Ground Zero Dust: What Was in It and How It Affected Health

When the World Trade Center towers collapsed on September 11, 2001, they released a huge cloud of dust over lower Manhattan. Researchers found it was mostly coarse particles of pulverized building materials, laced with harmful substances including asbestos, lead and cancer-linked chemicals, and highly alkaline, which irritates the airways.

Thousands of responders and residents later developed breathing and digestive problems, and some developed cancers. Today the federal World Trade Center Health Program serves more than 145,000 responders and survivors. This guide explains what the dust contained, the health problems linked to it, and how to get care. For more on air quality and breathing, see our indoor air quality guides.

Jump to: Quick answer · What was in the dust · Health effects · Covered conditions · The WTC Health Program · FAQ

Quick answer

• Composition: about 95% coarse particles, containing pulverized cement, glass fibers, asbestos, lead, PAHs, PCBs, and dioxins and furans.
• Highly alkaline: pH 9.0 to 11.0, which researchers linked to airway irritation, persistent cough and asthma risk.
• Firefighters: a study of 10,116 firefighters found exposure-related increases in cough and airway hyperreactivity.
• Covered conditions include asthma, chronic rhinosinusitis, GERD, COPD, many cancers and PTSD.
• Help is available: the WTC Health Program, run by NIOSH (part of the CDC), is authorized until 2090 and has no enrollment deadline.

What was in the World Trade Center dust?

A 2004 review in Environmental Health Perspectives by researchers who studied the disaster described the dust this way:

Researchers linked the dust’s high alkalinity to irritation of the airways in people who breathed it.

How the dust affected health

The same review reported that the high alkalinity of the dust produced airway hyperreactivity (twitchy, easily irritated airways), persistent cough and an increased risk of asthma. In an evaluation of 10,116 New York City firefighters, researchers found exposure-related increases in cough and airway hyperreactivity, a pattern doctors often call “World Trade Center cough.”

The program covers not only rescue and recovery workers but also survivors who were in the dust or dust cloud, such as people who lived or worked nearby. Some conditions, such as certain cancers, can take years to appear, which is why the program sets minimum time periods for cancer coverage.

Conditions covered by the WTC Health Program

The CDC’s WTC Health Program covers 9/11-related conditions in several groups (the list is not exhaustive):

• Airway and digestive (aerodigestive) disorders: including asthma, chronic rhinosinusitis, gastroesophageal reflux disorder (GERD), and new-onset or WTC-worsened chronic obstructive pulmonary disease (COPD).
• Cancers: many types, including cancers of the respiratory system such as lung and bronchus. Minimum time periods between exposure and diagnosis apply.
• Mental health conditions: including post-traumatic stress disorder (PTSD).
• Musculoskeletal disorders: for WTC responders only.

The World Trade Center Health Program

According to the CDC, the program:

• Is a limited federal health care program that provides medical monitoring and treatment for 9/11-related conditions.
• Is administered by the National Institute for Occupational Safety and Health (NIOSH).
• Was created by the James Zadroga 9/11 Health and Compensation Act of 2010, extended in 2015, and is authorized until 2090.
• Serves more than 145,000 responders and survivors, and has no deadline to enroll.

Who can join: responders who did rescue, recovery, debris cleanup or related support work; survivors who were in the New York City disaster area in the dust or dust cloud on September 11, 2001; and responders at the Pentagon and in Shanksville, Pennsylvania. Visit the program’s website to check eligibility and apply.

If you were exposed

• Tell your doctor about your 9/11 exposure, even decades later.
• Watch for ongoing cough, wheezing, shortness of breath, sinus problems or heartburn, and get them checked.
• If you have asthma, keep your asthma action plan up to date; see our asthma guides.

This guide is general information, not medical or legal advice. Read our medical disclaimer.

Frequently asked questions

Was Ground Zero dust toxic?

Yes. Researchers found it contained asbestos, lead, PAHs, PCBs and dioxins, along with pulverized cement and glass fibers, and it was highly alkaline (pH 9.0 to 11.0), which irritated the airways.

What health problems are linked to 9/11 dust?

The CDC’s WTC Health Program covers airway and digestive disorders such as asthma, chronic rhinosinusitis, GERD and COPD, many cancers, mental health conditions such as PTSD, and, for responders, musculoskeletal disorders.

What is World Trade Center cough?

A persistent cough with irritable airways seen in people exposed to the dust. A study of more than 10,000 firefighters found exposure-related increases in cough and airway hyperreactivity.

Is it too late to join the WTC Health Program?

No. The CDC says there is no deadline to enroll, and the program is authorized until 2090.

Who is eligible for the WTC Health Program?

9/11 responders, survivors who were in the New York City disaster area in the dust or dust cloud, and responders at the Pentagon and Shanksville, Pennsylvania. Check the program’s website for details.

Sources

• Landrigan PJ, Lioy PJ, Thurston G, et al. Health and environmental consequences of the World Trade Center disaster. Environ Health Perspect. 2004;112(6):731-739.
• Centers for Disease Control and Prevention. About the World Trade Center Health Program. Updated September 9, 2026.
• Centers for Disease Control and Prevention. WTC Health Program covered conditions. Updated March 30, 2026.

Last reviewed: October 21, 2026.