Air and Water Purity
Air and water purity (Forensic Science)
Although challenges to air and water purity have always existed, the assault has taken on forbidding aspects since the advent of the industrial age. So ubiquitous are the sources of air and water pollution that they have become woven into the fabric of everyday modern life. However, it is important to note that although much pollution comes from the processes of industry and commerce, pollution is also a product of natural biological and geographic processes. It should also be kept in mind that purity and pollution are relative. For example, although oxygen is necessary to animal life, it is highly toxic to certain organisms that flourish in an atmosphere of methane, which would be lethal to human beings.
Human-made pollutants come from the combustion of fuels that power ships, aircraft, motor vehicles, factories, and power-generating plants. Natural pollutants come from the discharges of wildfires and volcanoes. Pollutants also come from chemical discharges and landfill outgassing as well as military operations that generate nuclear fallout, pathogens, and toxic gases. Pollutants even ride the wind in the form of dust.
A notorious example of the damage inflicted when human activities alter the air’s chemistry comes in the form of chlorofluorocarbons (CFCs), which find wide applications as refrigerants, insulating foams, and solvents. CFCs eventually make their way into the stratosphere, where the ultraviolet (UV) rays of sunlight...
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Water Quality (Forensic Science)
The quality of naturally occurring freshwater may be degraded through natural sources such as bedrock salts or sediment containing organic material. Additional degradation of water quality may be caused by human manipulation, such as fertilizers and petroleum products. When water pollution comes from a single source such as a sewage-outflow pipe, it is called point-source pollution; when the exact source of pollution is not as clear, as in agricultural or urban runoff, it is called non-point-source pollution.
The principal water polluters are industry and agriculture. Rain helps to cleanse air of pollutant emissions from motor vehicles, factories, and heating boilers, but the pollutants ultimately find their way into groundwater and streams. More direct forms of water pollution come from industrial discharges, construction detritus, and agricultural runoff. All these forms of pollution change the chemistry of water, changing its acidity, conductivity, and temperature. Nitrogen runoff fertilizes water, causing it to be choked with new vegetation.
The consequences to human society of impure water are alarming. Intractable diarrhea is a leading cause of death around the world among children under five, and its main cause is degraded drinking water. Cholera, a potentially deadly bacterial infection that plagues much of the underdeveloped world, requires only clean drinking water and proper sanitation to be eliminated as a...
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Air Quality (Forensic Science)
Air pollution not only threatens the health of human beings but also compromises the well-being of animal and plant life. It degrades bodies of freshwater, thins the atmosphere’s protective ozone layer, and creates haze that shrouds the beauty of nature. The EPA attempts to sustain reasonable levels of air purity through regulatory enforcement and voluntary programs, such as Energy Star and Commuter Choice. Through the federal Clean Air Act of 1990, the EPA restricts the amounts of specific pollutants allowed into the atmosphere to help protect public health.
Under the surveillance of the EPA are these broad categories of atmospheric pollutants: aerosols, asbestos, carbon monoxide, chlorofluorocarbons, ground-level ozone, hazardous air pollutants, hydrochlorofluorocarbon refrigerants, lead, mercury, methane gas, nitrogen oxides, particulate matter, propellants, radon, refrigerants, sulfur oxides, and volatile organic compounds. The EPA is armed with government regulations. Through a cooperative effort that involves private industry and state and local governments, the agency calls for the discontinuation of ozone-depleting substances, the elimination of specified toxic chemicals, and the treatment of polluted areas.
To assess air quality, the EPA’s Office of Air Quality Planning and Standards (OAQPS) monitors specific pollutants that can harm human health, the environment, and property. All common throughout the United...
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Further Reading (Forensic Science)
Friedlander, Sheldon K. Smoke, Dust, and Haze: Fundamentals of Aerosol Dynamics. 2d ed. New York: Oxford University Press, 2000. Written by a prominent authority on aerosols, this textbook designed for advanced undergraduates and graduate students covers basic concepts, lab techniques, and many practical applications.
Godish, Thad. Air Quality. 4th ed. Boca Raton, Fla.: Lewis, 2004. Up-to-date and comprehensive overview, appropriate for both undergraduate and graduate students, covers a wide variety of issues affecting air quality, with attention to atmospheric chemistry and the impact of polluted air on human health and the environment. Also covers public policy issues and risk assessment.
Heinsohn, R. J., and R. L. Kabel. Sources and Control of Air Pollution. Upper Saddle River, N.J.: Prentice Hall, 1998. Engineering textbook offers broad coverage of both natural and human-made sources of air pollution and methods for preventing or reducing pollution.
Nathanson, Jerry A. Basic Environmental Technology: Water Supply, Waste Management, and Pollution Control. 5th ed. Upper Saddle River, N.J.: Prentice Hall, 2007. Provides a clearly written introduction to water supply, waste management, and pollution control that is ideal for students with limited background in the hard sciences and engineering.
Novotny, Vladimir. Water Quality: Diffuse Pollution and Watershed...
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Air and Water Purity (World of Forensic Science)
Humans are susceptible to contaminated air and water. Breathing in air that is laden with a noxious substance can cause illness or even death. Similarly, drinking water that contains an inorganic or organic poison, or an infectious microorganism can be debilitating or lethal.
Both water and air are particularly vulnerable to contamination by some bacteria and protozoa, and by their toxic products. While the contamination of air and water can be inadvertent, the noxious substances can also be introduced deliberately. Chemicals can also be dispersed in water and by air. A recent example occurred in 1995, when the Japanese cult Aum Shinrikyo released sarin gas into the Tokyo subway system. The poisonous gas attack killed 12 people and sickened 5,000.
As another example, in the months following September 11, 2001, there were several deliberate releases of anthrax spores into the air following the opening of contaminated letters. As well, the vulnerability of water supplies to contamination with a variety of infectious organisms has been recognized.
An amount as small as a glass of water can be contaminated with a quantity of organic or inorganic poison or microbe sufficient to cause harm. Even if the water has been chlorinated, disease causing microorganisms such as Giardia and Cryptosporidium are resistant to chlorine, as are bacterial toxins.
Technologies exist to kill the microorganisms that might be present (disinfection) or to completely remove the microbes and chemicals from the air or water (purification). These technologies, however, are usually designed to remove naturally occurring or polluting contaminants.
Groundwater or surface water treatment focuses on providing water that is fit to drink. Typically, the water is filtered to remove large debris. Some jurisdictions also pass the water through microfilters that remove objects as small as viruses from the treated water. Most drinking water is treated with chlorine or chlorine-containing compounds to kill any bacteria. Other treatments that are gaining widespread acceptance include the use of ultraviolet light, ozone, and other chemicals such as bromine. Water can also be purified by techniques involving reverse osmosis and steam distillation, although these techniques are not typically used, as they are expensive and purify relatively small volumes of water at one time.
Treatment and monitoring ensure that the water emerging from the treatment plant is safe to drink and that it remains that way all the way to the consumer's tap. However, these measures are not intended to thwart a deliberate contamination.
Yet for large surface water supplies, the volume of water alone makes the possibility of deliberate contamination remote. For example, it has been estimated that the contamination of the Crystal Springs Reservoir, which supplies some of the water for San Francisco, California, with enough hydrogen cyanide to harm anyone who drinks a glass of water would require over 400,000 metric tons of the poison. Similarly, huge amounts of bacteria or viruses would be required.
Air is vulnerable to contamination with a variety of bacteria, viruses, and fungi that are light enough to become dispersed in air currents. When inhaled, the microbes can cause infections. Chemicals and toxins can also float in the air, to be inhaled or settle onto exposed skin.
Air purification has long been possible using filters. Bacteria, viruses, and even some inorganic chemicals can be retained on specialized filters. These filters are mainly suitable for laboratories or relatively small, specifically designed ventilation systems. In large indoor environments such as malls or sizeable office buildings, and in the open air, air purification is virtually impossible.
Contamination of the open air poses a similar problem as the contamination of a large volume of water, namely the amount of poisonous agent that is required. For example, estimates are that hundreds of pounds of anthrax spores would be needed to achieve a massive contamination of the population of a large city.
The release of toxic agents into a more limited area such as an office building or a home is more plausible.
SEE ALSO Air plume and chemical analysis; Bioterrorism; Organic compounds; Toxins.