hen we breathe in, air enters our nose where dust and other particles are filtered out--the 1st line of defense. Here the air is warmed and moistened before it travels down, past the throat, through the windpipe or trachea. The trachea and other air passages are lined with a sticky mucus that traps germs and particles before they enter our lungs--our 2nd line of defense.

Impact on Economy 

 Special cells called cilia have tiny waving hairs that push this mucus up and out of our lungs along with all the pollution it has trapped--our 3rd line of defense. After the air flows down the trachea, it passes into two large tubes called bronchi that carry air into our lungs and then into smaller and smaller branches called bronchioles. The bronchioles lead to tiny air sacs, the alveoli, which transfer oxygen to the blood and remove carbon dioxide that makes the same return trip when we breath out. Here, there is even a 4th line of defense, the alveolar macrophages. These scavenger cells eat foreign particles and bacteria that would make us sick.

HOW DOES POLLUTED AIR CHANGE THINGS?

hen we breathe polluted, smoggy air, tiny toxic air particles sneak past the natural filters in our nose. Smog irritates the trachea making it hard to breathe in and out. In the bronchi and bronchioles, air pollution can paralyze or even destroy the cilia cells, which allows dirt and germs to build up in the mucus and leaves the lungs defenseless against infections. Ozone kills the alveolar macrophages that eat up foreign particles and bacteria. Smog also damages the alveoli so they can't transfer oxygen as well as they should. All of this can strain our heart, our lungs, our whole body. Breathing months and years of smoggy air may cause premature aging of the lungs and make us susceptible to infection, heart disease, and even cancer.

Next - The Nitty Gritty on 6 Harmful Pollutants...