Chemical and biological terrorism is quickly
moving off the paperback-thriller page and the movie screen into the real world. Last May,
only four days after President Clinton announced a presidential directive to strengthen
the government's management of chemical and biological crises, The New York Times revealed
that the Aum Shinrikyo cult, which in 1995 killed a dozen people by releasing nerve gas in
Tokyo subways, had on nine previous occasions sprayed deadly organisms, including anthrax,
over wide areas of Tokyo and nearby U.S. military bases. Bad weather and weak strains of
germs apparently blunted those attacks.
 EETD's Helmut Feustel, Joan Daisey and Rich Sextro
-- shown here holding a gas mask -- are working to mitigate the effects of terrorist
attacks before they happen.
Photo by Don Fike
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"So far our domestic terrorists seem to prefer bombs," says Joan Daisey of
Berkeley Lab's Environmental Energy Technologies Division (EETD), "but an effective
chemical or biological attack, although a rare event, would have terrible consequences. We
can't ignore the possibility."
Since 1996 the Department of Energy has mounted a multi-laboratory effort to improve
response to terrorist attack through its Chemical and Biological Nonproliferation Program.
One area of study is known as "Transport and Fate" -- an innocent (if
ominous-sounding) term for what happens to gases and particles as they travel through
buildings, subways and urban areas.
"Our goal is to support incident-response teams," Daisey explains, "not
only by helping them plan what to do in real time, but by seeing what modifications can be
made to mitigate possible effects in advance."
Transport and Fate team members began by surveying virtually all existing computer
models that could simulate chemical and biological releases in an urban environment --
even though none of the models were designed with terrorism in mind.
The aim is "to provide rules of thumb to first responders," says Daisey.
"Because we need to get something out there right away, on the first cut we assume
only air flow matters, that there are no losses of the chemical or biological agent."
The next step is to refine the models. "On the next cut, we need to know where the
contaminants go. For one thing, that tells us where to put detectors."
Of the four DOE national laboratories in the Transport and Fate collaboration, says
Daisey, Los Alamos and Livermore are concentrating on outdoor and urban areas, Argonne is
studying subways, and Berkeley Lab studies buildings.
All the labs are working to develop state-of-the-art modeling capabilities, which will
be tested in case studies.
Subways have peculiar problems, including the piston effects of trains moving in
tunnels and the sometimes subtle interconnections of subways, buildings, and streets. As
for outdoor spaces, "even though pollution studies have driven outdoor models for 50
years, there are still unanswered questions," Daisey says.
Energy-efficient buildings have been a major research area for EETD since the oil
crises of the 1970s. Over a period of eight years, an international team led by Helmut
Feustel of EETD developed a computer model dubbed COMIS (Conjunction of Multizone
Infiltration Specialists), which treats buildings as interlacing systems of paths along
which air masses flow among hundreds of separately defined zones. COMIS is the basis for
DOE's Transport and Fate work on interiors.
Despite many years of work, the COMIS model must be extended, although, says Daisey,
"we know where many of the holes are. We haven't done well with stairwells, for
example, because of the temperature gradient, and as yet we can't predict dispersion in
large rooms where the air is not well mixed." Modeling only a minute of real time
with adequate computational fluid dynamics can take a long time; new techniques are needed
-- specifically "better and faster lumped parameter modules" -- to extend the
COMIS model.
When it comes to modeling, "accounting for deposition losses of chemicals is
relatively straightforward; we have to study chemical interactions, including absorption
and desorption," Daisey says, but of the chemicals and gases used by terrorists,
"a lot of them are just glorified pesticides." She notes that although chemicals
are typically quick acting, if released inside a building they may reach the outside only
very slowly.
Biological agents are a different matter. "In the current COMIS model we treat
bio-aerosols as collections of particles with a single average deposition rate, but we are
now integrating the MIAQ4 model developed by Bill Nazaroff and Glenn Cass to account for
particle deposition by size, surface orientation and air turbulence. Particle size, air
movement, and air filtration all affect deposition losses in buildings." Nazaroff is
with Berkeley Lab's EETD and UC Berkeley, and Cass is with Cal Tech.
Since air in most buildings is recirculated, germs may be widely transported within
minutes. Yet depending on how quickly the disease organisms take effect, it may be days
before a biological attack is detected, if ever. Daisey points out, however, that
"filtration systems don't just protect against terrorism; we always have aerosols
with us. Good filtration can reduce the incidence of colds and flu."
Accurately modeling the transport of contaminants in a building is one challenge; just
as important is correctly characterizing the building.
"Complex buildings change from season to season. If you want to evacuate the
building, do you shut off the HVAC systems? For how long? If there are two systems
slopping over, it matters," Daisey says.
EETD's Rich Sextro and Helmut Feustel are leading the effort to improve methods for
characterizing complex buildings in order to make accurate modeling of airflow and
pollutant transport possible.
Meanwhile, in an effort to get useful information to the quick-response teams as soon
as possible, Daisey and her colleagues have concentrated their efforts on the kinds of
buildings that offer the most attractive targets. "In terms of airflow and other
variables, we're trying to generalize office buildings, shopping malls, auditoriums,
hospitals, and so on," she explains. "Terrorists are not likely to strike a
residential suburb. The targets are places with lots of people."
Attempts -- so far inept -- to carry chemical and biological terrorism to the U.S.
homeland have already been made. The Lab's EETD researchers hope that their efforts, in
partnership with Livermore, Los Alamos and Argonne, will help to mitigate any such
attempts in the future.
