Air and Breathing
Air QualityAir is a mixture of gases and aerosols. Humans add thousands of volatile gases to air, creating a chemical soup that changes light transmission through the atmosphere and exposes all living creatures to toxins and carcinogens. Suspended particles in the air (aerosol) are important to the behavior of whole atmosphere and play a key role in determining human disease.
Over land up to a quarter of the total airborne particulates are pollens, fungal spores, bacteria, viruses, plant and animal matter. Air inside buildings contains local aerosols that are often more concentrated and more toxic than outdoor air. The term dust refers to the larger particles in the aerosol that settle on walls and furniture. A smoker in the living room of a house produces a toxic aerosol that permeates the rest of the house. Smoke particles settle on walls and every object in a room so that a smoker leaves a trail of contamination that non-smokers smell as soon as they enter the room.
Indoor air contains a living aerosol of microorganisms that infect or trigger allergic reactions. Spores of bacteria and fungi are microscopic and may persist for months or years. You can see the indoor aerosol under the right lighting conditions, such a sunlight streaming through a window. The abundance of microorganisms, even in a very clean house, surprises most people who have tests done to assess air quality.
Ozone: In the 20th century, it became obvious that gases created by human activity changed the chemical composition of the troposphere and stratosphere with negative impacts on human survival. Large ozone holes appeared over the Antarctic and the Arctic Polar regions. Smaller areas of ozone depletion were recorded over other, more-populated regions of the Earth. Increases in surface UV-B radiation have been recorded wherever stratospheric ozone was depleted. A scientific consensus was reached that human-produced chemicals were responsible for ozone depletion. Combinations of volatile chemicals containing chlorine, fluorine, bromine, carbon, and hydrogen were responsible; carbon tetrachloride, and methyl chloroform were used in refrigeration, air conditioning, and as solvents. Halons, which contain carbon, bromine, fluorine, and chlorine were also implicated. An international agreement was achieved so that many governments outlawed CFCs, halons, carbon tetrachloride, and methyl chloroform.
Re Ozone See World Meteorological Organization/United Nations Environment Programme report, Scientific Assessment of Ozone Depletion: 1998 (WMO Global Ozone Research and Monitoring Project-Report No. 44, Geneva, 1999).