It may seem hard to believe but every day we breathe in more than 10,000 liters of air. Depending on the degree of pollutants in that air, the human lungs can either cope with it or not. As I write these words, I can’t help but think of one of the “I Love Lucy” episodes where she and Ethel get a job in a candy factory hand wrapping expensive chocolates as they come down a conveyor belt. Early on, the belt moves slowly and the girls do fine. But as it speeds up, they can no longer keep up with the wrappings and resort to what many of you will remember as hilarious alternatives. Unfortunately, our lungs don’t have a sense of humor and when overtaxed they become ill.
Luckily our lungs have a number of good coping mechanisms, both mechanical and immunologic. The airway epithelium cells have very tight junctions which create an excellent barrier. In addition, the micro-cilia in the lungs are constantly beating to “fan” pollutants out of the lungs. Finally, mucus production can trap particulates and dilute gases and vapors thereby reducing their toxicity. Surfactant, a second cousin to mucus, also is very effective in diluting and detoxifying gaseous pollutants including ozone.
There are a variety of immunologic defense mechanisms, most of which work by removing free radicals and reducing oxidative stress on the delicate lung tissues. However, when exposure is too great or prolonged over time these systems fail with two negative consequences. One is inflammation which leads to lung damage and scarring and the development of COPD. The other is greater propensity for infection. If the tight junction barrier is faulty it allows microbes easier penetration into lung tissue. And, if the protective immune responses are over-taxed, they can’t adequately shift from pollution protection to microbial defense.