metals in the very fine mode can be tied to liberation of those metals that are both present in elevated concentrations in the debris and have depressed volatility temperatures caused by the presence of organic materials and chlorine.

Introduction

The collapse of the World Trade Center structures (South Tower, North Tower, and WTC 7) presented two very different types of air pollution events:

1. Initial fires and collapse-derived “dust storm” 2. Continuing emissions from the debris piles

Both cases shared the unusual aspect of a massive ground level source of particulate matter in a highly populated area with potential health impacts. EPA (Devlin, 2002) summarized 5 causal factors most likely to explain the statistically solid data connecting fine PM2.5 aerosols and human health.

1.Biological aerosols (bacteria, molds, viruses…)

2.acidic aerosols

3.very fine/ultra fine ( < 0.1 µm) insoluble aerosols

4.fine transition metals

5.high temperature organics

We especially needed to ascertain if these potentially causal factors were present in the WTC plumes.

The presence of fuels, including diesel and electrical insulating oils and combustible materials in the WTC buildings, and lack of oxygen were two factors that allowed the fire to burn for over 3 months. In order to better understand these aerosols, a DELTA Group rotating DRUM impactor was shipped to New York and set up on the roof of the DOE Environmental Measurement Laboratory (EML) at 201 Varick Street, 45 m above ground level and roughly 1.5 km NNE of the World Trade Center site. The DRUM operated until Late December, after the last surface fires had been extinguished. (Cahill et al, 2004)