Plant Genome
Researchers working on the plant genome project are respectful of its
more celebrated sibling, the human genome project, but they also can't help
being a bit envious in a good-natured sort of way. The U.S. Department of
Agriculture's Plant Genome Research Program is trying to map up to 40 different
genomes at a fraction of the cost it takes to map human DNA.
"Would that we could have their budget," said Jerry Miksche,
head of the U.S. Department of Agriculture's Plant Genome Research Program.
"But then, humans get cancer. Plants don't." Still, Miksche says,
the efforts cooperate closely and share the latest mapping techniques and
processes.
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Green genes. DNA mapping of loblolly pines may give clues
to protecting forests. North Carolina State University |
The federal agency started to develop the plant genome project in 1987,
but funding wasn't approved until the 1990 farm bill passed Congress. Then,
in 1991, about $14 million became available, and in 1992, another $13 million
was disbursed to 97 grantees. "We really need about ten times that
amount, at least $100 million for five years, to meet our goals," notes
Miksche. His goal: "By 1996, I want to put genes that improve agriculture
in the hands of crop breeders." That means a plethora of genetically
altered food and plant products on the horizon.
What makes the program so arduous is that although scientists believe
a typical plant has approximately 50,000-plus genes, fewer than a human
genome, plant DNA varies widely across species, as would be expected. Different
pines may share 90% of their genes, and grasses like wheat and barley may
be substantially similar, but there is little genetic agreement between
corn, peanuts, and cottonwood trees.
Another problem has been choosing the species to study. "If we target
soybeans, then the corn people and other commodity groups go bonkers,"
Miksche says. The answer, so far, has been to spread funding to academic
and federal researchers in 33 states. Among the states with the biggest
contracts are California, Michigan, Iowa, North Carolina, Washington, and
Texas.
Still, the fledgling program is counting some successes and a lot of
enthusiasm. Efforts are underway to find markers for every million nucleotides
in the genomes of dozens of major crops and trees. And the federal repository
for plant genome information, the National Agricultural Library, is set
to officially open soon in Beltsville, Maryland.
The University of Georgia is in the middle of a major project to map
the genome of a peanut. Researchers at the University of Washington are
producing what they dub "super trees." Using the information they
have learned from mapping cottonwood trees, they have increased their growing
time to the point that they resemble an annual harvest of plants. They hope
to use the trees as a new source of fiber for pulp and paper makers and,
eventually, for biofuels.
At Texas Tech University, scientists have used their own information,
as well as that from the National Agricultural Library, to create new plants,
such as a variety of wheat, that are able to withstand intense weather fluctuations--hot
to cold and drought to flooding. Texas Tech's onions can even grow in freezing
temperatures.
Perhaps one of the largest projects is the North American Barley Genome
Mapping Project, involving 50 scientists in 26 university and federal laboratories
in the United States and Canada. The reproductive and breeding characteristics
of barley make it one of the top crop plants used for genetic map modeling.
The goal is to identify as many economically important barley genes as possible
and determine where they are located among the plant's seven pairs of chromosomes.
This mapping will enable growers to produce better plants by manipulating
genes in barley that promote high yield, malting and brewing quality, nutritional
value, stress hardiness, and pest resistance.
Especially promising are efforts to find genes that will reduce the need
for pesticides and fertilizers. Using a technique called mapped-based cloning,
Cornell University researcher Steven Tanksley has recently located the gene
that allows tomatoes to resist a common disease produced by Pseudomonas
bacteria. The next step will be to implant that gene in plants that cannot
fight off the pathogen. Researchers at Harvard University and USDA's Agricultural
Research Center are working on characterizing the complex genetic system
that allows legumes such as soybeans, garden peas, and beans to help fix
nitrogen in the soil. Enhancing the symbiosis between a plant and its neighboring
microorganisms could reduce the need for fertilizers.
New techniques in gene mapping are making plant mapping easier. To construct
genetic maps of forest trees, North Carolina State University's Forest Biotechnology
Research Consortium is using a technique called random amplified polymorphic
DNA (RAPD) developed by DuPont. The RAPD technology allows researchers to
duplicate very short pieces of DNA from a loblolly pine, then compare genetic
variations between these bits and other sections. Once hundreds of these
genetic variations are plotted and their associations with other sections
of DNA determined, a genetic map emerges that allows scientists to determine
where genes fall in relation to markers. Ronald Sederoff, a professor of
forestry and genetics, said that only a year ago mapping a loblolly pine
would have taken four years and $1 million. This spring, researchers mapped
it using RAPD in 60 days, at a fraction of the cost. Another technique called
amplified fragment length polymorphic is also on the horizon, according
to Miksche. It's much like RAPD, but even faster and more discriminating.
Efforts to map plant genomes have been aided by the agricultural industry,
but their findings are often private, Miksche said. The controversy that
has sprung from one of their efforts, the famous "Flavor Saver"
tomato, however, portends future public debate over the safety and efficacy
of genetically altered food. Miksche said he is ready for "a good public
discussion," but hopes that it is "waged on scientific rather
than emotional grounds."
A Healthy Peace in the Middle East
More than 50 senior scientists from academic institutions and government
agencies from nine Middle East countries (Bahrain, Egypt, Israel, Jordan,
Kuwait, Lebanon, Saudi Arabia, the United Arab Emirates, and Yemen) and
from the occupied territories on the West Bank and the Gaza Strip, along
with U.S. and Canadian scientists, met for the first time to address environmental
health risks in the Middle East. The scientists gathered in Cairo September
6-11 to attend the Environmental Health Conference for the Middle East
Region. The conference was hosted by Cairo University and sponsored by the
Fogarty International Center of the National Institutes of Health, the International
Development Research Centre of Canada, and NIEHS.
Middle East meets West. Participants of the
conference represented Bahrain, Egypt, Gaza Strip, Israel, Jordan, Kuwait,
Saudi Arabia, and the United States. |
The purpose of the conference was to identify and seek possible interventions
for environmental health risks that are unique to the individual countries
in the Middle East or that present significantly elevated threats to occupational
or environmental health. Misuse of pesticides and other agricultural chemicals,
disposal of solid and chemical wastes, urban air pollution, water quality,
environmental impacts of industrialization, and the adverse effects of wind-blown
dusts and intense heat were identified as posing serious public health problems
in the region. Several participants noted that infectious diseases associated
with poor sanitation, food contamination, and overcrowding remain major
causes of morbidity and mortality in many areas of the Middle East.
Scientists from the Middle East expressed concern and frustration about
the fact that the dramatic environmental impacts of population changes and
agricultural, technological, and industrial advances in the region have
been identified and characterized by scientists but are apparently unrecognized
by government officials and the general public. In response to this concern,
participants proposed the formation of a committee of scientists who will
meet regularly to address specific environmental and occupational health
risks that exist in the Middle East and to develop strategies to reduce
these risks.
The scientists stressed that the committee members would have the expertise
to design programs that protect human health but that would not threaten
the processes of economic and industrial development or the social, cultural,
and religious values of the nations in the region. Because the committee
includes wide regional representation, environmental concerns that affect
several countries can be resolved by programs that cross national borders.
The conference took place just as the intention of the Palestinian Liberation
Organization and Israel to seek a peace accord was announced. As news of
the potential agreement reached Cairo, it gave added impetus to the creation
of the regional committee. As one participant pointed out on the closing
day of the conference, "We all come from developing countries but we
are not from poor countries. We each have an obligation as scientists to
convince our governmental leaders that our effort is an important part of
the peace process and must be maintained as a regional effort."
Browner and Babbitt Meet the Press
EPA Administrator Carol Browner and Interior Secretary Bruce Babbitt
faced tough questions on the Superfund law, the Endangered Species Act,
and other issues at a meeting of environmental journalists held October
22-24.
Browner and Babbitt spoke separately on the two laws, both of which are
up for reauthorization, at the Third Annual Meeting of the Society of Environmental
Journalists held at Duke University. Browner outlined three areas of reform
in the Superfund law to be presented to Congress. First, she said, the process
of determining which sites get cleaned up and who pays for it needs to be
made more fair. Browner emphasized goals to decrease litigation including
limits on liability of people who contribute only small amounts to toxic
sites and a streamlined settlement process. Second, the cleanup process
needs to be made more efficient and consistent. Third, Browner said that
more community involvement is needed in the cleanup of hazardous waste sites
and in decisions over future use of remediated dump sites. Said Browner,
"EPA needs to listen to the community right from the start about how
the land should be used in the future. That will help us determine the remedy.
Where an industrial plant is going to move in, it may not make sense to
clean up every trace of contamination--but if you're planning to build a
school or a home or a playground on that site, that's a different story."
Carol Browner--Community involvement is key
to good environmental regulation. |
Browner detailed her goals to make EPA more responsive to the needs of
the public by eliminating gridlock and red tape, emphasizing pollution prevention,
increasing community involvement, and outreach and communication to the
public. She discussed several major areas of congressional debate in which
EPA will play a substantial role in forming policy including food safety,
the Clean Water Act, and the Safe Drinking Water Act.
Browner promised the EPA would reform "our antiquated regulatory
system" of pesticides by seeking stiffer penalties for pesticide manufacturers
who don't cooperate with EPA inquiries. She proposed a "registration
sunset" of 15 years during which time the EPA could monitor a chemical's
safety and after which manufacturers would have to supply research results
to the EPA to maintain registration of their products. "That's putting
the burden on the people who have the information to send it to us rather
than us having to reinvent the wheel," she said.
Browner said the EPA is seeking to strengthen the two laws specifically
concerned with water pollution by focusing on runoff and other nonpoint
sources and by building pollution prevention, technological innovation,
and community participation into the laws.
Bruce Babbitt--The rights of citizens to a
healthy environment must be balanced with the rights of individual property
owners. |
In his speech on the renewal of the federal Endangered Species Act, originally
passed in 1973, Babbitt focused on opposition to the act by the Wise Use
movement and their attempts to codify compensation by the government for
environmental regulations that infringe on personal property rights in H.R.
1388, the Just Compensation Act of 1993. Babbitt attacked the act, which
would give property owners the right to demand reimbursement of cleanup
costs and other environmental measures from the federal government, saying,
"The maxim 'make polluters pay' would be replaced by a new legal rule:
'it pays to pollute; the government will reimburse your costs.'"
Babbitt cited examples of the implications of what he deemed "this
proposed raid on the public treasury" including a situation in the
Kesterson National Wildlife refuge in California in which polluted runoff
waters caused massive numbers of ducks and geese to die. Under H.R. 1388,
farmers forced to clean up irrigation discharges could demand reimbursement
from the Interior Department. In another situation, the National Marine
Fisheries Service issued a regulation requiring shrimpers to use a turtle
exclusion device to protect endangered Kemp Ridley sea turtles from entaglement
and death in their nets. H.R. 1388 would require the government to pay for
costs of compliance.
Babbitt compared environmental regulations to planning and zoning laws
which sometimes limit the freedoms of individual property owners in the
interest of providing benefits to the whole community. "Regulatory
actions taken for a valid public purpose have had some consequences that
inconvenience people," he said.
Babbitt said that there is no evidence that the habitat conservation
provisions of the Endangered Species Act have placed widespread hardship
on landowners. Said Babbitt, "I can't predict the future, but I can
say that in the 20 years that the Endangered Species Act has been in place,
and despite the fact that more than 800 species throughout the U.S. are
now protected by it, not one instance has yet occurred in which a landowner
anywhere was so affected by the requirements of the Endangered Species Act
that he has taken advantage of the claims court to seek compensation for
a governmental taking of his property."
Among the proposals Babbitt offered that would conserve habitats while
imposing the least burden on private lands are use of public lands whenever
possible as habitat reserves, mitigation fees paid by developers which are
used to pay for conservation measures on lands set aside as reserves, and
new approaches to land management such as density transfers which allow
more dense development in exchange for preserving open space.
At the conference, attended by more than 200 environmental journalists,
including 14 minority journalist fellows, Browner commended the press for
"helping Americans to see the connections between environmental issues
and their own lives."
Percs of the Job
On 22 September 1993, the EPA announced that contamination of indoor
air and groundwater by perchloroethylene (perc), the most widely used solvent
in the dry-cleaning industry, presents problems that warrant additional
federal actions and promulgated a final rule aiming to reduce cancer risks
among workers exposed to the chemical.
Perc has been shown to be carcinogenic in laboratory animals and according
to the International Agency for Research on Cancer, "is possibly carcinogenic
to humans." Perc has a generally noticeable and detectable odor at
50 ppm. The major short- and intermediate-term exposure responses to perc
are reported to be central nervous system depression. Irritation of the
eyes, nose, and throat are common. Symptoms of exposure include nausea,
headache, anorexia, vertigo, dizziness, and euphoria. In some cases death
has occurred due to anesthesia and narcosis.
According to Peter Infante, director of the Occupational Safety and Health
Administration's Office of Standards and Review, "the final rule standard
for occupational exposure to 25 ppm of perc was promulgated by OSHA in 1989
but was vacated by the circuit court on 7 July 1992, largely because the
court did not agree to simultaneous standards setting for multiple chemicals."
Thus the OSHA standard reverted back to 100 ppm. The EPA rule calls for
a reduction in perc emissions and is the first national emissions standard
for hazardous air pollutants (NESHAP) issued by EPA to regulate 189 toxic
chemicals under the 1990 Clean Air Act.
The new EPA rule applies to businesses that gross more than $75,000 a
year and bans new purchases of transfer machines, which consist of separate
washers and dryers. All cleaners are required to install dry-to-dry machines
when existing equipment is replaced, which combine washing and drying in
the same place and emit considerably less perc. EPA expects the rule will
cut fugitive perc emissions in half. For large dry cleaners that potentially
emit 10 tons of perc a year, room enclosures will be required for transfer
operations of solvent-laden clothes from washers to dryers.
According to the U. S. International Trade Commission, nearly 242,000
pounds of perc were produced and used in the United States in 1992. In the
first half of 1993, close to 154,000 pounds were manufactured, representing
a 27% increase. In addition to use as a dry-cleaning solvent, perc is used
for metal degreasing, as a general solvent, and has been used against nematodes
and trematodes in animals and humans.
According to an EPA source, the agency considered seeking an extension
of the court deadline for the final rule to more fully investigate perc
issues. However, administrators believed such a delay would have postponed
the health and environmental benefits of the rule for an extended and unacceptable
period of time. EPA determined that the best environmental protection would
be achieved by issuing the rule as expeditiously as possible and deciding
subsequently how to best address remaining indoor air pollution and groundwater
contamination associated with perc dry cleaners. To that end, EPA convened
a public meeting November 3-4 at the New York-Pennsylvania Hotel in
New York, which was attended by 90 people.
Lyme Vaccine Makes Outdoors Safe Again
Lyme disease has stricken 50,000 Americans since it was discovered in
1976. Now a group of researchers at Yale University have developed a vaccine
against Lyme disease that may allow people living in high-risk areas to
again enjoy the outdoors.
"You constantly have to think about it; you worry when your grandchildren
go outside, and do tick checks every night," said Ellen Jacko of Block
Island, Rhode Island, where the vaccine will be tested. "I'm old enough
to remember polio. It reminds me of the way parents were afraid to let kids
go into the swimming pool."
Although Lyme disease is easily treated early in the course of the illness,
its first symptoms are often overlooked. In later stages Lyme can produce
neurologic problems, arthritis, and abnormal heart rhythms. Alan Elwell,
a resident of Block Island, said that one of his sons missed a year of school
due to paralysis from Lyme and a second son was rushed to the hospital with
heart problems from the disease. "We all have our horror stories,"
he said.
The disease is a major problem in areas where ticks, small rodents, and
deer are prevalent. Many people in the coastal Northeast have been infected,
as well as people in parts of New Jersey, California, and Minnesota. On
Block Island, which is mostly wild and undeveloped and is home to more than
700 deer, 1 in 20 people contract Lyme disease each summer.
Because people who contract Lyme disease and recover without the aid
of antibiotics are immune to subsequent infections, researchers knew it
was possible to develop a vaccine. The problem was that some of the worst
symptoms of the disease were believed to be due to an over-agressive immune
response, making it impossible to use the whole spirochete organism to produce
the vaccine.
Researchers quickly focused their attention on a protein of the spirochete
that causes Lyme. The protein, called OSP-A, was isolated, its gene cloned
and inserted into E. coli, and the protein mass produced by the bacteria.
Tests in animals showed that the vaccine made from this protein not only
cured the disease, it cured any infected ticks on the animal.
"This is a vaccine that works in a unique way," said Andrew
Spielman of the Harvard School of Public Health. "It kills the organism
in the gut of the tick when it ingests a blood meal."
So far, testing suggests that the vaccine does not provoke aberrant immune
reactions thought to contribute to Lyme arthritis and neurologic effects
of the disease such as Bell's palsy, a temporary paralysis of the facial
muscles. Although some people treated with the OSP-A vaccine have produced
unusually high levels of antibodies, Fred Kantor of Yale University believes
that these high levels of antibodies simply indicate that such people have
been infected for a long time and have organisms in areas of their bodies
where the immune system cannot get to them.
"Could the vaccine cause a chronic relapsing disease or an adverse
reaction?" said Kantor. "I suppose it could, but the evidence
is that it doesn't happen. I feel the chances of a problem are remote enough
that I will be happy to take it."
Mapping out Health
Researchers at NIEHS have been exploring a system that uses geographic
information for environmental health research. A geographic information
system (GIS) may potentially be used to characterize environmental exposures
in relation to demographic variables for specific population groups, identify
populations at high risk for environmental disease to target prevention
programs, and analyze environmental epidemiological data to generate or
test specific hypotheses. A recent seminar organized by NIEHS and the North
Carolina Department of Environment, Health and Natural Resources (NCDEHNR)
brought researchers from local universities and other organizations together
to discuss research involving GIS.
A GIS can be defined as a computer system of hardware, software, and
procedures designed to support the capture, management, manipulation, analysis,
modeling, display (mapping), and output of data by geographic location.
For any application there are five generic questions that a GIS can answer:
What is at a particular location? Where is a location that meets a particular
condition? What has changed at the location since a specific time or event?
What spatial patterns exist? What if specific events occur or a population
is exposed? Many of these applications are useful for environmental health
research.
Using GIS to describe potential environmental exposures by location,
race, and socioeconomic factors within specific population groups is essential
to documenting problems related to environmental equity. NIEHS has begun
a GIS project to identify and gather environmental exposure and demographic
databases to examine this issue. Examples of exposure databases include
several EPA files such as the Toxic Releases Inventory (TRI), which includes
yearly data on the release of 300 toxic chemicals, and CERCLIS and RCRIS,
which include information on the location of waste sites. The demographic
information is contained in the 1990 U.S. Census. Exposure databases include
spatial information that allows for an analysis of potential toxic exposures
by state, county, and census block groups and can be correlated with the
available census variables including race and income level. Currently, these
analyses are being carried out in several North Carolina counties as well
as counties in California and West Virginia. The results will be presented
at the "Symposium on Health Research and Needs to Ensure Environmental
Justice," scheduled for February 10-12 in Washington, DC.
Toxic towns. Geographic information systems
enable researchers to follow trends in environmental health. Brent Cooke |
Last year NIEHS funded a study conducted by the NCDEHNR that took advantage
of GIS methodology to identify populations at high risk for childhood lead
poisoning. In this study, numerous risk factors with spatial identifiers
known to be related to childhood lead poisoning were identified and entered
into a model to highlight geographic areas that contain environmental and
socioeconomic risk factors for lead poisoning. The data on socioeconomic
risk factors came from the 1990 U.S. Census. These risk factors included
per capita income, percent housing built before 1950, percent African-American
population, a poverty index (which was a combination of percent female-headed
households with children under 18 years, percent homes owner-occupied, and
percent of children under 6 years old in poverty), percent of population
receiving public assistance, and median house value. Other databases were
evaluated for their use in the model, including TRI to identify environmental
point source releases of lead, the road network system to identify proximity
to major roads, and EPA's STORET and AIRS databases, which include water
and air quality data. The analysis was performed for several counties within
North Carolina down to the census-block group level. The results yielded
a spectrum of low- to high-risk block groups within the counties. This methodology
needs to be validated in the field by sampling predicted high- and low-risk
populations and comparing the actual risk measured by blood lead levels
with the risk predicted by the model.
Although GIS has not been used extensively in environmental epidemiology,
studies to generate and test hypotheses are beginning to emerge. As environmental
exposure databases compatible with GIS are developed, linkages will be possible
with health and disease data. Much of the health and disease data can be
related to spatial/geographic variables; this primarily involves the use
of addresses of residence or information to identify census tract or block,
county, or zip code. Databases of interest include cancer and birth defects
registries, mortality files, hospital discharge files, and other survey
data or registries. The NCDEHNR has embarked on several environmental epidemiologic
studies using GIS. One such study includes an analysis of brain cancer (from
the North Carolina Cancer Registry) and proximity of residence to electric
power lines (surrogate of exposure to electric and magnetic fields). Examples
of other studies that might be considered include childhood asthma related
to environmental exposures, breast cancer related to environmental and demographic
factors, and birth defects related to living near hazardous waste sites.
Through a Glass, Darkly
Lately it appears that even a substance as ubiquitous as glass wool (fiberglass)
is not insulated from controversy. The potential listing of glass wool in
the Seventh Annual Report on Carcinogens has government and industry scientists
at odds over the material's potential for causing cancer.
The Annual Report on Carcinogens is mandated by Congress as part of the
Community Mental Health Extension Centers Act of 1978 and prepared by the
National Toxicology Program. The report lists all substances that are either
known carcinogens or may reasonably be anticipated to be carcinogens. Glass
wool has been recommended for listing in the report because of evidence
of its carcinogenicity in experimental animals (rats and hamsters) published
in an International Agency for Research on Cancer monograph in 1988. Following
a 1990 notice in the Federal Register that the NTP was planning to
list glass wool in the annual report, the North American Insulation Manufacturers
Association (NAIMA) submitted several petitions to the Secretary of Health
and Human Services requesting a deferral of the listing pending a reexamination
of the scientific studies assessing the carcinogenicity of glass wool and
review of the criteria used by the NTP to list substances. A reexamination
and review are underway.
Currently the criteria for listing a substance in the Annual Report on
Carcinogens are based on those used by IARC for classifying carcinogens.
For a substance to be considered a known carcinogen, the criteria are "sufficient
evidence of carcinogenicity" from studies in humans "which indicates
a causal relationship between the agent and human cancer." For a substance
to be reasonably anticipated to be a carcinogen, the criteria are "limited
evidence of carcinogenicity" from studies in humans, "which indicates
that causal interpretation is credible, but that alternative explanations,
such as chance, bias, or confounding, could not adequately be excluded,"
or "sufficient evidence of carcinogenicity" from studies in experimental
animals "which indicates that an increased incidence of malignant tumors
in multiple species or strains, or in multiple experiments (preferably with
different routes of administration or using different dose levels), or to
an unusual degree with regard to incidence, site or type of tumor, or age
at onset." Additional evidence may be provided by data concerning dose-
response effects as well as information on mutagenicity or chemical structure.
The controversy surrounding the listing of glass wool concerns whether
inhalation studies in the rodents are the only appropriate model in rats
by which to evaluate glass wool's carcinogenic potential in humans. The
bone of contention between government and industry is the route of exposure
to glass wool by which rats are subjected during testing. The rat is an
obligate nose breather, whereas humans breathe through the nose and mouth.
In addition to inhalation studies, rats and hamsters were given intraperitoneal
injections and intratracheal instillations of glass wool fibers. According
to NAIMA, this route of administration artificially places high concentrations
of fibers at a target site and avoids the natural defense mechanism of the
rat. NAIMA contends that only studies of rodents exposed to glass wool by
inhalation should be considered in evaluating its toxicity. Although tumors
have been produced in most glass wool inhalation studies in rodents, tumors
have not been observed at statistically significant levels when compared
to controls.
Intraperitoneal injection studies in rats and intratracheal instillation
studies in rats and hamsters have produced significant numbers of tumors,
including mesotheliomas, sarcomas, and, rarely, carcinomas. It is on the
basis of these studies that IARC reported that although there is inadequate
evidence for the carcinogenicity of glass wool in human epidemiology studies,
there is sufficient evidence in experimental animals to consider glass wool
potentially carcinogenic to humans. The view of the NTP is that listing
a substance in the annual report is a method of hazard identification and
one of the first steps taken in determining the risk associated with exposure
to an environmental agent. The listing of glass wool in the Annual Report
on Carcinogens is based on a "strength of the evidence" evaluation
which the NTP concluded glass wool met.
The selection of glass wool for listing as a substance reasonably anticipated
to be a carcinogen has been reviewed by two federal scientific review groups
that evaluate candidate substances to ensure they meet the criteria for
inclusion in the annual report. Both groups determined that glass wool meets
the criteria and recommended it be listed.
Last Update:August 18, 1998