U.S. Gov. "tests" how toxins can be spread in a NYC midtown attack

Government scientists have set up a network of sensors around midtown Manhattan to study how the city´s skyscrapers and concrete canyons would affect the spread of wind-borne toxins in a chemical, biological or radiological terrorist attack.

Chemicals known as tracer gases will be released at several locations between tomorrow and Aug. 26 in tests sponsored by the U.S. Homeland Security Department, Defense Department, Environmental Protection Agency, and Energy Department, officials said today.

The Urban Dispersion tests, in preparation for two years, come two weeks after New York police began randomly searching the bags of subway riders in response to terrorist bombings in London. Data from the tests will help emergency response planning, said Thomas Kiess, a Homeland Security official.

"The results of the study will help us take comprehensive responses in the first few hours or the first few days of a terrorist attack," Kiess said at a press briefing.

Low concentrations of perfluorocarbon and sulfur hexafluoride, which are colorless, odorless and biologically inert gases, will be released over six days, when weather permits, the scientists said.

The spread of the gases will be measured by 180 sampling devices attached to light poles, atop buildings, and in subways, from 36th Street to 61st Street, and from 3rd Avenue to 10th Avenue, officials said.

Similar but separate tests were conducted at Grand Central Terminal in June.