Hydrazine Dietary Exposure and Risk Assessment DP Number: 0 420404 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

MEMORANDUM 

DATE: June 4, 2014 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

SUBJECT: Hydrazine. Screening Level Cancer Aggregate Dietary (Food and Drinking 

Water) Exposure and Risk Assessment as Part of the Maleic Hydrazide 

Registration Review. 

PC Code: None (hydrazine), 051501 (maleic 

hydrazide, and 051503 (maleic hydrazide, 

potassium salt). 

DP Barcode: D420404 

Decision No.: 481781 Registration No.: NA 

Petition No.: none 

Risk Assessment Type: Dietary 

TXR No.: Not Applicable 

Regulatory Action: Registration Review 

Case No.: 0381 (maleic hydrazide) 

CAS No.: 302-01-2 (hydrazine ); 123-33-1 

(maleic hydrazide), and 28382-15-2 (maleic 

hydrazide, potassium salt) 

MRID No.: None 40 CFR: Not Applicable 

B . C K hll". E . IS .. ~~ n.dDJ-~\~ , FROM: onme ropp- o 1g1an, nvuonmenta ctentlst _L) '-"'UUf( (.) 

Risk Assessment Branch IV (RABIV), Health Effec~ en (HED) (7509P) 

THROUGH: n V. Hummel, Senior Chemist ),l.JV 

RABIV, HED (7509P) 

Thurston 

and 

Morton, Senior 'st 

$ ~ ~ 

David Hrdy, Senior Biologi 17: 

Dietary Exposure Science A ISory u~c 1 AC), HED (7509P) 

TO: Ricardo Jones, Chemical Review Manager #51 

Tom Moriarty, Team Leader 

RMIB1, Pesticide Re-Evaluation Division (7508P) 

Executive Summary 

Screening level hydrazine cancer aggregate dietary (food and drinking water) exposure and risk 

assessments were conducted using the Dietary Exposure Evaluation Model software with the 

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Hydrazine Dietary Exposure and Risk Assessment DP Number: 0420404 

Food Commodity Intake Database (DEEM-FCID) Version 3.16. This software uses 2003-2008 

food consumption data from the U.S. Department of Agriculture's (USDA's) National Health 

and Nutrition Examination Survey, What We Eat in America, (NHANES/WWEIA). The 

analyses were conducted as part of the maleic hydrazide registration review to verify that the 15 

ppm (0.0015%) Agency stipulated upper limit ofhydrazine in the technical grade of maleic 

hydrazide, which was set in ca. 1982 at the close of the maleic hydrazide Special Review (then 

called Rebuttable Presumption Against Registration or RP AR), remains adequate. This 

memorandum was reviewed by two peer reviewers ofthe DESAC per DESAC SOP 2012.1. 

Maleic hydrazide and its potassium salt are currently registered for food/feed uses on onions and 

potatoes. There is no registered use ofhydrazine. No hydrazine metabolism and/or magnitude 

of the residue data for crops and/or livestock are available for dietary exposure and risk 

assessments. Hence, screening level cancer dietary exposure and risk assessments for hydrazine 

resulting from the registered uses of maleic hydrazide were conducted using anticipated residue 

estimates for hydrazine based on available maleic hydrazide data and assumed that the estimated 

ratio of. maleic hydrazide to hydrazine in the technical grade of maleic hydrazide (100% to 

0.0015%) remained unchanged in formulated end-use products and in/on crops through 

application/deposition/translocation and beyond. Furthermore, it assumed that the transfer of 

residues ofhydrazine in cattle tissue and milk was not significantly greater than the transfer of 

total residues of maleic hydrazide (i.e., the total radioactive residues (TRR) in livestock 

commodities based on metabolism data). Thus, exposure for hydrazine was estimated at 

0.0015% of the estimated exposure for maleic hydrazide. In the absence of chemical-specific 

processing data for hydrazine, DEEM default processing factors were used for potato 

flakes/granules/flour (6.5) and dried beef (1.92) and the maximum theoretical concentration 

factor for potato (5.0) was used for potato chips. In the absence of percent crop treated data, 

100% crop treated was assumed. A Tier 1 estimated drinking water concentration (EDWC) for 

hydrazine based on fate data for hydrazine was also used. 

The estimated exposure of the general U.S. population to hydrazine (food and drinking water) 

from the registered uses of maleic hydrazide and assuming that the technical grade of the maleic 

hydrazide contains 15 ppm (0.0015%) ofhydrazine is 2.63538E-07 mg/kg/day. Applying the 

Q1* of 3.0 (mg/kg/day)"1 to the exposure value results in a cancer risk estimate of 8 x w-7. This 

estimate is consider conservative and is does not underestimate risk. The major contributors 

were potatoes and potato chips. 

I. Introduction 

Dietary risk assessment incorporates both exposure and toxicity of a given pesticide. 

References that discuss the acute and chronic risk assessments in more detail are available on the 

EPNpesticides web site: "Available Information on Assessing Exposure from Pesticides, A 

User's Guide," 21-JUN-2000, web link: http://www.epa.gov/fedrgstr/EPAPEST/2000/July/Day-12/606l.pdf; or see SOP 99.6 (20-AUG-1999). 

In 1976, maleic hydrazide went into Special Review (then called Rebuttable Presumption 

Against Registration or RP AR) because it met the risk criteria for oncogenic, mutagenic, and 

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Hydrazine Dietary Exposure and Risk Assessment DP Number: D420404

3 f 15

reproductive effects. A Data Call-In notice issued in 1980 resulted in suspension of the 

diethanolamine salt of maleic hydrazide (DEA-MH) when its manufacturers did not submit the 

required data. All DEA-MH registrations are now cancelled.

Based on other data submitted, EPA determined that the oncogenicity and reproductive effects 

triggers were not supported, and that only weak evidence supported the mutagenicity trigger. In 

concluding the RPAR in 1982, EPA allowed continued use of maleic hydrazide and its 

potassium salt , but established an upper limit of 15 ppm for hydrazine (associated with tumor 

induction) in technical grade maleic hydrazide. At this level, lifetime cancer risks for both 

dietary and worker exposure were not deemed to be of concern. The 1988 Maleic Hydrazide 

Registration Standard, 1994 Maleic Hydrazide Reregistration Eligibility Decision (RED) and 

2005 Maleic Hydrazide Tolerance Reassessment Eligibility Decision (TRED) continued to limit 

hydrazine in the technical product to 15 ppm.

There is no record of a hydrazine dietary risk assessment conducted by HED in the current 

databases. This hydrazine cancer dietary risk assessment is being conducted as part of the maleic 

hydrazide registration review to verify that the 15 ppm (0.0015%) Agency stipulated upper limit 

of hydrazine in the technical grade of maleic hydrazide, which was set in ca. 1982 at the close of 

the maleic hydrazide Special Review (then called Rebuttable Presumption Against Registration 

or RPAR), remains adequate. 

II. Residue Information

Maleic hydrazide and its potassium salt are currently registered for food/feed uses on onions and 

potatoes, as well as several terrestrial non-food crops, including fallow land. Its major use is on 

tobacco. There are several currently registered technical grade products (400-97, 19713-25, 

19713-26 and 51873-10) with maleic hydrazide at 95% or higher. Assuming the 15 ppm 

(0.0015%) Agency stipulated upper limit of hydrazine in the technical grade of maleic hydrazide, 

this would mean an estimated ratio of maleic hydrazide to hydrazine in the technical grade 

product of roughly 100% to 0.0015%. 

There is no registered use of hydrazine and no tolerances for hydrazine are established. No 

hydrazine metabolism and/or magnitude of the residue data for crops and/or livestock are 

available for dietary exposure and risk assessments. Hence, screening level cancer dietary 

exposure and risk assessments for hydrazine resulting from the registered uses of maleic 

hydrazide were conducted using anticipated residue estimates for hydrazine based on available 

maleic hydrazide data and assumed that the estimated ratio of maleic hydrazide to hydrazine in 

the technical grade of maleic hydrazide (100% to 0.0015%) remained unchanged in formulated 

end-use products and in/on crops through application/deposition/translocation and beyond. 

Thus, exposure for hydrazine was estimated at 0.0015% of the estimated exposure for maleic 

hydrazide. Furthermore, it assumed that the transfer of residues of hydrazine in cattle tissue and 

milk was not significantly greater than the transfer of total residues of maleic hydrazide (i.e., the 

total radioactive residues (TRR) in livestock commodities based on metabolism data). 

Based on the premises and assumptions above, anticipated residues were estimated as follows. 
Hydrazine Dietary Exposure and Risk Assessment DP Number: D420404

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Average residues of hydrazine in/on dry bulb onions and potatoes were estimated at 0.0015% of 

the average residues of maleic hydrazide determined in field trials conducted with maleic 

hydrazide at the maximum registered use rates of maleic hydrazide. Since maleic hydrazidetreated potato culls and potato processing waste can be fed to cattle, residues of hydrazine in 

cattle tissues and milk were estimated at 0.0015% of the maximum total residues of maleic 

hydrazide in cattle tissues and milk (i.e., total radioactive residue (TRR) levels from the goat 

metabolism study) from feeding a reasonably balance ruminant diet. In the absence of chemicalspecific processing data for hydrazine, DEEM default processing factors were used for potato 

flakes/granules/flour (6.5) and dried beef (1.92) and the maximum theoretical concentration 

factor for potato (5.0) was used for potato chips. In the absence of percent crop treated data, 

100% crop treated was assumed. These anticipated residues were approved by the Anticipated 

Residues (ARs) Focus Group of ChemSAC (4/15/14) and are summarized in the table below.

Table 1. Anticipated Residues (ARs) Approved by the ARs Focus Group of ChemSAC (4/15/14) for Use in the 

Screening Level Hydrazine Cancer Dietary Exposure and Risk Assessment.

RAC Food

Forms

Blending

Classification1

Data

Source

%

Crop

Treated

Processing

Factors

Screening Level 

Chronic ARs (ppm)2

Onion and Potato Commodities

Onion

bulb NB

ARs for hydrazine based on onion 

field trial data (MRID 42567805) for 

maleic hydrazide and assumed 15 

ppm (0.0015%) hydrazine in the 

maleic hydrazide technical product. 

See Attachment 4 for details.

100

DEEM

Default

1

40.7E-6

dried B

DEEM

Default

9.0

Potato

tuber PB or NB

ARs for hydrazine based on potato 

field trial data (MRID 42567804) for 

maleic hydrazide and assumed 15 

ppm (0.0015%) hydrazine in the 

maleic hydrazide technical product.

See Attachment 4 for details.

DEEM

Default

1

245E-6

chips B Max 5.03

granules

/flakes B

DEEM

Default

flour B 6.5

Meat and Milk Commodities

Liver ARs for hydrazine based on goat metabolism data 

(MRID 46867202) for maleic hydrazide and 

assumed 15ppm (0.0015%) hydrazine in the 

maleic hydrazide technical product.

See Attachment 4 for details. 

DEEM

Default

1

3.6E-6

Kidney 7.3E-6

Meat 0.8E-6

Beef, dried DEEM

default

1.92

Fat DEEM

Default

1

0.1E-6

Milk 1.1E-6

1. Classification: blended (B), partially blended (PB), not blended (NB).

2. Estimates are not in correct scientific notation but expressed in terms of E-6 for convenience of DEEM input.

3. In the absence of specific hydrazine data, used the maximum theoretical concentration factor for potato

(5.0) listed in GLN 860.1520.
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III. Percent Crop Treated Information

No percent crop treated data are available for the uses of maleic hydrazide on onion and potato. 

IV. Drinking Water Data

EFED generated screening level estimated drinking water concentrations (EDWCs) for 

hydrazine in surface and ground waters using GENeric Estimated Environmental Concentration 

(GENEEC) and Pesticide Root Zone Model for Ground Water (PRZM-GW), 

respectively. Modeling for hydrazine was based on fate data for hydrazine obtained from open 

literature, maximum use rates for maleic hydrazide and the assumption that the ratio of hydrazine 

to maleic hydrazide in the technical remained unchanged in formulated end-use products, 

through application/deposition and beyond. The highest modeled EDWC for hydrazine was 

1.02E-3 ppb (Groundwater (Post Breakthrough Average)). [Email from I. Abdel-Saheb to B. 

Cropp-Kohlligian dated 5/9/14.]

The drinking water models and their descriptions are available at the EPA internet site: 

http://www.epa.gov/oppefed1/models/water/. 

V. DEEM-FCID Program and Consumption Information

The hydrazine cancer dietary exposure assessment was conducted using the DEEM-FCID, 

Version 3.16, which incorporates 2003-2008 consumption data from USDA’s 

NHANES/WWEIA. The data are based on the reported consumption of more than 20,000 

individuals over two non-consecutive survey days. Foods “as consumed” (e.g., apple pie) are 

linked to EPA-defined food commodities (e.g., apples, peeled fruit - cooked; fresh or N/S; baked; 

or wheat flour - cooked; fresh or N/S, baked) using publicly available recipe translation files 

developed jointly by USDA/ARS and EPA. For chronic exposure assessment, consumption data 

are averaged for the entire U.S. population and within population subgroups. For a chronic 

dietary exposure assessment, an estimate of the residue level in each food or food-form (e.g., 

orange or orange juice) on the food commodity residue list is multiplied by the average daily 

consumption estimate for that food/food form to produce a residue intake estimate. The resulting 

residue intake estimate for each food/food form is summed with the residue intake estimates for 

all other food/food forms on the commodity residue list to arrive at the total average estimated 

exposure. Exposure is expressed in mg/kg body weight/day. 

VI. Toxicological Information

The US EPA National Center for Environmental Assessment (NCEA) has classified hydrazine as 

a Group B2, probable human carcinogen (USEPA, 1999). The classification is based on tumors 

identified in mice, rats, and hamsters following oral, inhalation or intraperitoneal administration 

of hydrazine and hydrazine sulfate. Hydrazine was mutagenic in numerous assays. For the HED 

cancer dietary exposure and risk assessment, the oral cancer slope factor is most relevant. 

NCEA relied on a hydrazine sulfate (in water) gavage study in mice for the dose-response data

for the oral cancer slope factor. Liver hepatomas were observed in CBA/cb/Se male mice 
Hydrazine Dietary Exposure and Risk Assessment DP Number: D420404

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(Biancifiori, 1970). The oral cancer slope factor for hydrazine is 3.0 (mg/kg/day)-1using the 

linearized multistage procedure. The carcinogenicity of hydrazine is discussed in EPA’s 

Integrated Risk Information System (IRIS, 2002). 

VII. Results/Discussion 

The estimated exposure of the general U.S. population to hydrazine (food and drinking water) 

from the registered uses of maleic hydrazide and assuming that the technical grade of the maleic 

hydrazide contains 15 ppm (0.0015%) of hydrazine is 2.63538E-07 mg/kg/day. Applying the 

Q1* of 3.0 (mg/kg/day)-1to the exposure value results in a cancer risk estimate of 8 x 10-7. This 

estimate is consider conservative and is does not underestimate risk. The major contributors 

were potatoes and potato chips. Although there are a number of uncertainties, conservative 

assumptions were used in the anticipated residue estimates and dietary assessment including: 

field trial data reflecting maximum use rates, metabolism data for cattle tissues and milk, DEEM 

default processing or maximum theoretical concentration factors, 100% crop treated and a Tier 1 

drinking water estimate. 

VIII. Characterization of Inputs/Outputs

No hydrazine metabolism and/or magnitude of the residue data for crops and/or livestock are 

available for dietary exposure and risk assessments. Hence, a screening level cancer dietary 

exposure and risk assessment for hydrazine resulting from the registered uses of maleic 

hydrazide was conducted using anticipated residue (AR) estimates for hydrazine based on 

available maleic hydrazide data and assuming that the technical grade of the maleic hydrazide 

contained 15 ppm (0.0015%) of hydrazine. Thus, exposure for hydrazine was estimated at 

0.0015% of the estimated exposure for maleic hydrazide. Average residues of hydrazine in/on 

dry bulb onions and potatoes were estimated at 0.0015% of the average residues of maleic 

hydrazide determined in field trials conducted at the maximum registered use rates of maleic 

hydrazide. Residues of hydrazine in cattle tissues and milk were estimated at 0.0015% of the 

total radioactive residue (TRR) levels determined in the maleic hydrazide goat metabolism study 

adjusted for a 1x feeding level. In the absence of chemical-specific processing data for 

hydrazine, DEEM default processing factors were used for potato flakes/granules/flour (6.5) and 

dried beef (1.92) and the maximum theoretical concentration factor for potato (5.0) was used for 

potato chips. In the absence of percent crop treated data for maleic hydrazide, 100% crop treated 

was assumed. 

Confidence in the estimates in/on dry bulb onions and potatoes assumes that the combined 

effects of deposition to foliage and subsequent translocation to bulbs/tubers and environmental 

forces over several weeks on residues of hydrazine and maleic hydrazide will not significantly 

increase the percent of hydrazine to maleic hydrazide realized in/on the maleic hydrazide-treated 

RACs. Further, the confidence in the estimates in meat and milk assumes that residues of 

hydrazine will not transfer to tissues and milk to a significantly greater degree than total residues 

of maleic hydrazide. These uncertainties are likely offset by the conservative assumptions used 

in the anticipated residue estimates and dietary assessment including: field trial data for dry bulb 

onions and potatoes reflecting maximum use rates, metabolism data for cattle tissues and milk, 
Hydrazine Dietary Exposure and Risk Assessment DP Number: D420404

7 f 15

DEEM default processing or maximum theoretical concentration factors and 100% crop treated. 

IX. Conclusions

The estimated exposure of the general U.S. population to hydrazine (food and drinking water) 

from the registered uses of maleic hydrazide and assuming that the technical grade of the maleic 

hydrazide contains 15 ppm (0.0015%) of hydrazine is 2.63538E-07 mg/kg/day. Applying the 

Q1* of 3.0 (mg/kg/day)-1to the exposure value results in a cancer risk estimate of 8 x 10-7. This 

estimate is consider conservative and is does not underestimate risk.

X. List of Attachments

• Attachment 1: Cancer Residue Input File

• Attachment 2: Cancer Results File - Food and Drinking Water

• Attachment 3: Major Contributors - CCC Report

Attachment 4: Anticipated Residue (AR) Estimates Approved by the ARs Focus Group

of ChemSAC (4/15/14)
Hydrazine Dietary Exposure and Risk Assessment DP Number: D420404

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Attachment 1: Cancer Residue Input file

Filename: Hydrazine Food and Water 4 21 14.R08

Chemical: Hydrazine

RfD(Chronic): 0 mg/kg bw/day NOEL(Chronic): 0 mg/kg bw/day

RfD(Acute): 0 mg/kg bw/day NOEL(Acute): 0 mg/kg bw/day Q*= 3

Date created/last modified: 04-21-2014/16:33:18 Program ver. 3.16, 03-08-d

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

 EPA Crop Def Res Adj.Factors Comment

 Code Grp Commodity Name (ppm)* #1 #2 

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

0103296000 1C Potato, chips 245.000000 5.000 1.000 

0103297000 1C Potato, dry (granules/ flakes) 245.000000 6.500 1.000 

0103297001 1C Potato, dry (granules/ flakes)-b 245.000000 6.500 1.000 

0103298000 1C Potato, flour 245.000000 6.500 1.000 

0103298001 1C Potato, flour-babyfood 245.000000 6.500 1.000 

0103299000 1C Potato, tuber, w/peel 245.000000 1.000 1.000 

0103299001 1C Potato, tuber, w/peel-babyfood 245.000000 1.000 1.000 

0103300000 1C Potato, tuber, w/o peel 245.000000 1.000 1.000 

0103300001 1C Potato, tuber, w/o peel-babyfood 245.000000 1.000 1.000 

0301237000 3A Onion, bulb 40.700000 1.000 1.000 

0301237001 3A Onion, bulb-babyfood 40.700000 1.000 1.000 

0301238000 3A Onion, bulb, dried 40.700000 9.000 1.000 

0301238001 3A Onion, bulb, dried-babyfood 40.700000 9.000 1.000 

3100044000 31 Beef, meat 0.800000 1.000 1.000 

3100044001 31 Beef, meat-babyfood 0.800000 1.000 1.000 

3100045000 31 Beef, meat, dried 0.800000 1.920 1.000 

3100046000 31 Beef, meat byproducts 7.300000 1.000 1.000 

3100046001 31 Beef, meat byproducts-babyfood 7.300000 1.000 1.000 

3100047000 31 Beef, fat 0.100000 1.000 1.000 

3100047001 31 Beef, fat-babyfood 0.100000 1.000 1.000 

3100048000 31 Beef, kidney 7.300000 1.000 1.000 

3100049000 31 Beef, liver 3.600000 1.000 1.000 

3100049001 31 Beef, liver-babyfood 3.600000 1.000 1.000 

3600222000 36 Milk, fat 1.100000 1.000 1.000 

3600222001 36 Milk, fat-baby food/infant formu 1.100000 1.000 1.000 

3600223000 36 Milk, nonfat solids 1.100000 1.000 1.000 

3600223001 36 Milk, nonfat solids-baby food/in 1.100000 1.000 1.000 

3600224000 36 Milk, water 1.100000 1.000 1.000 

3600224001 36 Milk, water-babyfood/infant form 1.100000 1.000 1.000 

3600225001 36 Milk, sugar (lactose)-baby food/ 1.100000 1.000 1.000 

8601000000 86A Water, direct, all sources 1.020000 1.000 1.000 

8602000000 86B Water, indirect, all sources 1.020000 1.000 1.000 

*Correct Values: Residue values (ppm) as entered must be multiplied by the reviewer by E-06.
Hydrazine Dietary Exposure and Risk Assessment DP Number: D420404

9 f 15

Attachment 2: Cancer Results File - Food and Water

US EPA Ver. 3.16, 03-08-d

DEEM-FCID Chronic analysis for HYDRAZINE NHANES 2003-2008 2-day

Residue file name: Hydrazine Food and Water 4 21 14.R08

 Adjustment factor #2 NOT used.

Analysis Date 04-21-2014/16:40:27 Residue file dated: 04-21-2014/16:39:12

Q* = 3 

===============================================================================

 Total exposure by population subgroup

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

 Total Exposure

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

 Population mg/kg Lifetime risk*

 Subgroup body wt/day* (Q*= 3)

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

Total US Population 0.263538 7.91E-01

Reviewer Calculated Results* 2.63538E-7* 8E-7*

*Reviewer Calculated Results: Residue values as entered into the Residue Input File (see 

Attachment 1) must be multiplied by the reviewer by E-06; hence, total exposure results (i.e., 

mg/kg/day and Lifetime risk) have been multiplied by the reviewer by E-06 and expressed in 

correct scientific notation.

Attachment 3: Major Contributors - CCC Report

U.S. EPA Ver. 3.16, 03-08-d

DEEM-FCID Chronic analysis for HYDRAZINE NHANES 2003-2008 2-day

Residue file name: Hydrazine Food and Water 4 21 14.R08

 Adjustment factor #2 NOT used.

Analysis Date 04-21-2014/16:40:27 Residue file dated: 04-21-2014/16:39:12

Q* = 3 

===============================================================================

 Complete commodity contribution analysis for 

 Total US Population

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

Crop Group = (1) Root and Tuber Vegetables

 Exposure analysis

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

 Residue Adjustment mg/kg Lifetime risk*

 Food name (ppm x E-06)* Factors body wt/day* (Q*= 3)

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

Potato, chips (0103296000):

 FoodForm N/S 245.000000 5.000 1.000 0.0508302E-06* 1.52E-07*

Potato, tuber, w/o peel (0103300000):

 FoodForm N/S 245.000000 1.000 1.000 0.1149151E-06* 3.45E-07*

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

* Reviewer Calculated Results: Residue values as entered into the Residue Input File (see 

Attachment 1) must be multiplied by the reviewer by E-06; hence, total exposure results (i.e., 

mg/kg/day and Lifetime risk) have been multiplied by the reviewer by E-06 and LIfetime risk is 

expressed in correct scientific notation.
Hydrazine Dietary Exposure and Risk Assessment DP Number: D420404

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Attachment 4: Anticipated Residues (ARs) Approved by the ARs Focus Group of 

ChemSAC (4/15/14)

Maleic hydrazide and its potassium salt are currently registered for food/feed uses on onions and 

potatoes, as well as several terrestrial non-food crops, including fallow land. Its major use is on 

tobacco. There are several currently registered technical grade products (400-97, 19713-25, 

19713-26 and 51873-10) with maleic hydrazide at 95% or higher. Assuming the 15 ppm 

(0.0015%) Agency stipulated upper limit of hydrazine in the technical grade of maleic hydrazide, 

this would mean an estimated ratio of maleic hydrazide to hydrazine in the technical grade 

product of roughly 100% to 0.0015%. (or 1 to 1.5E-5).

There is no registered use of hydrazine and no tolerances for hydrazine are established. No 

hydrazine metabolism and/or magnitude of the residue data for crops and/or livestock are 

available for dietary exposure and risk assessments. Hence, screening level anticipated residues 

for hydrazine are based on available maleic hydrazide data and assume that the estimated ratio of 

maleic hydrazide to hydrazine in the technical grade of maleic hydrazide (1 to 1.5E-5 based on 

0.0015% Agency stipulated upper limit of hydrazine in the technical grade of maleic hydrazide) 

remains unchanged in formulated end-use products and in/on crops through 

application/deposition/translocation and beyond. Furthermore, it assumes that the transfer of 

residues of hydrazine in cattle tissue and milk is not significantly greater than the transfer of total 

residues of maleic hydrazide (i.e., the total radioactive residues (TRR) in livestock commodities 

based on metabolism data). 

Based on the premises and assumptions above, anticipate residues were estimated as follows. 

Average residues of hydrazine in/on dry bulb onions and potatoes were estimated at 0.0015% of 

the average residues of maleic hydrazide determined in field trials conducted with maleic 

hydrazide at the maximum registered use rates for maleic hydrazide. In the absence of specific 

processing data for hydrazine, DEEM default processing factors were used for potato 

flakes/granules/flour (6.5) and the maximum theoretical concentration factor for potato (5.0) was 

used for potato chips. In the absence of percent crop treated data for maleic hydrazide, 100% 

crop treated was assumed. Since maleic hydrazide-treated potato culls and potato processing 

waste can be fed to cattle, residues of hydrazine in cattle tissues and milk were estimated at 

0.0015% of the maximum total residues of maleic hydrazide in cattle tissues and milk (i.e., total 

radioactive residue (TRR) levels from the goat metabolism study) from feeding a reasonably 

balance ruminant diet. 

Detailed Considerations

Chemical Identity 

Maleic hydrazide is a solid at room temperature and is very soluble in water and methanol. 

Hydrazine is a colorless oily liquid, fuming in air with a penetrating odor resembling that of 

ammonia. The nomenclature of maleic hydrazide and hydrazine is presented in Table 4.1. The 

available physicochemical properties of hydrazine are presented in Table 4.2; available maleic 

hydrazide data for the same properties are also provided for comparison. 
Hydrazine Dietary Exposure and Risk Assessment DP Number: D420404

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Table 4.1. Maleic Hydrazide and Hydrazine Nomenclature

Chemical structure

NH

N

OH

O

Common name Maleic hydrazide

Company experimental name MH

IUPAC name 6-hydroxy-2H-pyridazin-3-one

CAS name 1,2-dihydro-3,6-pyridazinedione

CAS registry number 123-33-1

Molecular Formula C4-H4-N2-O2

Formula Weight 112.1

Chemical Structure H2N—NH2

Common name Hydrazine 

Company experimental name NA

IUPAC name Hydrazine

CAS name Hydrazine

CAS registry number 302-01-2

Molecular Formula H2N—NH2

Formula Weight 32.0

Table 4.2. Physicochemical Properties of Maleic Hydrazide (Technical Grade) and Hydrazine.

Parameter Maleic Hydrazide Hydrazine

Value Reference Value Reference

Water 

solubility 

4507 ppm at 25 C USDA/ARS 

Pesticide Properties 

Database

Miscible EPA Air Toxics Web Site

http://www.epa.gov/ttn/atw/hlthef/

Vapor pressure hydrazin.html 

at 25 C

7.5 E-8 14.4 mm Hg

Octanol/water 

partition 

coefficient (log 

Kow)

0.011 at pH 7 0.08
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Maleic Hydrazide Directions for Use

Maleic hydrazide and its potassium salt are registered for use on onions and potatoes. The 

maximum use rate for onion is 1 application at 2 lb ai/A with a 10-day PHI. The maximum use 

rate for potato is 1 application at 3 lb ai/A with a 4-6 weeks PHI.

Screening Level AR Estimates for Hydrazine in/on Onion and Potato RACs

Onion and Potato Metabolism Data

D162009/D164425/D168996, E. Zager, 10/28/91

Maleic Hydrazide RED, T. Morton, 9/1/2005

The qualitative nature of the residue in plants is adequately understood for the current 

registrations, based on studies conducted on onions and potatoes. These studies indicate that 

maleic hydrazide is translocated in plants, but not metabolized extensively. 

Field grown onions were treated with ring-labeled [14C]maleic hydrazide at 2.07 lb ai/A (ca 1x 

the maximum registered use rate). Whole plants and bulbs were collected at 1 hour and 2 weeks 

following the application. The maximum total radioactive residues (TRR) in/on bulbs were 29.1 

ppm and 180 ppm dry weight maleic hydrazide equivalents at 1 hour and 2 weeks, respectively. 

Field grown potatoes were treated with ring-labeled [14C]maleic hydrazide at 2.89 lb ai/A (ca 1x 

the maximum registered use rate). Vines and tubers were collected at 1 hour, 2 weeks and 8 

weeks following the application. The maximum total radioactive residues (TRR) in/on tubers 

were 0.3 ppm, 176 ppm and 160 ppm dry weight maleic hydrazide equivalents at 1 hour, 2 weeks 

and 8 weeks, respectively. 

Onion and Potato Field Trial Data

D187782, W. Smith, 7/19/93; MRID 42567805 (onion) and MRID 42567804 (potato)

Maleic hydrazide crop field trials were conducted on potatoes and onions using application 

methods, timings, and rates which reflect the current use patterns of active formulation of maleic 

hydrazide. The AOAC hydrazine distillation method deemed adequate for data collection was 

used to detect maleic hydrazide and the subject data were supported by adequate storage stability 

data.

Onion field trials were conducted in 15 geographically representative tests each with a single 

broadcast application of the 2.25 lb/gal EC formulation made at 2 lbs ai/A, using ground 

equipment delivering 10 - 126.6 gal/A. Onion samples were harvested from each test 10-11 days 

post-treatment. 

Potato field trials were conducted in 14 geographically representative tests each with a single 

broadcast application of the 2.25 lb ai/gal EC formulation made at a target rate of 3 lbs ai/A 

using ground equipment delivering 8.87 - 44.9 gal/A. Samples of potatoes each were harvested 

from each test 20-21 days post-treatment. 
Hydrazine Dietary Exposure and Risk Assessment DP Number: D420404

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Table 4.3. Summary of Residue Data from Onion and Potato Crop Field Trials.

Maleic Hydrazide Residue Levels Found (ppm)1 Reviewer Calculated Average 

Hydrazine Residue Level (ppm)3

n Min. Max. LAFT2 HAFT2 Median Mean Std. Dev.

Onions (Field Trials Reflect One Application at 2.0 lb ai/A; PHI 10-11 days)

15 <0.22 9.48 0.38 7.44 1.29 2.71 2.29 40.7E-6

Potato Tubers (Field Trials Reflect One Application at 3.0 lb ai/A; PHI 20-21 days)

14 <1.2 60.894 2.17 47.6 11.7 16.3 13.8 245E-6

1 Except for sample min/max, values reflect per trial averages; n = no. of field trials. For calculation of median, 

mean, and standard deviation, the LOQ (0.22 ppm for onion and 1.2 ppm for potato) was used for any results 

reported as <LOQ. 

2 LAFT = lowest average field trial; HAFT = highest average field trial.

3 Calculated Average Hydrazine Residues = Mean Maleic Hydrazide Residues x 1.5E-5 (i.e. 15 ppm or 0.0015% in 

technical). Estimates are not in correct scientific notation but expressed in terms of E-6 for convenience of DEEM 

input.

4 The currently established tolerance for residues of maleic hydrazide in/on potato is 50 ppm. The high value of 

60.89 ppm was determined to be an outlier by the Dixon Q-test compared to the five other samples from field trials 

conducted in ME (D187782, W. Smith, 7/19/93). 

Conclusions. The onion and potato field trial data are appropriate for estimating anticipated 

residues (ARs) of hydrazine in/on onions and potatoes. These estimates are screening level and 

assume that the combined effects of deposition to foliage and subsequent translocation to 

bulbs/tubers and environmental forces over several weeks on residues of hydrazine and maleic 

hydrazide will not significantly increase the percent of hydrazine to maleic hydrazide (0.0015%

to 100%) realized in/on the maleic hydrazide-treated RACs.

Screening Level AR Estimates for Hydrazine in/on Potato Processed Commodities

In the absence of potato processing data for hydrazine, the maximum theoretical concentration 

factor for potato is 5x will be applied to potato chips and the DEEM default concentration factor 

6.5x will be applied to dried potato commodities. 

Screening Level AR Estimates for Hydrazine in Livestock Commodities

Maleic hydrazide is registered for use on potatoes. Potato culls and potato processing waste can 

be fed to cattle. According to Table 1 Feedstuffs (revised July 2008), these feedstuffs are among 

the most commonly fed to feedlot beef (up to 30% of the diet from all potato commodities) and 

high-production dairy cattle (up to 10% of the diet from all potato commodities), and are usually 

mixed together. There are no registrations for maleic hydrazide on any poultry or swine 

feedstuff; hence, there is no expectation of finite residues in poultry or swine.

Dietary burdens for maleic hydrazide were calculated for beef and dairy cattle using the percent 

dry matter and percent diet specified in Table 1 Feedstuffs (revised July 2008). Given that this is 

a cancer assessment, residues of maleic hydrazide in potato culls and potato processing waste 

were estimated based on average field trial values for potato tubers (16.3 ppm) and the maximum 

theoretical concentration factor for processing waste (4.0x; GLN 860.1520). Also, it was 
Hydrazine Dietary Exposure and Risk Assessment DP Number: D420404

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assumed that on average potato culls and processing waste would be fed to cattle on a 50:50 

basis. 

Table 4.4. Calculation of Dietary Burdens of Maleic Hydrazide Residues to Cattle.

Crop Commodity Type1 Residue2%DM %Diet3

Dietary 

Contribution4

ppm input ppm

Beef Cattle (80% CC; 15% R; 5% PC)2

Potato Culls CC 16.3 Ave 20 15 12.2

Processing Waste CC 65.2 15 15 65.2

Untreated N/A

CC 0

N/A N/A

50 0

R 0 15 0

PC 0 5 0

Total - - - - - 100 77

Dairy Cattle (45% CC; 45% R; 10% PC)2

Potato Culls CC 16.3 Ave 20 5 4.1

Processing Waste CC 65.2 15 5 21.7

Untreated N/A

CC 0

N/A N/A

35 0

R 0 45 0

PC 0 10 0

Total - - - - - 100 26

1 R = Roughage; CC = Carbohydrate concentrate; PC = Protein concentrate.

2 Potato Culls = Average Maleic Hydrazide Residues in/on Potato = 16.3 ppm

 Potato Processing Waste = Ave. Potato Residues (16.3 ppm) x Max. Theoretical Conc. Factor (4.0x) = 65.2 ppm

3 Table 1 Feedstuffs (revised July 2008). Potato culls and processing waste are usually mixed together. The

 maximum for all potato commodities in the beef and dairy diet are 30% and 10%, respectively. For this cancer

 assessment, it was assumed that on average potato culls and processing waste would be fed to cattle on a 50:50

 basis. 

4 Contribution = ([residue /% DM] X % diet) for beef and dairy cattle

Ruminant Metabolism

D326395/D326396/D336734, S. Hummel, 3/7/14; MRID 46867202 (Goat Metabolism)

In the maleic hydrazide goat metabolism study, lactating goats were fed at 522.2 ppm with 

[14C]maleic hydrazide in the feed, which is about 6.8x the estimated beef cattle dietary burden 

(77 ppm) and about 20x the estimated dairy cattle dietary burden (26 ppm). The total radioactive 

residues (TRR) were 0.7006-1.447 ppm in milk, 1.619 ppm in liver, 3.301 ppm in kidney, 0.368 

ppm in muscle, and 0.052 ppm in fat. Radioactivity in milk appeared to plateau by Day 2. Most 

of the administered dose was excreted (83.23%), with the majority (~64.89%) excreted in the 

urine.
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Table 4.5. Total Radioactive Residues (TRR) in Milk and Tissues Following Oral Dosing with 

[14C]maleic hydrazide at 522.2 ppm in the Diet for 3.5 Consecutive Days

Matrix Collection 

Timing

% Administered 

Dose

TRR found, 

expressed as 

maleic hydrazide

equivalents

(ppm)

TRR at 1x 

feeding level, 

expressed as 

maleic hydrazide

equivalents

(ppm)

Reviewer 

calculated 

hydrazine at 1x 

feeding level2

(ppm)

Milk Day 1-4 0.14 (All days) 1.4467 (max) 0.071 1.1E-6

Liver At sacrifice 0.09 (All edible 

tissues)

1.619 0.238 3.6E-6

Kidney At sacrifice 3.301 0.485 7.3E-6

Muscle At sacrifice 0.368 0.054 0.8E-6

Fat At sacrifice 0.052 0.008 0.1E-6

1 TRR determined both at the in-life facility and the analytical laboratory. The TRR values determined at the in-life 

facility were used for all calculations. 

2 Hydrazine = TRR (expressed as maleic hydrazide equivalents) at 1x feeding level X 1.5E-5 (i.e. 15 ppm or 

0.0015% in technical). Estimates are not in correct scientific notation but expressed in terms of E-6 for convenience 

of DEEM input.

Conclusions. TRR values from livestock metabolism data which are limited to transfer of 

residues in tissues and milk are appropriate for estimating anticipated residues of hydrazine in 

cattle tissues and milk. These estimates are conservative and assume substantially similar 

transfer of hydrazine residues and maleic hydrazide residues in tissues and milk. There is no 

evidence that residues of hydrazine will be incurred in tissues and milk at a substantially higher 

level than the TRR.