E-mails R. Avaltroni 2002

NYC 9/11 Public Portal Document

about could have received material from the World Trade Center site half the time.

The samples were periodically shipped back to Davis, where the DELTA Group analyzed the samples for size, shape and composition. They used a suite of seven techniques including synchrotron-induced X-ray fluorescence (at DOE's Advanced Light Source at Lawrence Berkeley Laboratory), scanning transmission ion microscopy and proton elastic scattering analysis (at DOE's Lawrence Livermore National Laboratory), and soft beta mass measurements and scanning electron microscopy (at UC Davis).

"The UC Davis DELTA Group's ability to measure and analyze particle size, composition and time continuously, day and night, is unequaled," Cahill said.

All analyses were done on a volunteer basis and will be available as public documents. We report today on the data from Oct. 2 through Oct. 31, 2001.

Airborne particles and human health

In general, there are myriad ways that materials released into the air can affect human health. What the particles are made of matters; so do size, shape and quantity.

The DELTA team analyzed the samples for the unique chemical and physical signatures of dozens of substances, including elements from concrete and glass, such as silicon; from burning fuel oil, such as sulfur, vanadium and nickel; and from burning computers and electrical systems, such as lead. They also looked for organic, or carbon-based, compounds from burning wood, plastic and carpets. And they tested for glass shards and asbestos.

Some of these materials are known to cause health problems in some people when they are inhaled in sufficient amounts. Sulfur, for example, can irritate lung tissues. Lead can damage the central nervous system. Some carbon-based compounds can cause cancer. So can the mineral asbestos.

Just as the composition of inhaled particles can affect health, so can size.

The team analyzed the particles by size in eight ranges from coarse (12 micrometers to 5 micrometers in diameter) to very fine (0.24 micrometers to 0.09 micrometers in diameter). Most of the ultrafine mode (particles less than 0.1 micrometers) was not collected.

Coarse particles are typically filtered by the nose or coughed out of the throat and upper lungs. They can irritate the mucous membranes, causing coughs and nosebleeds. In some individuals, they can cause allergic reactions such as dry eyes; nose, throat and skin irritation; coughing, sneezing and respiratory distress. They can also cause breathing problems or aggravate pre-existing breathing problems, such as asthma.

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