Written by international experts in the field, this book sets outthe scientific arguments for and against the use of methyl bromidewhich is both naturally occurring and also a man-made productbelieved to have played a significant role in the depletion of theozone layer. Methyl bromide is a widely used fumigant in agriculture,horticulture and the preservation of structural materials. The fateof this natural and man-made chemical is the focus of much fiercedebate with scientific, political, social, environmental andeconomic arguments for and against the production and use of thischemial. This book does not set out to convince the reader of apredetermined viewpoint. Its purpose is to set out the scientificdebate covering the major relevant fields including agriculture,atmospheric chemistry, oceanography, environmental sciences,chemistry, biology and toxicology, as well as two chapters onpotential alternatives to methyl bromide. The authors who havecontributed to this book are all experts who have played pivotalroles in the international debate on methyl bromide.

Methyl bromide is gaseous pesticide used to fumigate soil, crops, commodity warehouses, and commodity-shipping facilities. Up to 17 million pounds of methyl bromide are used annually in California to treat grapes, almonds, strawberries, and other crops. Methyl bromide is also a known stratospheric ozone depleter and, as such, is scheduled to be phased out of use in the United States by 2005 under the United Nations Montreal Protocol. In California, the use of methyl bromide is regulated by the Department of Pesticide Regulation (DPR), which is responsible for establishing the permit conditions that govern the application of methyl bromide for pest control. The actual permits for use are issued on a site-specific basis by the local county agricultural commissioners. Because of concern for potential adverse health effects, in 1999 DPR developed a draft risk characterization document for inhalation exposure to methyl bromide. The DPR document is intended to support new regulations regarding the agricultural use of this pesticide. The proposed regulations encompass changes to protect children in nearby schools, establish minimum buffer zones around application sites, require notification of nearby residents, and set new limits on hours that fumigation employees may work. The State of California requires that DPR arrange for an external peer review of the scientific basis for all regulations. To this end, the National Research Council (NRC) was asked to review independently the draft risk characterization document prepared by DPR for inhalation exposure to methyl bromide. The task given to NRC's subcommittee on methyl bromide states the following: The subcommittee will perform an independent scientific review of the California Environmental Protection Agency's risk assessment document on methyl bromide. The subcommittee will (1) determine whether all relevant data were considered, (2) determine the appropriateness of the critical studies, (3) consider the mode of action of methyl bromide and its implications in risk assessment, and (4) determine the appropriateness of the exposure assessment and mathematical models used. The subcommittee will also identify data gaps and make recommendations for further research relevant to setting exposure limits for methyl bromide. This report evaluates the toxicological and exposure data on methyl bromide that characterize risks at current exposure levels for field workers and nearby residents. The remainder of this report contains the subcommittee's analysis of DPR's risk characterization for methyl bromide. In Chapter 2, the critical toxicological studies and endpoints identified in the DPR document are evaluated. Chapter 3 summarizes DPR's exposure assessment, and the data quality and modeling techniques employed in its assessment are critiqued. Chapter 4 provides a review of DPR's risk assessment, including the adequacy of the toxicological database DPR used for hazard identification, an analysis of the margin-of-exposure data, and appropriateness of uncertainty factors used by DPR. Chapter 5 contains the subcommittee's conclusions about DPR's risk characterization, highlights data gaps, and makes recommendations for future research.

Distributed to some depository libraries in microfiche.

Provides information on the scientific evidence that emissions from human uses of methyl bromide are depleting the ozone layer; the availability of economical and effective alternatives to the pesticide's agricultural uses; the effects of banning the pesticide on U.S. trade in agricultural commodities; and the EPA's authority under the Clean Air Act to exempt essential uses from the phaseout. Charts, tables and graphs.

Methyl bromide (MeBr), used as a fumigant to control several soil-borne pests in various crops, is a strong ozone depleter, and governments and international agencies aware of the problem have agreed to establish a programme to phase out its use. As a result, some literature on new MeBr alternatives is available that describes the feasibility and disadvantages of each new pest control measure. Some of these publications result from workshops and symposia organized in different countries by the United Nations Environment Programme and by the United Nations Industrial Development Organization. The present report provides information on successful alternatives in some countries or regions where MeBr is being phased out. Although the report often shows the lack of already validated alternatives, particularly for a region such as Africa, the material provides enough elements on the technical and economic success of a variety of alternatives to assist agricultural researchers and extensionists in carrying out further studies and/or for validation. The material can also serve as a reference, particularly for the training of trainers.