide may be applied may be large and the actual application 

dates are unknown, or vary for different regions of the country. Such variability is caused by the 

temporal proximity of a pesticide application to rain events. As with all model estimates, the 

values presented here should not be viewed as precise estimates.

In addition, registered labels for hydrogen cyanamide products include a language requiring a 

900 ft buffer between the site of application and “the mean high water mark for intertidal areas, 

surface waters, rivers, streams, or their flowing tributaries” to limit the potential for exposure of 

hydrogen cyanamide to aquatic environments. While aquatic EECs were modeled using a 900 ft 

buffer for drift, the Agency does not currently have a method for modeling the impact of a buffer 

on run-off. Therefore, EECs are primarily driven by the modeled run-off, which assumes no 

buffer between the site of application and the water body. Given the rapid degradation of 

hydrogen cyanamide in soil, this is a major source of uncertainty in the aquatic exposure and 

subsequent risk assessment. As a result of this limitation risks to aquatic organisms may be 

overestimated. 

4.4.3. Effects Uncertainties

An area of uncertainty for this assessment surrounds potential chronic risk to birds. Current data 

on mallard duck are inadequate to derive a definitive NOAEC or make a definitive determination 

of risk (effects were noted at all test concentrations). While a second avian reproduction study 

on mallard duck that results in derivation of a NOAEC would reduce uncertainty, chronic risks 

are already identified for birds based on the available bobwhite quail data. Therefore, additional 

data on the mallard duck is not necessary at this time. In addition, acute toxicity data is not 

available for a passerine species; however, given the magnitude of difference needed to reduce 

application rates such that risk is below the level of concern, this data is unlikely to change the 

risk assessment.

There is also uncertainty surrounding the potential for chronic risks to fish. Current data on the 

freshwater species, rainbow trout, are not adequate to derive a definitive NOAEC because effects 

were noted at all test concentrations. This represents a substantial data gap in the analysis. Since 

the available LOAEC is within one order of magnitude of the highest EEC, chronic risk to 

freshwater fish cannot be precluded. However, the magnitude of biological effects observed at 
-Page 59 of 115-

the lowest concentration level appears to be close to the limit of statistical and biological 

signifigance. In addition, as discussed previously the aquatic EECs do not take into consideration 

the impacts of the required 900 ft buffer on run-off. Therefore, the benefits of receiving another 

early life stage study to define a NOAEC may not be substantial. 

Chronic toxicity data was not avaible for estuarine/marine fish. It is not possible to calculate an 

acute-to-chronic ratio (ACR) because only a non-definitive NOAEC is available for the 

freshwater fish. This represents a substantial data gap in the analysis. 

Another area of uncertainty surrounds the potential for chronic risks to estuarine/marine 

invertebrates because this data is not available. While there is uncertainty associated with 

applying the acute to chronic ratio (ACR) for the daphnid (most sensitive freshwater 

invertebrate) to the mollusk (most sensitive estuarine/marine invertebrate) because of the 

differences in life history, applying the ACR to the mollusk and the less sensitive Mysid shrimp 

can be used to bracket the potential risks to estuarine/marine invertebrates. When the ACR was 

used to estimate chronic toxicity to the eastern oyster, RQs ranged from 0.09 to 1.0, indicating 

potential for risks to estuarine/marine mollusks from chronic exposure from hydrogen cyanamide 

use on cherries. Additionally, when the ACR for the daphnid were applied to the acute toxicity 

value available for the pink shrimp (LC50 = 6300 ppb), RQs ranged from 0.03 to 0.36, suggesting 

that the potential for chronic risk to crustaceans is low. With this information chronic risks to 

mollusks can not be precluded but risks to crustaceans are likely low. 

Additionally, the Agency has only received data for two species of non-vascular aquatic plants, 

instead of the four species typically required. Without this data risks to these taxa of aquatic 

plants may be underestimated.

There are considerable uncertainties associated with the available plant toxicity data. For 

seedling emergence, definitive EC25 and NOAEC values were not calculable for the most 

sensitive dicot species (lettuce) in the available seedling emergence study. As a result, risks to 

non-listed plant species could not be calculated and RQs for listed species were calculated based 

on the LOAEC value (0.056 lbs a.i./A). RQs may underestimate the magnitude of risk to listed 

species exposed to hydrogen cyanamide via run-off and spray drift. In addition, phytotoxicity 

observed in the control group was greater than 25% for one species (oat) in the vegetative vigor 

study. This suggests that growing conditions may not have been optimal for this species or cross 

contamination may have occurred. As a result, this data could not be used in the AgDrift analysis 

to calculate buffer distances. Risks may be underestimated for plants with similar toxicity to oat. 

In addition, the EC25 value for the most sensitive dicot species (tomato) should be interpreted 

with caution, as it is not bracketed by the test concentrations.

5. Federally Threatened and Endangered (Listed) Species Concerns

Section 7 of the Endangered Species Act, 16 U.S.C. Section 1536(a)(2), requires all federal 

agencies to consult with the National Marine Fisheries Service (NMFS) for marine and 
-Page 60 of 115-

anadromous listed species, and/or the United States Fish and Wildlife Service (USFWS) for 

listed wildlife and freshwater organisms, if they are proposing an "action" that may affect listed 

species or their designated critical habitat. Each federal agency is required under the Act to 

ensure that any action they authorize, fund, or carry out is not likely to jeopardize the continued 

existence of a listed species or result in the destruction or adverse modification of designated 

critical habitat. To jeopardize the continued existence of a listed species means "to engage in an 

action that reasonably would be expected, directly or indirectly, to reduce appreciably the 

likelihood of both the survival and recovery of a listed species in the wild by reducing the 

reproduction, numbers, or distribution of the species" (50 C.F.R. § 402.02).

To facilitate compliance with the requirements of the Endangered Species Act (subsection 

(a)(2)), the Office of Pesticide Programs has established procedures to evaluate whether a 

proposed registration action may directly or indirectly appreciably reduce the likelihood of both 

the survival and recovery of a listed species in the wild by reducing the reproduction, numbers, 

or distribution of any listed species (USEPA, 2004). After the Agency’s screening level risk 

assessment is conducted, if any of the Agency’s listed species’ LOCs are exceeded for either 

direct or indirect effects, an analysis is conducted to determine if any listed or candidate species 

may co-occur in the area of the proposed pesticide use or areas downstream or downwind that 

could be contaminated from drift or runoff/erosion. If listed or candidate species may be present 

in the proposed action area, further biological assessment is undertaken. The extent to which 

listed species may be at risk is considered, which then determines the need for the development 

of a more comprehensive consultation package, as required by the Endangered Species Act.

The federal action addressed herein is the proposed new registration of hydrogen cyanamide on 

agricultural use sites it is expected that its use could occur nationwide.

5.1. Action Area 

For listed species assessment purposes, the action area is considered to be the area affected 

directly or indirectly by hydrogen cyanamide use and not merely the immediate area where 

hydrogen cyanamide is applied. At the initial baseline, the risk assessment considers broadly 

described taxonomic groups and conservatively assumes that listed species within those broad 

groups are co-located with the pesticide treatment area. This means that listed terrestrial plants 

and wildlife are assumed to be located on or adjacent to the treated site and listed aquatic 

organisms are assumed to be located in a surface water body adjacent to the treated site. The 

assessment also assumes that the listed species are located within an assumed area, which has the 

relatively highest potential exposure to the pesticide, and that exposures are likely to decrease 

with distance from the treatment area. 

5.2. Taxonomic Groups Potentially at Risk 

If the assumptions associated with the baseline action area result in RQs that are below the listed 

species LOCs, a "no effect" determination conclusion is made with respect to listed species in 

that taxa, and no further refinement of the action area is necessary. Furthermore, RQs below the 

listed species LOCs for a given taxonomic group indicate no concern for indirect effects on listed 
-Page 61 of 115-

species that depend upon the taxonomic group for which the RQ was calculated. However, in 

situations where the screening assumptions lead to RQs in excess of the listed species LOCs for a 

given taxonomic group, a potential for a "may affect" conclusion exists and may be associated 

with direct effects on listed species belonging to that taxonomic group or may extend to indirect 

effects upon listed species that depend upon that taxonomic group as a resource. In such cases, 

additional information on the biology of listed species, the locations of these species, and the 

locations of use sites are considered to determine the extent to which screening assumptions 

regarding an action area apply to a particular listed organism. These subsequent refinement steps 

will consider how this information would impact the action area for a particular listed organism 

and potentially include areas of exposure that are downwind and downstream of the pesticide use 

site.

Assessment endpoints, exposure pathways, and the conceptual models addressing proposed new 

hydrogen cyanamide uses, and the associated exposure and effects analyses conducted for the 

hydrogen cyanamide baseline risk assessment are in Sections 2 to 3. The assessment endpoints 

used in the baseline risk assessment include those defined operationally as reduced survival and 

reproductive impairment for both aquatic and terrestrial animal species and survival, 

reproduction, and growth of aquatic and terrestrial plant species from both direct acute and 

chronic exposures. These assessment endpoints are intended to address the standard set forth in 

the Endangered Species Act requiring federal agencies to ensure that any action they authorize 

does not appreciably reduce the likelihood of both the survival and recovery of a listed species in 

the wild by reducing the reproduction, numbers, or distribution of the species. Risk estimates 

(RQs) which, integrating exposure and effects, are calculated for broad based taxonomic groups 

in the screening-level risk assessment presented in Section 4.

Both acute endangered species and chronic risk LOCs are considered in the baseline risk 

assessment to identify direct and indirect effects to taxa of listed species. This section identifies 

direct effect concerns, by taxa that are triggered by exceeding endangered LOCs in the baseline 

risk assessment, with an evaluation of the potential probability of individual effects for exposures 

that may occur at the established endangered species LOC. Data on exposure and effects 

collected under field and laboratory conditions are evaluated to make determinations on the 

predictive utility of the direct effect screening assessment findings to listed species. Potential for 

direct effects to listed taxa are described in Table 5.1 below. 
-Page 62 of 115-

Table 5.1. Potential Effects to Federally Listed Taxa Associated with Direct Effects from 

the Registered Uses of Hydrogen Cyanamide.

Listed Plant Taxon Potential Direct Effects

Terrestrial and semi-aquatic 

plants – monocots and dicots Yes

Aquatic nonvascular plants Uncertain7,8

Aquatic vascular plants No

Listed Animal Taxon Potential Direct Effects

Acute Chronic

Terrestrial invertebrates Uncertain1 ND

Mammals Yes2,3,5 Yes3,5

Birds Yes2,4,5 Yes4,5

Reptiles Yes2,4,5 Yes

Amphibians No effect6 Uncertain7,9

Freshwater fish No effect6 Uncertain7,9

Freshwater invertebrates No effect6 No effect10

Mollusks No effect6 ND

Estuarine/marine fish No effect6 Uncertain7,11

Estuarine/marine invertebrates No effect6 No effect7,12

ND Not determined. 1 Although no effects were seen in the acute contact toxicity tests with honey bees, the limit dose (36.2 μg a.i./bee) was not high 

enough to preclude risk at the listed species LOC, based on the relatively high hydrogen cyanamide EECs for registered uses.

2 Risks to terrestrial animals from exposure to hydrogen cyanamide are extensive as a result of the high application rates currently 

registered for use. 

3 Based on its reported toxicity to mammals, the maximum application rate that would not result in acute or chronic risk concerns 

is 0.65 lb a.i./A or 0.005 lb a.i./A, respectively. Chance of individual effect for listed species is 1 in 1 at derived RQ. 4 Based on its reported toxicity to birds, the maximum application rate that would not result in acute risks is 0.32 lb a.i./A, while 

the application rate that would not result in chronic risks is 0.64 lb a.i./A. Chance of individual effect for listed species is 1 in 1 at 

derived RQ.

5 Risk may be limited by geographic and temporal use patterns of hydrogen cyanamide (i.e., it is only for use on a nectarines, 

peaches, blackberries, blueberries, figs, apples, cherries, grapes, and kiwi fruits; it is subject to several geographic use 

restrictions; and is only applied December through March). 6 Risk of direct effects from acute aquatic exposure to formulated hydrogen cyanamide is expected to be below the LOC. 

7 EECs are primarily driven by the modeled run-off, which assumes no buffer between the site of application and the water body. 

Hydrogen cyanamide degrades rapidly in soil (aerobic soil half-life of 12 hours in sandy loam soil), and the aerobic aquatic 

metabolism half-life value of 5.28 days represents the 90th percentile of the upper confidence bound for the mean of the two 

available half-life values (3.2 days in a pond system and 1.2 days in a stream system). Therefore chronic risks to aquatic 

organisms may be overestimated. 8 The acute listed species RQ is equal to the LOC for non-vascular plants exposed to hydrogen cyanamide from the cherry use 

only. EECs would only need to drop ~1% to result in RQs below the level of concern.

9 Current data on the freshwater species, rainbow trout, are not adequate to derive a definitive NOAEC because effects were 

noted at all test concentrations. Since the available LOAEC is within one order of magnitude of the highest EEC, chronic risk to 

listed freshwater fish cannot be precluded. However, the magnitude of biological effects observed at the lowest concentration 

level appears to be close to the limit of statistical and biological significance.

10 Risk of direct effects from chronic aquatic exposure to formulated hydrogen cyanamide is expected to be below the LOC. 11 Chronic toxicity data was not available for estuarine/marine fish. It is not possible to calculate an acute-to-chronic ratio (ACR) 

because only a non-definitive NOAEC is available for the freshwater fish. This represents a substantial data gap in the analysis. 

Based on the available acute toxicity data, estuarine/marine fish exhibit similar toxicity as freshwater fish so it is likely that they 

exhibit similar toxicity on a chronic exposure basis.

12 Though chronic toxicity data is not available for estuarine/marine invertebrates, RQs calculated based on an ACR for the 

daphnid are well below the chronic risk LOC.
-Page 63 of 115-

5.2.1. Probit Dose-Response Analysis 

The Agency uses the probit dose-response relationship as a tool for providing additional 

information on the potential for acute direct effects to aquatic and terrestrial animals (USEPA, 

2004). As part of this evaluation, the acute RQ for listed species is presented in terms of the

chance of an individual event (i.e., mortality or immobilization) should exposure at the EEC 

actually occur for a species with sensitivity to hydrogen cyanamide on par with the acute toxicity 

endpoint selected for RQ calculation. To accomplish this interpretation, the Agency uses the 

slope of the dose-response relationship available from the toxicity study used to establish the 

acute toxicity measures of effect for each taxonomic group that is relevant to this assessment. 

The individual effects probability associated with the acute RQ is based on the mean estimate of 

the slope and an assumption of a probit dose-response relationship. In addition to a single effects 

probability estimate based on the mean, upper and lower estimates of the effects probability are 

also provided to account for variance in the slope, if available. Based on the available acute 

toxicity for hydrogen cyanamide, a summary of the probit dose-response analysis is provided in 

Table 5.2. If no dose response information is available to estimate a slope for this analysis, a 

default slope assumption of 4.5 (with lower and upper bounds of 2 to 9) (Urban and Cook, 1986) 

is used. 

Individual effect probabilities are calculated based on an Excel spreadsheet tool IECV1.1 

(Individual Effect Chance Model Version 1.1) developed by the U.S. EPA, OPP, Environmental 

Fate and Effects Division (June 22, 2004). The model allows for such calculations by entering 

the mean slope estimate (and the 95% confidence bounds of that estimate) as the slope parameter 

for the spreadsheet. The desired threshold for the probability of an individual effect is entered as 

the listed species LOC. In addition, the probability of an individual effect is also derived based 

on the calculated acute RQ, if available.
-Page 64 of 115-

Table 5.2. Summary of Hydrogen cyanamide Probit Dose Response Analysis for Listed 

Species

Taxa (study type) Acute Effect

Slope (95% C.I.)

Chance of Individual 

Effect at Listed Species 

LOC (95% C.I.)

Chance of Individual 

Effect at Derived Acute 

RQ1,2,3,4,5,6 (95% C.I.)

Bird oral dose

Mortality

Default Slope = 4.5

(2-9)

1 in 3.34E+40

(1 in 6.32E+14 to 1 in 

9.03E+78)

1 in 1

(1 in 1 to 1 in 1)1

Bird dietary No mortality observed Not calculated; no 

mortality observed

Not calculated; no 

mortality observed

Mammal oral dose

Mortality

Default Slope = 4.5

(2-9)

1 in 3.34E+40

(1 in 6.32E+14 to 1 in 

9.03E+78)

1 in 1

(1 in 1 to 1 in 1)2

Freshwater Fish

Mortality 

Slope = 8.65

(3.49 – 13.81)

1 in 9.03E+28

(1 in 3.57E+05 to 1 in 

5.68E+71)

1 in 1.32E+120

(1 in 4.41E+20 to 1 in 

4.41E+303)

3

Estuarine/Marine Fish

Mortality 

Slope = 15 

(9.17 – 21.29)

1 in 2.46E+84

(1 in 2.44E+32 to 1 in 

2.78E+168E+31)

1 in 1.0E+16

(1 in 6.38E+134 to 1 in 

1.0E+16)

4

Freshwater invertebrates

Immobilization 

Slope = 7.70 

(4.58 – 10.83)

1 in 4.57E+23

(1 in 7.87E+08 to 1 in 

4.58E+44)

1 in 2.14E+31

(1 in 6.53E+11 to 1 in 

4.84E+60)

5

Estuarine/Marine 

invertebrates

Shell Deposition

Default Slope = 4.5 

(2 – 9)

1 in 4.18E+08

(1 in 2.16E+02 to 1 in 

1.75E+31)

1 in 6.33E+09

(1 in 3.86E+02 to 1 in 

7.49E+35)

6

1

Acute RQ for bird oral dose = 38.6

2

Acute RQ for mammal oral dose = 6.11

3

Acute RQ for freshwater fish = 0.002. 4

Acute RQ for estuarine/marine fish = 0.002 5

Acute RQ for freshwater invertebrates = 0.03. 6

Acute RQ for estuarine/marine invertebrates = 0.04

As shown in Table 5.2, the probability for acute direct effects (i.e., mortality) to individual listed 

bird and mammal (based on the most sensitive species, bobwhite quail or laboratory rat) and the 

highest derived RQ values is 1 in 1. The chance of individual effects for fish, based on the most 

sensitive species, rainbow trout, is 1 in 1.32X10120. The chance of an individual effect for aquatic 

invertebrates, based on the most sensitive species, Eastern oyster, is 1 in 6.33X1009. This is base 

don a default slope of 4.5. If the slope was steeper the chance of an individual effect would 

decrease further (slope of 9; 1 in 7.49X1035). 
-Page 65 of 115-

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Cyan- amide (H2NCN) in a Water/Sediment System: Lab Project 

Number: 88-02053. Unpublished study prepared by BCO Analytical 

Serv- ices. 22 p. 

42178412 Schmidt, J. (1990) Anaerobic Soil Metabolism of ?carbon 14|-
-Page 68 of 115-

Cyanamide: Lab Project Number: 38439. Unpublished study 

prepared by ABC Labs, Inc. 286 p. 

42178413 Schmidt, J. (1990) Supplemental Report of the Anaerobic Soil 

Metabolism of ?carbon 14|-Cyanamide: Lab Project Number: 

384391. Unpublished study prepared by ABC Labs, Inc. 89 p. 

42211203 Schmidt, J. (1991) Supplemental Report of the Anaerobic Soil 

Metabolism of ?carbon 14|-Cynanamide: Final Supplemental 

Report: Lab Project Number: 384391. Unpublished study prepared 

by ABC Labs., Inc. 89 p. 

162-4 Aerobic aquatic metab.

MRID Citation Reference

45382202 Volkl, S. (2000) (Carbon 14)-Cyanamide Route and Rate of 

Degradation in Aerobic Aquatic Systems: Lab Project Number: 

744952. Unpublished study prepared by RCC, Ltd. 177 p. 

163-1 Leach/adsorp/desorption

MRID Citation Reference

42178414 Rudel, H. (1990) Determination of the Adsorption/Desorption of 

Hydrogencyanamide: Lab Project Number: SKW-01/7-13. 

Unpublish- ed study prepared by Fraunhofer-Institut fur 

Umweltichemie und Okotoxikologie. 38 p. 

42178415 Rombke, J. (1990) Determination of the Soil Column Leaching of 

Alzodef According to the BBA Guideline for the Testing of Plant 

Protection Products Adopted December 1986: Lab Project 

Number: BE-EA-77-89-01-LEA2. Unpublished study prepared by 

Battelle Europe. 25 p. 

164-1 Terrestrial field dissipation

MRID Citation Reference

148013 Crowther, E.; Richardson, H. (1932) The decomposition of calcium 

cyanamide in the soil and its effects on germination, nitrifi- cation 

and soil reaction. J. Agric. Sci. 22:300-334. 

148015 SKW Trostberg AG (1978) [Degradation of Hydrogen Cyanamide 
-Page 69 of 115-

in Seve- ral Soils]. Unpublished translation of Modellversuche zum 

Abbau des Herbiziden Wirkstoffs Cyanamid in Drei Verschiedenen 

Boeden. 4 p. 

148018 Amberger, A.; Niederbudde, E. (1977) Reaction of Calcium 

Cyanamide and Its Metabolites at Metal Oxides in Quartz Sand 

and Soils. Unpublished translation of Umsetzung von Kalkstickstoff 

und dessen Metaboliten an Metalloxiden in Quarzsand und Boeden 

pre- pared by SKW Trostberg and the University of Munich. 4 p. 

42178416 Siemer, S. (1991) Field Dissipation of Hydrogen Cyanamide 

(Dormex) in Soil. Unpublished study prepared by Siemer & 

Associates, Inc. 457 p. 

165-1 Confined rotational crop

MRID Citation Reference

45797401 Huang, M. (2002) Uptake of (Carbon 14)-(Inert Ingredient) 

Residues in Soil by Rotational Crops Under Flooded Confined 

Conditions: Lab Project Number: 602CA. Unpublished study 

prepared by Bayer CropScience. 28 p. {OPPTS 860.1850} 

NON Guideline

44804701 Kendall, T.; Nixon, W. (1998) Analytical Method Verification for the 

Determination of Hydrogen Cyanamide Residues in Saltwater: 

Final Report: Lab Project Number: 248C-101. Unpublished study 

prepared by Wildlife International Ltd. 27 p.

6.2. Submitted Ecotoxicity Studies

71-1 Avian Single Dose Oral Toxicity – 014002 Cyanamide Eco

MRID Citation Reference

153783 Robaidek, E. (1985) Avian Single-dose Oral LD50 Bob White Quail 

(Colinus virginianus) [Using Hydrogen Cyanamide]: Revised Final 

Report: Study No. 6026-504. Unpublished study prepared by 

Hazleton Laboratories America, Inc. 33 p. 

153784 Robaidek, E. (1985) Avian Dietary LC50 Mallard Duck (Anas 

platyrhynchos) [Using Hydrogen Cyanamide]: Final Report: Study 

No. 6026-508. Unpublished study prepared by Hazleton Labora-
-Page 70 of 115-

tories America, Inc. 15 p. 

71-2 Avian Dietary Toxicity

MRID Citation Reference

153785 Robaidek, E. (1985) Avian Dietary LC50 Bob White Quail (Colinus 

virginianus) [Using Hydrogen Cyanamide]: Final Report: Study No. 

6026-507. Unpublished study prepared by Hazleton Laboratories 

America, Inc. 16 p. 

42178401 Lynn, S.; Grimes, J.; Smith, G. (1991) Aqueous Hydrogen Cyanamide Solution: A Dietary LC50 Study with the Mallard: Lab Project 

Number: 248-105. Unpublished study prepared by Wild- life 

International Ltd. 19 p. 

42178402 Lynn, S.; Grimes, J.; Smith, G. (1991) Aqueous Hydrogen 

Cyanamide Solution: A Dietary LC50 Study with the Northern 

Bobwhite: Lab Project Number: 248-104. Unpublished study 

prepared by Wildlife International Ltd. 19 p. 

71-4 Avian Reproduction

MRID Citation Reference

45797201 Johnson, A. (2001) Cyanamide 50% Solution Assessment to 

Determine the Effects on Reproduction in the Bobwhite Quail: Lab 

Project Number: STB 017/003921: STB/017. Unpublished study 

prepared by Huntingdon Life Science, Ltd. 307 p. 

72-1 Acute Toxicity to Freshwater Fish

MRID Citation Reference

148043 Barrows, B. (1985) The Acute Toxicity of Hydrogen Cyanamide to 

the Rainbow Trout (---), in a Static Test System: Project No. 85E038RT. Unpublished study prepared by Biospherics Inc. 11 p. 

148044 Riechenbach-Klinke (1975) Research Report on the Fish Toxicity 

of the Product Alzogur. Unpublished translation of Gutachten ueber 

die Fischtoxizitaet des Praeparates Alzogur prepared by SKW 

Trostberg AG and Institut fuer Zoologie und Hydrobiologie Fachbereich Tiermedizin der Universitaet Muenchen. 4 p. 
-Page 71 of 115-

153786 McAllister, W.; Bowman, J.; Cohle, P. (1985) Acute Toxicity of LH 

21,810 A to Bluegill Sunfish (Lepomis macrochirus): Static Acute 

Toxicity Report #33401. Unpublished study prepared by Analytical Bio-Chemistry Laboratories, Inc. 54 p. 

72-2 Acute Toxicity to Freshwater Invertebrates

MRID DOC NUM Citation Reference

148046 2026760 Adema, D. (1983) The Acute Toxicity of Alzodef to Daphnia 

magna: Report No. R 83/198. Unpublished study prepared by 

Netherlands Organization for Applied Scientific Research. 13 p. 

72-3 Acute Toxicity to Estuarine/Marine Organisms

MRID Citation Reference

44804702 Gettmann, W.; Drottar, K.; Kruegar, H. (1998) Hydrogen 

Cyanamide: A 96-Hour Flow-Through Acute Toxicity Test with the 

Sheepshead Minnow (Cyprinodon variegatus): Final Report: Lab 

Project Number: 248A-103. Unpublished study prepared by Wildlife 

International Ltd. 41 p. 

44804703 Gettmann, W.; Drottar, K.; Kruegar, H. (1998) Hydrogen 

Cyanamide: A 96-Hour Flow-Through Acute Toxicity Test with the 

Saltwater Mysid (Mysidopsis bahia): Final Report: Lab Project 

Number: 248A-102. Unpublished study prepared by Wildlife 

International Ltd. 42 p. 

44804704 Gettmann, W.; Drottar, K.; Kruegar, H. (1998) Hydrogen 

Cyanamide: A 96-Hour Shell Deposition Test with the Eastern 

Oyster (Crassostrea virginica): Final Report: Lab Project Number: 

248A-104. Unpublished study prepared by Wildlife International 

Ltd. 40 p. 

72-4 Fish Early Life Stage/Aquatic Invertebrate Life Cycle Study

MRID Citation Reference

44076701 Rhodes, J.; O'Brien, K. (1995) Early Life-Stage Toxicity of 

Hydrogen Cyanamide to the Rainbow Trout (Oncorhynchus 

mykiss) Under Flow-Through Conditions: Final Report: Lab Project 

Number: 41943: FIFRA 72-4 RBT. Unpublished study prepared by 

ABC Labs., Inc. 297 p. 
-Page 72 of 115-

44076702 Murrell, H.; Leak, T. (1995) Chronic Toxicity of Hydrogen 

Cyanamide to Daphnia magna Under Flow-Through Test 

Conditions: Final Report: Lab Project Number: 41942: ABC 41942: 

FIFRA E-72-4-B. Unpublished study prepared by ABC Labs., Inc. 

121 p. 

122-1 Seed Germination/Seedline Emergence and Vegetable Vigor

MRID Citation Reference

45380701 Meister, A. (2000) Effects of Cyanamide L 500 on the Vegetative 

Nontarget Plant Species: Tier I: Vegetative Vigor Limit Test: Final 

Report: Lab Project Number: 7042087: 851-002. Unpublished 

study prepared by Institut fur Biologische Analytik und Consulting

IBACON GmbH. 64 p. {OPPTS 850.4150} 

45380702 Meister, A. (2000) Effects of Cyanamide L 500 on the Seedling 

Emergence of Nontarget Plant Species: Tier I: Seedling 

Emergence Limit Test: Final Report: Lab Project Number: 

7041086: 851-001. Unpublished study prepared by Institut fur 

Biologische Analytik und Consulting IBACON GmbH. 89 p. 

{OPPTS 850.4100} 

122-2 Aquatic plant growth

MRID Citation Reference

40380101 Siemer, S. (1986) 1985 Residue Studies Conducted on Grapes 

with Dormant Applications of Dormex. Unpublished compilation 

pre- pared by SKW Trostberg AG. 86 p. 

45382201 Hertl, J. (2000) Toxicity of SKW Cyanamide L 500 to Anabaena 

flos-aquae in an Algal Growth Inhibition Test: Final Report: Lab 

Project Number: 6677210. Unpublished study prepared by Institut 

fur Biologische Analytik und Consulting IBACON GmbH. 78 p. 

45406601 Seyfried, B. (2000) Toxicity of Cyanamide L 500 to 

Pseudokirchneriella subcapitata (Formerly Selenastrum 

capricornutum) in a 96-Hour Algal Growth Inhibition Test: Lab 

Project Number: 744963. Unpublished study prepared by RCC Ltd. 

76 p. {OPPTS 850.5400} 

45406602 Hertl, J. (2000) Toxicity of SKW Cyanamide L 500 to the Aquatic 

Plant Lemna gibba in a Growth Inhibition Test: Final Report: Lab 

Project Number: 6679240. Unpublished study prepared by Institut 

fur Biologische Analytik und Consulting IBACON GmbH. 76 p. 

{OPPTS 850.4400} 
-Page 73 of 115-

141-1 Honey bee acute contact

MRID Citation Reference

43866902 Atkins, E. (1989) Bee Adult Toxicity Dusting Test: (Dormex 4.0 SL): 

Lab Project Number: 492. Unpublished study prepared by 

University of California, Riverside. 26 p. 
-Page 74 of 115-

Appendix A. Submitted Ecological Effects Data for Hydrogen Cyanamide

Table A.1. Submitted Terrestrial Ecological Effects Data for Hydrogen Cyanamide

OCSPP 

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are Data 

Needed for 

Risk 

Assessment?

Current Additional Data Need

850.2100 Avian oral 

toxicity

00153783 Acceptable Yes Acceptable acute avian acute oral 

toxicity data were not submitted for a 

passerine species, which is now 

required under the 40 CFR Part 158 

data requirements. Though the 

available data indicates hydrogen 

cyanamide has low toxicity to avian 

species, the currently registered 

application rates are sufficiently high 

to trigger concern. In addition, 

passerine species may be more or less 

sensitive to this chemical as a result 

of their higher metabolic rate and 

differing metabolic pathways. An 

avian oral toxicity study is needed for 

a passerine species. A passerine study 

protocol must be submitted for 

review by the Agency prior to 

initiation of the study. 

850.2200 Avian dietary 

toxicity 

42178402 Acceptable No --

42178402 Acceptable

850.2300 Avian 

reproduction

45797201 Supplemental Yes Avian reproduction studies should be 

conducted with an upland game bird 

species and a waterfowl species as 

required under the 40 CFR Part 158. 

Reproduction data are needed for a 

waterfowl species.

850.3020 Honey bee 

acute contact 

toxicity

43866902 Acceptable No --

850.3030 Honey bee 

residue on 

foliage

(None) (N/A) No --

850.3040 Field testing 

for pollinators

(None) (N/A) No --

850.4100 Terrestrial 

plant toxicity:

Tier I and II

seedling 

emergence

45380702

48404301

Supplemental No --
-Page 75 of 115-

Table A.1. Submitted Terrestrial Ecological Effects Data for Hydrogen Cyanamide

OCSPP 

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are Data 

Needed for 

Risk 

Assessment?

Current Additional Data Need

850.4150 Terrestrial 

plant toxicity:

Tier I and II 

vegetative 

vigor

48404302 Supplemental No --

Table A.2. Submitted Aquatic Ecological Effects Data for Hydrogen Cyanamide

OCSPP

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are Data 

Needed for Risk 

Assessment?

Justification and Assumptions 

EPA will Make in Absence of 

Data 

850.1010 Freshwater 

invertebrate 

acute toxicity

00148046 Acceptable No --

850.1025

850.1035

Estuarine/Marine

invertebrate 

acute toxicity 

44804704 Acceptable No --

44804703 Acceptable

850.1075 Freshwater fish 

acute toxicity 

00148043 Acceptable No --

00153786

850.1075 Estuarine/Marine

fish acute 

toxicity 

44804702 Acceptable No --

850.1300 Freshwater 

invertebrate 

life cycle 

44706702 Acceptable No --

850.1350 Estuarine/Marine

invertebrates 

life cycle 

(None) (N/A) Yes The proposed uses of hydrogen 

cyanamide may result in exposure 

to estuarine/marine invertebrates. 

An ACR is not appropriate because 

the freshwater acute and chronic 

data are based on the daphnid, 

which does not have a similar life 

history to the most sensitive 

estuarine/marine invertebrate 

species studied in the acute test (i.e.,

eastern oyster). While hydrogen 

cyanamide is only moderately toxic 

to estuarine/marine invertebrates 

based on acute exposure, the 

proposed application rates are 

sufficiently high to potentially 

trigger concerns. Therefore this 

study is requested to reduce the 

uncertainty. 

850.1400 Freshwater fish 

early-life stage

44076701 Supplemental No --
-Page 76 of 115-

Table A.2. Submitted Aquatic Ecological Effects Data for Hydrogen Cyanamide

OCSPP

Guideline

Data 

Requirement

Submitted 

Studies 

(MRID)

Study 

Classifications

Are Data 

Needed for Risk 

Assessment?

Justification and Assumptions 

EPA will Make in Absence of 

Data 

850.1400 Estuarine/Marine

fish 

early-life stage

(None) (N/A) Yes While this data is not currently 

available, and an ACR from the 

freshwater fish species is not 

possible because only a nondefinitive endpoint is available, risk 

to estuarine/marine fish is expected 

to be low. This information would 

be useful for reducing uncertainties 

but will not likely change the risk 

conclusions. 

850.1500 Fish life cycle (None) (N/A) No --

850.4400 Aquatic plant 

growth:

Tier II vascular 

plants

45406602 Acceptable No --

850.5400 Aquatic Plant 

Growth:

Tier II algae

45382201 Supplemental Yes --

45406601 Supplemental
-Page 77 of 115-

Appendix B. Catalogue of Submitted Environmental Fate Studies for Hydrogen 

cyanamide.

Submitted Environmental Fate Studies for Hydrogen cyanamide, their Review Classifications, 

and Classification Justifications. 

Guideline Study Title MRID Classification Comments

Are data 

adequate for 

Risk 

Assessment?

Current Additional 

Data Need

835.2120 Hydrolysis 48023547 Acceptable

Study was conducted at 50oC. 

Hydrogen cyanamide was stable at 

pHs 4, 7, and 9.

Yes None

835.2240

Photodegradation 

in Water 48023548 Supplemental

Study duration was not sufficient. A 

large amount of parent remained 

undegraded at the termination of the 

study. Half-lives are of uncertain 

value.

Yes

An acceptable aqueous 

photolysis study 

conducted for a 

sufficient duration is 

recommended to 

confirm the results 

reported from the 

reviewed studies.

Photodegradation 

in River Water 48023549 Supplemental

Study duration was not sufficient. A 

large amount of parent remained 

undegraded at the termination of the 

study. Half-lives are of uncertain 

value.

Quantum Yield 

of Hydrogen 

cyanamide

48023550 Supplemental

Dark controls were not used. 

Irradiation lamp was not compared to 

natural sunlight (mercury vapor lamp 

was used). 

835.2410 Photodegradation 

on Soil -- -- Study not required since this is a seed treatment. -- --

835.4100 Aerobic Soil 

Metabolism

48023552 Supplemental

German soils. Study duration was not 

sufficient to characterize the 

degradation of the parent and 

formation and decline of major 

degradates. Half-lives were 

extrapolated beyond the study 

duration and thus are of uncertain 

value. Comparison to intended use 

sites in the US was not provided.

Yes

An acceptable aerobic 

soil metabolism study 

conducted for a 

sufficient duration to 

characterize the decline 

of the parent and 

formation and decline 

of major degradates is 

recommended to 

reduce the uncertainty 

regarding the aerobic 

degradation of 

hydrogen cyanamide

48023553 Supplemental

US soils. Study duration was 

insufficient to completely 

characterize the degradation of the 

parent and formation and decline of 

major degradates.

48023554 Supplemental

Study was conducted using a 

hydrogen cyanamide-pyrazolyl-AAP 

as the starting material. Extraction 

methods were not exhaustive, 

multiple extraction methods should 

have been explored. Major 

degradates were not identified. 

Comparison to intended use sites in 

the US was not provided.
-Page 78 of 115-

Guideline Study Title MRID Classification Comments

Are data 

adequate for 

Risk 

Assessment?

Current Additional 

Data Need

835.4200 Anaerobic Soil 

Metabolism 48023555 Acceptable

A large amount of parent material 

remained undegraded at the study 

termination (70-74%). Half-lives are 

extrapolated beyond the duration of 

the study. An additional study 

conducted for a longer duration will 

not likely improve the results. 

German soils were used in the study 

and were not compared to intended

use sites in the US.

No None

835.4300 Aerobic Aquatic 

Metabolism 48023556 Supplemental

Unexplained variability in the 

reported data (uncharacterized 

decline of the parent and major 

degradates). Anglerweiher 

water:sand system should not be used 

for risk assessment. Hoenniger 

Weiher water :sandy loam system is 

acceptable for risk assessment.

Yes

An additional 

acceptable aerobic 

aquatic study that 

includes a different 

water: sediment system 

is recommended to 

address the potential 

variability that exists 

between multiple 

aquatic systems.

835.4400

Anaerobic 

Aquatic 

Metabolism

48023557 Supplemental

A large amount of parent material 

remained undegraded at the study 

termination (86-90%; 120 DAT). 

Hydrogen cyanamide was just 

beginning to dissipate from the 

sediment; a study conducted for a 

sufficient determination may 

determine whether hydrogen 

cyanamide was in fact dissipating 

from the sediment. Half-live are 

extrapolated and are of uncertain 

value. System was only moderately 

reducing. Only a single 

water:sediment system was studied.

Yes

Two water:sediment

systems are 

recommended from 

studies conducted for a 

sufficient duration to 

reduce the uncertainty 

regarding the anaerobic 

degradation. However, 

it is unlikely that 

additional studies 

would produce 

significantly different 

results.

835.1230

Mobility - 

Adsorption / 

Desorption

48023546 Supplemental

Residues were not accounted for in 

the intercalated solution in the initial 

adsorption step and each desorption 

step. Registrant-calculated percent 

adsorption values could not be 

confirmed due to lack of raw data. 

None of the test soils had OM 

content <1%. Foreign soils were used 

for the study, comparison 

information to intended US use sites 

was not provided. Yes

An acceptable 

adsorption/desorption 

study is recommended 

to address uncertainties 

identified in the study 

reviews.

48023544 Supplemental

Study was conducted using a major 

transformation product (hydrogen 

cyanamide-hydroxy butyl). 

Registrant-calculated percent 

adsorption values could not be 

confirmed due to lack of raw data. 

None of the test soils had an OM 

content <1%. Foreign soils were used 

for the study, comparison 

information to intended US use sites 

was not provided.
-Page 79 of 115-

Guideline Study Title MRID Classification Comments

Are data 

adequate for 

Risk 

Assessment?

Current Additional 

Data Need

48023545 Supplemental

Study was conducted using a major 

transformation product (hydrogen 

cyanamide-pyrazolyl-AAP). 

Registrant-calculated percent 

adsorption values could not be 

confirmed due to lack of raw data. 

None of the test soils had an OM 

content <1%. Foreign soils were used 

for the study, comparison 

information to intended US use sites 

was not provided.

835.6100 Terrestrial Field 

Dissipation 

48023558 Unacceptable

Reported dissipation half-lives are 

comparatively shorter than other field 

studies (orders of magnitude). 

Additional dissipation routes (e.g., 

runoff) were not measured, therefore 

there is some other dissipation route 

occurring that has not been accounted 

for. Exhaustive extraction methods 

were not investigated. Depth of 

sampling was insufficient.

Yes

An acceptable 

terrestrial field 

dissipation study that 

studies the proposed 

use patterns (seed 

treatment) is 

recommended to 

address the 

uncertainties identified 

in the study reviews.

48023559 Supplemental

Test application rate was conducted 

at an exaggerated rate (10x proposed 

maximum labeled rate). Exhaustive 

extraction methods were not 

investigated. Depth of sampling was 

insufficient.

48023560 Supplemental

Test application rate was conducted 

at an exaggerated rate (10x proposed 

maximum labeled rate). Exhaustive 

extraction methods were not 

investigated. Depth of sampling was 

insufficient. Reported LOQ did not 

compare to validated LOQ.

48023561 Supplemental

Test application rate was conducted 

at an exaggerated rate (10x proposed 

maximum labeled rate). Exhaustive 

extraction methods were not 

investigated. Reported LOQ did not 

compare to validated LOQ.

48023562 Supplemental

Test application rate was conducted 

at an exaggerated rate (10x proposed 

maximum labeled rate). Exhaustive 

extraction methods were not 

investigated. Reported LOQ did not 

compare to validated LOQ.

48023563 Supplemental

Test application rate was conducted 

at an exaggerated rate. Exhaustive 

extraction methods were not 

investigated. Reported LOQ did not 

compare to validated LOQ.
-Page 80 of 115-

Guideline Study Title MRID Classification Comments

Are data 

adequate for 

Risk 

Assessment?

Current Additional 

Data Need

48023564 Supplemental

Study was conducted in ecoregions 

dissimilar to the intended use sites in 

the US. Comparisons to intended use 

sites in the US were not provided. 

Application rates were not verified 

using data from the monitoring 

devices (e.g., filter paper).

835.6200 Aquatic Field 

Dissipation 48023565 Supplemental

Test application rate was conducted 

at an exaggerated rate. Exhaustive 

extraction methods were not 

investigated. Reported LOQ did not 

compare to validated LOQ. Study 

was conducted on rice. Plant samples 

were analyzed for parent and 

degradates. Hydroxy butyl and a 

carboxylic acid degradate were 

detected in plant samples at low 

levels. Storage stability was not 

demonstrated for the longest storage 

period (MRID 48023722)

Yes

Although not required 

for current action, 

future actions with 

aquatic uses would 

require a second study 

in an aquatic system.

850.1730 Fish 

Accumulation 48023589 Acceptable

Low BCFs indicate that hydrogen 

cyanamide will not bioconcentrate in 

aquatic food webs. Mean TRR values 

were used in the calculation of BCFs. 

EPA typically uses maximum TRR 

values from whole fish, edible, and 

viscera tissues when calculating 

BCFs, however mean TRR values do 

not change the conclusions that 

would be drawn by using maximum 

values.

Yes None

860.1380

Storage stability 

in soil

48023719

48176601 Acceptable

Initial study MRID 48176601was not 

conducted for sufficient duration. 

Together these two studies satisfy the 

guideline requirement.

Yes

None

Storage Stability 48023722 Supplemental

Study duration was insufficient. 

Stability was demonstrated through 

222 days, however it should have 

been conducted for at least as long as 

the longest storage period (362 days).

An acceptable storage 

stability study in water 

conducted for a 

sufficient duration, 

using water from the 

aquatic field 

dissipation study.
-Page 81 of 115-

Appendix C. PE5 Output File

stored as HcyanamideORapples.out

Chemical: Hcyanamide

PRZM environment: ORappleSTD.txt modified Tueday, 29 May 2007 at 14:00:08

EXAMS environment: pond298.exv modified Thuday, 29 August 2002 at 16:33:30

Metfile: w24232.dvf modified Wedday, 3 July 2002 at 09:06:10

Water segment concentrations (ppb)

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly

1961 24.57 22.69 18.22 10.32 7.339 1.843

1962 2.74 2.631 2.054 1.244 0.8947 0.2255

1963 0.985 0.9051 0.6488 0.3615 0.2583 0.06491

1964 0.985 0.9252 0.7195 0.4323 0.3115 0.07825

1965 0.985 0.9179 0.693 0.3973 0.282 0.07079

1966 0.985 0.9233 0.7442 0.4453 0.3181 0.0798

1967 0.985 0.9191 0.8011 0.5014 0.3661 0.0926

1968 13.75 12.64 9.089 4.983 3.531 0.8835

1969 12.36 11.81 9.633 5.841 4.174 1.045

1970 26.51 24.58 18.25 10.4 7.457 1.877

1971 71.64 67.33 52.47 31.82 23.06 5.825

1972 0.9863 0.9194 0.6948 0.3966 0.283 0.07106

1973 0.985 0.917 0.6898 0.399 0.2849 0.07146

1974 3.441 3.223 2.569 1.525 1.09 0.2741

1975 1.136 1.064 0.8905 0.5362 0.3882 0.09799

1976 0.985 0.9248 0.7218 0.4377 0.3166 0.0797

1977 0.985 0.9144 0.6809 0.3914 0.2785 0.06994

1978 7.684 7.116 5.34 3.04 2.16 0.5414

1979 32.41 30.98 23.6 13.24 9.334 2.334

1980 0.9854 0.9174 0.6944 0.4042 0.2881 0.07216

1981 1.048 0.9765 0.848 0.5234 0.3737 0.09378

1982 2.808 2.684 2.06 1.262 0.9263 0.2341

1983 39.02 37.14 29.07 16.07 11.32 2.831

1984 1.709 1.614 1.222 0.7621 0.5457 0.1371

1985 15.3 14.67 11.54 6.919 4.958 1.247

1986 0.9853 0.9162 0.7981 0.4629 0.3273 0.08198

1987 1.08 1.02 0.872 0.5308 0.3766 0.09412

1988 0.985 0.9179 0.6929 0.3988 0.2832 0.07082

1989 0.985 0.9346 0.7679 0.4731 0.3357 0.08392

1990 15.32 14.66 11.56 6.684 4.717 1.179

Sorted results

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

0.032258064516129 71.64 67.33 52.47 31.82 23.06 5.825

0.0645161290322581 39.02 37.14 29.07 16.07 11.32 2.831

0.0967741935483871 32.41 30.98 23.6 13.24 9.334 2.334

0.129032258064516 26.51 24.58 18.25 10.4 7.457 1.877

0.161290322580645 24.57 22.69 18.22 10.32 7.339 1.843

0.193548387096774 15.32 14.67 11.56 6.919 4.958 1.247

0.225806451612903 15.3 14.66 11.54 6.684 4.717 1.179

0.258064516129032 13.75 12.64 9.633 5.841 4.174 1.045
-Page 82 of 115-

0.290322580645161 12.36 11.81 9.089 4.983 3.531 0.8835

0.32258064516129 7.684 7.116 5.34 3.04 2.16 0.5414

0.354838709677419 3.441 3.223 2.569 1.525 1.09 0.2741

0.387096774193548 2.808 2.684 2.06 1.262 0.9263 0.2341

0.419354838709677 2.74 2.631 2.054 1.244 0.8947 0.2255

0.451612903225806 1.709 1.614 1.222 0.7621 0.5457 0.1371

0.483870967741936 1.136 1.064 0.8905 0.5362 0.3882 0.09799

0.516129032258065 1.08 1.02 0.872 0.5308 0.3766 0.09412

0.548387096774194 1.048 0.9765 0.848 0.5234 0.3737 0.09378

0.580645161290323 0.9863 0.9346 0.8011 0.5014 0.3661 0.0926

0.612903225806452 0.9854 0.9252 0.7981 0.4731 0.3357 0.08392

0.645161290322581 0.9853 0.9248 0.7679 0.4629 0.3273 0.08198

0.67741935483871 0.985 0.9233 0.7442 0.4453 0.3181 0.0798

0.709677419354839 0.985 0.9194 0.7218 0.4377 0.3166 0.0797

0.741935483870968 0.985 0.9191 0.7195 0.4323 0.3115 0.07825

0.774193548387097 0.985 0.9179 0.6948 0.4042 0.2881 0.07216

0.806451612903226 0.985 0.9179 0.6944 0.399 0.2849 0.07146

0.838709677419355 0.985 0.9174 0.693 0.3988 0.2832 0.07106

0.870967741935484 0.985 0.917 0.6929 0.3973 0.283 0.07082

0.903225806451613 0.985 0.9162 0.6898 0.3966 0.282 0.07079

0.935483870967742 0.985 0.9144 0.6809 0.3914 0.2785 0.06994

0.967741935483871 0.985 0.9051 0.6488 0.3615 0.2583 0.06491

0.1 31.82 30.34 23.065 12.956 9.1463 2.2883

Average of yearly averages: 0.724999333333333

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run:

Output File: HcyanamideORapples

Metfile: w24232.dvf

PRZM scenario: ORappleSTD.txt

EXAMS environment file: pond298.exv

Chemical Name: Hcyanamide

Description Variable Name Value Units Comments

Molecular weightmwt 42.04 g/mol

Henry's Law Const. henry 2.68E-10 atm-m^3/mol

Vapor Pressure vapr 0.00375 torr

Solubility sol 7.8E5 mg/L

Kd Kd mg/L

Koc Koc 7.3 mg/L

Photolysis half-life kdp 29 days Half-life

Aerobic Aquatic Metabolism kbacw 5.28 days Halfife

Anaerobic Aquatic Metabolism kbacs 70 days Halfife

Aerobic Soil Metabolism asm 1.5 days Halfife

Hydrolysis: pH 7 0 days Half-life

Method: CAM 2 integer See PRZM manual

Incorporation Depth: DEPI 0 cm

Application Rate:TAPP 19.7 kg/ha

Application Efficiency: APPEFF0.99 fraction

Spray Drift DRFT 0.001 fraction of application rate applied to pond

Application Date Date 04-02 dd/mm or dd/mmm or dd-mm or dd-mmm

Record 17: FILTRA

IPSCND1

UPTKF

Record 18: PLVKRT
-Page 83 of 115-

PLDKRT

FEXTRC 0.5

Flag for Index Res. Run IR EPA Pond

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

stored as HcyanamidePAapples.out

Chemical: Hcyanamide

PRZM environment: PAappleSTD_V2.txt modified Tueday, 20 May 2008 at 13:00:22

EXAMS environment: pond298.exv modified Thuday, 29 August 2002 at 16:33:30

Metfile: w14751.dvf modified Wedday, 3 July 2002 at 09:06:14

Water segment concentrations (ppb)

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly

1961 1.897 1.821 1.507 0.9318 0.6663 0.1661

1962 4.35 4.243 3.428 2.076 1.471 0.365

1963 1.229 1.173 0.9529 0.5592 0.3902 0.09679

1964 0.985 0.9401 0.7635 0.4636 0.3283 0.08124

1965 0.985 0.9401 0.8334 0.5313 0.3772 0.09353

1966 2.673 2.589 2.108 1.263 0.8978 0.2231

1967 0.985 0.9402 0.7949 0.5042 0.3573 0.08903

1968 0.985 0.9401 0.7537 0.4365 0.3052 0.07563

1969 0.985 0.9378 0.756 0.4593 0.3217 0.07976

1970 0.985 0.9401 0.7681 0.4815 0.3407 0.08451

1971 15.66 14.96 12.02 7.473 5.314 1.322

1972 0.9852 0.9404 0.7623 0.4637 0.3293 0.08169

1973 0.985 0.9401 0.7467 0.4287 0.3017 0.07505

1974 1.903 1.816 1.436 0.8534 0.5931 0.147

1975 2.743 2.615 2.123 1.342 0.9633 0.2394

1976 0.985 0.9269 0.7153 0.4088 0.2849 0.07051

1977 13.97 13.48 10.28 5.679 3.965 0.9828

1978 0.9852 0.9403 0.762 0.4647 0.3279 0.08147

1979 12.74 12.31 9.581 5.391 3.79 0.9411

1980 3.586 3.423 2.743 1.644 1.154 0.2854

1981 153 146 119 71.03 49.59 12.3

1982 0.9877 0.9428 0.7663 0.4763 0.3406 0.08526

1983 0.985 0.9518 0.7781 0.4597 0.3257 0.08108

1984 13.73 13.15 10.71 6.868 4.94 1.23

1985 8.905 8.499 6.844 4.015 2.822 0.7012

1986 8.227 7.853 6.237 3.632 2.554 0.6335

1987 7.018 6.698 5.25 3.03 2.137 0.5302

1988 0.9851 0.9402 0.7606 0.4512 0.3188 0.07898

1989 6.937 6.714 5.396 3.228 2.284 0.568

1990 18.97 17.88 13.56 7.584 5.301 1.317

Sorted results

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

0.032258064516129 153 146 119 71.03 49.59 12.3

0.0645161290322581 18.97 17.88 13.56 7.584 5.314 1.322

0.0967741935483871 15.66 14.96 12.02 7.473 5.301 1.317

0.129032258064516 13.97 13.48 10.71 6.868 4.94 1.23

0.161290322580645 13.73 13.15 10.28 5.679 3.965 0.9828

0.193548387096774 12.74 12.31 9.581 5.391 3.79 0.9411
-Page 84 of 115-

0.225806451612903 8.905 8.499 6.844 4.015 2.822 0.7012

0.258064516129032 8.227 7.853 6.237 3.632 2.554 0.6335

0.290322580645161 7.018 6.714 5.396 3.228 2.284 0.568

0.32258064516129 6.937 6.698 5.25 3.03 2.137 0.5302

0.354838709677419 4.35 4.243 3.428 2.076 1.471 0.365

0.387096774193548 3.586 3.423 2.743 1.644 1.154 0.2854

0.419354838709677 2.743 2.615 2.123 1.342 0.9633 0.2394

0.451612903225806 2.673 2.589 2.108 1.263 0.8978 0.2231

0.483870967741936 1.903 1.821 1.507 0.9318 0.6663 0.1661

0.516129032258065 1.897 1.816 1.436 0.8534 0.5931 0.147

0.548387096774194 1.229 1.173 0.9529 0.5592 0.3902 0.09679

0.580645161290323 0.9877 0.9518 0.8334 0.5313 0.3772 0.09353

0.612903225806452 0.9852 0.9428 0.7949 0.5042 0.3573 0.08903

0.645161290322581 0.9852 0.9404 0.7781 0.4815 0.3407 0.08526

0.67741935483871 0.9851 0.9403 0.7681 0.4763 0.3406 0.08451

0.709677419354839 0.985 0.9402 0.7663 0.4647 0.3293 0.08169

0.741935483870968 0.985 0.9402 0.7635 0.4637 0.3283 0.08147

0.774193548387097 0.985 0.9401 0.7623 0.4636 0.3279 0.08124

0.806451612903226 0.985 0.9401 0.762 0.4597 0.3257 0.08108

0.838709677419355 0.985 0.9401 0.7606 0.4593 0.3217 0.07976

0.870967741935484 0.985 0.9401 0.756 0.4512 0.3188 0.07898

0.903225806451613 0.985 0.9401 0.7537 0.4365 0.3052 0.07563

0.935483870967742 0.985 0.9378 0.7467 0.4287 0.3017 0.07505

0.967741935483871 0.985 0.9269 0.7153 0.4088 0.2849 0.07051

0.1 15.491 14.812 11.889 7.4125 5.2649 1.3083

Average of yearly averages: 0.770211

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run:

Output File: HcyanamidePAapples

Metfile: w14751.dvf

PRZM scenario: PAappleSTD_V2.txt

EXAMS environment file: pond298.exv

Chemical Name: Hcyanamide

Description Variable Name Value Units Comments

Molecular weightmwt 42.04 g/mol

Henry's Law Const. henry 2.68E-10 atm-m^3/mol

Vapor Pressure vapr 0.00375 torr

Solubility sol 7.8E5 mg/L

Kd Kd mg/L

Koc Koc 7.3 mg/L

Photolysis half-life kdp 29 days Half-life

Aerobic Aquatic Metabolism kbacw 5.28 days Halfife

Anaerobic Aquatic Metabolism kbacs 70 days Halfife

Aerobic Soil Metabolism asm 1.5 days Halfife

Hydrolysis: pH 7 0 days Half-life

Method: CAM 2 integer See PRZM manual

Incorporation Depth: DEPI 0 cm

Application Rate:TAPP 19.7 kg/ha

Application Efficiency: APPEFF0.99 fraction

Spray Drift DRFT 0.001 fraction of application rate applied to pond

Application Date Date 20-02 dd/mm or dd/mmm or dd-mm or dd-mmm

Record 17: FILTRA

IPSCND1
-Page 85 of 115-

UPTKF

Record 18: PLVKRT

PLDKRT

FEXTRC 0.5

Flag for Index Res. Run IR EPA Pond

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

stored as HcyanamideNCapples2.out

Chemical: Hcyanamide

PRZM environment: NCappleSTD.txt modified Tueday, 29 May 2007 at 13:58:16

EXAMS environment: pond298.exv modified Thuday, 29 August 2002 at 16:33:30

Metfile: w03812.dvf modified Wedday, 3 July 2002 at 09:05:50

Water segment concentrations (ppb)

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly

1965 14.17 13.25 10.61 6.496 4.62 1.151

1966 2.026 1.971 1.623 1.046 0.7592 0.1904

1967 0.985 0.9361 0.7685 0.465 0.3262 0.08116

1968 0.985 0.9401 0.7776 0.4846 0.3441 0.08558

1969 4.465 4.221 3.362 2.095 1.508 0.3759

1970 0.9851 0.9273 0.738 0.4424 0.3116 0.07748

1971 10.39 9.851 7.777 4.686 3.332 0.8305

1972 1.85 1.747 1.386 0.89 0.6359 0.1583

1973 0.985 0.9303 0.7868 0.4659 0.327 0.08143

1974 0.985 0.9244 0.7945 0.4593 0.3214 0.07987

1975 0.985 0.9203 0.7036 0.4126 0.2925 0.0728

1976 0.985 0.9118 0.6889 0.3891 0.2719 0.06746

1977 0.985 0.9306 0.74 0.429 0.2987 0.07412

1978 0.985 0.9394 0.7745 0.4817 0.3408 0.08484

1979 0.985 0.9342 0.7539 0.4453 0.3118 0.07746

1980 0.985 0.935 0.7569 0.4638 0.3279 0.08131

1981 12.01 11.29 8.807 5.157 3.638 0.9058

1982 2.589 2.429 1.896 1.126 0.7992 0.1989

1983 8.51 8.017 6.827 4.107 2.939 0.7345

1984 3.449 3.241 2.519 1.539 1.124 0.2814

1985 6.614 6.244 4.939 2.813 1.998 0.4976

1986 0.9851 0.9214 0.7084 0.4131 0.2906 0.07226

1987 0.985 0.9287 0.7329 0.4383 0.3114 0.07754

1988 0.985 0.9314 0.7431 0.4462 0.3156 0.07844

1989 0.985 0.9259 0.7234 0.4163 0.2919 0.07269

1990 6.634 6.325 5.204 3.002 2.134 0.5317

Sorted results

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

0.037037037037037 14.17 13.25 10.61 6.496 4.62 1.151

0.0740740740740741 12.01 11.29 8.807 5.157 3.638 0.9058

0.111111111111111 10.39 9.851 7.777 4.686 3.332 0.8305

0.148148148148148 8.51 8.017 6.827 4.107 2.939 0.7345

0.185185185185185 6.634 6.325 5.204 3.002 2.134 0.5317
-Page 86 of 115-

0.222222222222222 6.614 6.244 4.939 2.813 1.998 0.4976

0.259259259259259 4.465 4.221 3.362 2.095 1.508 0.3759

0.296296296296296 3.449 3.241 2.519 1.539 1.124 0.2814

0.333333333333333 2.589 2.429 1.896 1.126 0.7992 0.1989

0.37037037037037 2.026 1.971 1.623 1.046 0.7592 0.1904

0.407407407407407 1.85 1.747 1.386 0.89 0.6359 0.1583

0.444444444444444 0.9851 0.9401 0.7945 0.4846 0.3441 0.08558

0.481481481481481 0.9851 0.9394 0.7868 0.4817 0.3408 0.08484

0.518518518518518 0.985 0.9361 0.7776 0.4659 0.3279 0.08143

0.555555555555556 0.985 0.935 0.7745 0.465 0.327 0.08131

0.592592592592593 0.985 0.9342 0.7685 0.4638 0.3262 0.08116

0.62962962962963 0.985 0.9314 0.7569 0.4593 0.3214 0.07987

0.666666666666667 0.985 0.9306 0.7539 0.4462 0.3156 0.07844

0.703703703703704 0.985 0.9303 0.7431 0.4453 0.3118 0.07754

0.740740740740741 0.985 0.9287 0.74 0.4424 0.3116 0.07748

0.777777777777778 0.985 0.9273 0.738 0.4383 0.3114 0.07746

0.814814814814815 0.985 0.9259 0.7329 0.429 0.2987 0.07412

0.851851851851852 0.985 0.9244 0.7234 0.4163 0.2925 0.0728

0.888888888888889 0.985 0.9214 0.7084 0.4131 0.2919 0.07269

0.925925925925926 0.985 0.9203 0.7036 0.4126 0.2906 0.07226

0.962962962962963 0.985 0.9118 0.6889 0.3891 0.2719 0.06746

0.1 10.876 10.2827 8.086 4.8273 3.4238 0.85309

Average of yearly averages: 0.270016923076923

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run:

Output File: HcyanamideNCapples2

Metfile: w03812.dvf

PRZM scenario: NCappleSTD.txt

EXAMS environment file: pond298.exv

Chemical Name: Hcyanamide

Description Variable Name Value Units Comments

Molecular weightmwt 42.04 g/mol

Henry's Law Const. henry 2.68E-10 atm-m^3/mol

Vapor Pressure vapr 0.00375 torr

Solubility sol 7.8E5 mg/L

Kd Kd mg/L

Koc Koc 7.3 mg/L

Photolysis half-life kdp 29 days Half-life

Aerobic Aquatic Metabolism kbacw 5.28 days Halfife

Anaerobic Aquatic Metabolism kbacs 70 days Halfife

Aerobic Soil Metabolism asm 1.5 days Halfife

Hydrolysis: pH 7 0 days Half-life

Method: CAM 2 integer See PRZM manual

Incorporation Depth: DEPI 0 cm

Application Rate:TAPP 19.7 kg/ha

Application Efficiency: APPEFF0.99 fraction

Spray Drift DRFT 0.001 fraction of application rate applied to pond

Application Date Date 04-02 dd/mm or dd/mmm or dd-mm or dd-mmm

Record 17: FILTRA

IPSCND1

UPTKF

Record 18: PLVKRT

PLDKRT
-Page 87 of 115-

FEXTRC 0.5

Flag for Index Res. Run IR EPA Pond

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

stored as HcyanamideFLblueberries.out

Chemical: Hcyanamide

PRZM environment: GAPeachesSTD.txt modified Tueday, 29 May 2007 at 13:54:56

EXAMS environment: pond298.exv modified Thuday, 29 August 2002 at 16:33:30

Metfile: w03813.dvf modified Wedday, 3 July 2002 at 09:04:32

Water segment concentrations (ppb)

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly

1961 0.985 0.8803 0.6695 0.2939 0.1959 0.04831

1962 0.985 0.9137 0.6783 0.2988 0.1992 0.06701

1963 0.985 0.9237 0.757 0.3469 0.2313 0.07919

1964 0.985 0.9194 0.6771 0.291 0.194 0.0766

1965 0.985 0.9085 0.6604 0.2881 0.1921 0.0641

1966 0.985 0.9071 0.6741 0.2951 0.1968 0.06948

1967 0.985 0.8984 0.6344 0.2724 0.1816 0.06302

1968 9.152 8.528 6.436 2.785 1.857 0.475

1969 3.248 3.017 2.251 1.295 0.926 0.2841

1970 0.985 0.8918 0.6215 0.2679 0.1786 0.06963

1971 36.76 32.72 21.44 8.818 5.879 1.464

1972 32.73 30.3 20.35 8.105 5.404 1.696

1973 7.81 7.216 5.281 2.967 2.076 0.561

1974 0.985 0.9003 0.6377 0.2752 0.1835 0.05594

1975 0.985 0.9076 0.6575 0.2864 0.1909 0.06075

1976 2.42 2.266 1.671 0.7406 0.4938 0.1397

1977 0.985 0.9077 0.6674 0.4102 0.2894 0.119

1978 0.985 0.8981 0.6263 0.2681 0.1788 0.06597

1979 2.047 1.87 1.313 0.5908 0.3939 0.1139

1980 0.985 0.9039 0.645 0.279 0.186 0.08219

1981 9.371 8.655 6.33 2.77 1.846 0.473

1982 2.701 2.511 1.878 1.05 0.7289 0.2361

1983 0.985 0.9112 0.7251 0.3202 0.2135 0.07295

1984 2.667 2.388 1.561 0.6742 0.4495 0.1324

1985 0.985 0.9155 0.7112 0.3185 0.2123 0.09539

1986 1.394 1.278 0.9076 0.3918 0.2612 0.08704

1987 0.985 0.8926 0.6092 0.2584 0.1722 0.06644

1988 0.985 0.9045 0.6469 0.2801 0.1867 0.0613

1989 6.199 5.81 4.565 1.887 1.258 0.3245

1990 2.805 2.542 1.737 0.8757 0.6001 0.1916

Sorted results

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

0.032258064516129 36.76 32.72 21.44 8.818 5.879 1.696

0.0645161290322581 32.73 30.3 20.35 8.105 5.404 1.464

0.0967741935483871 9.371 8.655 6.436 2.967 2.076 0.561

0.129032258064516 9.152 8.528 6.33 2.785 1.857 0.475

0.161290322580645 7.81 7.216 5.281 2.77 1.846 0.473

0.193548387096774 6.199 5.81 4.565 1.887 1.258 0.3245

0.225806451612903 3.248 3.017 2.251 1.295 0.926 0.2841

0.258064516129032 2.805 2.542 1.878 1.05 0.7289 0.2361
-Page 88 of 115-

0.290322580645161 2.701 2.511 1.737 0.8757 0.6001 0.1916

0.32258064516129 2.667 2.388 1.671 0.7406 0.4938 0.1397

0.354838709677419 2.42 2.266 1.561 0.6742 0.4495 0.1324

0.387096774193548 2.047 1.87 1.313 0.5908 0.3939 0.119

0.419354838709677 1.394 1.278 0.9076 0.4102 0.2894 0.1139

0.451612903225806 0.985 0.9237 0.757 0.3918 0.2612 0.09539

0.483870967741936 0.985 0.9194 0.7251 0.3469 0.2313 0.08704

0.516129032258065 0.985 0.9155 0.7112 0.3202 0.2135 0.08219

0.548387096774194 0.985 0.9137 0.6783 0.3185 0.2123 0.07919

0.580645161290323 0.985 0.9112 0.6771 0.2988 0.1992 0.0766

0.612903225806452 0.985 0.9085 0.6741 0.2951 0.1968 0.07295

0.645161290322581 0.985 0.9077 0.6695 0.2939 0.1959 0.06963

0.67741935483871 0.985 0.9076 0.6674 0.291 0.194 0.06948

0.709677419354839 0.985 0.9071 0.6604 0.2881 0.1921 0.06701

0.741935483870968 0.985 0.9045 0.6575 0.2864 0.1909 0.06644

0.774193548387097 0.985 0.9039 0.6469 0.2801 0.1867 0.06597

0.806451612903226 0.985 0.9003 0.645 0.279 0.186 0.0641

0.838709677419355 0.985 0.8984 0.6377 0.2752 0.1835 0.06302

0.870967741935484 0.985 0.8981 0.6344 0.2724 0.1816 0.0613

0.903225806451613 0.985 0.8926 0.6263 0.2681 0.1788 0.06075

0.935483870967742 0.985 0.8918 0.6215 0.2679 0.1786 0.05594

0.967741935483871 0.985 0.8803 0.6092 0.2584 0.1722 0.04831

0.1 9.3491 8.6423 6.4254 2.9488 2.0541 0.5524

Average of yearly averages: 0.246520333333333

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run:

Output File: HcyanamideFLblueberries

Metfile: w03813.dvf

PRZM scenario: GAPeachesSTD.txt

EXAMS environment file: pond298.exv

Chemical Name: Hcyanamide

Description Variable Name Value Units Comments

Molecular weightmwt 42.04 g/mol

Henry's Law Const. henry 2.68E-10 atm-m^3/mol

Vapor Pressure vapr 0.00375 torr

Solubility sol 7.8E5 mg/L

Kd Kd mg/L

Koc Koc 7.3 mg/L

Photolysis half-life kdp 29 days Half-life

Aerobic Aquatic Metabolism kbacw 5.28 days Halfife

Anaerobic Aquatic Metabolism kbacs 70 days Halfife

Aerobic Soil Metabolism asm 1.5 days Halfife

Hydrolysis: pH 7 0 days Half-life

Method: CAM 2 integer See PRZM manual

Incorporation Depth: DEPI 0 cm

Application Rate:TAPP 19.7 kg/ha

Application Efficiency: APPEFF0.99 fraction

Spray Drift DRFT 0.001 fraction of application rate applied to pond

Application Date Date 01-12 dd/mm or dd/mmm or dd-mm or dd-mmm

Record 17: FILTRA

IPSCND1

UPTKF

Record 18: PLVKRT
-Page 89 of 115-

PLDKRT

FEXTRC 0.5

Flag for Index Res. Run IR EPA Pond

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

stored as HcyanamideMIcherries.out

Chemical: Hcyanamide

PRZM environment: MICherriesSTD.txt modified Tueday, 29 May 2007 at 13:56:56

EXAMS environment: pond298.exv modified Thuday, 29 August 2002 at 16:33:30

Metfile: w14850.dvf modified Wedday, 3 July 2002 at 09:05:40

Water segment concentrations (ppb)

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly

1961 17.48 16.48 13.13 7.879 5.57 1.385

1962 10.17 9.692 7.515 4.206 2.907 0.7202

1963 15.74 15.02 12.21 7.052 4.946 1.227

1964 0.9854 0.9405 0.7452 0.4216 0.2903 0.07182

1965 0.985 0.9401 0.7666 0.4728 0.3313 0.08233

1966 0.985 0.938 0.7528 0.4571 0.3227 0.07999

1967 2.635 2.516 2.026 1.202 0.8498 0.2109

1968 0.9851 0.9345 0.7321 0.4114 0.2864 0.0708

1969 0.985 0.9401 0.7659 0.4445 0.3102 0.07704

1970 0.985 0.9401 0.7392 0.4141 0.2867 0.07099

1971 1.075 1.006 0.882 0.5464 0.3828 0.09479

1972 0.985 0.9401 0.7623 0.4621 0.3225 0.07983

1973 1.736 1.615 1.211 0.7812 0.5514 0.1367

1974 1.99 1.888 1.416 0.8648 0.6077 0.1507

1975 5.041 4.811 3.891 2.321 1.603 0.3968

1976 110 107 85.02 47.56 33.19 8.2

1977 13.64 13.09 10.06 5.456 3.748 0.9291

1978 0.9853 0.9404 0.7638 0.4581 0.3189 0.07918

1979 15.99 15.21 11.97 7.097 5.011 1.248

1980 0.9855 0.9406 0.7507 0.4371 0.3043 0.07553

1981 2.883 2.78 2.122 1.23 0.8605 0.2133

1982 113 108 87.59 51.86 35.82 8.883

1983 0.9883 0.9426 0.7609 0.4667 0.3328 0.08389

1984 0.985 0.9402 0.753 0.4412 0.3099 0.07667

1985 20.09 19.17 14.45 7.911 5.498 1.364

1986 100 96.12 74.98 40.75 28.1 6.963

1987 0.9874 0.9368 0.7213 0.3928 0.2693 0.06757

1988 1.136 1.075 0.9226 0.5673 0.3929 0.09696

1989 6.438 6.251 4.933 2.909 2.041 0.5066

1990 0.9852 0.9361 0.7474 0.4218 0.2945 0.07309

Sorted results

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

0.032258064516129 113 108 87.59 51.86 35.82 8.883

0.0645161290322581 110 107 85.02 47.56 33.19 8.2

0.0967741935483871 100 96.12 74.98 40.75 28.1 6.963
-Page 90 of 115-

0.129032258064516 20.09 19.17 14.45 7.911 5.57 1.385

0.161290322580645 17.48 16.48 13.13 7.879 5.498 1.364

0.193548387096774 15.99 15.21 12.21 7.097 5.011 1.248

0.225806451612903 15.74 15.02 11.97 7.052 4.946 1.227

0.258064516129032 13.64 13.09 10.06 5.456 3.748 0.9291

0.290322580645161 10.17 9.692 7.515 4.206 2.907 0.7202

0.32258064516129 6.438 6.251 4.933 2.909 2.041 0.5066

0.354838709677419 5.041 4.811 3.891 2.321 1.603 0.3968

0.387096774193548 2.883 2.78 2.122 1.23 0.8605 0.2133

0.419354838709677 2.635 2.516 2.026 1.202 0.8498 0.2109

0.451612903225806 1.99 1.888 1.416 0.8648 0.6077 0.1507

0.483870967741936 1.736 1.615 1.211 0.7812 0.5514 0.1367

0.516129032258065 1.136 1.075 0.9226 0.5673 0.3929 0.09696

0.548387096774194 1.075 1.006 0.882 0.5464 0.3828 0.09479

0.580645161290323 0.9883 0.9426 0.7666 0.4728 0.3328 0.08389

0.612903225806452 0.9874 0.9406 0.7659 0.4667 0.3313 0.08233

0.645161290322581 0.9855 0.9405 0.7638 0.4621 0.3227 0.07999

0.67741935483871 0.9854 0.9404 0.7623 0.4581 0.3225 0.07983

0.709677419354839 0.9853 0.9402 0.7609 0.4571 0.3189 0.07918

0.741935483870968 0.9852 0.9401 0.753 0.4445 0.3102 0.07704

0.774193548387097 0.9851 0.9401 0.7528 0.4412 0.3099 0.07667

0.806451612903226 0.985 0.9401 0.7507 0.4371 0.3043 0.07553

0.838709677419355 0.985 0.9401 0.7474 0.4218 0.2945 0.07309

0.870967741935484 0.985 0.938 0.7452 0.4216 0.2903 0.07182

0.903225806451613 0.985 0.9368 0.7392 0.4141 0.2867 0.07099

0.935483870967742 0.985 0.9361 0.7321 0.4114 0.2864 0.0708

0.967741935483871 0.985 0.9345 0.7213 0.3928 0.2693 0.06757

0.1 92.009 88.425 68.927 37.4661 25.847 6.4052

Average of yearly averages: 1.123826

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run:

Output File: HcyanamideMIcherries

Metfile: w14850.dvf

PRZM scenario: MICherriesSTD.txt

EXAMS environment file: pond298.exv

Chemical Name: Hcyanamide

Description Variable Name Value Units Comments

Molecular weightmwt 42.04 g/mol

Henry's Law Const. henry 2.68E-10 atm-m^3/mol

Vapor Pressure vapr 0.00375 torr

Solubility sol 7.8E5 mg/L

Kd Kd mg/L

Koc Koc 7.3 mg/L

Photolysis half-life kdp 29 days Half-life

Aerobic Aquatic Metabolism kbacw 5.28 days Halfife

Anaerobic Aquatic Metabolism kbacs 70 days Halfife

Aerobic Soil Metabolism asm 1.5 days Halfife

Hydrolysis: pH 7 0 days Half-life

Method: CAM 2 integer See PRZM manual

Incorporation Depth: DEPI 0 cm

Application Rate:TAPP 19.7 kg/ha

Application Efficiency: APPEFF0.99 fraction

Spray Drift DRFT 0.001 fraction of application rate applied to pond
-Page 91 of 115-

Application Date Date 24-03 dd/mm or dd/mmm or dd-mm or dd-mmm

Record 17: FILTRA

IPSCND1

UPTKF

Record 18: PLVKRT

PLDKRT

FEXTRC 0.5

Flag for Index Res. Run IR EPA Pond

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

stored as HcyanamideCAgrapes.out

Chemical: Hcyanamide

PRZM environment: CAgrapes_WirrigSTD.txt modified Tueday, 29 May 2007 at 13:42:54

EXAMS environment: pond298.exv modified Thuday, 29 August 2002 at 16:33:30

Metfile: w93193.dvf modified Wedday, 3 July 2002 at 09:04:24

Water segment concentrations (ppb)

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly

1961 0.985 0.8962 0.6203 0.3202 0.2223 0.05527

1962 87.74 81.58 59.67 31.74 21.7 5.365

1963 46.28 41.39 27.35 13.65 9.42 2.333

1964 0.9851 0.9083 0.6592 0.3501 0.2413 0.05963

1965 42.66 38.17 24.93 11.59 7.898 1.971

1966 0.9852 0.9077 0.6569 0.3315 0.2253 0.05581

1967 1.39 1.251 0.856 0.6516 0.5176 0.1299

1968 0.985 0.8822 0.5802 0.3877 0.2881 0.07148

1969 6.215 5.724 4.147 2.341 1.643 0.4069

1970 5.663 5.095 3.372 1.731 1.241 0.3077

1971 6.279 5.534 3.406 1.503 1.062 0.3048

1972 0.985 0.8941 0.6137 0.2939 0.1993 0.06264

1973 30.36 27.56 18.92 9.818 6.748 1.668

1974 0.9851 0.904 0.6449 0.3672 0.2673 0.06639

1975 0.985 0.8999 0.632 0.3305 0.2292 0.05675

1976 215 197 139 72.18 49.77 12.28

1977 0.9858 0.8911 0.6186 0.4022 0.2822 0.07021

1978 166 156 107 51.25 34.83 8.605

1979 1.962 1.785 1.2 0.6977 0.4784 0.1183

1980 14.14 12.76 8.563 4.427 3.065 0.7567

1981 0.985 0.8947 0.6155 0.4445 0.3231 0.08017

1982 1.469 1.381 0.9802 0.6646 0.5002 0.1246

1983 1.455 1.299 0.847 0.5855 0.4114 0.102

1984 3.006 2.735 1.895 0.9248 0.6287 0.1551

1985 0.985 0.8945 0.615 0.3164 0.2151 0.05314

1986 43.1 38.57 25.15 11.64 7.893 1.949

1987 3.128 2.831 1.922 1.005 0.683 0.1718

1988 2.939 2.552 1.87 1.133 1.004 0.2647

1989 1.375 1.216 0.766 0.658 0.4725 0.121

1990 1.809 1.535 0.8268 0.498 0.3983 0.1372

Sorted results

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

0.032258064516129 215 197 139 72.18 49.77 12.28
-Page 92 of 115-

0.0645161290322581 166 156 107 51.25 34.83 8.605

0.0967741935483871 87.74 81.58 59.67 31.74 21.7 5.365

0.129032258064516 46.28 41.39 27.35 13.65 9.42 2.333

0.161290322580645 43.1 38.57 25.15 11.64 7.898 1.971

0.193548387096774 42.66 38.17 24.93 11.59 7.893 1.949

0.225806451612903 30.36 27.56 18.92 9.818 6.748 1.668

0.258064516129032 14.14 12.76 8.563 4.427 3.065 0.7567

0.290322580645161 6.279 5.724 4.147 2.341 1.643 0.4069

0.32258064516129 6.215 5.534 3.406 1.731 1.241 0.3077

0.354838709677419 5.663 5.095 3.372 1.503 1.062 0.3048

0.387096774193548 3.128 2.831 1.922 1.133 1.004 0.2647

0.419354838709677 3.006 2.735 1.895 1.005 0.683 0.1718

0.451612903225806 2.939 2.552 1.87 0.9248 0.6287 0.1551

0.483870967741936 1.962 1.785 1.2 0.6977 0.5176 0.1372

0.516129032258065 1.809 1.535 0.9802 0.6646 0.5002 0.1299

0.548387096774194 1.469 1.381 0.856 0.658 0.4784 0.1246

0.580645161290323 1.455 1.299 0.847 0.6516 0.4725 0.121

0.612903225806452 1.39 1.251 0.8268 0.5855 0.4114 0.1183

0.645161290322581 1.375 1.216 0.766 0.498 0.3983 0.102

0.67741935483871 0.9858 0.9083 0.6592 0.4445 0.3231 0.08017

0.709677419354839 0.9852 0.9077 0.6569 0.4022 0.2881 0.07148

0.741935483870968 0.9851 0.904 0.6449 0.3877 0.2822 0.07021

0.774193548387097 0.9851 0.8999 0.632 0.3672 0.2673 0.06639

0.806451612903226 0.985 0.8962 0.6203 0.3501 0.2413 0.06264

0.838709677419355 0.985 0.8947 0.6186 0.3315 0.2292 0.05963

0.870967741935484 0.985 0.8945 0.6155 0.3305 0.2253 0.05675

0.903225806451613 0.985 0.8941 0.615 0.3202 0.2223 0.05581

0.935483870967742 0.985 0.8911 0.6137 0.3164 0.2151 0.05527

0.967741935483871 0.985 0.8822 0.5802 0.2939 0.1993 0.05314

0.1 83.594 77.561 56.438 29.931 20.472 5.0618

Average of yearly averages: 1.26343966666667

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run:

Output File: HcyanamideCAgrapes

Metfile: w93193.dvf

PRZM scenario: CAgrapes_WirrigSTD.txt

EXAMS environment file: pond298.exv

Chemical Name: Hcyanamide

Description Variable Name Value Units Comments

Molecular weightmwt 42.04 g/mol

Henry's Law Const. henry 2.68E-10 atm-m^3/mol

Vapor Pressure vapr 0.00375 torr

Solubility sol 7.8E5 mg/L

Kd Kd mg/L

Koc Koc 7.3 mg/L

Photolysis half-life kdp 29 days Half-life

Aerobic Aquatic Metabolism kbacw 5.28 days Halfife

Anaerobic Aquatic Metabolism kbacs 70 days Halfife

Aerobic Soil Metabolism asm 1.5 days Halfife

Hydrolysis: pH 7 0 days Half-life

Method: CAM 2 integer See PRZM manual

Incorporation Depth: DEPI 0 cm

Application Rate:TAPP 19.7 kg/ha
-Page 93 of 115-

Application Efficiency: APPEFF0.99 fraction

Spray Drift DRFT 0.001 fraction of application rate applied to pond

Application Date Date 09-02 dd/mm or dd/mmm or dd-mm or dd-mmm

Record 17: FILTRA

IPSCND1

UPTKF

Record 18: PLVKRT

PLDKRT

FEXTRC 0.5

Flag for Index Res. Run IR EPA Pond

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

stored as HcyanamideNYgrapes.out

Chemical: Hcyanamide

PRZM environment: NYGrapesSTD.txt modified Tueday, 29 May 2007 at 13:59:44

EXAMS environment: pond298.exv modified Thuday, 29 August 2002 at 16:33:30

Metfile: w14860.dvf modified Wedday, 3 July 2002 at 09:06:14

Water segment concentrations (ppb)

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly

1961 1.751 1.639 1.257 0.7949 0.5575 0.1382

1962 0.985 0.9382 0.7224 0.3883 0.2643 0.06534

1963 2.941 2.775 2.1 1.149 0.7938 0.1964

1964 0.985 0.933 0.722 0.3883 0.2651 0.06538

1965 0.985 0.9401 0.7882 0.4664 0.3198 0.07912

1966 1.371 1.273 1.009 0.6179 0.432 0.107

1967 0.985 0.9356 0.7147 0.394 0.2742 0.06784

1968 0.985 0.9307 0.7232 0.395 0.274 0.06766

1969 1.291 1.189 0.9583 0.5633 0.391 0.0969

1970 1.356 1.256 1.002 0.6024 0.416 0.103

1971 0.985 0.9402 0.7525 0.4469 0.3125 0.07745

1972 0.985 0.9401 0.7521 0.4436 0.3088 0.07645

1973 0.985 0.9194 0.7174 0.4079 0.2841 0.07035

1974 1.507 1.443 1.105 0.6384 0.4448 0.1103

1975 0.985 0.9402 0.7558 0.4433 0.3044 0.07528

1976 1.92 1.79 1.313 0.7922 0.5536 0.1368

1977 22.7 21.31 15.69 8.414 5.781 1.432

1978 2.587 2.469 2.081 1.22 0.8464 0.2098

1979 5.951 5.644 4.387 2.552 1.785 0.4428

1980 1.689 1.589 1.204 0.7395 0.5152 0.1275

1981 0.985 0.9377 0.7212 0.3935 0.2721 0.06733

1982 4.277 4.022 3.044 1.716 1.183 0.2929

1983 0.9851 0.9283 0.7075 0.3949 0.2733 0.06764

1984 0.985 0.9401 0.7256 0.3981 0.275 0.06784

1985 2.037 1.88 1.305 0.7197 0.4918 0.1217

1986 0.985 0.9273 0.6914 0.3653 0.2495 0.06168

1987 7.698 7.215 5.194 2.808 1.922 0.4749

1988 52.55 49.75 38.2 20.98 14.4 3.551

1989 25.83 24.73 20.07 11.65 8.071 1.998

1990 0.9855 0.9249 0.682 0.36 0.2474 0.06144

Sorted results

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

0.032258064516129 52.55 49.75 38.2 20.98 14.4 3.551
-Page 94 of 115-

0.0645161290322581 25.83 24.73 20.07 11.65 8.071 1.998

0.0967741935483871 22.7 21.31 15.69 8.414 5.781 1.432

0.129032258064516 7.698 7.215 5.194 2.808 1.922 0.4749

0.161290322580645 5.951 5.644 4.387 2.552 1.785 0.4428

0.193548387096774 4.277 4.022 3.044 1.716 1.183 0.2929

0.225806451612903 2.941 2.775 2.1 1.22 0.8464 0.2098

0.258064516129032 2.587 2.469 2.081 1.149 0.7938 0.1964

0.290322580645161 2.037 1.88 1.313 0.7949 0.5575 0.1382

0.32258064516129 1.92 1.79 1.305 0.7922 0.5536 0.1368

0.354838709677419 1.751 1.639 1.257 0.7395 0.5152 0.1275

0.387096774193548 1.689 1.589 1.204 0.7197 0.4918 0.1217

0.419354838709677 1.507 1.443 1.105 0.6384 0.4448 0.1103

0.451612903225806 1.371 1.273 1.009 0.6179 0.432 0.107

0.483870967741936 1.356 1.256 1.002 0.6024 0.416 0.103

0.516129032258065 1.291 1.189 0.9583 0.5633 0.391 0.0969

0.548387096774194 0.9855 0.9402 0.7882 0.4664 0.3198 0.07912

0.580645161290323 0.9851 0.9402 0.7558 0.4469 0.3125 0.07745

0.612903225806452 0.985 0.9401 0.7525 0.4436 0.3088 0.07645

0.645161290322581 0.985 0.9401 0.7521 0.4433 0.3044 0.07528

0.67741935483871 0.985 0.9401 0.7256 0.4079 0.2841 0.07035

0.709677419354839 0.985 0.9382 0.7232 0.3981 0.275 0.06784

0.741935483870968 0.985 0.9377 0.7224 0.395 0.2742 0.06784

0.774193548387097 0.985 0.9356 0.722 0.3949 0.274 0.06766

0.806451612903226 0.985 0.933 0.7212 0.394 0.2733 0.06764

0.838709677419355 0.985 0.9307 0.7174 0.3935 0.2721 0.06733

0.870967741935484 0.985 0.9283 0.7147 0.3883 0.2651 0.06538

0.903225806451613 0.985 0.9273 0.7075 0.3883 0.2643 0.06534

0.935483870967742 0.985 0.9249 0.6914 0.3653 0.2495 0.06168

0.967741935483871 0.985 0.9194 0.682 0.36 0.2474 0.06144

0.1 21.1998 19.9005 14.6404 7.8534 5.3951 1.33629

Average of yearly averages: 0.350333333333333

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run:

Output File: HcyanamideNYgrapes

Metfile: w14860.dvf

PRZM scenario: NYGrapesSTD.txt

EXAMS environment file: pond298.exv

Chemical Name: Hcyanamide

Description Variable Name Value Units Comments

Molecular weightmwt 42.04 g/mol

Henry's Law Const. henry 2.68E-10 atm-m^3/mol

Vapor Pressure vapr 0.00375 torr

Solubility sol 7.8E5 mg/L

Kd Kd mg/L

Koc Koc 7.3 mg/L

Photolysis half-life kdp 29 days Half-life

Aerobic Aquatic Metabolism kbacw 5.28 days Halfife

Anaerobic Aquatic Metabolism kbacs 70 days Halfife

Aerobic Soil Metabolism asm 1.5 days Halfife

Hydrolysis: pH 7 0 days Half-life

Method: CAM 2 integer See PRZM manual

Incorporation Depth: DEPI 0 cm

Application Rate:TAPP 19.7 kg/ha
-Page 95 of 115-

Application Efficiency: APPEFF0.99 fraction

Spray Drift DRFT 0.001 fraction of application rate applied to pond

Application Date Date 25-03 dd/mm or dd/mmm or dd-mm or dd-mmm

Record 17: FILTRA

IPSCND1

UPTKF

Record 18: PLVKRT

PLDKRT

FEXTRC 0.5

Flag for Index Res. Run IR EPA Pond

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

stored as HcyanamideCAkiwi.out

Chemical: Hcyanamide

PRZM environment: CAfruit_WirrigSTD.txt modified Tueday, 29 May 2007 at 13:42:32

EXAMS environment: pond298.exv modified Thuday, 29 August 2002 at 16:33:30

Metfile: w93193.dvf modified Wedday, 3 July 2002 at 09:04:24

Water segment concentrations (ppb)

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly

1961 0.985 0.8881 0.5954 0.2894 0.197 0.04868

1962 0.985 0.8937 0.6124 0.2999 0.2026 0.05002

1963 11.58 10.47 7.51 4.124 2.917 0.7237

1964 0.9851 0.8939 0.6129 0.3065 0.2084 0.05135

1965 119 107 69.67 32.35 21.85 5.4

1966 0.9854 0.8771 0.5627 0.2606 0.1752 0.04334

1967 10.75 9.674 6.572 3.674 2.58 0.6381

1968 0.985 0.88 0.5718 0.3638 0.2513 0.06195

1969 9.36 8.222 5.048 2.234 1.637 0.4061

1970 126 113 74.16 35.9 24.33 6.007

1971 24.6 21.68 13.34 5.87 3.994 1.016

1972 1.103 0.8612 0.5205 0.234 0.1576 0.06091

1973 1.16 1.057 0.7236 0.5184 0.3542 0.08744

1974 2.027 1.811 1.202 0.6057 0.4109 0.1014

1975 0.985 0.8953 0.6248 0.3229 0.2208 0.05453

1976 0.985 0.8922 0.608 0.3047 0.2071 0.05099

1977 0.985 0.8913 0.6278 0.3166 0.2142 0.0529

1978 25.6 22.44 13.68 6.371 4.322 1.067

1979 0.9853 0.8751 0.5572 0.2593 0.1747 0.04313

1980 9.138 8.22 5.466 2.654 1.802 0.4438

1981 1.197 1.075 0.7058 0.5004 0.3453 0.08528

1982 7.945 7.516 5.382 2.71 1.874 0.4632

1983 80.64 71.96 46.58 22.35 15.15 3.74

1984 0.9851 0.8682 0.5387 0.2469 0.1662 0.04093

1985 0.985 0.8882 0.5958 0.2838 0.1908 0.04708

1986 17.43 15.29 10.31 4.687 3.178 0.7842

1987 5.667 5.065 3.471 1.759 1.23 0.3058

1988 25.11 21.79 15.05 6.434 4.401 1.099

1989 49.38 43.67 27.41 15.36 10.46 2.584

1990 6.26 5.215 2.375 1.715 1.177 0.329

Sorted results

Prob. Peak 96 hr 21 Day 60 Day 90 Day Yearly
-Page 96 of 115-

0.032258064516129 126 113 74.16 35.9 24.33 6.007

0.0645161290322581 119 107 69.67 32.35 21.85 5.4

0.0967741935483871 80.64 71.96 46.58 22.35 15.15 3.74

0.129032258064516 49.38 43.67 27.41 15.36 10.46 2.584

0.161290322580645 25.6 22.44 15.05 6.434 4.401 1.099

0.193548387096774 25.11 21.79 13.68 6.371 4.322 1.067

0.225806451612903 24.6 21.68 13.34 5.87 3.994 1.016

0.258064516129032 17.43 15.29 10.31 4.687 3.178 0.7842

0.290322580645161 11.58 10.47 7.51 4.124 2.917 0.7237

0.32258064516129 10.75 9.674 6.572 3.674 2.58 0.6381

0.354838709677419 9.36 8.222 5.466 2.71 1.874 0.4632

0.387096774193548 9.138 8.22 5.382 2.654 1.802 0.4438

0.419354838709677 7.945 7.516 5.048 2.234 1.637 0.4061

0.451612903225806 6.26 5.215 3.471 1.759 1.23 0.329

0.483870967741936 5.667 5.065 2.375 1.715 1.177 0.3058

0.516129032258065 2.027 1.811 1.202 0.6057 0.4109 0.1014

0.548387096774194 1.197 1.075 0.7236 0.5184 0.3542 0.08744

0.580645161290323 1.16 1.057 0.7058 0.5004 0.3453 0.08528

0.612903225806452 1.103 0.8953 0.6278 0.3638 0.2513 0.06195

0.645161290322581 0.9854 0.8939 0.6248 0.3229 0.2208 0.06091

0.67741935483871 0.9853 0.8937 0.6129 0.3166 0.2142 0.05453

0.709677419354839 0.9851 0.8922 0.6124 0.3065 0.2084 0.0529

0.741935483870968 0.9851 0.8913 0.608 0.3047 0.2071 0.05135

0.774193548387097 0.985 0.8882 0.5958 0.2999 0.2026 0.05099

0.806451612903226 0.985 0.8881 0.5954 0.2894 0.197 0.05002

0.838709677419355 0.985 0.88 0.5718 0.2838 0.1908 0.04868

0.870967741935484 0.985 0.8771 0.5627 0.2606 0.1752 0.04708

0.903225806451613 0.985 0.8751 0.5572 0.2593 0.1747 0.04334

0.935483870967742 0.985 0.8682 0.5387 0.2469 0.1662 0.04313

0.967741935483871 0.985 0.8612 0.5205 0.234 0.1576 0.04093

0.1 77.514 69.131 44.663 21.651 14.681 3.6244

Average of yearly averages: 0.862894333333334

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run:

Output File: HcyanamideCAkiwi

Metfile: w93193.dvf

PRZM scenario: CAfruit_WirrigSTD.txt

EXAMS environment file: pond298.exv

Chemical Name: Hcyanamide

Description Variable Name Value Units Comments

Molecular weightmwt 42.04 g/mol

Henry's Law Const. henry 2.68E-10 atm-m^3/mol

Vapor Pressure vapr 0.00375 torr

Solubility sol 7.8E5 mg/L

Kd Kd mg/L

Koc Koc 7.3 mg/L

Photolysis half-life kdp 29 days Half-life

Aerobic Aquatic Metabolism kbacw 5.28 days Halfife

Anaerobic Aquatic Metabolism kbacs 70 days Halfife

Aerobic Soil Metabolism asm 1.5 days Halfife

Hydrolysis: pH 7 0 days Half-life

Method: CAM 2 integer See PRZM manual

Incorporation Depth: DEPI 0 cm
-Page 97 of 115-

Application Rate:TAPP 19.7 kg/ha

Application Efficiency: APPEFF0.99 fraction

Spray Drift DRFT 0.001 fraction of application rate applied to pond

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

Record 17: FILTRA

IPSCND1

UPTKF

Record 18: PLVKRT

PLDKRT

FEXTRC 0.5

Flag for Index Res. Run IR EPA Pond

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

stored as HcyanamideGApeaches.out

Chemical: Hcyanamide

PRZM environment: GAPeachesSTD.txt modified Tueday, 29 May 2007 at 13:54:56

EXAMS environment: pond298.exv modified Thuday, 29 August 2002 at 16:33:30

Metfile: w03813.dvf modified Wedday, 3 July 2002 at 09:04:32

Water segment concentrations (ppb)

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly

1961 3.68 3.323 2.251 1.065 0.7249 0.1791

1962 0.488 0.4451 0.319 0.1633 0.1112 0.02744

1963 0.37 0.3435 0.2512 0.1189 0.08014 0.01978

1964 2.701 2.446 1.75 0.8607 0.5835 0.1436

1965 17.27 16.08 11.7 5.96 4.045 0.9984

1966 29.62 27.32 19.63 9.947 6.759 1.67

1967 0.3701 0.3421 0.247 0.1177 0.07929 0.01959

1968 0.37 0.3468 0.2649 0.1361 0.09239 0.02276

1969 1.199 1.112 0.8191 0.4379 0.2984 0.07372

1970 0.37 0.3398 0.2416 0.1182 0.07984 0.01971

1971 0.37 0.3392 0.2401 0.1225 0.08327 0.02056

1972 1.672 1.538 1.091 0.5412 0.3669 0.09037

1973 39.33 36.37 26.18 12.19 8.239 2.034

1974 0.3778 0.3569 0.256 0.1185 0.07995 0.01974

1975 12.74 11.53 7.751 3.759 2.556 0.6311

1976 0.37 0.3318 0.2172 0.09997 0.06742 0.01661

1977 0.37 0.341 0.2689 0.1312 0.08851 0.02184

1978 0.37 0.3455 0.2598 0.1325 0.08981 0.02217

1979 0.8054 0.7477 0.5151 0.2758 0.1873 0.04625

1980 0.37 0.341 0.2476 0.1252 0.08506 0.02094

1981 7.757 7.026 4.723 2.267 1.533 0.3783

1982 19.45 17.61 11.77 5.444 3.686 0.91

1983 73.92 67.6 47.39 23.3 15.84 3.912

1984 0.3702 0.3365 0.2382 0.1183 0.0802 0.01978

1985 0.37 0.3394 0.2391 0.1139 0.07698 0.019

1986 0.37 0.334 0.2237 0.1068 0.07216 0.01781

1987 0.37 0.3396 0.2444 0.1209 0.08205 0.02025

1988 0.9054 0.8341 0.5892 0.307 0.2086 0.05139

1989 4.145 3.77 2.487 1.175 0.7996 0.1975

1990 8.269 7.361 4.692 2.16 1.461 0.3607
-Page 98 of 115-

Sorted results

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

0.032258064516129 73.92 67.6 47.39 23.3 15.84 3.912

0.0645161290322581 39.33 36.37 26.18 12.19 8.239 2.034

0.0967741935483871 29.62 27.32 19.63 9.947 6.759 1.67

0.129032258064516 19.45 17.61 11.77 5.96 4.045 0.9984

0.161290322580645 17.27 16.08 11.7 5.444 3.686 0.91

0.193548387096774 12.74 11.53 7.751 3.759 2.556 0.6311

0.225806451612903 8.269 7.361 4.723 2.267 1.533 0.3783

0.258064516129032 7.757 7.026 4.692 2.16 1.461 0.3607

0.290322580645161 4.145 3.77 2.487 1.175 0.7996 0.1975

0.32258064516129 3.68 3.323 2.251 1.065 0.7249 0.1791

0.354838709677419 2.701 2.446 1.75 0.8607 0.5835 0.1436

0.387096774193548 1.672 1.538 1.091 0.5412 0.3669 0.09037

0.419354838709677 1.199 1.112 0.8191 0.4379 0.2984 0.07372

0.451612903225806 0.9054 0.8341 0.5892 0.307 0.2086 0.05139

0.483870967741936 0.8054 0.7477 0.5151 0.2758 0.1873 0.04625

0.516129032258065 0.488 0.4451 0.319 0.1633 0.1112 0.02744

0.548387096774194 0.3778 0.3569 0.2689 0.1361 0.09239 0.02276

0.580645161290323 0.3702 0.3468 0.2649 0.1325 0.08981 0.02217

0.612903225806452 0.3701 0.3455 0.2598 0.1312 0.08851 0.02184

0.645161290322581 0.37 0.3435 0.256 0.1252 0.08506 0.02094

0.67741935483871 0.37 0.3421 0.2512 0.1225 0.08327 0.02056

0.709677419354839 0.37 0.341 0.2476 0.1209 0.08205 0.02025

0.741935483870968 0.37 0.341 0.247 0.1189 0.0802 0.01978

0.774193548387097 0.37 0.3398 0.2444 0.1185 0.08014 0.01978

0.806451612903226 0.37 0.3396 0.2416 0.1183 0.07995 0.01974

0.838709677419355 0.37 0.3394 0.2401 0.1182 0.07984 0.01971

0.870967741935484 0.37 0.3392 0.2391 0.1177 0.07929 0.01959

0.903225806451613 0.37 0.3365 0.2382 0.1139 0.07698 0.019

0.935483870967742 0.37 0.334 0.2237 0.1068 0.07216 0.01781

0.967741935483871 0.37 0.3318 0.2172 0.09997 0.06742 0.01661

0.1 28.603 26.349 18.844 9.5483 6.4876 1.60284

Average of yearly averages: 0.399480333333333

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run:

Output File: HcyanamideGApeaches

Metfile: w03813.dvf

PRZM scenario: GAPeachesSTD.txt

EXAMS environment file: pond298.exv

Chemical Name: Hcyanamide

Description Variable Name Value Units Comments

Molecular weightmwt 42.04 g/mol

Henry's Law Const. henry 2.68E-10 atm-m^3/mol

Vapor Pressure vapr 0.00375 torr

Solubility sol 7.8E5 mg/L

Kd Kd mg/L

Koc Koc 7.3 mg/L

Photolysis half-life kdp 29 days Half-life

Aerobic Aquatic Metabolism kbacw 5.28 days Halfife

Anaerobic Aquatic Metabolism kbacs 70 days Halfife

Aerobic Soil Metabolism asm 1.5 days Halfife

Hydrolysis: pH 7 0 days Half-life
-Page 99 of 115-

Method: CAM 2 integer See PRZM manual

Incorporation Depth: DEPI 0 cm

Application Rate:TAPP 7.4 kg/ha

Application Efficiency: APPEFF0.99 fraction

Spray Drift DRFT 0.001 fraction of application rate applied to pond

Application Date Date 14-02 dd/mm or dd/mmm or dd-mm or dd-mmm

Record 17: FILTRA

IPSCND1

UPTKF

Record 18: PLVKRT

PLDKRT

FEXTRC 0.5

Flag for Index Res. Run IR EPA Pond

Flag for runoff calc. RUNOFF none none, monthly or total(average of entire run)
-Page 100 of 115-

Appendix D. Example Terrestrial Exposure Model Inputs/Outputs

STIR

Input

Application and Chemical Information

Enter Chemical Name

Hydrogen 

cyanamide

Enter Chemical Use

Is the Application a Spray? (enter y or n) y

If Spray What Type (enter ground or air) air

Enter Chemical Molecular Weight (g/mole) 42.04

Enter Chemical Vapor Pressure (mmHg) 3.75E-03

Enter Application Rate (lb a.i./acre) 17.6

Toxicity Properties

Bird

Enter Lowest Bird Oral LD50 (mg/kg bw) 173

Enter Mineau Scaling Factor 1.15

Enter Tested Bird Weight (kg) 0.178

Mammal

Enter Lowest Rat Oral LD50 (mg/kg bw) 300

Enter Lowest Rat Inhalation LC50 (mg/L) 2.32

Duration of Rat Inhalation Study (hrs) 4

Enter Rat Weight (kg) 0.35

Output

Results Avian (0.020 kg )

Maximum Vapor Concentration in Air at Saturation 

(mg/m3) 8.48E+00

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 1.07E+00

Adjusted Inhalation LD50 7.46E+00

Ratio of Vapor Dose to Adjusted Inhalation LD50 1.43E-01 Proceed to Refinements

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 1.69E+00

Ratio of Droplet Inhalation Dose to Adjusted Inhalation 

LD50 2.27E-01 Proceed to Refinements

Results Mammalian (0.015 kg )

Maximum Vapor Concentration in Air at Saturation 

(mg/m3) 8.48E+00

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 1.34E+00

Adjusted Inhalation LD50 1.38E+02

Ratio of Vapor Dose to Adjusted Inhalation LD50 9.71E-03 Exposure not Likely Significant

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 2.13E+00

Ratio of Droplet Inhalation Dose to Adjusted Inhalation 

LD50 1.54E-02 Exposure not Likely Significant
-Page 101 of 115-

SIP

Table 1. Inputs

Parameter Value

Chemical name Hydrogen Cyanamide

Solubility (in water at 25oC; mg/L) 780000

Mammalian LD50 (mg/kg-bw) 300

Mammalian test species laboratory rat

Body weight (g) of "other" mammalian 

species

Mammalian NOAEL (mg/kg-bw) 0.0625

Mammalian test species laboratory rat

Body weight (g) of "other" mammalian 

species

Avian LD50 (mg/kg-bw) 173

Avian test species northern bobwhite quail

Body weight (g) of "other" avian species

Mineau scaling factor 1.15

Mallard NOAEC (mg/kg-diet) 0

Bobwhite quail NOAEC (mg/kg-diet) 153

NOAEC (mg/kg-diet) for other bird species

Body weight (g) of other avian species

NOAEC (mg/kg-diet) for 2nd other bird 

species

Body weight (g) of 2nd other avian species

Table 2. Mammalian Results

Parameter Acute Chronic

Upper bound exposure (mg/kg-bw) 96320.0000 96320.0000

Adjusted toxicity value (mg/kg-bw) 230.7482 0.0481

Ratio of exposure to toxicity 417.4248 2003638.8571

Conclusion*

Exposure through 

drinking water alone is a 

potential concern for 

mammals

Exposure through 

drinking water alone is a 

potential concern for 

mammals

Table 3. Avian Results

Parameter Acute Chronic
-Page 102 of 115-

Upper bound exposure (mg/kg-bw) 453600.0000 453600.0000

Adjusted toxicity value (mg/kg-bw) 124.6343 16.2636

Ratio of exposure to acute toxicity 3639.4474 27890.4301

Conclusion*

Exposure through 

drinking water alone is a 

potential concern for 

birds

Exposure through 

drinking water alone is a 

potential concern for 

birds

*Conclusion is for drinking water exposure alone. This does not combine all routes of exposure. 

Therefore, when aggregated with other routes (i.e., diet, inhalation, dermal), pesticide exposure through 

drinking water may contribute to a total exposure that has potential for effects to non-target animals.
-Page 103 of 115-

T-REX

Summary of Risk Quotient Calculations Based on Upper Bound Kenaga EECs

Table X. Upper Bound Kenaga, Acute Avian Dose-Based Risk Quotients

Size 

Class

(grams)

Adjusted

LD50

EECs and RQs

Short Grass Tall Grass Broadleaf Plants Fruits/Pods/Seeds Arthropods Granivore

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

20 124.63 4810.71 38.60 2204.91 17.69 2706.03 21.71 300.67 2.41 1884.20 15.12 66.82 0.54

100 158.67 2743.27 17.29 1257.33 7.92 1543.09 9.73 171.45 1.08 1074.45 6.77 38.10 0.24

1000 224.12 1228.20 5.48 562.92 2.51 690.86 3.08 76.76 0.34 481.04 2.15 17.06 0.08

Table X. Upper Bound Kenaga, Subacute Avian Dietary Based Risk Quotients

LC50

EECs and RQs

Short Grass Tall Grass Broadleaf Plants Fruits/Pods/Seeds Arthropods

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

5000 4224.00 0.84 1936.00 0.39 2376.00 0.48 264.00 0.05 1654.40 0.33

Size class not used for dietary risk quotients 

Table X. Upper Bound Kenaga, Chronic Avian Dietary Based Risk Quotients
-Page 104 of 115-

NOAEC 

(ppm)

EECs and RQs

Short Grass Tall Grass Broadleaf Plants Fruits/Pods/Seeds Arthropods

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

153 4224.00 27.61 1936.00 12.65 2376.00 15.53 264.00 1.73 1654.40 10.81

Size class not used for dietary risk quotients

Table X. Upper Bound Kenaga, Acute Mammalian Dose-Based Risk Quotients 

Size 

Class

(grams)

Adjusted

LD50

EECs and RQs

Short Grass Tall Grass Broadleaf Plants Fruits/Pods/Seeds Arthropods Granivore

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

15 659.35 4027.26 6.11 1845.83 2.80 2265.33 3.44 251.70 0.38 1577.34 2.3923 55.934 0.0848

35 533.48 2783.38 5.22 1275.71 2.39 1565.65 2.93 173.96 0.33 1090.16 2.0435 38.658 0.0725

1000 230.75 645.34 2.80 295.78 1.28 363.00 1.57 40.33 0.17 252.756 1.0954 8.963 0.0388

Table X. Upper Bound Kenaga, Acute Mammalian Dietary Based Risk Quotients

LC50 

(ppm)

EECs and RQs

Short Grass Tall Grass Broadleaf Plants Fruits/Pods/Seeds Arthropods

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

0 4224.00 #DIV/0! 1936.00 #DIV/0! 2376.00 #DIV/0! 264.00 ##### 1654.40 #DIV/0!

Size class not used for dietary risk quotients
-Page 105 of 115-

Table X. Upper Bound Kenaga, Chronic Mammalian Dietary Based Risk Quotients

NOAEC 

(ppm)

EECs and RQs

Short Grass Tall Grass Broadleaf Plants Fruits/Pods/Seeds/Large 

Insects Arthropods

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

25 4224.00 168.96 1936.00 77.44 2376.00 95.04 264.00 10.56 1654.40 66.18

Size class not used for dietary risk quotients 

Table X. Upper Bound Kenaga, Chronic Mammalian Dose-Based Risk Quotients

Size 

Class

(grams)

Adjusted 

NOAEL

EECs and RQs

Short Grass Tall Grass Broadleaf Plants Fruits/Pods/Seeds Arthropods Granivore

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

15 2.75 4027.26 1465.90 1845.83 671.87 2265.33 824.57 251.70 91.62 1577.34 574.15 55.93 20.36

35 2.22 2783.38 1252.17 1275.71 573.91 1565.65 704.34 173.96 78.26 1090.16 490.43 38.66 17.39

1000 0.96 645.34 671.21 295.78 307.64 363.00 377.56 40.33 41.95 252.76 262.89 8.96 9.32
-Page 106 of 115-

TerrPlant

TerrPlant v. 1.2.2

Green values signify user inputs (Tables 1, 2 and 4). 

Input and output guidance is in popups indicated by red arrows.

Table 1. Chemical Identity.

Chemical Name Hydrogen Cyanamide

PC code 14002

Use 6.8 lbs/A

Application Method Airblast

Application Form Spray 

Solubility in Water 

(ppm) 780000

Table 2. Input parameters used to derive EECs.

Input Parameter Symbol Value Units

Application Rate A 17.6 y

Incorporation I 1 none

Runoff Fraction R 0.05 none

Drift Fraction D 0.05 none

Table 3. EECs for Hydrogen Cyanamide. Units in y.

Description Equation EEC

Runoff to dry areas (A/I)*R 0.88

Runoff to semi-aquatic areas (A/I)*R*10 8.8

Spray drift A*D 0.88

Total for dry areas ((A/I)*R)+(A*D) 1.76

Total for semi-aquatic areas ((A/I)*R*10)+(A*D) 9.68

Table 4. Plant survival and growth data used for RQ derivation. Units are in y.

Seedling Emergence Vegetative Vigor

Plant type EC25 NOAEC EC25 NOAEC 

Monocot 0.44 0.041 7.9 7.2

Dicot 0.056 0.89 0.096

Table 5. RQ values for plants in dry and semi-aquatic areas exposed to Hydrogen Cyanamide 

through runoff and/or spray drift.*

Plant Type Listed Status Dry Semi-Aquatic Spray Drift

Monocot non-listed 4.00 22.00 2.00

Monocot listed 42.93 236.10 21.46

Dicot non-listed #DIV/0! #DIV/0! 0.99
-Page 107 of 115-

Dicot listed 31.43 172.86 15.71

*If RQ > 1.0, the LOC is exceeded, resulting in potential for risk to that plant group.
-Page 108 of 115-

Appendix E. Reported Hydrogen Cyanamide Ecological Incident Summaries in the EIIS 

Database

Table E-1. Hydrogen Cyanamide Incident Report Summaries

Incident # Organism(s) 

Affected

Certainty of 

Involvement

Legality of 

Use Description

I000423-

001

Grape Probable Misuse

(Accidental)

Siemer & Associates reported 

an incident of defoliation of 

lemon trees in several groves in 

the Coachella Valley (Riverside 

County), California. The 

damage to the lemon trees was 

believed to be caused by the 

use of Dormex (A.I. 

Cyanamide) to a grape 

vineyard. Dormex was 

allegedely applied during 

stormy weather using a high 

pressure sprayer. The label 

states to use a low pressure 

sprayer and only when weather 

conditions do not favor drift.

I016036-

022

Kiwifruits Possible Registered 

Use

The California Dept. of 

Pesticide Regulations reported 

an incident in which a total of 

380 acres of kiwifruits were 

damaged. One firm owns the 

kiwifruits but they are located 

in several areas and were not 

all sprayed at the same time. 

Dormex was applied during 

January and February, 2004, as 

was Valent Volck Supreme Oil 

Spray more than three weeks 

apart. A burning of buds was 

observed on the kiwi vines 

where both products were 

applied. Damage amounted to 

about a 20% loss of crop. A 

label for Dormex use on 

kiwifruit in Australia states 

"dormant sprays containing oil 

should not be made closer than 

14 days before or after Dormex 

application." This would 

suggest that the combination of 
-Page 109 of 115-

Table E-1. Hydrogen Cyanamide Incident Report Summaries

Incident # Organism(s) 

Affected

Certainty of 

Involvement

Legality of 

Use Description

the two products is potentially 

harmless.