Pollutant Particle Size vs. Impact on Humans
Worldwide air pollution is responsible for large numbers of deaths and cases of respiratory disease. Enforced air quality standards, like the Clean Air Act in the United States, have reduced the presence of some pollutants. However that is not a worldwide effort and has at best only been partially effective. We must protect ourselves from the effects of these pollutants if we are to remain healthy while living in the present environments.
Sources of air pollution: The major single source of air pollutants is the combustion (burning) of fossil fuels (coal, oil, and gas) to run industrial machines and generate electricity. All anthropogenic pollutants can be traced to some extent to this source. A second major source of pollutants is the incomplete combustion of fuel in cars, trucks, railroad trains, airplanes, and other forms of transportation. Smaller amounts of pollutants are released during the incineration of solid wastes and by a variety of industrial processes.
In some cases, pollutants are released by these sources directly to the air and are known, therefore, as primary pollutants. Sulfur dioxide, oxides of nitrogen, and carbon monoxide are all primary pollutants. In other cases, materials released by a source undergo a chemical reaction in the atmosphere and are converted to a secondary pollutant. Examples of secondary pollutants are ozone and peroxyacyl nitrates (PANs), major components of the form of air pollution known as smog.
Specialized forms of air pollution: Under specialized conditions, certain forms of air pollution have developed that are so dramatic or so serious that they have been given special names. These conditions include smog, acid rain, the greenhouse effect, and ozone depletion.
The term smog actually applies to two quite different atmospheric conditions. The term itself comes from a combination of the words smoke and fog. One form of smog, known as industrial smog, is produced when sulfur dioxide, particulates, and other pollutants released by industrial and household burning of fossil fuels is trapped by a thermal inversion. A thermal inversion is an atmospheric condition in which a layer of cold air is trapped by a layer of warm air above it. Some of the most dramatic photographs of urban areas covered by air pollution are those that show a city smothered in a cloud of smog.
A second form of smog is photochemical smog, produced when oxides of nitrogen, produced largely by internal-combustion engines (those most often used in automobiles, for example), react with oxygen in the air to form a complex mixture of pollutants that includes ozone, PANs, and other organic compounds. Photochemical smog often has a similar appearance and similar effects to those of industrial smog. Indeed, in most cities, the two forms of smog occur in combination with each other.
A complete list of air pollutants would include nearly two dozen solids, liquids, and gases. It would include well-known pollutants such as sulfur oxides and carbon monoxide and less-familiar materials such as pesticides and fluorides. In terms of the quantities of pollutants released in a year, the five materials that cause the most damage are sulfur oxides, oxides of nitrogen, carbon monoxide, particulate matter, and volatile organic compounds.
Sulfur oxides, oxides of nitrogen, and carbon monoxide are chemical compounds. Particulate matter and volatile organic compounds are groups of related pollutants. The term particulate refers to tiny specks of solid matter in the atmosphere, including smoke, haze, pollen, aerosols, and tiny particles of carbon. Volatile organic compounds are organic liquids, such as benzene, toluene, the xylenes, and trichloromethane that change easily (volatilize) to a gas.
Effect of air pollutants: By definition, all forms of air pollution have some harmful effect on humans, other animals, plants, or other materials in the environment. For example, carbon monoxide is a well-known toxic gas that reduces the blood's ability to transport oxygen. Prolonged exposure to carbon monoxide can cause heart and respiratory disorders; headaches, nausea, and fatigue; and, at high enough concentrations, coma and death. The oxides of both sulfur and nitrogen attack the human respiratory system, leading to irritated eyes and throat and impaired breathing (at low concentrations), and to emphysema, bronchitis, and lung cancer (at higher concentrations).
The effects of particulate matter are wide, from preventing photosynthesis (food production) in plants to clogging the breathing passages in lungs (leading to respiratory disorders). Particulate matter also soils buildings, statutes, and other objects, leading to their decay and deterioration.
… The smaller they are, the harder we fall
The size of the pollutant particles is directly linked to their potential for causing health problems. The United States Environmental Protection Agency (EPA) is very concerned about particles that are 10 micrometers (microns) in diameter or smaller. These are the particles that generally pass through the nose and throat and enter the lungs. Once inhaled, these particles can affect the heart and lungs and cause serious health effects. The EPA groups particle pollution into two categories:
"Inhalable coarse particles," such as those found near roadways and dusty industries, are larger than 2.5 microns and smaller than 10 microns in diameter.
"Fine particles," such as those found in smoke and haze, are 2.5 microns in diameter and smaller. These particles can be directly emitted from sources such as forest fires, or they can form when gases emitted from power plants, industries, and automobiles react in the air.
How small is 2.5 microns? A single hair from your head averages about 70 microns in diameter – making it 30 times larger than the largest fine particle.
Particle pollution (also called particulate matter or PM) is the term for a mixture of solid particles and liquid droplets found in the air. Some particles, such as dust, dirt, soot, or smoke, are large or dark enough to be seen with the naked eye. Particles visible to the eye are equal to or greater than 50 microns in size. Smaller particles can only be visually detected using a microscope.
Pollution particles come in many sizes and shapes and can be made up of hundreds of different chemicals. Some, known as PRIMARY PARTICLES are emitted directly from a source such as construction sites, unpaved roads, fields, smokestacks or fires. Others form in the atmosphere from complicated reactions of chemicals such as sulfurous and nitrogen oxides that are emitted from power plants, industries and automobiles. These particles, known as SECONDARY PARTICLES, make up most of the fine particle pollution in the country.
The EPA attempts to regulate emissions of inhalable particles (fine and coarse). Particles larger than 10 micrometers (sand and large dust) are not regulated by the EPA.
Fibers - SLIGHT health effect
Fibers - visible, macroscopic filaments - are usually man-made. They
come from clothing, carpeting, upholstery, or paper. One sees fibers floating in bright shafts of sunlight. They settle in calm air, drift along the floor and tangle into "dust bunnies" in corners and under beds. Coarse filters can strain fibers out of the air, but removing them isn’t greatly important because they pose more of a housekeeping than a health problem.
Silts - MODERATE health effect
Silts - microscopic particles - stay suspended in calm air. Common silts are airborne soil, smoke, allergens (pollens, fungus & mildew spores), bacteria and viruses. They are not individually visible to the naked eye, but in large numbers, form visible haze or smoke. Silts are pulled out of the air stream and held tightly by the attracting fibers of electrostatic filters. Silts may cause allergies.
Molecules - LARGE health effect
Odors and molecular irritants - sub-microscopic molecules - are about
1/10,000 the size of the smallest silts. Molecular irritants are especially threatening because they travel into the lungs, dissolve and enter the bloodstream. They are the only pollutants which actually enter our bodies. Molecules are completely unaffected by particle filters. Fortunately, they are efficiently "sponged up" by adsorbents.
Particles size of different matter
Clay 0.02 micron to 2
Silt 2 microns to 20
Fine Sand 20 microns to 200
Coarse Sand 200 microns to 2,000
Gravel 2,000 microns to >2,000
Smog 0.001 micron to 2
Clouds/Fog 2 microns to 70
Mist 70 microns to 200
Drizzle 200 microns to 500
Rain 500 microns to 10,000
Plant Spores 10 microns to 30
Pollen 10 microns to 100
Viruses 0.003 micron to 0.05
Bacteria 0.3 micron to 30
Human Hair 30 microns to 120
Visible to the Eye 50 microns to >50
Gas Molecules 0.0003 micron to 0.005
Tobacco Smoke 0.01 micron to 1
Milled Flour 1 micron to 80
Nebulizer Drops 1 micron to 20
Combustion Nuclei 0.01 micron to 0.1
Metal Fumes 0.001 micron to 1
Ultrafine Particles less than 0.1 micron
Our knowledge of particulate pollution, prompted our development of a handy new product. It is Athma-Pure Nosefilters, a means of breathing clean air. Our Athma-Pure filters are charcoal activated and MERV rated to filter and adsorb particulates from 2 to 500 microns. You can easily dispose of the device with the filters or reuse the device by cleaning it with regular liquid soap and replacing our refill filters.
One each of Athma-Pure device with Nosefilters costs about $1.25.