Air Testing After Sept. 11 Is Both Perplexing and Reassuring

The ground-level atmosphere of Lower Manhattan has become one of the most intensely studied and sampled environments on the planet. Air monitors have been hung from trees and strapped to the belts of truck drivers. At least 11,000 people who worked at ground zero have had chest X-rays. Thousands more have been interviewed by researchers. What has been learned, scientists say, will have a far-reaching effect on urban disasters in the future.

Whether the Sept. 11 attack continues to have serious repercussions on the environment and public health, though, remains an open question as the cleanup of the World Trade Center site nears completion.

Many scientists and physicians say the accumulated evidence so far suggests a glancing blow: thousands of people developed coughs from the fires and dust, or were nauseated by the smells, but most have fully recovered. The exposures, even to things like asbestos, those experts say, were too short to cause widespread cancer or other lung diseases. On a scale of 1 to 10, if a 10 is an event like the poison gas release in Bhopal, India, that killed thousands in 1984, anything over 5 leaves permanent health consequences, and a 1 has no effect at all, then the trade center attack appears to have been a 3 or a 4, according to an informal survey by The New York Times of scientists, doctors and researchers involved in the health assessments. Others say it is too soon to tell.

What they agree on is that the many scientific and medical investigations into the effects of Sept. 11 are revealing an unforeseen complexity