WEDNESDAY, Sept. 11 (HealthDay) -- Fires so savage they burned for three months. Mountains of dust. Huge clouds of minute and potentially harmful particles spewed across great patches of the city.
In the apocalyptic moments after the terrorist attack that toppled the World Trade Center's Twin Towers a year ago today, lower Manhattan was covered in what many experts believe was an unprecedented shower of pollutants, dust, pulverized glass, concrete and other building materials.
Winds carried the vast, acrid plume across the East River to Brooklyn, then, in the coming days, northward up the island of Manhattan, across the Hudson River to New Jersey, as far away as Pennsylvania.
Yet, a year after the disaster that claimed more than 2,800 lives, the land, water and air of New York City have displayed remarkable resilience. Although some rooftops still shoulder pockets of dust and thousands of apartments still need to be cleaned, experts say the worst health threats passed early and quickly.
There have been, however, reports of short-term health ills, particularly respiratory problems among firefighters and rescue workers, as well as some people working and living near Ground Zero. During the six months after the terrorist attacks, 333 firefighters had coughs severe enough they required more than four consecutive weeks of medical leave.
But based on environmental readings that began immediately after the buildings collapsed, the risk of long-term harm to most of those in lower Manhattan one year ago today is believed to be slight, health experts say.
"I've looked critically at the occupational exposure data, and they all seem pretty consistent," says Kenneth Wallingford, an industrial hygienist at the National Institute for Occupational Safety and Health.
The Environmental Protection Agency (EPA), which began monitoring lower Manhattan and Brooklyn the day of the attacks, suspended its sampling in June. During that time, sensors at roughly 20 sites across New York City took tens of thousands of readings for dangerous chemicals and pollutants. These substances included lead, mercury and cadmium and toxins such as benzene and dioxin and asbestos.
"The outdoor sampling has generally shown no presence or very low
levels of pollutants in recent months," the agency said this summer. "The fires have been out for months, recovery activities are completed, and our sampling generally shows that air quality in lower Manhattan is back to normal levels prior to September 11."
Mary Mears, an EPA spokeswoman, says, "Most of our samples, even during the worst-case-scenario of right on
the pile in the fires, were generally not at levels that we thought elevated." Readings for lead and mercury showed occasional spikes upward, but nothing consistent or alarming.
Moreover, the surges tended to occur at Ground Zero, not in areas a short walk away. This suggests the health risks
they posed would apply more to rescue and cleanup workers, not residents, health experts say.
For instance, of the more than 10,000 readings for asbestos taken by
the EPA during the nine-month period, only 22 registered higher than 70
fibers per square centimeter. That figure is the government's maximum safe level for schools that have had the fire retardant removed, and officials consider it a conservative standard.
Asbestos, which can cause lung cancer, was one of the more hazardous contaminants released by the collapsing buildings. But many scientists believe the size of an asbestos fiber is as important as its presence in the lungs. Particles below 5 microns in length aren't so risky, they say, although not all scientists agree.
Ninety percent of the asbestos fibers the EPA detected were under 5
microns, Mears says.
"The asbestos that was present [in the Twin Towers fallout] was in extremely short fibers, which are minimally toxic -- if at all," says Morton Lippmann, who directs the Human Exposure and Health Effects program at New York University School of Medicine's department of environmental medicine.
Lippmann adds that half the mass of the settled dust in lower Manhattan was larger than 50 microns in diameter -- about the size of a printed period -- while only 1 percent was "fine matter."
A 50-micron particle won't penetrate deep into the lungs. It can lodge in the nose and throat and irritate the upper airways, and that could have happened to rescue and cleanup workers who didn't wear masks, he says.
This may help to explain some of the studies that have turned up evidence of a "World Trade Center cough."
In addition to those firefighters whose coughs led to medical leave, a new Centers for Disease Control and Prevention report estimates that 500 firefighters may eventually qualify for a disability retirement due to respiratory problems.
That same report, released Monday, surveyed 414 households in lower Manhattan in late October and early November. The most common symptoms were nose or throat irritations (66 percent), eye irritation (50 percent), and coughing (47 percent).
The highly alkaline concrete dust, as well as vaporized window glass, unleashed by the towers' collapse are likely to blame for the World Trade Center cough, says Paul Lioy, an environmental scientist at the University of Medicine and Dentistry of New Jersey and Rutgers University.
Fortunately, most of the people who lived and worked in the critically affected area of Manhattan, below Canal Street, were evacuated or at work elsewhere when the towers fell. Disaster workers, instead, bore the brunt of whatever substances were in the air.
Mears says her agency has had a hard time conveying the message that temporary respiratory problems don't necessarily spell long-term trouble.
The EPA has been accused by some of downplaying the health hazards of September 11, a charge Mears says is both disheartening and false. Data from EPA sensors, from New York City and New York state, and from the Occupational Safety and Health Administration all show the same thing, she says.
"There's a very large body of information out there that shows us
there's probably no long-term health risk here," she says.
Even if the environment in New York City now seems as clean as it was before 9/11, officials can't rule out that the catastrophe could have a lasting health effect on some people -- such as firefighters and rescue workers -- exposed, however briefly, to contaminants.
So, the U.S. Department of Health and Human Services is collaborating
with the New York City Department of Health on a "World Trade Registry"
to track between 100,000 and 200,000 people exposed to contaminants.
The registry will use a mix of tools, from periodic surveys to comparisons with other registries that collect data on rates of cancers and death over time.
"It's not a snapshot in time; it's looking at them consistently and periodically," says Sharon Campolucci, deputy director for health studies at the Agency for Toxic Substances and Disease Registry.
"Millions of people were under the plume of smoke," adds Dr. Polly Thomas, of the New York City health department. "We were able to enroll a very small portion of people who were in the plume, but if there were any health effects we should be able to identify them."
What To Do
To learn more about how the nation has prepared for the possibility of another terrorist attack, visit this CDC Web site.
