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Despite public misgivings,
pesticides are fundamentally important for agricultural productivity, and our
food supply will continue to depend on pest control that uses pesticides and
other organic agrochemicals. Integrated pest management techniques are generally
designed to reduce pesticide use, and will continue to use well-timed and well
selected pesticides to control pest populations to economic levels.
The understanding of the impact of
pesticides on humans and the environment has undergone substantial improvements
in the past two decades. The analytical methods to detect and quantitate
pesticides has improved dramatically as has the ability to predict the transport
and transformation of these contaminants. Yet many problems remain, and the
following examples are presented.
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On July 14, 1991, approximately 19,000 liters of
metam sodium (sodium methyldithiocarbamate) was accidentally released
into the Sacramento River when a railroad car derailed and overturned
into the river. The release resulted in a plume which effectively
sterilized 65 kilometers of the river downstream from the spill. Metam
sodium is a fungicide, nematicide and herbicide with fumigant action
activity due to the primary decomposition product, methyl
isothiocyanate (MITC). Although this compound has been used for over
20 years, the environmental fate of the compound was not well
understood, and issues of plant uptake from water and air,
photochemistry of MITC in air, and the significance of hydrolysis
rates became important due to concerns about exposure to persons
living near the spill site.
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In 1991 the General Accounting Office released a
study entitled "Pesticides: EPA Could Do More to Minimize
Groundwater Contamination". A large part of this study discussed
the improvements necessary to understand sorption and transport of
pesticides. Pesticides are found in groundwater, and additional
research is needed to understand transport processes.
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Benomyl is an important fungicide for a variety of
fruit products, and has been used extensively for over 30 years. Yet
in the past four years, serious problems have arisen due to
unexplained phytotoxic effects. The result has been a large number of
lawsuit.; which have resulted in over $500 million of settlement
costs. In this case, additional research is required to understand the
effects of the formulations of this chemical on plants.
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Methyl bromide is a critically important fumigant
for a variety of high-value crops. However, because of its volatility
and application methods, up to 80% is released to the atmosphere.
Concerns about methyl bromide and stratospheric ozone depletion have
caused the U.S. and other major industrialized nations to move towards
phase out of this fumigant, which is likely to cause serious impacts
for those crops that require fumigation. If better methods can be
developed to control atmospheric release, it is possible that
continued use may be allowed for those crops where no alternatives
exist. This requires a better understanding of the environmental
chemistry of methyl bromide, both in regard to its degradation in
soils and its transport under a variety of conditions in soils. |
These examples highlight the breadth of important
research still required for the efficient and effective use of pesticides in the
future. By bringing together a group of environmental chemists and toxicologists
whose approaches span fundamental to applied research perspectives on these
topics, W-45 can make a significant contribution to understanding the
transformation, exposure, and effects of pesticide residues.
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