UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

MEMORANDUM 

Date: June 2, 2015 

SUBJECT: Chlorpyrifos Methyl: Tier I Review of Human Incidents for Draft Risk 

Assessment 

PC Code: 059102 

Decision No.: 503280 

Petition No.: NA 

Risk Assessment Type: NA 

TXRNo.:NA 

MRIDNo.:NA 

DP Barcode: 0426989 

Registration No.: NA 

Regulatory Action: NA 

Case No.: NA 

CAS No.: 5598-13-0 

40CFR: NA 

Ver.Apr.OS 

FROM: 

Toxicology 

Elizabeth Evans, 

and Epidemiology 

Environmental 

Branch 

Protection Specialist 

~ 

~ 

Health Effects Division (7509P) 

and 

Shanna Recore, Industrial Hygienist 

Toxicology and Epidemiology Branch 

Health Effects Division (7509P) 

THROUGH: David J. Miller, Acting Branch Chie 

Toxicology and Epidemiology Branc 

Health Effects Division (7509P) 

TO: Danette Drew, Risk Assessor 

Risk Assessment Branch 

Health Effects Division (7509P) 

and 

Joel Wolf, Chemical Review Manager 

Risk Management & Implementation Branch 2 

Pesticide Re-evaluation Division (7508P) 

Summary and Conclusions 

Chlorpyrifos-methyl was previously reviewed in 2009 (M. Hawkins, 11 /24/09, D370451). At 

the time, there were no incidents reported for chlorpyrifos methyl in IDS from 2002- November 

2009. Upon review of these incidents, it was concluded that, as there were no incidents reported, 

there was not a concern that would warrant further investigation at the time 

Page 1of5 
The current IDS analysis from January 1, 2010 through May 21, 2015, shows one incident 

reported involving chlorpyrifos-methyl in Main IDS involving multiple active ingredients and 13 

incidents involving multiple active ingredients reported to Aggregate IDS. There were no single 

chemical incidents reported to IDS. 

The query of SENSOR-Pesticides 1998-2011 identified 9 incidents involving chlorpyrifosmethyl but there have been no reports since 2004. 

The Agricultural Health Study (AHS) is also a potential source of information associated with 

human health effects associated with certain pesticides. Chlorpyrifos-methyl is not included in 

the AHS, thus no AHS information is available for this chemical. 

Detailed Review 

I. ACTION REQUESTED 

Chlorpyrifos-methyl is being considered under the FQP A-mandated Registration Review 

program established to review, on a 15 year cycle, pesticides for which a Re-registration 

Eligibility Decision has been made. One component of the Agency's Registration Review 

Program is consideration of human incident data. In conjunction with a human health risk 

assessment based on other data sources, such human incident data can assist the Agency in better 

defining and characterizing the risk of pesticides/pesticide products. 

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 

Chlorpyrifos-methyl is a general use organophosphate insecticide registered for use on stored 

grain (for protection of stored food, feed oil, and seed grains against injury from stored grain 

weevils, moths, borers, beetles and mealworms including granary weevil, rice weevil, red flour 

beetle, confused flour beetle, saw-toothed grain beetle, Indian meal moth, and Angoumois grain 

moth, lessor grain borers), seed treatment, grain bin and warehouse. 

For this evaluation, both 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 chlorpyrifos-methyl (PC Code: 

Page 2of5 
059102). The purpose of the database search is to identify potential patterns in the frequency 

and severity of the health effects attributed to chlorpyrifos methyl exposure. 

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: 

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

more detail with regard to case specific. 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 

pesticide 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. 

From January 1, 2010 to May 21 , 2015, there were no incidents reported to Main IDS involving 

the single active ingredient, chlorpyrifos-methyl. There was one incident reported to Main IDS, 

involving multiple active ingredients including chlorpyrifos-methyl and deltamethrin that is 

classified as moderate severity. This incident involved a 30 year old male who was cleaning a 

spill of a one ton container of wheat seed that had been treated with the product (Registration 

Number 264-992). He used a bucket to pick up the seed and move them to a different container. 

Approximately 4 hours after contacting the seeds, he began to develop a rash on his neck and 

chest, shortness of breath, and facial swelling. His symptoms persistent until the next and he 

went to emergency department. He was treated with atropine and his symptom resolved. 

From January 1, 2010 to March 18, 2015, there were 13 incidents reported to Aggregate IDS 

involving chlorpyrifos-methyl. These incidents were classified as minor severity. Overall there 

were few incidents reported to IDS involving chlorpyrifos-methyl. 

b. SENSOR-Pesticides 

The SENSOR-Pesticides database covers 12 states from 1998-2011 , 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' 

Page 3of5 
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 focuses on occupational 

pesticide incidents, and is of particular value in providing that information. A state SENSOR 

contact specialist attempts to follow-up with cases and obtains medical records to verify 

symptoms, circumstances surrounding the exposure, severity, and outcome. Using standardized 

protocol and case definitions derived from poison center reporting, SENSOR coordinators at 

State Departments of Health enter the incident interview description provided by the case, 

medical report, physician and patient into the SENSOR data system. The SENSOR data system 

is accessible to participating states and EPA. 

A query of SENSOR-Pesticides 1998-2011 identifies a total of nine cases, stemming from nine 

events, involving chlorpyrifos-methyl (pc code 059102). Of these, seven cases involved the 

single active ingredient chlorpyrifos-methyl. Four of the seven single ai cases involved 

chlorpyrifos-methyl applications to grain storage facilities (the remaining three cases provide no 

discemable case information). There have been no case reports involving chlorpyrifos-methyl 

since 2004. 

Of the seven cases single ai chlorpyrifos-methyl cases, two cases were high in severity, one case 

was moderate in severity, and four cases were low in severity. In one high severity case, a truck 

driver was near an application made to a wheat storage facility. He developed neurological 

symptoms including confusion, headache, and blurred vision, gastrointestinal symptoms and 

rapid heartbeat. He was transported later that evening by his wife to the local ER. He was given 

atropine, stabilized, and admitted for two days. The second high severity case appears to have 

been a residential exposure; however this case was lost to follow-up and no descriptive case 

information is provided. The moderate severity case involved a worker mixing/loading the 

pesticide at a grain manufacturing facility. Of the remaining four low severity cases, two 

involved grain facility exposures and two provided no case details. Of the seven single ai cases: 

six cases experienced neurological symptoms (chiefly headache) and five cases had 

gastrointestinal symptoms (nausea and vomiting), three cases had ocular symptoms, two cases 

had dermal symptoms, two cases had respiratory symptoms and one case experienced 

cardiovascular symptoms. 

Although two cases were high in severity, there is a low frequency of cases and there have been 

no case reported to SENSOR-Pesticides since 2004. 

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. Chlorpyrifos-methyl is not included in the 

AHS. 

Page 4of5 
CONCLUSION 

Based on the low frequency of incidents reported to both IDS and SENSOR-Pesticides, there 

does not appear to be a concern at this time. The Agency will continue to monitor the incident 

information and if a concern is triggered, additional analysis will be conducted. 

Page 5of5