UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

MEMORANDUM 

Date: January 23, 2014 

SUBJECT: Imazapyr: Tier I Review of Human Incidents 

PC Code: 128821, 128829 

Decision No.: 486732 

Petition No.: NA 

DP Barcode: 04 17421 

Registration No.: NA 

Regulatory Action: NA 

Risk Assessment Type: NA Case No.: NA 

TXR No.: NA CAS No.: 81334-34-1 , 81510-83-0 

MRID No.: NA 40CFR: NA 

FROM: Shanna Recore, Industrial Hygienist 

Toxicology and Epidemiology Branch 

Health Effect Division (7509P) 

and 

Elizabeth Evans, Environmental Protection Specialist 

Toxicology and Epidemiology Branch 

Health Effects Division (7509P) .{1/ 'J,//1;, 

THROUGH: David Miller, Acting Branch Chi6,:). 

Toxicology and Epidemiology Branch 

Health Effects Division (7509P) 

TO: Mohsen Sahafeyan, Risk Assessor 

Risk Assessment Branch VT 

Health Effects Division (7509P) 

and 

Wilhelmena Livingston, Chemical Review Manager 

Risk Management & Implementation Branch 2/4 

Pesticide Re-evaluation Division (7508P) 

Summary and Conclusions 

Ver.Apr.08 

Based on the low severity and relatively low frequency of incident cases reported for imazapyr in 

both IDS and SENSOR-Pesticides, there does not appear to be a concern at this time that would 

warrant further investigation. Ortho® GroundClear® Vegetation Killer Concentrate (Reg No 

239-2657) does appear to be implicated in a disproportionate amount of incidents which may be 

attributable to high use of this product by consumers. The Agency will continue to monitor the 

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incident information and if a concern is triggered, additional analysis will be included in the risk 

assessment. 

Detailed Review 

I. ACTION REQUESTED 

This review is intended to fulfill our requirement to docket summaries of incident data that were 

reported to the Agency, as well as to ensure human incident data and the Agricultural Health 

Study (AHS) are part of the problem formulation phase of registration review. Reports of 

adverse health effects allegedly due to a specific pesticide exposure (i.e., an " incident") are 

largely self-reported and therefore, generally speaking, neither exposure to a pesticide or 

reported symptom (or the connection between the two) is validated or otherwise confirmed. 

Typically, causation cannot be determined based on incident data. However, incident 

information can be an important source of feedback to the Agency: incidents of severe outcome, 

or a suggested pattern or trend among less severe incidents, can signal the Agency to further 

investigate a particular chemical or product. Observational epidemiology studies relate the risk 

of disease, e.g., cancer, and exposure to an agent such as a pesticide product in the general 

population or specific sub-groups like pesticide applicators. 

II. BACKGROUND 

Imazapyr is part of the imidazolinone chemical class. Imazapyr is a systemic, non-selective, preand post-emergent herbicide used for the control of a broad range of terrestrial and aquatic 

weeds, and controls plant growth by preventing the synthesis of branched-chain amino acids. 1 

For this evaluation, both the OPP Incident Data System (IDS) and the Centers for Disease 

Control and Prevention/National Institute for Occupational Safety and Health (CDC/NIOSH) 

Sentinel Event Notification System for Occupational Risk-Pesticides (SENSOR) databases were 

consulted for pesticide incident data on the active ingredient Imazapyr (PC codes: 128821 and 

128829). The purpose of the database search is to identify potential patterns in the frequency 

and severity of the health effects attributed to Imazapyr exposure. Imazapyr is not included in 

the AHS, and therefore this study does not provide information for this report. 

Ill. RESULTS/DISCUSSION 

a. IDS (Incident Data System) 

OPP's IDS includes reports of alleged human health incidents from various sources, including 

mandatory Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) Section 6(a)(2) reports 

from registrants, other federal and state health and environmental agencies, and individual 

consumers. Since 1992, OPP has compiled these reports in IDS. IDS contains reports from 

across the U.S. and most incidents have all relevant product information recorded. Reports 

submitted to the IDS represent anecdotal reports or allegations only, unless otherwise stated in 

the report. 

1 Excerpt from Imazapyr RED, found online at: http://www.epa.gov/oppsrrd 1/REDs/imazapyr red.pdf 

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IDS records incidents in one of two modules: Main IDS and Aggregate IDS: 

o Main IDS contains incidents resulting in higher severity outcomes and provides 

more detail with regard to case specifics. This system stores incident data for 

death, major and moderate incidents, and it includes information about the 

location, date and nature of the incident. Main IDS incidents involving only one 

active ingredient (as opposed to pesticide products with multiple active 

ingredients) are considered to provide more certain information about the 

potential effects of exposure from the pesticide. 

o Aggregate IDS contains incidents resulting in less severe human incidents (minor, 

unknown, or no effects outcomes). These are reported by registrants only as 

counts in what are aggregate summaries. 

For the Main IDS, from January I, 2008 to January 9, 2014, there were 3 incidents reported for 

single chemical only in the database. These incidents were classified as moderate severity. There 

were 75 additional incidents reported involving more than one chemical. Two of these incidents 

were classified as major severity. Two incidents were classified as major severity; however, 

upon further review these incidents could not be directly linked to the product used (Table 1). 

The other 73 incidents were classified as moderate severity. 

T a bl e I M . am IDS M aJOr . I nc1 'd ents D escnpt10ns fi or Im azapyr. 

Homan Incident I Chemical: Tmazapyr I PC Codes: 128821 and 128829 

Incident 

Package Incident Reg 

Report Date Location Number Product Name Incident Descriptjon 

An adult male sprayed the product. He 

does not recall having any ocular exposure 

to the solution at the time of the 

application and he did not experience any 

ocular irritation or redness at the time of 

the exposure. A week later, he began to 

GROUNDCLEAR lose some vision in his right eye. The 

TRlOXTOTAL patient was evaluated by an unspecified 

019978- 000239- VEGETATION ocular specialist who found a problem with 

0044 1 7/12/2008 fL 02657 KILLER I the patient's blood flow to his optic nerve. 

An adult male used product. Two or 3 days 

later, he went to ICU and was diagnosed as 

GROUNDCLEAR having Pneumonia and was placed in a 

TRIOX TOTAL medically induced coma. No background 

024071- 000239- VEGETATION information of the patient's exposure to AI 

00147 4/15/2012 VA 02657 KILLER I was provided. 

In Aggregate IDS, from January 1, 2008 to January 9, 2014, there were 279 reported incidents 

involving imazapyr. One incident was classified as unknown or no effects and 278 incidents 

were classified as minor severity. 

Ortho® GroundClear® Vegetation Killer Concentrate (Reg No 239-2657) appears to be 

implicated in a large number of incidents in both Aggregate (71 %) and Main IDS (77%). This 

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product is used on residential control of unwanted vegetation in areas such as driveways, 

walkways, patios and fence rows. In addition to Imazapyr (0.8%), this product contains the 

active ingredient Glyphosate (5%). This may be potentially attributable to the high use of this 

product by consumers. 

b. SENSOR-Pesticides 

The SENSOR-Pesticides database covers 11 states from 1998-2009, although reporting varies 

from state to state. Cases of pesticide-related illnesses are ascertained from a variety of sources, 

including: reports from local Poison Control Centers, state Department of Labor workers' 

compensation claims when reported by physicians, reports from State Departments of 

Agriculture, and physician reports to state Departments of Health. Although both occupational 

and non-occupational incidents are included in the database, SENSOR-Pesticides focuses on 

occupational pesticide incidents, and is of particular value in providing that information. The 

state coordinator at each of the 11 respective state Departments of Health conducts case followup activities such as obtaining medical records to verify symptoms and severity. Using 

standardized protocol and case definitions derived from poison center reporting, the state 

SENSOR-Pesticide coordinator enters the incident information into the state-based system which 

is sent to NIOSH annually to be aggregated. 

A SENSOR-Pesticides query from 1998-2009 identifies a total of 49 cases involving imazapyr, 

stemming from 38 events. A total of21 out of 49 cases were drift-related. Of these, 46 cases 

involved multiple active ingredients and three cases involved a single active ingredient. 

Two single active ingredient (ai) cases were exposed to Arsenal Herbicide (EPA reg# 241-273) 

and one case was exposed to Arsenal 5-0 Herbicide (EPA reg# 241-308). One of these cases 

was work-related and two were not work-related. Two of the cases were low in severity and one 

case was moderate in severity. The moderate severity case occurred in Florida in 2002 and 

involved a 14-year old; unfortunately the narrative for this case is blank therefore exposure 

scenario is unknown. One case reported dermal symptoms, two cases reported gastrointestinal 

symptoms, and all three cases reported nervous system symptoms such as headache, weakness 

and dizziness. 

It may be of note that of the 46 multiple ai cases, 14 were related to aerial application to forest 

lands, 13 of which were drift -related. One aerial application to a forest was an event that 

involved six occupationa.l cases, the event occurred in Louisiana in 2006 and the event 

description states "Six loggers were exposed to herbicides from a helicopter application while 

logging in pine forest". Another multiple exposure event from aerial application to forest 

resulted in four bystander cases; the event occurred in Texas in 1998 and the event description 

states, "Residents live next to forest land. The land was sprayed with pesticides. The family was 

exposed through drift and mist." 

c. Agricultural Health Study (AHS) 

The AHS is a high quality, prospective epidemiology study evaluating the link between pesticide 

use and various health outcomes including cancer. The AHS includes private and commercial 

pesticide applicators and their spouses. If there are AHS findings relevant to a particular 

pesticide going through registration review, the Agency will ensure they are considered in the 

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problem formulationlscoping phase of the process and, if appropriate, fully reviewed in the risk 

assessment phase of the process. The AHS includes information on use of 50 different pesticide 

active ingredients commonly used in agriculture. Imazapyr is not included in the AHS, and 

therefore this study does not provide information for this report. 

IV. CONCLUSION 

Based on the low severity and relatively low frequency of incident cases reported for imazapyr in 

both IDS and SENSOR-Pesticides, there does not appear to be a concern at this time that would 

warrant further investigation. Ortho® GroundCiear® Vegetation Killer Concentrate (Reg No 

239-2657) does appear to be implicated in a disproportionate amount of incidents which may be 

attributable to high use of this product by consumers. The Agency will continue to monitor the 

incident information and if a concern is triggered, additional analysis will be included in the risk 

assessment. 

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