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MALAIC HYDRAZIDE FINAL WORK PLAN 

Introduction

This is the Environmental Protection Agency’s (EPA’s) Final Work Plan (FWP) for the 

registration review of maleic hydrazide. The FWP includes the expected registration 

review timeline. The FWP also addresses public comments received concerning the 

Preliminary Work Plan in the Summary Document, which was posted in the maleic 

hydrazide registration review docket (EPA-HQ-OPP-2009-0387), and any other 

comments concerning the initial docket postings. The Summary Document provided 

information on what EPA knows about the pesticide and what additional risk analyses 

and data or information the Agency believes are needed to make a registration review 

decision. 

The Agency is implementing the new registration review program and will review each 

registered pesticide every 15 years to determine whether it continues to meet the Federal 

Insecticide, Fungicide, and Rodenticide Act (FIFRA) standard for registration. Changes 

in science, public policy, and pesticide use practices will occur over time. The 

registration review program is intended to make sure that, as the ability to assess risk 

evolves and as policies and practices change, all registered pesticides continue to meet 

the statutory standard. The public phase of registration review begins when the initial 

docket is opened for each case. Information on this program is provided at: 

http://www.epa.gov/oppsrrd1/registration_review/. 

Maleic hydrazide, case 0381, consists of two pesticides (maleic hydrazide and maleic 

hydrazide potassium salt). Maleic hydrazide and maleic hydrazide potassium salt 

(hereafter referred to as maleic hydrazide ) are growth regulating herbicides registered for 

use on tobacco, onions, non-bearing citrus, potatoes, turf, airports, industrial land, lawns, 

recreational areas, ornamental plants, residential areas, and utility and rights-of-way land. 

Maleic hydrazide is formulated as a technical chemical, water dispersible granule, 

emulsifiable concentrate, and ready-to-use solution. 

Comments Received on Preliminary Work Plan

One comment was received on the maleic hydrazide Preliminary Work Plan (PWP) 

during the 60-day public comment period, which began on September 23, 2009 and 

closed on November 23, 2009. This comment did not change the work plan or timeline 

established in the PWP. In addition, through the PWP, EPA solicited comments on three 

specific topics: environmental justice, water body impairment, and trade irritants. No 

comments or information were received during the comment period concerning these 

topics. 
 

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Risk Assessment and Data Needs

Ecological Risk: 

• The most recent ecological risk assessment was completed in March of 1994 in 

support of the EFED Summary Reregistration Eligibility Document for maleic 

hydrazide. 

• The Agency has not conducted a risk assessment that supports a complete 

endangered species determination. The ecological risk assessment planned during 

registration review will allow the Agency to determine whether the use of maleic 

hydrazide has “no effect” or “may affect” federally listed threatened or 

endangered species (listed species) or their designated critical habitats. When an 

assessment concludes that a pesticide’s use “may affect” a listed species or its 

designated critical habitat, the Agency will consult with the U.S. Fish and 

Wildlife Service and/or National Marine Fisheries Service (the Services), as 

appropriate. 

• The Agency anticipates needing the following data in order to conduct an 

endangered species and non-target ecological risk assessment for maleic 

hydrazide. 

o (GLN 850.2100) Avian oral toxicity (Passerine species) 

o (GLN 850.1400) Fish early-life stage toxicity (freshwater) 

o (GLN 850.1300) Daphnid chronic toxicity 

• The Agency has identified hydrazine as a contaminant in technical grade maleic 

hydrazide. As part of the registration review of maleic hydrazide, the Agency 

will review open literature for additional data on hydrazine and compare the 

modeled expected environmental concentration (EEC) values to the available 

aquatic toxicity data. 

• For more information regarding the status and review of ecological fate and 

effects of maleic hydrazide, please refer to the document: Registration Review – 

Preliminary Problem Formulation for the Ecological Risk Assessment of Maleic 

Hydrazide in the maleic hydrazide registration review docket (EPA-HQ-OPP2009-0387).

Human Health Risk: 

• The most recent human health assessment for maleic hydrazide was completed in 

September of 2005 in support of the Tolerance Reassessment Eligibility Decision 

(TRED). 
 

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• Based upon a 28-day inhalation toxicity study which was submitted in January of 

2009, the Agency anticipates a potential revision of the occupational and 

residential assessments. 

• At the time of the TRED, risk to residential users of maleic hydrazide was not 

considered by the Agency because products were limited to professional 

applicators only. However, since that time, new labels have been approved that 

permit application by homeowners. Therefore, the Agency anticipates that the 

registration review of maleic hydrazide may also include a residential handler 

assessment. 

• The Agency anticipates conducting a new aggregate assessment that will 

incorporate data from the anticipated residential assessment. 

• The most recent drinking water assessment was completed in May of 2005, and is 

anticipated to be adequate for risk assessment purposes during the registration 

review of maleic hydrazide. 

• The Agency anticipates requiring the following studies, in accordance with the 

revised CFR Part 158, to conduct a comprehensive human health risk assessment 

for the registration review of maleic hydrazide. 

o (GLN 870.7800) Immunotoxicity study 

o (GLN 870.6200a) Acute neurotoxicity 

o (GLN 870.6200b) Subchronic neurotoxicity 

• Hydrazine is a contaminant in technical grade maleic hydrazide for which the 

Agency established an upper limit of 15 ppm. 

• For more information on the status and review of the human health effects of 

maleic hydrazide, please refer to the document: Maleic Hydrazide: Human Health 

Scoping Document in Support of Registration Review in the maleic hydrazide 

registration review docket (EPA-OPPTS-OPP-2009-0387) for a detailed 

discussion of previous human health assessments. 

Timeline

EPA has created the following estimated timeline for the completion of the maleic 

hydrazide registration review. 

Registration Review for Maleic Hydrazide 

Projected Registration Review Timeline 

Milestone Date 

Opening the Docket 

Open Docket & Public Comment Period for Maleic Hyrazide September 2009 

Close Public Comment Period November 2009 
 

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Case Development 

Final Work Plan January 2010 

Issue DCI Oct. – Dec. 2010 

Data Submission Oct. – Dec. 2012 

Open Public Comment for Preliminary RA Apr. – June 2014 

Close Public Comment Period July – Sept. 2014 

Registration Review Decision 

Open Public Comment for Proposed Registration Review Decision Oct. – Dec. 2014 

Close Public Comment Period Jan. – Mar. 2015 

Final Reg. Review Decision and begin post-decision follow-up 2015 

Total 6 years 

Summary of Comments Received During Docket Opening

The maleic hydrazide registration review docket was open for a 60-day public comment 

period which began on September 23, 2009. During that time, the FIFRA Endangered 

Species Task Force (FESTF) submitted a comment which is summarized below. The 

comment did not change the work plan or timeline set out in the preliminary work plan. 

Consequently, this document makes final the work plan for the maleic hydrazide 

registration review process. 

Comment from FESTF 

The FESTF submitted a comment requesting that any technical registrant for 

maleic hydrazide who is not a member of the FESTF (or a company having met 

its data compensation obligations) be asked to provide a formal offer-to-pay to 

FESTF for reliance on their data. In their comment, FESTF also noted that 

Chemtura Corporation is already entitled to rely on FESTF data; however Drexel 

Chemical Company (Drexel) and Fair Products, Inc, are not FESTF members.

 

EPA Response 

The Agency thanks FESTF for its comment and will consider this information as 

it conducts the maleic hydrazide registration review process. 

Next Steps 

The Agency will develop a data call-in (DCI) notice for the data gaps listed under the 

“Risk Assessment and Data Needs” section above. 

Both an ecological risk assessment, which will include an endangered species 

assessment, and a human health risk assessment will be conducted as detailed in the 

“Risk Assessment and Data Needs” section above.