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EXECUTIVE SUMMARY
The United Nations declared 1998 the International Year of the
Ocean. Activities during the past year have provided a renewed
appreciation for the resources obtained from the ocean, the effects
of human activities on the health of the ocean, and the importance
of the ocean in regulating the world's climate. The more we learn
about ocean processes and ocean life, the more we realize how
critical the ocean will be for the future well-being of humankind.
Human health is one of the areas strongly influenced by the ocean.
There are negative impacts such as the spread of infectious
diseases, coastal weather hazards, and harmful algal blooms, and
positive impacts such as the use of marine organisms to develop new
medical treatments and a better understanding of biological
processes.
In recognition of the International Year of the Ocean, the
National Research Council held a workshop on the Ocean's Role in
Human Health in June, 1998. The workshop brought together members
of the ocean sciences and biomedical communities to identify areas
where improved understanding of marine processes and systems has
the potential to reduce public health risks and enhance our
existing biomedical capabilities. This document serves as an
overview, based partly on discussions at the workshop, of the
impacts of the ocean on human health with emphasis on (1)
elucidating connections between the ocean and human health, (2)
evaluating the present state of knowledge about these connections,
and (3) suggesting how current and future efforts may be directed
so that we can anticipate and respond to future health needs and
threats.1
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Page 1
EXECUTIVE SUMMARY
The United Nations declared 1998 the International Year of the
Ocean. Activities during the past year have provided a renewed
appreciation for the resources obtained from the ocean, the effects
of human activities on the health of the ocean, and the importance
of the ocean in regulating the world's climate. The more we learn
about ocean processes and ocean life, the more we realize how
critical the ocean will be for the future well-being of humankind.
Human health is one of the areas strongly influenced by the ocean.
There are negative impacts such as the spread of infectious
diseases, coastal weather hazards, and harmful algal blooms, and
positive impacts such as the use of marine organisms to develop new
medical treatments and a better understanding of biological
processes.
In recognition of the International Year of the Ocean, the
National Research Council held a workshop on the Ocean's Role in
Human Health in June, 1998. The workshop brought together members
of the ocean sciences and biomedical communities to identify areas
where improved understanding of marine processes and systems has
the potential to reduce public health risks and enhance our
existing biomedical capabilities. This document serves as an
overview, based partly on discussions at the workshop, of the
impacts of the ocean on human health with emphasis on (1)
elucidating connections between the ocean and human health, (2)
evaluating the present state of knowledge about these connections,
and (3) suggesting how current and future efforts may be directed
so that we can anticipate and respond to future health needs and
threats.1
1 Because of
the complex nature of both human health and ocean processes, and
the limited scope of this study, the related issues of secondary
effects of pollution and the contribution of the ocean to the
world's food supply are not examined in this report.
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Connections between the Ocean and
Human Health
Marine Processes that Threaten Public
Health
The ocean acts as a conduit for many human diseases. The
distribution of viral, bacterial, and protozoal agents and algal
toxins in marine habitats depends on the interplay of currents,
tides, and human activities. The primary route of human exposure is
through ingestion of contaminated seafood, but illness can also
result from direct contact with seawater during recreational or
occupational activities and from contact through aerosols (sea
spray) containing toxins.
Disease-causing organisms can be spread by several different
marine processes. Coastal and estuarine circulation patterns
influence the frequency and geographic pattern of harmful algal
blooms. Nutrient loading from heavy run-off also poses problems of
anoxia and contributes to the proliferation of algae. Also,
circulation of waters through estuaries and coastal areas plays a
role in determining where and when the risks of contamination by
human pathogens are highest. Pathogens from human or animal waste
contaminate coastal and estuarine areas through freshwater runoff
from sewers, rivers, and streams. Viruses (e.g., hepatitis A and
poliovirus) and bacteria (E. coli and Salmonella) of
fecal origin become concentrated in filter-feeding shellfish such
as oysters and clams. Marine pathogenic bacteria (e.g., Vibrio
cholera) and harmful algal species can invade new areas through
the transport of organisms in the ballast water of ships. Thus
shipping activities can introduce a disease from one part of the
world into a new location causing ecological, economic, and human
health problems. Harmful algal species can also be transported
great distances by major ocean currents such as the Gulf Stream.
Finally, international trade transmits algal toxins and pathogens
through commerce in seafood.
In addition to these specific health threats from infectious and
toxic organisms, there are both seasonal and periodic public health
concerns that arise from severe weather and climate variability.
Climate and weather are determined through interdependent
atmospheric and oceanic processes. The world ocean functions as a
huge reservoir of heat and moisture that fuels weather systems.
These weather systems in turn affect the ocean by wind-driven
mixing of surface and deep waters and by changes in sea level
dependent on barometric pressure, winds, and melting of polar ice
caps during warm periods.
The most vivid and direct impacts of the ocean on human health
arise in coastal areas that are subject to tsunamis, storm surges,
heavy rainfall and flooding, and severe winds. High water
associated with torrential rains, storm surges, and tsunamis result
in the highest mortality. However, lingering economic losses from
damage caused by severe weather like a tropical storm can cause an
overall decrease in public health in developing countries through
increased poverty and the loss of housing, hospitals, and public
sanitation systems.
The incidence and intensity of severe weather systems are
affected by the recurring climatic patterns known as the El
Niño / Southern Oscillation (ENSO)
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and the North Atlantic Oscillation (NAO). These phenomena
originate from shifts in the temperature and flow of ocean water
masses and affect global weather systems, bringing droughts to some
regions and torrential storms to others. In addition to the direct
effects on coastal areas described above, these weather patterns
can have impacts on inland areas through shifts in temperature and
rainfall patterns which affect the density and distribution of
disease-causing organisms.
The observed increase in global average temperature over the
past century has generated concern that the world may be entering a
period of global warming in excess of normal climatic variation
(Nichols et al., 1995). Such a change in the heat balance of the
ocean-atmosphere system could lead to dramatic effects on climate
and local weather patterns. This has the potential to affect the
frequency and severity of tropical storms and periodic events like
ENSO (Gray, 1984; Gray et al., 1993; Gray et al., 1994; Landsea et
al., 1994). Also, shifts in temperature and rainfall patterns
influence the distribution of organisms that cause human diseases,
including harmful algae, waterborne agents such as the pathogenic
vibrios, and vectors of disease such as mosquitoes that carry
malaria, dengue fever, and yellow fever. There may be public health
effects due to unusual temperature extremes, air pollution, and the
availability of fresh water and food.
Contributions of Marine Biodiversity
to Biomedicine
In addition to recognizing the health problems associated with
the ocean, this report describes how the ocean provides society
with an essential biomedical resource through the rich diversity of
marine organisms. Plants, animals, and microbes have provided
either the source or the concept for more than half of the
pharmaceuticals currently on the market. The emphasis has
traditionally been on using terrestrial organisms, but despite
continued and more sophisticated searches for new bioactive agents,
there has been a decreasing return in molecular diversity, and
hence new drug compounds. At the same time, many of the bacteria
that cause life-threatening disease have become resistant to
existing antibiotics, making the need for new drug discovery more
urgent. Also, new bioactive agents are needed to overcome the
limitations of our current arsenal of drugs for treating cancer and
other diseases. Because the diversity of life at higher taxonomic
levels is greater in the ocean than on land, marine organisms offer
a promising source of novel compounds with therapeutic potential. A
number of these compounds are already under investigation or
development by the pharmaceutical industry for the treatment of
diseases such as cancer. Nevertheless, there are significant
challenges to be surmounted in collecting organisms from marine
environments and uncovering new compounds with potential value as
pharmaceuticals. Meeting these challenges will require cooperation
and new programs that bring together scientists from both the
oceanographic and biomedical communities.
Marine biodiversity also benefits medical research because
scientists use marine organisms as models for basic research on
biological and disease processes.
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Marine organims are valued as experimental models for studies of
essential molecular, cellular, and physiological processes. The
diversity of oceanic life helps scientists investigate and
understand the evolutionary basis of many fundamental processes
such as the biochemical basis of learning and memory, the mechanics
of cell division, and the physiology of salt tolerance in the
kidney. Also, unique properties found in marine organisms
facilitate the investigation of complex biological processes. For
example, scientists have exploited the unusually large diameter of
the giant axon in a squid neuron to study the electrophysiology of
nerve impulses. In addition, marine animal models have provided
insights into the origin of human diseases such as diabetes and
cancer.
Conclusions
In this section we present three approaches to further our
understanding of the ocean's role in human health that cross-cut
the specific issues described in each chapter.
I. Information Resources for Improved
Prediction and Prevention of Marine Public Health Disasters
Prediction and prevention of public health disasters
precipitated by ocean phenomena depend on establishing an
historical baseline of high quality observations. Predictions of
marine events that affect health depend critically on the quality
of the data used to develop and test models. To examine recurring
and long term climate variations, observations need to be collected
regularly over periods long enough to distinguish patterns. This
requires an ongoing commitment to monitoring and analysis from both
funding agencies and scientists. The advent of automated data
gathering of physical and biological measurements has created the
requirement for comprehensive, structured databases. Also, access
to the databases must include query-driven retrieval systems.
Through the establishment of baselines and documentation of trends,
these systems will help researchers evaluate the implications of an
ecological disturbance or a climatological event.
Priorities for Monitoring
Programs
The following activities are important for gathering information
needed to address the health issues discussed in this report:
1. Collection of baseline observations of
physical ocean properties to monitor climate variation on a global
scale.
Climate change represents not only a
variation in global average temperature, but also a patchwork
pattern of change in temperature, severity of storms, rainfall and
drought, ocean circulation, and upwelling frequency. All of these
changes will affect the ecosystems on which many human communities
depend.
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2. Measurement of oceanic (e.g., upper
ocean heat content) and atmospheric (e.g., jet stream level winds,
storm core dynamics) variables to improve tropical storm
predictions.
Although disastrous events such as
tropical storms cannot be prevented, improved predictions can help
reduce the costs. It is estimated that the expense of evacuating a
coastal area in the southern U.S. in preparation for a hurricane is
approaching $1M per mile of coast (OFCM, 1997). Hence better
predictions of the site of landfall could dramatically reduce the
expense of the storm and the disruption of coastal communities.
3. Collection of an organized, ongoing
compilation of health statistics, particularly in developing
countries that lack extensive public health infrastructure, to
allow retrospective analysis of the effects of oceanic events on
human health.
Reduction and prevention of human health
threats from oceanic phenomena requires determination of cause and
effect, which is possible only by correlating oceanographic and
atmospheric data with reliable reporting from the public health
sector. First, it is important that infectious diseases and algal
toxin poisonings by correctly diagnosed. Second, information on the
frequency, location, and date of disease outbreaks needs to be
accurately reported and made available to the international health
community. Finally, the efficacy and comprehensiveness of disease
surveillance programs need to be evaluated. Associations between
environmental events such as El Niño and changes in human
disease patterns will require an historical perspective.
Participation by experts in many fields and by the appropriate
international agencies will be needed to document, evaluate, and
develop mitigation strategies. Professional societies in the
disciplines of microbiology, meteorology, oceanography,
parasitology, and epidemiology should be involved in the
establishment of research priorities and methodological
development.
4. Documentation of harmful algal blooms
(HABs)
The reports of HABs have been increasing,
with higher frequency of occurrence and greater geographic range of
several species since the early 1970s. Accurate species
identification is needed during a bloom to track species dispersal
and identify toxin hazards. Increased monitoring of water
conditions will allow comparisons before, during, and after an
algal bloom to determine the physical, chemical, and biological
factors that promote blooms of specific harmful algal species.
Effective mitigation efforts will depend on the identification of
the causes of the increasing incidence and geographic distribution
of HABs.
II. New Technological Approaches to
Help Reduce Risks to Human Health
New technologies offer greater opportunities to explore and
understand the ocean and marine life. Satellite oceanography and
molecular probes (to monitor both ocean chemistry and the
contamination of coastal waters by pathogens or
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algal toxins) provide more detailed information about marine
environments than previous methods. Piloted and remotely operated
submersible vehicles make it possible to study and retrieve new
species from the underexplored ocean floor. Although great advances
have been made in their development, implementation of these new
technologies has not yet been fully realized.
Priorities for Implementation
Several of the technologies that could help address current and
future health issues include:
1. Drifting and moored sensors (monitored
by satellite), although not a new technology, need to be deployed
more widely to accurately track ocean processes. Similarly,
continued submersible development is needed to study and collect
deep sea organisms.
2. Biological sensors will improve in
situ measurements of biological processes in marien coastal
waters and allow higher sensitivity measurements of water quality
(including specific nutrients, oxygen, pH, species-specific
monitoring of algae and bacteria).
3. DNA probes and antibody-based tests
will provide more sensitive and specific detection of pathogens in
marine waters as a supplement to the current standard, the coliform
test, which acts as an indirect indicator of fecal pollution (i.e.,
sewage).
4. More accurate, cost-effective methods
for detecting algal toxins in seafood, based on the molecular
properties of the toxins.
III. Contributions of Marine Organisms
to Medicine and Research
The diversity of life in the ocean has the potential to
contribute to the development of effective new treatments of human
diseases and a greater understanding of human biology. However, the
level of effort expended to use this marine resource for biomedical
applications has been modest compared to the potential benefits
(NRC, 1994a).
Priorities for Marine Biomedical
Research
Several of the promising areas for marine biomedical research
include:
1. Exploration of marine biodiversity for
discovery of new pharmaceutically-active compounds
The extent of marine biodiversity remains
unknown because of both the relative inaccessibility of the
habitats and, in the case of microorganisms, difficulty in
culturing and classifying new species. Partnerships between
industry and academia need to be encouraged to provide
cross-disciplinary expertise and to offset the expense of
investigating the potential value of marine species in the
development of new therapeutics.
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2. Understanding of the molecular
mechanisms for natural marine toxin action on organisms.
There are three reasons for understanding
the molecular mechanism of marine algal toxins: 1) to provide
structural information needed to develop drugs that will interfere
with the toxin's biological activity, 2) to develop less expensive
methods for detecting toxins in contaminated seafood, and 3) to use
toxins as tools for investigating the biochemistry of the nervous
system.
3. Development of techniques to culture
species with biomedical value.
One limitation on the use of marine
organisms is their availability. Harvesting of species either for
research or for extraction of a biologically active compound is
expensive and may deplete the natural population. Aquaculture, cell
culture, microbial fermentation, and recombinant DNA techniques can
provide alternative sources of material for research and drug
development.
4. Expansion of drug discovery efforts
beyond anti-cancer compounds
Current programs have promoted drug
discovery efforts for cancer therapy through the matching of
compounds from non-traditional sources (such as marine organisms)
with the screening and development potential of the pharmaceutical
industry. Similar approaches would benefit drug discovery efforts
for other disorders including neurodegenerative, cardiovascular,
and infectious diseases.
5. Encourage training and research to
expand our knowledge of marine organisms.
The use of marine organisms in biomedical
research and in drug development depends on knowledge of marine
biology—the natural history, taxonomy, physiology, molecular
biology, and biochemistry of various species. As academic biology
and other science departments become increasingly subdivided into
specialized fields, it is important to encourage a
multidisciplinary approach to exploring the diversity of life in
the ocean and to provide opportunities for students and researchers
to study organisms that are representative of marine diversity.
Pursuit of the priorities outlined above
will promote the development of better strategies for reducing the
health problems arising from marine natural hazards, climate
change, and disease-causing organisms, and will support
opportunities for using marine organisms to develop new treatments
for human diseases.
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Representative terms from entire chapter:
harmful algal
