Blog #2 Particle size, occupational disease & respiratory system

How particle size is related to occupational disease and respiratory system

A quick crash course on the respiratory system

The human respiratory system is a group of organs whose main function is taking in oxygen and expelling carbon dioxide. The lungs exchange these gases as we breathe. Red blood cells take oxygen from the lungs and carry it throughout the body.

During this process, red blood cells collect carbon dioxide and transport it back to the lungs, that carbon dioxide leaves the body when we exhale. When there is a decrease in oxygen its knows as hypoxia and no oxygen in the body is known as anoxia; after about four minutes without oxygen, brain cells begin to die, which can lead to brain damage and ultimately death. 

Particle Size

In industrial hygiene, particulate matter is defined as small which is less than 100 micrometers in diameter, pieces of solid materials, liquid droplets, or microbiological organisms. Since Particles smaller than about 0.001 µm start to act like gases and they are not particulate matter.

The five primary mechanisms of particle deposition are inertial impaction, interception, sedimentation, electrostatic attraction, diffusion. Because long, narrow asbestos fibers can travel through the lung and penetrate much deeper a non-fibrous particle with a diameter equal to the length of the fiber. This can result in scarring of the lungs and cancer.

 “Whether or not an airborne particle is inhaled depends on its aerodynamic diameter, the velocity of the surrounding air, and the persons’ breathing rate. How particles then proceed through the respiratory tract to the different regions of the lungs, and where they are likely to deposit, depend on the particle aerodynamic diameter, the airway dimensions and the breathing pattern.”

-     http://www.who.int/occupational_health/publications/airdust/en/

Large particles greater than > 0.5μM are usually inhaled through Impaction and Sedimentation. “Sedimentation is settlement by gravity and tends to occur in larger airways. Inertial impaction occurs when an airstream changes direction especially in the nose but also in other large airways.”

“Interception applies mainly to irregular particles such as asbestos or other fibrous dusts which by virtue of their shape can avoid sedimentation and inertial impaction. However they are intercepted by collision with walls of bronchioles especially at bifurcations or if the fibers are curved.”

Small particles less than > 0.5μM are usually inhaled through Diffusion. “Diffusion is the behavior of very small aerosol particles which are randomly bombarded by the molecules of air. It significantly influences deposition beyond the terminal bronchioles.”

-    http://www.agius.com/hew/resource/lung.htm

Effects

Pneumoconiosis is the accumulation of dust in the lungs and the tissue reaction to its presence. Two types of pneumoconiosis are coal workers pneumoconiosis and silicosis.

Silicosis is caused by pronged exposure to silica dust can be,

-    Classic Silicosis

-    Accelerated Silicosis

-    Acute Silicosis

Occupations at risk include,

-    Sandblasting

-    Miners – including coal miners

-    Quarry workers

-    Millers

-    Pottery Workers

-    Foundry

Asbestosis

-     Pulmonary Fibrosis caused by Asbestos exposure

Seen to cause:

-    Lung Cancer

-    Pleural Disease

-    Pleural Plaques

-    Diffuse pleural thickening

-    Pleural effusion

-    Rounded atelectasis

-    Malignant Mesothelioma

Inhalation Fever

      

Metal fume fever

-    Caused by metal fumes (Zinc Oxide, Copper, Magnesium, Aluminum etc.)

Organic Toxic Dust Syndrome

-    Caused by contaminated vegetables, moldy hay, compost, wood.

Pontiac Fever

-    Caused by water sources with legionella

Humidifier Fever

-    Caused by humidifiers/AC units

 Mill/Grain Fever  

-    Caused by Plant/Grain dust with endotoxins

Other diseases of the respiratory system include asthma, bronchial cancer, chronic beryllium disease and chronic bronchitis.