UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OCT 1 3 2011 

MEMORANDUM 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

SUBJECT: BEAD Chemical Profile for Registration Review: Paraquat Dichloride (061601) 

FROM: 

THRU: 

Sunil Ratnayake, Biologist n 

Biological Analysis Branch .. ;\. I\.X./<-----

JihadAlsadek,Economist JV~ fr .A-~ Science Information and Analysis Branch 

Derek Berwald, Economist o. r ~ VA \ .p Economic Analysis Branch ~ ~ ~ Biological and Economic Analysis Divisi (7503P) 

Arnet Jones, Chief 

Biological Analysis Branch 

Diann Sims, Chief 

Science Information and Analysis Branch 

~ ~ Timothy Kiely, Chief \ A " 

Economic Analysis Branch VV\.. 

Biological and Economic Analy' ivision (7503 

TO: Christina Scheltema, Chemical Review Manager 

Risk Management and Implementation Branch 3 

Pesticide Re-evaluation Division (7508P) 

Product Review Panel date: June 22, 2011 

INTRODUCTION 

The purpose of this document is to convey usage information and a broad overview of the pest 

management roles of pesticides that are beginning to undergo registration review. The 

anticipated audience consists of the team of EPA staff currently evaluating the registration status 

of Paraquat Dichloride (061601), and eventually the general public. This document builds upon 

the data already provided in the "Usage and Label Use Data Packages" that are also provided to 
Registration Review teams by BEAD. The document is based on infonnation and data available 

to BEAD as of June 22, 2011. 

Paraquat dichloride is a non-selective herbicide which belongs to the bipyridyliums class of 

herbicides and it is applied to the foliage of weed plants as a burn-down treatment. Also, it can 

be applied as a band, spot, or directed treatment after the crop emergence. In the United States, 

paraquat dichloride was first registered in 1964 and became the most widely used herbicide until 

the registration of glyphosate (pesticide news, 1996). The mode of action of this class of 

herbicide is the inhibition of the photosynthesis process. The activity of paraquat dichloride 

depends on the sunlight and affected plants shows quick wilting and desiccation. Paraquat 

dichloride is also applied,as a pre-harvest desiccation treatment on some crops including cotton 

(peterson et al. 2001). 

USE SITES 

Agricultural Use Sites 

Cereal and oil seed crops, cotton, fruit and nut crops, and vegetables 

Non-Agricultural Use Sites 

Airports, conservation reserve lands, fallow lands, right of way, non-crop areas, lawns and 

storage yards. 

COMMON FORMULATIONS AND APPLICATION METHODS 

Paraquat dichloride is fonnulated as flowable and emulsifiable concentrates only. Application 

methods are aerial, broadcast, band treatment, directed spray, ground spray, spot treatment, 

spray, and tree wound treatment. This herbicide should not be applied through any type of 

irrigation systems. 

USAGE 

Agricultural 

Based on private market pesticide usage data from 1998-2010, the annual total agricultural usage . 

averaged approximately 3 million pounds active ingredient for 7 million treated acres, for an 

overall average application rate of 0.4 lbs. a.i. per acre. 

From 1998-2010, the crops with most pounds used are cotton (25%), com (23%), soybeans (9%), 

and almonds (7%). Crops with most treated acres are cotton (37%), com (20%), soybeans (8%), 

peanuts (5%), and almonds (4%) and alfalfa (4%). 

On average, the states With the most agricultural use in tenns of pounds a.i. applied are 

California (23%), Texas (17%), and Georgia (5%) 

(Proprietary Data, 1998-2010). 

Non-Agricultural 

Lawn Care Operators (LCOs) used about 3,000 pounds a.i. of paraquat dichloride in 2004. The 

use of paraquat dichloride in nurseries/greenhouses was almost 2,000 lbs. a.i. in 2002 and 2004 

and decreased to less than 1,000 lbs. a.i. in 2006 (Kline and Company, Inc 2002-2006). 

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USE TRENDS 

Figure 1 provides usage trends, in terms of pounds applied, for paraquat dichloride's leading 

agricultural markets. The use of paraquat dichloride on almonds, com, cotton, soybeans, and 

other crops fluctuated during the period 1998-2010. The data provided in this section is provided 

for preliminary scoping purposes only because the data have not been analyzed. 

Figure 1. Paraquat dichloride Usage Data 

4,500,000 -r--------------

• Other Crops 

PoundsA.I. • Soybeans 

• Cotton 

• Corn 

o +-..,..."-r--...,......,......,....-.-,..-.,...-...,,.-......-..~~ . Almonds 

"Other crops" include wine grapes (5%), alfalfa (4%), apples (4%), and table 

grapes/oranges/peanuts/peaches (2% each). 

Source: Proprietary Data, 1998-2010 

BIOLOGICAL ASPECTS RELEVANT TO PARAQUAT DICHLORIDE 

Unlike many other herbicides, paraquat is effective under low temperatures and when weeds are 

having little active growth. This is an important characteristic of paraquat and it helps for early 

season seedbed preparation. Rainfall soon after application has little or no effects on the 

performance of paraquat. The activity of paraquat is light dependent. In soil, paraquat is 

deactivated by tight adsorption to clay particles. Paraquat does not have residual activity and it 

can be applied before planting crops or seedling emergence (Syngenta Crop Protection, 2011). It 

has been reported that hairyfleabane (Conyza bonariensis), horse weed (Conyza canadensis), 

goosegrass (Eleusine indica), dotted duckweed (Landoltia punctata), and American black 

nightshade, (Solanum americanum) have developed resistance to the mode of action of this class 

of herbicides (WSSA, 2011). 

HISTORY OF BEAD ASSESSMENTS FOR PARAQUAT DICHLORIDE 

There have been only two recent analyses of paraquat by BEAD. In 2006, BEAD analysts 

considered the market effects from entry of generic paraquat into the herbicide market. There 

was considerable uncertainty in their estimates, but they found that costs to consumers of 

paraquat may be reduced $6 to 9 million per year as a result of cost competition from generics 

(Kim et al, 2006). In 2005, the registrant applied for registration of a new paraquat product that 

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contained additional emetic and a gelling agent, which might reduce poisoning from ingesting 

paraquat. BEAD was asked to evaluate the additional costs to growers and estimate the value of 

reduced deaths that might result from these additional protections, if the new formulation 

replaced the old. The additional cost of the new formulation to growers was small, and unlikely 

to result in users switching to alternative pesticides, although the aggregate costs were estimated 

to be from $1.8 to $ 2.3 million. The value of reduced illnesses was dominated by the value 

from reducing deaths, over $15 million per year if 2.4 deaths were prevented each year, on 

average. However, there was no way to determine if illnesses actually would be prevented by 

the changes, so the benefit estimated by BEAD was the range $0 to $15.4 million per year (Zinn 

and Kim, 2005). 

DATA NEEDS RELEVANT TO BEAD'S FUTURE WORK ON PARAQUAT 

DICHLORIDE 

Obtaining additional information on the following items would improve future BEAD 

assessments of the importance of paraquat dichloride and may be required as part of the 

registration review of this pesticide. 

Use on/in fallow land, airports, commercial buildings, conservation reserve program land, 

fencerows, right-of-way, areas around commercial/industrial buildings including pumping 

stations and pipelines pumping stations, substations, and storage areas. 

REFERENCES 

International Survey of Herbicide Resistant Weeds. 2011. http://www.weedscience.org/In.asp. 

Proprietary Data, 1998-2010. 

Kim, J., Istanbul, Y., and A. Grube, Economic Impacts a/Generic Paraquat Entry, April 27, 

2006. 

Kline and Company, Inc 2002-2006. 

Paraquat. 1996. Pesticides News. No.32, June 1996, p20-21. http://www.panuk.org/pestnewsl Actives/paraquat.htm. 

Paraquat Fact Sheet. 2011. Syngenta Crop Protection. http://paraquat.comlspanishlnodeIl94. 

Peterson, D, Thompson, D. R. Regehr, D. L. and K. AI-Khatib, 2001. Herbicide Mode of Action. 

Publication of Agricultural Experiment Station and Cooperative Extension Service. 

Kansas State University. http://www.northeastcropadvisers.orglherbicidemode.pdf. 

Zinn, N., and J. Kim, 2005. Paraquat Assessment, D323223. OPPIBEAD memorandum. 

December 8, 2005. 

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