UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

MEMORANDUM 

Date: May 22, 2013 

SUBJECT: Methyl Bromide: Review of Human Incidents 

PC Code: 053201 DP Barcode: 0411151 

Decision No.: 476573 

Petition No.: NA 

Risk Assessment Type: NA 

TXRNo.: NA 

MRID No.: NA 

Registration No.: NA 

Regulatory Action: NA 

Case No.: NA 

CAS No.: 74-83-9 

40CFR: NA 

Ver.Apr.08 

Elizabeth Evans, Environmental Protection Specialist G 

Toxicology and Epidemiology Branch c;'e_ . .d~ C] 

Health Effects Division (7509P) l. ?'"· 

FROM: 

and 

Shanna Recore, Industrial Hygienist \ ~ " 1) 

Toxicology and Epidemiology Branch ~\.J.L~ ILC.~(JA...__,L Health Effects Division (7509P) ;{} 

THROUGH: David J. Miller, Acting Branch hief\~;)/J./1., /fJ.I?Jf!f ?.otJ 

Toxicology and Epidemiology Branch 

Health Effects Division (7509P) 

TO: Matthew Lloyd, Risk Assessor 

Risk Assessment Branch VII 

Health Effects Division (7509P) 

and 

Susan Bartlow, Chemical Review Manager 

Risk Management & Implementation Branch IV 

Pesticide Reevaluation Division (7508P) 

Summary and ConcJusions 

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

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

effect. These safety measures are required to increase protections for agricultural workers and 

bystanders. Due to the fact that these safety measures were only recently required, there is 

insufficient information available to determine if they have impacted the frequency of incidents 

Page 1 of 11 
occurring. 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 Agricultural Health Study (AHS) is also a potential source of information associated with 

human health effects associated with certain pesticides. Methyl bromide is included in the AHS, 

and this report includes a summary of evaluations of methyl bromide use in association with 

cancer outcomes reported in the AHS. 

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 ofthe 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 

Methyl bromide is a broad-spectrum fumigant chemical that can be used as an acaricide, 

antimicrobial, fungicide, herbicide, insecticide, nematicide, and vertebrate control agent. Methyl 

bromide's most prevalent use pattern is as a soil fumigant. 1 Methyl bromide is commonly 

formulated as pressurized gas applied as a soil fumigant via soil injection or deep drip irrigation. 

Methyl bromide can be used post-harvest via injection into an enclosure chamber, structure, or 

under a tarp. Methyl bromide is registered for use on the soils of all vegetable, fruit and nut 

crops, structural fumigation, post harvest treatment of commodities (e.g. dates, figs, raisins, 

walnuts) and non-food uses (logs for export). 

The 2006 TREDIRED found inhalation risks of concern for occupational handlers involved in 

methyl bromide applications and tarp perforation/removal activities. Risks are also of concern 

for workers who may re-enter treated areas shortly after fumigation or tarp perforation has been 

completed. Monitoring and modeling data indicate that there can be risks of concern associated 

with methyl bromide use at a broad range of distances from treated fields, depending on 

1 Methyl Bromide factsheet: http://www.epa.gov/oppsrrd I /REDs/factsheets/methylbromide-fs.pdf 

Page 2 of11 
Page 3 of 11

application method, emission control methods employed, application rate, and size of the area 

treated.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 Methyl bromide (PC Code: 

053201). The purpose of the database search is to identify potential patterns in the frequency and 

severity of the health effects attributed to Methyl bromide 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. AHS authors have observed associations for certain 

cancer sites (gastric and prostate), as well as chronic bronchitis. These study results, as well as 

supporting information from studies performed external to the AHS, are summarized below.

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. 

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 1, 2008 to February 19, 2013, there were there were 4 incidents 

reported for single chemical only in the database. There was 1 major severity incident, 1 

moderate severity incident, 1 minor severity incident and 1 incident had no effects reported. 

 

2

Ibid. 
Page 4 of 11

These incidents are further described in Table 1. There were 9 additional incidents reported 

involving more than one chemical. Overall, there are few incidents involving methyl bromide

reported to IDS. 

In Aggregate IDS, from January 1, 2008 to February 19, 2013, there were 4 reported incidents 

involving methyl bromide. These incidents were classified as minor severity.
Page 5 of 11

Table 1. Main IDS Major Incidents for the single chemical Methyl Bromide

Human 

Incident Chemical: Methyl Bromide PC Code: 053201

Incide

nt 

Packa

ge 

Repor

t

Inciden

t Date

Locati

on

Reg 

Numb

er

Product 

Name

Exposu

re 

Severit

y Codes Incident Description

01958

0 -

00001

4/15/20

08

Aubur

n, WA

METHYL 

BROMIDE H

Over fifty employees were exposed to methyl bromide in a building. 

No adverse reaction reported, only exposure.

01996

9 -

00001

8/16/20

08 NE

00578

5-

00011

METH-OGAS 100 HB

The owner of a pest control service company and an employee 

increased the pressure of the cylinder containing methyl bromide 

with nitrogen. This is a misuse that caused the methyl bromide 

cylinder to explode. Both individuals were taken to the hospital. 

Neither had clinical signs of methyl bromide exposure. One 

individual was released. The other individual had part of his leg 

amputated due to the fragmentation of the cylinder.

02150

8 -

00001

11/4/20

09

Mader

a, CA

00885

3-

00002-

01122

0

M B C 

CONCENTR

ATE HD

An applicator was performing individual vine-site fumigation with a 

hand-held injection probe. During application the cylinder broke and 

a small amount of product sprayed the applicator who was wearing 

all required PPE. He immediately performed all on-site 

decontamination steps. He experienced eye and respiratory irritation 

and was taken to the hospital. After a 4-hour observation period, the 

applicator was released and approved to go back to work.

02188

5 -

00001

1/1/201

0

Carson

, CA

00578

5-

00041

METH-OGAS Q HC

Two cold storage employees reported adverse effects; possibly from 

methyl bromide off-gassing from treated fruit (grapes). Both 

employees experienced difficulty breathing, sinus infections and 

respiratory irritation, unsteady gait, and dizziness.

http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6027a4.htm?s_c

id=mm6027a4_w
Page 6 of 11

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 query of SENSOR-Pesticides 1998-2009 identifies a total of 119 cases, stemming from 67 

events, involving methyl bromide. Ninety two percent of cases were work-related. There were 3 

fatalities, 2 high severity cases, 46 moderate severity cases and 68 low severity cases. Fifty-six

cases involved a single active ingredient and 57 cases involved a combination of methyl bromide 

and chloropicrin. Of the 56 single ai cases, there were two fatalities, two high severity cases, 21 

moderate severity cases, and 31 low severity cases. Of the 57 cases involving exposure to both 

methyl bromide and chloropicrin, there was one fatality, 20 moderate severity cases and 36 low 

severity cases. Symptoms reported for all cases are summarized in Table II.

Table II. SENSOR-Pesticides 1998-

2009: Reported Health Effects for 

MeBr Cases

N=119

Health Effect Count

Dermal 39

Ocular 70

Respiratory 79

Gastrointestinal 53

Renal 2

Nervous System 65

Cardiovascular 15

Misc. 18

* Cases may report multiple health 

effects

Fatality descriptions

Two incidents from one event in Texas in 2002, single AI, relationship to pesticide exposure was 

coded as “definite;” however, intentional exposure was suspected but unknown as case 1 died, 

the following is case detail:
Page 7 of 11

“Details of exposure are unclear due to the fact that case died before explaining what happened. 

There were two cans of Methyl Bromide found outside the residence and all application devices 

were found hidden in garage. 2nd victim stated that case came home already exposed to 

chemical. 2nd victim stated that he tried to help 1st victim and was exposed himself. Victim #1's 

8 year old child came home, found dad in bed sick and laid next to him and became exposed. 

Victim's #1 & #2 both died from the exposure. (#1 died 2/5/02 and #2 died 3/24/02)”

A synopsis of the severe symptoms recorded for these two fatalities include: cardiac 

arrest, pulmonary edema, respiratory depression, ataxia, and seizure.

The third fatality occurred in California in 2009 and involved methyl bromide and chloropicrin, 

product name Helena MBC-33 soil fumigant (EPA Reg. No. 8853-3). A handler was filling a 

drum of MBC and chloropicrin and it ruptured and exploded.

Table III. SENSOR-Pesticides 1998-

2009: MeBr Cases by Year

N=119

Year of Exposure Count

1998 8

1999 44*

2000 13

2001 10

2002 14

2003 2

2004 6

2005 2

2006 8

2007 1

2008 4

2009 7

*31 of these 1999 cases were attributable to one MeBr/Chloropicrin drift event described below.

Multiple case events

In Florida in 1999: 31 individual cases were reported for one exposure event. Employees 

working at or near a tomato packing house received varied levels of exposure resultant from a 

MeBr/chloropicrin spill and drift. All 31 cases were low in severity and symptoms included 

respiratory irritation, headache and burning eyes.

Chloropicrin and MeBr

Because chloropicrin and methyl bromide are often co-formulated, the symptoms of these cases 

were reviewed to determine if the symptoms reported could be distinguished as attributable to 

either chloropicrin or methyl bromide.

Of the 57 methyl bromide and chloropicrin cases, the most commonly reported health effects 

involved the eye (n=46) such as eye irritation and lacrimation, also respiratory effects (n=46) 
Page 8 of 11

including upper respiratory pain and cough. These symptoms are consistent with chloropicrin 

exposure.3 Of the 57 methyl bromide and chloropicrin cases, 29 reported a nervous system 

effect, generally a headache. Although it is difficult to determine which active ingredient was 

responsible for the health effects, it appears that symptoms most frequently reported (burning, 

watery eyes and respiratory irritation) are consistent with chloropicrin exposure. 

Soil Fumigation vs. Commodity Cases

SENSOR-Pesticides records the application site of the event, defined as “location where the 

application or event associated with the exposure took place.” Of the 119 methyl bromide cases 

reported in SENSOR-Pesticides, 57 occurred on a farm. The remaining 62 occurred elsewhere, 

such as “industrial facilities” (n=35). This variation in location of the incidents is important 

because it shows that both soil fumigation and commodity incidents have both been reported. 

Some examples of commodity fumigation cases are summarized here. Three Longshoremen

were unloading imported logs that had been fumigated and were exposed. Another commodity 

case involved a shipping clerk unloading fumigated baskets from Asia.

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.

In the Agricultural Health Study (AHS), researchers have identified an association between 

lifetime use of methyl bromide and both gastric and also prostate cancers, as well as prevalent 

chronic bronchitis among female spouses enrolled in the AHS. Given the low prevalence of 

fumigant use in the AHS, this Tier I summary also refers to studies outside of the AHS to 

provide a more accurate reflection of potential methyl bromide carcinogenicity. Hughes-Barry et 

al. (2012) reported an association between methyl bromide and gastric cancer. Using the 

intensity-weighted exposure metric (adjusted for use of personal protective equipment), authors 

observed a three-fold increased risk of gastric cancer comparing the upper methyl bromide group 

to the non-exposed group (OR 3.13 (95% CI 1.25, 7.80), and researchers reported a significant 

monotonic increase in risk by increasing exposure (p for trend 0.02). In a study of California 

farm workers, Mills and Yang (2007) reported a link with gastric cancer and methyl bromide 

exposure of a similar magnitude and direction (OR 4th quartile versus lowest methyl bromide 

exposure category 2.38 (95% CI 1.06, 5.37) (Mills and Yang et al. 2007). 

Alavanja et al. (2003) initially reported a link between methyl bromide and prostate cancer 

(Alavanja et al. 2003), however these finding were not replicated in more recent follow-up 

analyses (Hughes-Barry et al. 2012). In the early study, methyl bromide was among only a few 

substances which were associated with prostate cancer regardless of a family history of prostate 

cancer among a first degree relative (top quintile versus no exposure: odds ratio (OR) 3.47 (95% 

 

3 Recognition and Management of Pesticide Poisonings: 5th Edition. Pg. 157
Page 9 of 11

CI 1.57, 8.76), p for trend 0.004). Authors note that fumigant use in the AHS cohort is low due to 

crops typically grown in IA and NC, and the use of methyl bromide, while always low, 

decreased further over the time period since cohort enrollment (1993-2007). In the latter 

analysis, the authors did replicate the earlier finding of an association with prostate cancer 

among those enrolled in the AHS cohort earlier (1993-1995) versus later (1995-1997) in cohort 

enrollment period, suggesting a link among those more highly exposed who enrolled in the study 

earlier (Hughes-Barry et al. 2012). It should be strongly noted that a lack of finding of an 

association with prostate cancer in the follow-up analysis is not supportive of the conclusion of 

no association, since the prevalence of methyl bromide use is low, and decreasing in these study 

states. Methyl bromide use is greater in California than either of the two AHS study states. In a 

recent population-based case control study (study period 2005-06), residential proximity to 

agricultural fields treated with methyl bromide was associated with an increased risk of prostate 

cancer (OR 1.62 (95% CI 1.02, 2.56) (Cockburn et al. 2011). The same authors also noted a nonsignificantly elevated risk of prostate cancer among farm workers in California (Mills and Yang 

2003). 

In a study of prevalent chronic bronchitis (questionnaire based self report outcome 

determination: “has a physician ever told you have chronic bronchitis?”), authors reported a link 

with methyl bromide (1.82 (95% CI 1.02, 3.24) controlling for age, state and other pesticide 

exposures (Valcin et al. 2007). This is a preliminary study and authors could not discern clearly 

between methyl bromide and other specific pesticide exposures and other correlated farm 

activities among female spouses due to the collection limited exposure information. 

IV. CONCLUSION

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

pesticides (chloropicrin, dazomet, metam sodium/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 among 

soil fumigants including methyl bromide, 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. 

Only half the SENSOR-Pesticides cases were exposed to methyl bromide on a farm; 35 cases 

were exposed in an industrial facility. Therefore the commodity fumigation incidents are 

reported, while somewhat less than soil fumigation incidents, they warrant continued monitoring 

as well as soil fumigation incidents.

In the AHS, authors noted a monotonically increasing trend of gastric cancer risk by increasing 

methyl bromide exposure; an association of a similar magnitude and direction was also reported 

among a highly exposed population of California farm workers. Early, strong associations with 

prostate cancer dissipated over time, perhaps due to decreasing prevalence of use of methyl 

bromide in the AHS cohort, as noted by the authors. However, a link with prostate cancer has 
Page 10 of 11

been reported in both highly exposed samples of the general population (California residents 

living near methyl bromide treated fields), and a California farm worker population in similar 

study periods. Other cancer-methyl bromide links hypothesized in the open literature could not 

be evaluated in the AHS due to the small number of methyl bromide exposed testicular and 

lymphoma cancer cases. Fumigant use in the AHS is low; this obviates the ability the evaluate 

associations between methyl bromide use and many different anatomical cancer sites. Therefore, 

a lack of association should not be interpreted as evidence of no true association. Authors of 

studies in other highly exposed occupational and non-occupational populations have reported 

similar associations to the AHS and will also be considered in EPA’s evaluation to provide a full 

evaluation of the carcinogenic potential of methyl bromide.
Page 11 of 11

References

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pesticides and prostate cancer risk in the Agricultural Health Study cohort. Am J

Epidemiol. 2003 May 1;157(9):800-14. PubMed PMID: 12727674.

Barry KH, Koutros S, Lubin JH, Coble JB, Barone-Adesi F, Beane Freeman LE,

Sandler DP, Hoppin JA, Ma X, Zheng T, Alavanja MC. Methyl bromide exposure and

cancer risk in the Agricultural Health Study. Cancer Causes Control. 2012

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Cockburn M, Mills P, Zhang X, Zadnick J, Goldberg D, Ritz B. Prostate cancer

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28. PubMed PMID: 21447478; PubMed Central PMCID: PMC3121318.

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PubMed PMID: 17196584.

Mills PK, Yang R. Prostate cancer risk in California farm workers. J Occup

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