Jan. 5, 2005
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Flame
Retardant Exposure Linked to House Dust
Common
house dust may be an important source of a potentially dangerous
class of chemicals called polybrominated diphenyl ethers
(PBDEs), according to an exploratory study* by researchers
at the National Institute of Standards and Technology (NIST)
and the Environmental Protection Agency (EPA). Recent studies
by others have found that PBDE concentrations are increasing
rapidly both in the environment and in human blood, fat tissue
and breast milk.
PBDEs
have been used widely in consumer products for years because
they are effective flame retardants, greatly
increasing
the fire safety of products ranging from carpeting and cushions
to televisions, computers and coffee makers. Toxicological
data on PBDEs are still limited, but the compounds have been
implicated in developmental, reproductive, neurotoxicity
and thyroid effects in rats, mice and fish, and may be carcinogenic.
Researchers in Europe and the United States found concentrations
of PBDEs higher in Americans than in Europeans, although
it
is not known if these levels affect human health.
While
some PBDE exposure may accumulate through diet, the new study
found that house dust and the home environment
are likely
additional sources.
The NIST/EPA
survey of 17 homes in the Washington, D.C., and Charleston,
S.C., areas found high
concentrations of
PBDEs
in household dust, ranging from 700 to 30,100 nanograms
per gram. Researchers analyzed both dust from floors
and clothes
dryer lint for 22 variants of commercial PBDEs and found
PBDEs in every sample.
Although
the new study is limited, say researchers, it highlights
the need to study house dust
as the primary
source of PBDE
exposure. In particular, the authors note that small
children are more at risk than adults to dust exposures
since they
are more prone to putting dusty hands and toys in their
mouths.
For further
information, see www.nist.gov/public_affairs/releases/PBDE_dust.htm.
*H.
Stapleton, N. Dodder, J. Offenberg, M. Schantz and S.Wise. “Polybrominated
Diphenyl Ethers in House Dust and Clothes Dryer
Lint.” Environmental
Science and Technology, published online Dec.
29, 2004.
Tiny,
Atom-based Detector Senses Weak Magnetic Fields
A
low-power, magnetic sensor about the size of a grain of rice
that can detect magnetic field changes as small as 50 picoteslas—a
million times weaker than the Earth's magnetic field—has
been demonstrated by researchers at the National Institute
of Standards and Technology (NIST). Described in the Dec.
27 issue of Applied Physics Letters,* the device
can be powered with batteries and is about 100 times smaller
than current
atom-based sensors with similar sensitivities, which typically
weigh several kilograms (about 6 pounds).
The
new magnetic sensor is based on the principles of a NIST
chip-scale atomic
clock, announced in August 2004. Expected
applications for a commercialized version of the new sensor
could include hand-held devices for sensing unexploded
ordnance, precision navigation, geophysical mapping to
locate minerals
or oil, and medical instruments.
Like
the NIST chip-scale clock, the new magnetic sensor can
be fabricated and assembled
on semiconductor wafers
using
existing techniques for making microelectronics and microelectromechanical
systems (MEMS). This offers the potential for low-cost
mass production of sensors about the size of a computer
chip.
When packaged with associated electronics, the researchers
believe the mini magnetometer will measure about 1 cubic
centimeter or about the size of a sugar cube.
Magnetic
fields are produced by the motion of electrons either
in the form of an electrical current or in certain
metals
such as iron, cobalt and nickel. The NIST miniature
magnetometer is sensitive enough to detect a concealed
rifle about
12 meters (40 feet) away or a six-inch-diameter steel
pipeline
up to 35 meters (120 feet) underground. The sensor
works by detecting minute changes in the energy levels
of electrons
in the presence of a magnetic field.
For
further information, see www.nist.gov/public_affairs/releases/CSMagnetometer.htm.
*P.
Schwindt, S. Knappe, V. Shah, L. Hollberg, J. Kitching,
L. Liew, J. Moreland. "Chip-scale atomic magnetometer." Applied
Physics Letters. 27 Dec. 2004
Convention
Center Implosion Site for Radio Experiments
Experiments
aimed at improving emergency radio communications were
performed by researchers from the National Institute
of Standards and Technology (NIST) at the old Washington
Convention Center in downtown Washington, D.C., before,
during and after its implosion on Dec. 18, 2004.
The
NIST work, which supports public safety programs of
the U.S. departments of Homeland Security and Justice,
is intended
to help improve the communications capabilities of first
responders. First responders who rely on radio communications
often lose signals in shielded or complex environments
such as the basements or elevator shafts of buildings.
It also
is very difficult to detect radio signals through the dense
rubble of a building that has collapsed as a result of
a natural disaster or terrorist attack.
To
simulate disaster environments, NIST is using real-world “laboratories”—buildings
that are scheduled to be imploded as part of construction
and recycling projects. The NIST team placed a set of
about 25 battery-operated transmitters at various locations
in
the old Washington Convention Center prior to demolition.
The transmitters emitted signals near the frequency bands
used by emergency personnel and mobile telephones. Scientists
monitored and mapped the strength of signals sent by
the transmitters to receivers outside the building before,
during and after the implosion.
To
detect the weak signals, the researchers used a variety
of techniques, including connecting radio receivers to
metal debris
in the rubble
as improvised antennas and converting radio signals
to visual images like Morse code (see image below). NIST
researchers
hope
to develop reliable, cost-effective tools that can
be retrofitted to existing radio systems to assist emergency
personnel
in locating and perhaps communicating with rescuers
and
other
survivors trapped inside a collapsed building.
For
more information, see www.nist.gov/public_affairs/releases/demolition_dcconv.htm.
Media
Contact:
Laura
Ost, laura.ost@nist.gov,
(301) 975-4034
Novel
Zigzag Shape Gives Sensors Magnetic Appeal
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The
graphic above shows how the direction of magnetization
within a NIST zigzag magnetic sensor follows the
shape of the device. The green and orange areas of
the sensors act like tiny bar magnets with their
north and south poles at a 45-degree angle to the
centerline of the sensor.
Click
here for a high resolution version of this image.
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Scientists
at the National Institute of Standards and Technology (NIST)
have designed tiny magnetic sensors in a "zigzag" shape
that are simpler in design and likely will be cheaper to
make than conventional magnetic sensors used in portable
devices. The new sensors could someday be used to measure
magnetic fields in applications such as compasses, weapons
detection, medicine and non-destructive evaluation of structural
materials.
Described
in the Dec. 13, 2004, issue of Applied Physics Letters,*
the NIST sensors are made of a thin film
of nickel
and iron
and are 35 micrometers long and 5 micrometers wide, with
nanoscale design elements at the edges. The zigzag design
produces the
equivalent of many tiny bar magnets oriented with their north
and south poles at a 45-degree angle to the centerline of
the sensor (see image above). The device senses magnetic
fields
using a small electrical current sent down the centerline.
Tiny changes in the magnetic field surrounding the sensor—such
as when a steel weapon passes near it—will increase
the resistance to the current and will be detected as an
increase
in voltage.
Portable
magnetic sensors typically include multiple aluminum strips
that alternate diagonally across the sensor.
The new
zigzag sensors are expected to produce clearer signals
(less electronic "noise") by confining the current
to the center of the device and by eliminating edge imperfections
that can result in nanoscale magnetic fluctuations.
The
project is part of an interdisciplinary NIST effort
to design nanoscale sensors with improved detection levels.
NIST scientists experimented with sensor width, length
and
other
dimensions to achieve the desired performance. Engineering
of the sensors was supported by theoretical work using
NIST-developed imaging and modeling tools.
*F.C.S.
da Silva, W.C. Uhlig, A.B. Kos, S. Schima, J. Aumentado,
J. Unguris, and D.P. Pappas. Zigzag-shaped magnetic
sensors. Applied Physics Letters, Vol. 85, pp.
6025-6027, Dec. 13, 2004.
Media
Contact:
Laura
Ost, laura.ost@nist.gov,
(301) 975-4034
NIST/EPA
Study Aims at Healthy Indoor Climate
New
building owners might want to double check
the performance of their ventilation systems
before accepting the door keys from their
contractors. A National Institute of Standards
and Technology (NIST) analysis* of a recent
Environmental
Protection Agency (EPA)
survey of 100 representative U.S. public
and commercial buildings found that actual
post-construction ventilation conditions
are often different than expected based
on the building design.
The
analyzed data showed frequent instances of
underventilation, a condition that can cause
poor air quality, occupant discomfort and even
illness, as well as overventilation, a situation
that can boost energy costs dramatically.
The NIST researchers said such findings highlight
the importance of early testing of a ventilation
system's ability to achieve design intent.
The differences between actual versus the predicted
ventilation rates also argue for subsequent
regular maintenance checks. They noted instances
where building engineers could not find ventilation
systems plans or found the ventilation system
equipment itself inaccessible and urged building
designers and operators to remedy the situations.
A
key goal of the U.S. EPA Building Assessment
Survey and Evaluation (BASE) study was to define
the status of the existing U.S. building stock
with respect to indoor air quality, ventilation
and occupant perceptions of environmental conditions.
NIST's analysis and the original data should
be useful for establishing standardized protocols
for future indoor air quality studies, examining
the relationship between symptoms reported by
occupants and building characteristics, and
developing guidance on building design, construction,
operation and maintenance.
*
A. Persily, J. Gorfain, Analysis of Ventilation
Data from the U.S. Environmental Protection
Agency Building Assessment Survey and Evaluation
(BASE) Study, NISTIR 7145, is available
at http://www.bfrl.nist.gov/pdf/BASE-final.pdf.
Media
Contact:
John
Blair, john.blair@nist.gov,
(301) 975-4261
Quick
Links
NIST/TA
Team Up With "Big 3" on Manufacturing
Senior
executives of the U.S. Department of Commerce’s
Technology Administration and the U.S. automotive
industry have signed a memorandum of agreement
establishing a new partnership to facilitate technological
research and technology policy analysis focused
on improving the manufacturing competitiveness
of the U.S. automotive industry. The signing ceremony
took place in December in Southfield, Mich.,
at the headquarters of the United States Council
for Automotive Research (USCAR).
The
partnership, the United States Alliance for Technology
and Engineering
for Automotive Manufacturing
(U.S. A-TEAM), will bring together scientists and
engineers from the Department’s National Institute
of Standards and Technology (NIST), DaimlerChrysler,
Ford Motor Company and General Motors to conduct
precompetitive research activities with the potential
to contribute to the future competitiveness of the
U.S. automotive industry. The
U.S. A-TEAM will focus its initial technical research
efforts in digital/virtual
tools, plant
floor controllers and ergonomics.
The
Department’s
Office of Technology Policy also will work with
the automotive industry to explore new research
and development
and manufacturing production paradigms in the global
automotive industry and their implications for
U.S. policies in areas such as science and technology,
standards, international trade, education and training,
and telecommunications and information technology.
For
further information, see www.nist.gov/public_affairs/releases/auto_mou.htm.
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