[Aaron Brown, Cnn Anchor:] Recovery crews at the World Trade Center and people who live nearby are concerned about what might be in the air and all that ash that's up there. CNN's Brian Palmer has more on that.
[Don Carson, International Operating Engineers Union:] A lot of these buildings are going to have to come down.
[Brian Palmer, Cnn Correspondent:] The crane and heavy equipment workers of the International Operating Engineers Union will bring them down. Don Carson runs their hazardous materials program.
[Carson:] This is potentially a hazardous waste dump with all the chemicals.
[Palmer:] Materials used to build and run the twin towers asbestos and fiberglass for insulation, freon for air-conditioning were released into the air when they collapsed, along with smoke from burning debris.
[Carson:] We've concluded that there are some spots where we have found some elevated levels of asbestos above the allowable limits.
[Palmer:] Stirring up concern about the health effects of breathing tainted air. [on camera]: This is a pretty amazing advantage point here.
[Carson:] There's a lot going on here, but you can see the smoke, and that's the concern about having the respiratory protection.
[Palmer:] It's unpleasant, but not dangerous, say city, state and federal environmental authorities.
[Mayor Rudy Giuliani , New York:] It is monitored constantly and it is not in any way dangerous. It is well below any level of problems and any number of ways in which you test it.
[Palmer:] But independent studies from around ground zero show concentrations of pollutants higher than official samples.
[Dr. Stephen Levin, Mt. Sinai Hospital:] There's virtually no chance that people living in the community or people working in offices nearby the site will develop the scarring lung disease that asbestos can cause in occupationally exposed workers.
[Palmer:] Residents still worry about other pollutants. Alon and Blake Vaknin, eight months pregnant, watched the first tower collapse from their apartment a block away, then fled with their daughter, Maia.
[Blake Vaknin, Resident:] A random sampling of air might show nothing but a small percentage, but that small percentage throughout the whole day, and then maybe it increases, decreases, increases, decreases, increases, decreases. You know, I'm pregnant. I don't want my baby to it just concerns me.
[Palmer:] The Vaknins say they won't be moving back any time soon. At ground zero, where experts are concerned about workers, precautions are taken. The rubble is hosed down to control dust. Respirators are issued to all workers. But that doesn't mean they aren't at risk.
[Carson:] They're working 12-hour shifts day after day. These adverse health effects won't show up two, three, four, five years from now, and as I said, we're going to have a secondary tragedy here if that's not addressed.
[Palmer:] Carson does say that if safety procedures are followed long term, the potential threat should be low.
[Bill Rapetti, Crane Operator:] I take my clothes off. I put them in a plastic bag before I get home and I wash them separately.
[Palmer:] Recovery workers say the hazards are part of the job.
[John Powers, Local 14, Iuoe:] You've got to kind of trust the people that are here to monitor it and look after you. Honestly, the only answer is, no matter what, this is going to have to be done.
[Palmer:] And what needs to be done, the dirty, dangerous job of clearing rubble in the hope of finding remains, giving the families of those killed at least some small measure of peace. Brian Palmer, CNN, New York.