Methyl Bromide and Stratospheric Ozone Depletion
Methyl Bromide and Stratospheric
Wayne A. Morrissey
Information Research Specialist in Science and Technology
Knowledge Services Group
Methyl Bromide (MeBr), a widely used pesticide in agriculture, is regulated for its
potential ozone-depleting effects in the Earth’s stratosphere. Controls on production,
emissions, and trade are mandated internationally under the 1987 Montreal Protocol on
Substances that Deplete the Ozone Layer (the Protocol) and domestically under Title VI
of the U.S. Clean Air Act. A ban on production for nonessential uses occurred on
December 31, 2004, but the Protocol still regulates post-2004 production for critical
uses. U.S. agribusinesses have sought exemptions from the Environmental Protection
Agency (EPA) to produce MeBr for certain critical uses after the ban. Exemptions are
resisted by some Protocol parties and environmental advocates who seek a rapid,
definitive ban on production and use. Chemical companies maintain that they cannot
foresee development of effective chemical substitutes for all uses of MeBr in the near
term, and agricultural producers indicate they may have to rely on less economical and
less effective treatments. Production allowances for MeBr for 2005-2008 have since
been approved under the Protocol, and the EPA has approved allocations for registered
U.S. users. Due to declining production of manufactured MeBr, the EPA would permit
commercial trade of pre-2005 inventories. This report will be updated as warranted.
Methyl Bromide (MeBr) plays an important role in international agriculture because
of its effectiveness in killing insects and plant pathogens. MeBr is used extensively for
“pre-planting” and “post-harvest” treatment of crops. It also is used for “quarantine and
pre-shipping (QPS)” treatment of agricultural commodities and containers used in
international importing and exporting of agricultural goods.
In the mid-1980s, a group of atmospheric scientists discovered that when gaseous
emissions of MeBr rise into the upper atmosphere, they are decomposed by sunlight.
Bromine oxide (BrO), a powerful ozone-depleting substance (ODS), is released as a
byproduct.1 After BrO rises to the stratosphere ozone layer (between 9-22 miles above
Earth’s surface), it is highly chemically reactive and causes the density of ambient ozone
(O3) to thin. This thinning increases exposure to different wavelengths of ultraviolet (UV)
radiation at the surface. The ozone layer traps most harmful forms of short-wave UV-B
radiation from space. Biologists warn that exposure to UV-B can be genetically damaging
to life forms at the cellular level.2 Conversely, UV-A radiated from the sun can penetrate
the ozone layer and reach the Earth’s surface. Although less harmful than UV-B
exposure, UV-A can cause some forms of fatal skin cancers and blindness in humans.3
MeBr Use and Emissions
As a pesticide, MeBr is proven effective at killing molds, other fungi, insects, and
worm (nematode) infestations of crops. In 1991, 66,000 metric tons (Mt) of MeBr were
produced globally, and predominantly for agricultural uses.4 That tonnage became the
baseline from which a stepped-down phaseout was scheduled under the Protocol and the
Figure 1. Methyl Bromide Use
by Application and Emissions
Per Unit Discharged (%)
MBr Application Emissions (B)
Pre-Planting P o st -H a r ve st
Source: Produced by CRS using U.N. Environmental Program (UNEP) global baseline data for
1 David Fahey, National Oceanic and Atmospheric Administration Aeronomy Lab, reprinted as
Scientific Assessment of Ozone Depletion: 2002, “Twenty Questions and Answers About the
Ozone Layer,” U.N. World Meteorological Organization, Geneva, March 2003.
2 Ozone Secretariat, U.N. Environmental Program (UNEP), “Environmental Effects of Ozone
Depletion: 1998,” published in Journal of Photo Chemistry and Photobiology, vol. 46, nos. 1-3,
October 1998. UV radiation is classified by its wavelength.
3 U.N. World Meteorological Organization (WMO), U.N. Environmental Program (UNEP),
Scientific Assessment of Ozone Depletion: 1994, Ch. 10, “Methyl Bromide,” [Global Ozone
Research and Monitoring Project — Report No. 37].
4 A metric ton (Mt) is about 1.1 U.S. tons.
Figure 1, shows that in agricultural uses, typically about 80% of manufactured MeBr
is for fumigating soils prior to planting to prevent root damage. Another 20% is used as
a pesticide to treat post-harvested commodities such as fruits, vegetables, dried foodstuffs,
stored grains, cut flowers, and timber. It is also used in this capacity to treat wooden
crates and shipping palettes and to fumigate crop storage facilities. About 1% of total is
used for quarantine and pre-shipment (QPS) treatments in global agricultural trade.
The profile of emissions differs for various uses. About 50% of MeBr is emitted into
the atmosphere during controlled pre-planting applications.5 Post-harvest and QPS
applications can result in up to 80% of emissions discharged if not conducted in a
contained environment (emissions scenario A). Contained uses may still account for 5%
and 1% losses to the atmosphere, respectively (emissions scenario B).
Critical Use Allowances (CUAs)
U.S. agribusinesses and small farm owners alike are concerned about a possible
future ban of MeBr production. They anticipate higher costs of doing agricultural
business because of diminishing supplies, lack of viable or economically feasible
alternatives (for some uses), and possible future restrictions on international trade of U.S.
agricultural products if treatment with MeBr were to be prohibited. In the spring of 2003,
the United States was among 13 countries that petitioned the Protocol parties for Critical
Use Allowances (CUAs) to produce MeBr after its post-2004 ban of nonessential uses.6
Critical Stock Allowances (CSAs). CSAs, were since approved under the
Protocol to supplement declining production and diminishing supplies of manufactured
MeBr for agricultural use. The EPA and similar agencies on behalf of industrialized
countries petitioned Protocol parties to allow trading inventories of “pre-phaseout” floor
stocks of MeBr. Only countries that are party to the Protocol are permitted CSAs to
acquire inventories from other parties with surpluses. Additionally, parties acquiring
MeBr floor stocks have to remain beneath an overall annual cap that includes annual
consumption (i.e., CUAs approved for new production of MeBr for domestic use or MeBr
imported from other parties) and CSAs. The annual cap is a percentage of 1991 global
production approved for interested parties by the Protocol. On December 13, 2005, the
EPA had issued a notice of a proposed rulemaking to permit trade of preexisting stocks
of MeBr and to allocate supplemental Critical Stock Allowances (CSAs).7 In January
2006, the EPA announced a notice-and-comment period for U.S. CSAs. It also updated
a schedule of registered U.S. MeBr producers and users that could be eligible to trade pre-8
5 U.S. Department of Agriculture, Agricultural Research Service, “Methyl Bromide, Fumigation,”
[http://www.ars.usda.gov/Research/docs.htm?docid=10408&page=15], accessed Sept. 15, 2006.
6 Ozone Secretariat, Draft Decisions IX/1, Further Adjustments and Amendments to the Montreal
Protocol; IX/2, Critical-use Exemptions for Methyl Bromide (UNEP/OzL.Pro.9/6, 6/10/1997).
7 EPA, Rules and Regulations, “Protection of Stratospheric Ozone; Process for Exempting
Critical Uses of Methyl Bromide for the 2005 Supplemental Request,” Federal Register, vol. 70,
Dec. 13, 2005: 73604.
8 EPA, “Fact Sheet - Final Rule to Create a Critical Use Exemption to the Phaseout of Methyl
U.S. Steps Taken to Acquire CUAs of MeBr
In 1992, methyl bromide (MeBr) became regulated under the 1987 Montreal Protocol
as an ozone-depleting substance (ODS). A stepped-down phaseout of global production
was scheduled for December 31, 2004. The CAA Amendments of 1990 authorized EPA
to regulate MeBr under schedule H of Class-I of ODS in the CAA and in 1993, A U.S.
phaseout of MeBr was scheduled under Title VI, “Protection of Stratospheric Ozone.”9
In early 2003, the agricultural community urged the EPA to secure critical use
exemptions (CUEs) of MeBr for production in a post-2004 regulatory regimen. They
noted that this could be achieved in three ways: (1) by U.S. authority granted under the
Montreal Protocol; (2) deregulation of Protocol-approved quantities by the EPA; and (3)
congressional legislation to codify such actions. In March 2003, the EPA solicited
comments on a proposed rule to establish “exemptions for farmers’ critical uses of
MeBr.”10 Anticipating that Congress might approve implementing legislation, pressure
was put on the EPA by U.S. and international environmental groups who sought a ban on
production of MeBr for all U.S. uses by December 31, 2004. Instead, the EPA filed a
notice of proposed rulemaking, reiterating a decision made at an interim meeting of
Protocol parties that the action sends a “clear market signal” to U.S. chemical industries
and agribusinesses to pursue chemical substitutes or alternative treatments by 2015.11
In May 2003, the EPA initiated a Nomination for Critical Use Exemptions (NCUEs)
to produce MeBr after December 24, 2004. It received 57 petitions from commercial
growers who foresaw no economically feasible substitutes or alternative treatments for
certain agricultural applications in the near term. The petitions were either approved,
returned for additional information, or rejected outright. The EPA concluded that about
11,500 Mt of MeBr would be needed for the 2005 growing season alone.12 It submitted
final NCUEs for 2005 and 2006 to the U.N. Ozone Secretariat, requesting combined
CUAs of 17,383 Mt for those two years.13
Bromide for the Year 2006,”at [http://www.epa.gov/ozone/mbr/FR2006CUE_Factsheet.html].
9 The EPA listed MeBr as a “Class-I ODS” under the Clean Air Act, when it was determined to
have an Ozone Depletion Potential (ODP) of 0.75 (i.e., >0.2). (CFCs-11/12 have an ODP of
10 EPA, “Process for Exempting Critical Uses of Methyl Bromide ... Proposed Rule,” Federal
Register, vol. 69, Aug. 25, 2004: 52366-52402.
11 UNEP, March 2004, Adoption of Decisions, Decision Ex.I/1. Further adjustments relating to
the controlled substance in Annex E, Decision 81, Preamble, “Noting that, by 1 February 2006,
non-Article 5 Parties will submit national management strategies which will send a clear signal
on the phase-out of critical uses of methyl bromide.”
12 BNA, Inc., “Methyl Bromide Production for Export Can Continue Until 2005 under EPA
Rule,” Daily Environmental Report, vol. 82, Apr. 29, 2002, p. A-6.
13 EPA, Notice, “Request for Applications for Essential Use Exemptions to the Production and
Import Phaseout of Ozone Depleting Substances Under the Montreal Protocol for the Years 2006
and 2007,” Federal Register, vol. 69, Oct. 6, 2004: 59918-5990.
The Protocol parties as a whole have not always agreed with U.S. submissions for
CUAs. During international negotiations on production allowances for the 2005 growing
season, some Protocol parties had challenged the EPA’s submission for NCUEs. Because
of uncertainty about future supplies of MeBr for U.S. agricultural businesses, President
Bush and some Members of Congress considered withdrawal from the international
treaty.14 In the wake of U.S. concerns, and some compromises by DOS negotiators, it had
appeared to some observers that the U.S. position had gained greater support among
Protocol parties during negotiations for the 2006 growing season. When submitting U.S.
Nominations for Critical Use Exemptions (NCUEs) for 2007 to the Protocol Secretariat,
the EPA stated that future U.S. demands for MeBr would likely decline due to
introduction of promising alternatives for some applications in the marketplace.15
U.S. Negotiations under the Montreal Protocol. At the 15th Meeting of
Parties to the 1987 Montreal Protocol (MOP) held in November 2003 in Nairobi, Kenya,
the Department of State (DOS) had negotiated NCUEs approved by the EPA for the 2005-
2006 growing seasons. To manufacture MeBr for those NCUEs, the EPA recommended
CUAs of 39% of 1991 baseline production levels for 2005 and 37% for 2006. (See Table
During negotiations, some delegates questioned whether, “for the United States, what was17
being sought was truly essential.” Decisions about final MeBr production allowances
for industrialized countries were deferred until the 16th MOP held in Prague, The Czech
Republic in November 2004. Parties awaited “needs analysis” by the U.N. Environmental
Program (UNEP) Methyl Bromide Technical Options Committee (MBTOC) that would
estimate total international tonnage of MeBr needed for 2005-2006.
An “Extraordinary MOP” (EMOP/1) held in February 2004 in Montreal, Canada,
authorized U.S. CUAs for 2005 at 37.5% of 1991 tonnage level, or 9,562 Mt. This
amount included a supplemental CUA of 2.5%, or 638 Mt and came closer to what the
United States had originally sought for 2005. However, U.S. negotiators were warned
that CUAs could be reduced to 27% of 1991 baseline, or 6,900 Mt, for the 2006 growing
season. Protocol parties at a second meeting (EMOP/2), held in July 2005 in Montreal,th
Canada approved final U.S. CUAs for 2006 at 32%, or 8,160 Mt. At the 17 MOP, held
in December 2005 in Dakar, Senegal Protocol parties approved U.S. CUAs of 26.3%, or
14 The Senate Committee on Foreign Relations considered Treaty Doc. 106-32, decided Oct. 2,
2002, which restricted international trade of MeBr among Montreal Protocol parties except by
exporting and importing licenses approved by Protocol parties. U.S. withdrawal from the treaty
would mean a loss of exporting privileges with other industrialized and Article 5(1) parties.
15 EPA, “Methyl Bromide for U.S. ‘Critical Uses’ Continues Steady Decline Under International
Ozone Layer Protection Treaty,” EPA Newsroom (online), Nov. 13, 2006, available at
[http://yosemite.epa.gov/opa/ad mp r e s s . n s f/4d84d5d9a719de8c85257018005467c2/9cd6a77b0
cdfc7eb85257225005a88ae!OpenDocument], accessed Dec. 6, 2006.
16 EPA, “U.S. Government Nominates Critical Use Exemptions for Methyl Bromide: Materials
Submitted to the Ozone Secretariat of the United Nations, [EPA] Environmental News, Feb. 7,
17 Andrew Revkin, “U.S. Seeks Exemptions for Pesticide, European Union Leads Critics as
Ozone Talks Open in Nairobi,” New York Times, Nov. 11, 2003, p. 3.
6,749 Mt for 2007 growing season, or about 91% of EPA’s request.18 This amount
included 5,100 Mt, or 20% of baseline, for new production and imports (CUAs), and
1,658 Mt, or 6.25%, authorized for CSAs.19 The Parties also approved a supplemental
request of 0.03% of U.S. baseline tonnage, or 7.7 Mt for 2006 uses. At the 18th MOP in
November 2006 in New Delhi, India, the United States was authorized 21% of baseline,
or 5,355 Mt: CUAs were 18% of base line, or 4,595 Mt, and CSAs of 760 Mt. The EPA
submitted NCUEs to the Ozone Secretariat and a combined request of CUAs of 25% of
baseline for 2008-2009. Protocol parties are reviewing NCUEs submitted for 2009.
Table 1. Requested and Allocated U.S. CUAs/CSAs for 2005-2008
(Tonnage/% 2001 U.S. baseline of 25,528 Mt)
EPA Nominated— 9,960 Mt8,889 Mt7,403 Mt6,385 Mt
39% 37% 29% 25%
Protocol Approved 25,528 Mt9,553 Mt8,082 Mt6,749 Mt5,355 Mt
100% 37% 32% 26% 21%
Source: EPA data, 2006, at [http://www.epa.gov/ozone/mbr/], accessed December 11, 2005.
Congressional Legislation. On February 15, 2006, Representative Radanovich
introduced H.R. 1257 to authorize U.S. production of MeBr proposed by EPA for the
2006-2007 growing seasons. The bill was referred to the House Committee on Energy
and Commerce, and to the Subcommittee on Energy and Air Quality.20 No further
legislative action occurred. Agricultural producers argued for annual production
allowances for MeBr through 2015. With continued access to MeBr, they stated, trade
in agricultural commodities would be on “a level playing field in the global marketplace.”
Under the Protocol, Mexico, Brazil, and China (Article 5(1) developing countries) can use
MeBr at agreed upon levels for domestic needs through 2015. Opponents of the bill were
mostly environmental interests who would ban U.S. production of MeBr in the near term.
Further, they have urged the EPA to ban all domestic uses of MeBr by 2015.21
18 EPA, Notice of Proposed Rulemaking: The 2007 Critical Use Exemption from the Phaseout
of Methyl Bromide, July 26, 2006 [Public Hearing, Docket No.: 2005-0538], at
[http://www.epa.gov/ozone/mbr/0721crit.html], accessed Sept. 12, 2006.
19 U.S. CSAs were first discussed at a hearing. See U.S. Congress, House Committee on Energy
and Commerce, Subcommittee on Energy and Air Quality, Methyl Bromide: Update on Achieving
the Requirements of the Clean Air Act and the Montreal Protocol, Hearing, [Serial No. 108-118]
July 21, 2004 (Washington: GPO, 2004).
20 U.S. Congress, House Committee on Government Reform, Subcommittee on Energy and
Resources, Methyl Bromide: Are U.S. Interests Being Served by the Critical Use Exemption
Process? Oversight Hearing, [Briefing Memorandum] Feb. 15, 2006, at [http://reform.house.gov/
ER/Hearings /Eve ntSingle.aspx?EventID=39507].
21 U.S. Congress, House Committee on Energy and Commerce, Subcommittee on Energy and Air
Quality, Status of Methyl Bromide under the Clean Air Act and the Montreal Protocol, Hearing
[Serial No. 108-55], June 3, 2003, (Washington: GPO, 2004).