New Study Of Ground Zero Air Shows Indoor Spaces Can Be Cleaned; Diesel Pollution Remains A Threat

"We knew that large amounts of very fine particles, which can get deep into a person's lungs and cause serious health problems, were released from the super-hot trade center debris piles," Cahill said. "Our new analysis shows that in the sites we tested, those very fine particles either never penetrated the indoor spaces or were effectively removed by professional cleaning."

The American Lung Association of the City of New York said the UC Davis results should reassure New Yorkers who have had their homes and offices professionally cleaned by a licensed asbestos and lead abatement contractor. Additionally, the association urged all residents who live in the affected area and who have not yet conducted a proper inspection and cleaning to contact local agencies to schedule one.

Cahill heads the UC Davis DELTA Group (for Detection and Evaluation of Long-range Transport of Aerosols), a collaborative association of aerosol scientists at several universities and national laboratories. The DELTA Group has made detailed studies of aerosols from the 1991 Gulf War oil fires, volcanic eruptions and global dust storms.

In February, the DELTA Group released what is still the most thorough analysis of the dust and smoke blown through lower Manhattan after the trade center collapse. That analysis found unprecedented clouds of very fine particles.

For the new study of indoor air, samples were collected in May at four sites in lower Manhattan -– two apartments and two offices –-to evaluate the persistence of very fine aerosols in indoor areas near the trade center.

The samples were analyzed for very fine particles of silicon, sulfur (sulfate), vanadium, nickel and lead, all of which the DELTA group had found to be abundant in outdoor air in October 2001. Results were compared against clean control sites and against an average exposure rate about one mile north-northeast of the trade-center site. Cahill found that the amounts of toxins at the four indoor sites studied were low and well within public health guidelines.

"This is good news for the residents and workers of lower Manhattan," said Peter Iwanowicz, director of environmental health for the American Lung Association of New York State. "We now know that when proper testing and mitigation are conducted, indoor spaces are as clean as, or in some instances cleaner than, before Sept. 11."

However, the study identified another health threat in the area. "The air samples confirmed that diesel pollution from the countless vehicles involved in the recovery and rebuilding effort is heavily concentrated downtown," said Cahill.

The recovery, cleanup and rebuilding of the World Trade Center site all employ large fleets of diesel vehicles, from construction trucks to back-up generators. At the three sites closest to Ground Zero where samples for the study were collected, the lev