UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

MEMORANDUM 

Date: February 6, 2014 

SUBJECT: Mesotrione: Tier I Review of Human Incidents 

PC Code: 122990 DP Barcode: 0417803 

Decision No.: 486616 

Petition No.: NA 

Risk Assessment Type: NA 

TXRNo.: NA 

MRID No.: NA 

Registration No.: NA 

Regulatory Action: NA 

Case No.: NA 

CAS No.: 104206-82-8 

40 CFR: NA 

Ver.Apr.08 

FROM: Elizabeth Evans, Environmental Protection Specialist ~ 

Toxicology and Epidemiology Branch ~ l ..r--v</~ 

Health Effects Division (7509P) 0 v 

and 

Shanna Recore, Industrial Hygienist 

Toxicology and Epidemiology Branch 

Health Effect Division (7509P) 

THROUGH: David Miller, Acting Branch Chief ( 

Toxicology and Epidemiology Bran 

Health Effects Division (7509P) 

TO: Sarah Levy, Risk Assessor 

Risk Assessment Branch I 

Health Effects Division (7509P) 

and 

1. Trujillo, Chemical Review Manager 

Risk Management & Implementation Branch 5 

Pesticide Re-evaluation Division (7508P) 

Summary and Conclusions 

Based on the low frequency and low severity of incident cases reported for mesotrione in both 

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

warrant further investigation. 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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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 

Mesotrione is a systemic, pre-emergent and post-emergent herbicide proposed for the selective 

contact and residual control of annual broadleaf weeds in field corn. 

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 mesotrione (pc code: 122990). The 

purpose of the database search is to identify potential patterns in the frequency and severity of 

the health effects attributed to mesotrione exposure. Mesotrione is not included in the AHS, and 

therefore this study does not provide information for this report. 

III. 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. 

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

1 http://www.epa.gov/oppOOOOI!chem_search/cleared_reviews/csr_pC-l22990_7-May-Ol _ ll5.pdf 

Page 2 of 4 
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 Jess 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 1, 2009 to January 15,2014, there were 2 incidents reported for 

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

severity. There were 13 additional incidents reported involving more than one chemical. One 

incident was classified as major severity and 12 incidents were classified as moderate severity. 

In Aggregate IDS, from January l, 2009 to January 15, 2014, there were 20 reported incidents 

involving mesotrione. These incidents were classified as minor severity. Overall, there are few 

incidents involving mesotrione reported to IDS. 

b. SENSOR-Pesticides 

The SENSOR-Pesticides database covers 11 states from 1998-2010, 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 query of SENSOR-Pesticides 1998-2010 identifies 4 cases, stemming from 3 events, involving 

mesotrione (pc code 122990). Multiple active ingredients were implicated in all 4 cases. 

Narratives are provided below in Table 1. Table 2 provides a summary of symptoms reported. 

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Table 1. SENSOR-Pesticides 1998-2010 

Mesotrione Case Descriptions 

N=4 

ID Year Severity Description 

NY00846 2004 Moderate Couple lives near com fields and experienced drift from application. Dog also 

ill. DEC sampled and had hits. 

NY00847 2005 Low Farm fields adjacent to home were sprayed while woman and dog outside. 

Vegetation there died. Sampling showed actives. 

MIO I993 2008 Low Applicator treated com in field across from his property in high winds. 

IA00437 2009 Low Exposed to seed chemicals at work - caused contact dermatitis. Did not wash 

off when exposed. 

Table 2. SENSOR-Pesticides 1998-2010: Reported 

Health .Effects for Mesotrione Cases 

N=4 

Health Effect # of Times Reported 

Nervous System 3 

Respiratory 2 

Gastrointestinal 0 

Dermal l 

Ocular I 

Cardiovascular 0 

*Cases may report multiple health effects 

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 

problem formulation/scoping 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. Mesotrione is not included in the AHS, and 

therefore this study does not provide information for this report. 

IV. CONCLUSION 

Based on the low frequency and low severity of incident cases reported for mesotrione in both 

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

warrant further investigation. 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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