LETTERS TO THE EDITORS
More than Amazing
To the Editors:
Gordon Gribble’s article "Amazing Organohalogens"
(July-August) gives considerable attention to natural sources of
organohalogens, but leaves out a major environmental problem that
may be on the horizon: The bulk of the polluting emissions of methyl
bromide and some other organohalogens in the atmosphere appears to
be coming from the oceans.
In 1998 the World Meteorological Organization published a report
showing that almost 50 percent of the methyl bromide in the
atmosphere is emitted by microorganisms in the ocean (Report
No. 44, "Scientific Assessment of Ozone Depletion"). This
effect may be aggravated by the increasing use of fertilizers that
release bioactive nitrogen, which reaches the oceans and effectively
force-feeds the microorganisms. The amount of bioactive nitrogen
doubled between 1900 and 2000, and has been increasing at an
escalating rate according to a recent conference report
(Science 2001 294:1268-1269). The emissions of
organohalogens from the oceans are likely to be increasing at the
same pace.
In addition to organohalogens, microorganisms in the ocean also emit
other greenhouse gases—so the increasing release of bioactive
nitrogen could be a major trigger for climate change as well as
ozone depletion. The increasing level of bioactive nitrogen is also
being cited as a cause of dead zones in the ocean due to microbial
overgrowth. Perhaps the major environmental problem needing a call
for action is the control of fertilizer nitrogen.
James A. Singmaster III
Fremont, California