Re: How do the air particles we see in the light affect our body.

	The human body has a number of defensive mechanisms to protect the body 
against harmful agents.  The first line of defense is a mechanical barrier, 
the skin.  Any part of the body exposed to the enviroment must be protected 
from harm.  Thus the body has specialized tissues to contact the 
environment. 
	Although the respiratory and gastrointestinal tracts are inside of our 
bodies they actually contact the environment.  In the case of the 
respiratory tract, this contact is through breathing.  For the 
gastrointestinal tract, this contact is through ingestion of food.  Both of 
these systems utilize mucosal tissues.  The mucosa are specialized cells 
which secrete, you guessed it, mucous.  
	The mucous we are most familiar with is that found in the nose.  Mucous 
contains proteins, DNA from dead cells, and carbohydrates that are very 
sticky.  You probably already know this if you have ever tried to blow your 
nose.  The stickiness of the mucous traps most particles that come into 
contact with it.  For example, if you spend any time in a very dusty area or 
near an open fire, you may find the mucous ("snot") in your nose turns brown 
(dust) or black (soot from the fire).
	In addition to the stickiness of mucous, in the respiratory system has 
an elaborate system to remove particles that make it past the nose.  This 
mucociliary system can be thought of as a mucous escalator.  The only 
direction trapped particles can go is up.  The cilia on these cells hand up 
the particles until they are deposited in the nose or mouth.  A second 
method the respiratory system uses is coughing.  This brings up large 
particles as well as mucous (phlegm).
	The types of particles you observed are generally not harmful to the 
body.  However, if you have allergies, you know that pollen and mold can 
create problems.  The effect of pollen and mold is not a natural harmful 
property of mold or pollen, but an abnormal response of the immune system to 
the presence of these particles.
	The mucous lining the respiratory and gastrointestinal tracts contain 
antibodies (IgE and IgA, respectively).  These antibodies bind to immune 
cells called mast cells and to things like pollen and mold.  Mast cells make 
and release histamines which make your nose run and eyes water.  Over-the-
counter drugs which help us with allergy symptoms are called antihistamines 
because they work by blocking the activity of the body's histamine.