How Post WTC Lung Disease Develops

During the 9/11 WTC terrorist attack, toxic dust, chemicals, fumes, asbestos and other toxic elements were present in the air and inhaled by all who were present. These airborne particles entered the respiratory tract; however, how far the particles traveled down into the respiratory tract, depended on the size, shape, density, and chemical and toxic properties of the particles. (To better understand how particles are deposited within the respiratory tract, Tour the Respiratory System.)

The deposition of particles within the airways and lungs causes dust diseases, such as asbestosis, mesothelioma and black lung disease. Deposition depends upon one of four actions: interception, impaction, sedimentation, and diffusion.

Post WTC Lung Disease - Particle Interception

When a particle travels close enough to an airway surface that it touches the surface of the airway, it is intercepted or deposited there. This is typically what happens when an asbestos fiber or similar fiber enters the airways. The size of these fibers causes them to be deposited in the bronchial tree because they are too large to pass through the width of the bronchial tree branches.

Post WTC Lung Disease - Particle Impaction

During inhalation, some particles impact or stick to a surface in the respiratory system where there is a bend in the air passages. The likelihood of impaction depends on the air velocity and the particle mass. Velocities are greater in the upper air passages. During exertion, such as heavy physical labor, breathing rates and, hence, air velocities increase throughout the system, and air enters the lungs more deeply during exertion.

Post WTC Lung Disease - Particle Sedimentation

Some particles will settle within the bronchi and bronchioles due to gravitational forces and air resistance. Particles settle in "dead-space" areas of the respiratory system where air is nearly stagnant (not moving). Sedimentation is most commonly seen during shallow breathing when particles of a larger aerodynamic diameter enter the airways.

Post WTC Lung Disease - Particle Diffusion

Diffusion is the most important mechanism for deposition in the small airways and alveoli. Smaller particles tend to move in a random motion and deposit on the lung walls mostly by chance. This movement is also known as the “Brownian Motion”. The effect increases as the size of the particles decreases.

How Post WTC Lung Disease Develops

When particles become lodged (i.e. they are unable to be expelled from the airways), they obstruct the motion of the cilia that line the airways. When cilia function are hindered, other particles, which are normally expelled by these cilia, can not be expelled. More and more particles become lodged, creating a breeding ground for bacteria to grow and overcome the respiratory system. Respiratory infections may follow and eventually a lung disease may develop. How quickly a lung disease can develop depends on many factors, such as the amount, type and size of the particles, and the development of respiratory infections.

The thickness of the dust cloud that lingered during the days following the 9/11 WTC attack is believed to have been great enough to cause severe damage to the respiratory system, causing lung disease to develop quickly. Some first responders who were present at Ground Zero when the attack occurred or who arrived on the site immediately after (and remained on site for many days or weeks after to help with cleanup), are too ill to work. Some workers, such as Felix Hernandez, Timothy Keller and James Zadroga, have already died.

Tour the Respiratory System

_{Source: Canadian Centre for Occupational Health & Safety (CCOHS)
Published: 05/13/06}