Methyl Bromide (MB) has been commercially used as a fumigant since the 1930s (MBTOC, 1994). Known for its versatility, MB is widely applied to control soilborne pests, including nematodes, fungi, weeds, and insects in high-value crops. Additionally, it has been extensively employed for managing pests such as insects and rodents in structures, transportation, and stored commodities. First proposed for postharvest pest control by Mr. Le Goupil in 1932, MB quickly gained popularity, particularly for whole-site fumigation of grain mills and bagged grain stacks, especially in the U.S. and Africa.
What makes MB particularly effective is its gaseous form, which allows it to penetrate effectively across a broad temperature range. Its quick action and ability to dissipate rapidly from treated environments result in minimal disruption to both crop production and commercial operations. This combination of features has made MB a widely adopted and essential fumigant across various industries.
MB was classified as a "controlled substance" under the Montreal Protocol in 1992 (Article 1 and Annex E). This decision arose from growing concerns not only about its contribution to ozone depletion but also its toxicity, safety risks, negative impacts on biodiversity, and potential for water pollution. Consequently, strict regulations were imposed on MB use.
The Protocol outlines four main categories of MB applications, each subject to different legal requirements: Non-QPS (quarantine and pre-shipment) fumigant uses, Laboratory and analytical (L&A) uses, QPS fumigant uses, and MB as a feedstock for manufacturing other chemicals. In 1995 and 1997, control schedules were established for two categories: non-QPS fumigant uses and L&A uses, as specified under Articles 2 and 5. These control measures included allowances for Critical Use Exemptions (CUE), where necessary.
Critical and emergency uses of methyl bromide (MB) may be permitted after its phaseout, provided they meet agreed criteria. For emergency uses, up to 20 metric tonnes may be allowed under Decision IX/7. In such cases, parties are encouraged to utilize existing MB stocks for critical uses, which must be reported to the Ozone Secretariat when a Critical Use Nomination (CUN) is submitted.
Quarantine and pre-shipment (QPS) uses, as well as MB used as a feedstock, are exempt from the reductions and phaseout schedules but remain subject to reporting requirements under the Protocol. Article 2H specifically exempts MB used for QPS treatments, which are generally applied to commodities traded between countries or across quarantine regions within a country. QPS treatments with MB serve several purposes: eliminating quarantine pests on perishable and durable commodities, rendering goods "practically free" of noxious pests and other organisms prior to shipment, and controlling exotic organisms of quarantine significance in soils, structures, and commodities.
Additionally, QPS applications are sometimes used domestically to prevent the spread of exotic pests that have recently been detected in a new region. These periodic treatments aim to contain and manage invasive species within national borders.
Methyl bromide (MB) fumigation remains a preferred treatment for certain perishable and durable commodities in international trade due to its well-established reputation for preventing the spread of quarantine pests. Regulatory authorities worldwide recognize its effectiveness, making it a trusted option in safeguarding against pest incursions.
Pre-shipment treatments target endemic pests, requiring less stringent pest control compared to quarantine treatments. Quarantine treatments, on the other hand, are specifically tailored to address host plants of potentially harmful quarantine pests. These treatments are usually approved through extensive bilateral or regional negotiations, which can take years to finalize. Such a process ensures a high level of protection against the introduction of damaging pests. Replacing MB for quarantine treatments can be challenging, as it has long been a proven, cost-effective, and readily available solution. However, many countries are now publishing regulations that include non-MB treatments, and ongoing research is encouraging the adoption of alternative QPS treatments.
With the phase-out of non-QPS (controlled) uses of MB nearly complete, QPS uses now account for about 97.5% of MB consumption by parties to the Montreal Protocol. As a result, MB for QPS purposes has become the largest non-controlled ozone-depleting substance (ODS) emission under the substances covered by the Protocol.
The phasing out of MB under the Montreal Protocol (Annex E) has contributed to over 30% of the decline in ozone-depleting chemical concentrations in the atmosphere, specifically in terms of Effective Equivalent Stratospheric Chlorine (EESC). This represents the single largest contribution to the recovery of the ozone layer from any chemical to date.
According to Decision IX/6 and others, alternatives to MB must be both technically and economically feasible. While no single chemical or non-chemical alternative has fully replaced MB as a soil fumigant, integrated pest management (IPM) programs, which combine various treatments, have yielded positive results. The effectiveness of soil treatments can be limited by factors such as the availability of active ingredients, climatic conditions, cultural practices, regulatory constraints, and economic considerations (Gullino et al. 2022). However, technically and economically viable alternatives to MB have been identified for nearly all infested structures and durable commodities, including most critical uses since 2005.
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RELATED PUBLICATIONS:
Minimising Quarantine and Pre-shipment (QPS) Uses of Methyl Bromide: Tools for Controlling, Monitoring and Reporting Booklet [July 2016]
This UNEP OzonAction publication is intended to help National Ozone Units understand why the close supervision of Methyl Bromide (MB) use in QPS applications is important for their countries' continued compliance with the Montreal Protocol. It provides information about how to correctly identify MB QPS uses, data management, reporting, stakeholder engagements, and how to control and prevent potential illegal trade of this ODS.
QPS uses of Methyl Bromide and their alternatives Fact Sheet [July 2015]
At the 1992 Meeting of the Parties in Copenhagen, methyl bromide (MB) was included as a controlled substance Ozone Depleting Substance, (ODS). Article 2H of the Protocol specifically excluded Quarantine and Pre-shipment (QPS) uses from control measures as it was considered that there were no alternatives to MB for the diverse range of treatments carried out for QPS.
Tracking Methyl Bromide Consumption for QPS Fact Sheet [July 2015]
Efficient tracking of methyl bromide (MB) use requires close monitoring and a full understanding of both controlled and exempted uses. The IPPC has developed a list of articles typically fumigated with MB for quarantine and pre-shipment (QPS) purposes, which facilitates collection and reporting of MB usage data.
Phasing out Methyl Bromide in Developing Countries: A Success Story and its Challenges Booklet [February 2014]
This booklet addresses the efforts undertaken to phase-out Methyl Bromide in developing countries, the lessons learned and what is pending to reach final phase-out. It further analyses factors that may impact or put at risk the continuity of the phase-out and possible ways to mitigate them.
