UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

MEMORANDUM 

Date: August 29, 2013 

SUBJECT: Metam Sodium, Metam Potassium, MITC: Review of Human Incidents 

PCCode:039003, 039002, 068193 

Decision No.: 477549 

Petition No.: NA 

Risk Assessment Type: NA 

TXRNo.:NA 

MRID No.: NA 

DP Barcode: 04 I 4492 

Registrat.ion No.: NA 

Regulatory Action: NA 

Case No.: NA 

CAS No.: 6734-80-1 , 137-42-8 

40CFR: NA 

Ver.Apr.08 

FROM: 

Tox

Elizabeth 

icology 

Evans, 

and Epidemiology 

Environmental 

Branch 

Protection Specialis

f~~ 

t ~ 

Health Effects Division (7509P) - 0--

and 

hanna Recore, Industrial Hygienist 

Toxicology and Epidemiology Branch 

Health Effects Division (7509P) 

THROUGHfbavid J. Miller, Acting Branch Chief 

Toxicology and Epidemiology Branch 

Health Effects Division (7509P) 

TO: Shalu Shelat, Risk Assessor 

Risk Assessment Branch VI 

Health Effects Division (7509P) 

and 

Jose Gayoso, Chemical Review Manager 

Risk Management & Implementation Branch II 

Pesticide Reevaluation Division (7508P) 

Summary and Conclusions 

In the 2008 Reregistration Eligibility Decision (RED) for Methyldithiocarbamate Salts (Metam 

sodium, Metam potassium) and Methyl Isothiocyanate (MITC), EPA identified acute inhalation 

as the main risk of concern for handlers (including persons involved in the application, and also 

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persons involved in tarp perforation and removal activities), workers, and bystanders. 1 While 

there is a low frequency of incidents reported in IDS and SENSOR-Pesticides for Metam 

potassium and MITC, SENSOR-Pesticides data does support the inhalation risk of concern 

identified in the RED for me tam sodium due to the frequency of reported incidents ( n= 131) and 

number of reported respiratory effects (59% of cases). 

On December 1, 2012 the final phase EPA-required new safety measures for soil fumigant 

pesticides (chloropicrin, dazomet, metam sodium, metam potassium, and methyl bromide) went 

into effect. These safety measures are required to increase protection for agricultural workers 

and bystanders. At the time of this report, there is insufficient information available to determine 

if the newly required safety measures have impacted the frequency of incidents occurring since 

implementation. However, the Agency will continue to monitor the incident information and 

provide an updated review of incident, considering pre- and post-mitigation incidents separately, 

when the information becomes available. The Agency will continue to monitor the incident 

information and provide an updated review of incident, considering pre- and post-mitigation 

incidents separately, when the information becomes available." 

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

human health effects associated with certain pesticides. These chemicals are not included in the 

AHS, and therefore this study does provide information for this report. 

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 

Metam sodium and metam potassium are non-selective soil fumigants with fungicidal, 

herbicidal, insecticidal, and nematicidal properties. MITC is highly volatile and is responsible 

for the fumigant properties of metam sodium and metam potassium. Metam sodium and metam 

potassium are used on a wide range of pests including fungi, plants, insects, and nematodes. As 

an agricultural soil fumigant, it is currently labeled for use on all food, feed, and fiber crops. It 

1 http://www.epa.gov/oppsrrd 1/reregistration/REDs/metamsodium-red.pdf 

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also is used pre-plant on turf grass, to control invading plant roots in drains and sewers, and for 

vegetation control along drained ponds and lakes (in California only). Metam sodium, metam 

potassium, and MITC are all registered as antimicrobial agents to control a number of 

microbiological pests, including bacteria and fungi. There are no residential uses. At the time of 

the RED, metam sodium had 39 registered uses whereas metam potassium had only 16 and 

MITC had one. Metam sodium is "one of the most widely used chemicals in agricultural in the 

United States ... "

2 

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 Methyldithiocarbamate salts and 

MITC (PC Code: 039003,039002, and 068193). The purpose ofthe database search is to 

identify potential patterns in the frequency and severity of the health effects attributed to 

Methyldithiocarbamate salts and MITC exposure. 

In addition, findings from the AHS were reviewed. The Agricultural Health Study (AHS) is a 

high quality, prospective epidemiology study evaluating the link between pesticide use and 

various health outcomes including cancer. These chemicals are not included in the AHS. 

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 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. 

2 R£0 Fact Sheet: Methyldithiocarbamate Salts - Metam Sodium/Potassium and MITC: 

http://www.epa.gov/oppOOOO 1/chem search/reg actions/reregistration/fs G-56 l 0-Jul-08.pdf 

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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. 

Metam Sodium: 

For the Main IDS, from January 1, 2008 to February 19, 2013, there were 5 incidents reported 

for single chemical only in the database. There was 1 additional incident reported involving 

more than one chemical. All of these incidents were classified as moderate severity generally 

involving ocular, respiratory, gastrointestinal, and dermal effects. Overall, there are few 

incidents involving metam sodium reported to IDS. 

In Aggregate IDS, from January 1, 2008 to February 19,2013, there were 8 reported incidents 

involving metam sodium. These incidents were classified as minor severity. 

Metam Potassium (039002): 

For the Main IDS, from January 1, 2008 to February 19, 2013, there was 1 incident reported for 

metam potassium in the database. This incident was classified as moderate severity which 

consisted of ocular symptoms. Overall, there are few incidents involving metam potassium 

reported to IDS. 

In Aggregate IDS, from January 1, 2008 to February 19, 2013, there was 1 reported incident 

involving metam potassium. This incident was classified as minor severity. 

MITC: 

For the Main IDS, from January 1, 2008 to February 19, 2013, there was one incident reported in 

the database involving MITC. This incident was classified as moderate severity and consisted of 

respiratory and neurological effects. 

In Aggregate IDS, from January 1, 2008 to February 19, 2013, there were 3 reported incidents 

involving MITC. These incidents were classified as minor severity. 

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. 

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Metam Sodium (039003) 

A query of SENSOR-Pesticides 1998-2009 identifies 136 cases, stemming from 60 events, for 

metam sodium. One hundred thirty one cases involved a single active ingredient and 5 cases 

involved multiple active ingredients. Of the 131 single active ingredient cases: 2 were high in 

severity, 24 were moderate in severity and 105 were low in severity. The high and moderate 

severity case descriptions are provided in Table 2. One hundred and four cases were workrelated. Ninety three of the 131 cases were exposed via drift/volatilization3

. Reported health 

effects are summarized in Table 1. 

Table 1. SENSOR-Pesticides 1998-2009: 

Reported Health Effects for Metam Sodium 

Cases 

N=13 1 

Health Effect # of Occurrences 

Dermal 32 

Ocular 80 

Respiratory 77 

Gastrointestinal 62 

Renal 3 

Nervous System 72 

Cardiovascular 13 

Misc. 14 

* Cases may report multiple health effects 

Multiple case drift/volatilization events 

(Only events with 15 or more cases are described here.) 

1. The first metam sodium drift/volatilization event reported to SENSOR occurred in 

Somerton, Arizona in 1999 and resulted in 19 SENSOR case reports after an application 

of the soil fungicide Nemasol426 (EPA reg # 5481 -423-34794) was made to field via 

sprinkler chemigation in preparation for planting cilantro. Field laborers 1/3 of a mile 

away from the application had inhalation exposure due to the application 

drift/volatilization. Workers experienced symptoms including burning and tearing of the 

eyes, upper respiratory pain and shortness of breath. Pesticide application violations 

were cited in this event but not specified further in the dataset. The event (AZ00053) is 

described in SENSOR as follows: 

On September 16, 1999, the Arizona Department of Agriculture (ADA) representative 

faxed a report of a pesticide exposure incident and the cluster of illnesses to the Office of 

Environmental Health (OEH). The gender and the age range for 32 of 35 crew members are: 17 

males, 15 females and 20 through 52 years of age. On September 12, 1999, the applying 

company had scheduled and applied the pesticide Nemaso/426, at 7:00p.m., by the sprinkler 

3 The SENSOR-Pesticides program defines drift as " .. . the movement of pesticides away from the treatment site. The 

pesticide spray, mist, fumes, or odor are carried from the target site by air." There is no clear distinction between 

cases exposed from volatilization versus spray drift when analyzing the SENSOR-Pesticides data. 

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Case 10 

AZ00097 

AZ00 119 

AZOO I34 

CA03433 

CA03520 

irrigation (chemigation) method, to an agricultural field in preparation for planting cilantro. 

The .field is located in Somerton, Arizona. The Nemaso/426 is a soil fungicide, but is considered 

a fumigant that contains 42% sodium ethyldithiocarbamate, as the active ingredient. Nemasol 

426 has a strong sulfur-like odor. Its vapors and aerosols can irritate eyes, nose and the 

respiratory passages. The Environmental Protection Agency (EPA) Registration Number for 

Nemaso/426 is 5481-423-34794, as provided on the pesticide label. 

2. Another drift/volatilization event occurred in California in 2008 and resulted in 18 

SENSOR case reports. Workers in a lettuce field were exposed via drift/volatilization 

from a nearby application ofVapam HL soil fumigant to a spinach field. Workers 

experienced symptoms including burning eyes and upper respiratory pain. A pesticide 

application violation was cited for this event but not further specified in SENSOR. The 

event (CA02555) was described as follows" Workers were in lettuce field while spinach 

field was treated- exposed via drift" 

3. Another drift/volatilization event occurred in Washington in 2008 involving a product 

named Me tam CLR and resulted in 19 case reports; 16 of which were residential cases 

including several young children. Symptoms experienced include eye burning/irritation, 

cough and upper respiratory pain. The event (W A02238) is described in SENSOR as 

follows: 

On Friday Oct 17, a strong odor consistent with fumigant vapors was reported in 

a residential area aqjacent to a treated field. DOH was able to collect information on 16 

of the 19 people who lived there. The 16 people includedfive children aged 17 days to 

six years old, four children aged 12-18 years old, and seven individuals aged 19-65 years 

old. All 16 reported eye irritation. Tearing, headache, nausea, abdominal cramping, 

coughing, shortness of breath, and burning in the nose and throat were also reported. 

Twelve of the 16 sought health care for symptoms. In addition, two visitors and an 

emergency responder reported exposure and irritant symptoms but did not seek health 

care. This incident occurred during application of a soil fumigant, through the central 

pivot irrigation system, on a 150 acre crop circle across the road. It appeared that 

temperature inversion on the afternoon of the 17th contributed to the off-site movement of 

vapors into the nearby homes. Strong smell in the residential area ... 

I Year I Severity 

1999 Moderate 

Moderate 

1999 

Moderate 

1999 

1998 Moderate 

!998 Moderate 

Table 2. SENSOR-Pesticides 1998-2009 

High and Moderate Severity Metam Sodium Cases (039003) 

I Case Narrative 

Inhalation exposure from a drifted pesticide. Sprinkler chemigation was used in a field one-third of a 

mile away. 

Inhalation exposure from a drifted pesticide. Sprinkler chemigation was used in a field one-third of a 

mile away. 

Water with metam sodium soaked the truck driver's shoes. feet. pants and legs. Dermal exposure. 

No case detail provided 

No case detail provided 

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Table 2. SENSOR-Pesticides 1998-2009 

High and Moderate Severity Metam Sodium Cases (039003) 

Case ID I Year I Severity I Case Narrative 

CA05474 1998 Moderate No case detail provided 

Moderate Delivering truck of metam sodium, stepped in dry white powder getting on his sock and boot chemically CA06367 1999 

burning both feet 

CA06829 1999. Moderate No case detail provided 

CA06887 1999 Moderate No case detail provided 

CA06895 1999 Modera.te No case detail provided 

CA07997 1999 Moderate No case detail provided 

CA07999 1999 Moderate No case detail provided 

CA08837 200 1 Moderate No case detail provided 

CA09020 2001 Moderate No case detail provided 

CAI0390 2002 Moderate No case detail provided 

CAI2060 2002 Moderate No case detail provided 

CAI3157 2003 Moderate No case detai l provided 

CAI3925 2004 Moderate He was hooking up sprinkler irrigation pipes when he entered a field that had been treated with vapam 

CA I4291 2005 High Exposed to pesticide drift when she entered a field in the morning after a nearby field was sprayed 

overnight 

Moderate He was applying pesticide by tractor next to a tield where another chemical was being applied by CAI4397 2005 sprinklers. 

FL02210 2007 Moderate 27 yr old got Vapam HL on his feet 2 days ago. He removed his socks and rinsed with water that day. 

FL03224 High Patient came into contact with Vapam. 

OR00215 1999 Moderate Was walking outside along road; saw huge cloud sitting over field. 50 ft from house; cloud came 

overhead; became symptomatic. 

Moderate A 41 y/o male was exposed when transferring product. Product spilled onto his boots and when he 

WA01287 2003 attempted to wash it off. Do 

Moderate On Friday Oct 17, a strong odor consistent with fumigant vapors was reported in a residential area WA02736 2008 adjacent to a treated field 

Moderate On Friday Oct 17, a strong odor consistent with fumigant vapors was reported in a residential area WA02742 2008 adjacent to a treated field 

*SENSOR-Pesticides Severity Index 

Death Human Fatality 

High Life threatening, requires >5 days lost work/time 

treatment 

Moderate Involves systemic effects 3-5 days lost work/time 

Minor Symptoms typically resolve <3 days lost work/time 

without treatment 

Metam Potassium (pc code 039002) 

A query of SENSOR-Pesticides 1998-2009 identifies 3 cases, stemming from 3 events, involving 

metam potassium; all 3 were single ai cases. Two cases were low in severity and one was 

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moderate in severity. The moderate severity case description states " ... experienced ocular and 

dermal symptoms after walking through his property that was overflowed with runoff from a 

potato field chemigation application. He wore irrigation boots and one boot had a hole in it. 

This resulted in a chemical burn to his foot. WSDA samples tested positive for residues from the 

adjacent chemigation application. " 

Methyl isothiocyanate (MITC); (pc code 068103) 

A query of SENSOR-Pesticides 1998-2009 identifies 2 cases, stemming from 2 events, involving 

MITC. Both cases involved exposures to multiple active ingredients. One case was low in 

severity and one case was moderate in severity. No narrative was recorded for either case. 

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. Metam Sodium, Metam Potassium and MITC 

are not included in the AHS. 

IV. CONCLUSION 

A number of cases involving metam sodium, particularly cases of occupational 

drift/volatilization, have been reported to SENSOR-Pesticides, including 2 multiple case drift 

events in 2008. Although most of these cases were low in severity; considering the frequency of 

reported incidents, this is a chemical of potential concern for both agricultural workers and 

bystanders. The frequency of incidents is likely related to the widespread use of the product in 

agriculture. With consideration for the mitigation efforts (which include both use and entry 

restrictions, additional PPE for applicators, expanded buffer zones) implemented; HED will 

continue to monitor the incident information as it becomes available and will provide an updated 

review of incidents during registration review. 

Based on the low frequency and severity of incident cases reported for Metam Potassium and 

MITC in both IDS and NIOSH 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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