260 Microbes and You 



aerosols by modifying some of the standard technics commonly 

 employed in bacteriology laboratories. 



PHYSICAL AND CHEMICAL FACTORS AFFECTING AIR AND 

 HUMAN HEALTH 



There is nothing wrong with being microbe-conscious, but like 

 anything else, the practice can be overdone. This is not a plea to 

 cast aside common sanitary practices which have been shown to 

 be important in reducing the spread of infection, but there are 

 sensible approaches to this business of learning to live in the 

 presence of hordes of parasites awaiting an opportunity to attack 

 and destroy us. 



Since the nose and mouth are commonly the portal of entry for 

 many organisms, and since these areas are sources of large numbers 

 of microorganisms, it behooves us to adhere to the accepted prac- 

 tice in modern sanitation of using a handkerchief or sanitary tissue 

 to stifle coughs and sneezes. All of us harbor potential pathogens 

 in our nose and throat; we may serve as healthy carriers of these 

 microbes. But these same organisms may be highly virulent to 

 other susceptible persons, while their normal bacterial flora, in 

 turn, may prove to be highly virulent for us. The carrier is the 

 best explanation we have for the fact that diseases do not die out. 



Those individuals unfortunate enough to be allergic to dust or 

 to pollen may lead a very uncomfortable existence. Various filters 

 have been devised to be worn in the nose of such afflicted persons, 

 but the results are variable and questionable. 



ULTRA-VIOLET LAMPS 

 Light having wavelengths from about 2000 to 3000 Angstrom 

 units is highly lethal to microorganisms, and this band is known as 

 the ultra-violet range. An Angstrom unit, the measurement em- 

 ployed to express wavelengths, has a value of 0.1 millimicron 

 (0.0001 micron) and is abbreviated A. A wavelength of 2536 A 

 is particularly lethal to bacteria. Sunlight contains a relatively 

 low concentration of ultra-violet rays which are reduced still fur- 

 ther bv dust, fog, moisture, etc., in the air, but artificial sources of 



