February 11, 2002: Study Raises Concerns over Environment near Ground Zero

The Delta Group releases a final report on air quality data collected in Manhattan between October and December, 2001 (see October 2, 2001-Mid-December, 2001). Thomas Cahill, PhD, Delta Group member, is a noted expert on composition and transport of ultra-fine airborne particles. Dr. Cahill explains that World Trade Center aerosols contained high levels of sulfur, sulfur-based compounds, and very fine silicon that probably came from the thousands of tons of glass that had been in the WTC buildings. The presence of these fine particles decreased during the month of October. The largest spike in very fine particle levels measured 58 micrograms per cubic meter which Cahill says was “an extremely high peak.” The sampling also indicated that there were almost always high concentrations of coarse particles—those about 12 micrometers to 5 micrometers in diameter—present in the air near the WTC site. “These particles simply should not be there,” Cahill says. “It had rained, sometimes heavily, on six days in the prior three weeks. That rain should have settled these coarse particles.” He says their presence suggests the hot debris pile was continually generating the larger particles. The study also determined the chemical composition of the dust it sampled. Some of the metals found in the air occurred at the highest levels ever recorded in the United States. Metals present at high levels included iron, titanium (some associated with powdered concrete), vanadium and nickel (often associated with fuel-oil combustion), copper and zinc. Mercury, lead, and asbestos were present at low levels. [On Earth, 2002; Dateline (Univ of Calif, Davis), 2/15/2002; Chemical and Engineering News, 2/18/2002]