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ORGANIC AND INORGANIC ENVIRONMENTAL POLLUTANTS IN AIR AND WATERS. SONIC AND ELECTROMAGNETIC POLLUTION
I.1. AIR POLLUTANTS
Maria José SANZ, José Vicente CHORDÁ
Air pollution started when tribesmen learned to use fire, and filled the air inside their living quarters with the products of incomplete combustion. But the biggest step forward was the Industrial Revolution, thus the predominant air pollution in the 19th century was smoke and ash from the burning of coal or oil in the boiler furnaces of stationary power plants, locomotives, vessels, home heating fireplaces and furnaces. During the 20th century, after recognition of the problem by countries like Great Britain and the United States, there were great changes in the technology of both the production of air pollution and its control, but not significant changes in the limiting legislation, regulations and understanding of the problem. But, as cities and industry grew in size, the problem increased in severity. Since the 30s the other air pollution problems as well as solutions up to some extent emerged. In the following sections are described the main air pollutants and problems identified today. Due to their different nature, the pollutants are separated in organic and inorganic compounds.
I.1.1. ORGANIC AIR POLLUTANTS
I.1.1.1. Volatile Organic Compounds (VOCs)
Volatile Organic Compounds are substances that contain carbon that evaporates easily. VOCs can be from natural or anthropogenic sources. Anthropogenic VOCs are present in exhaust fumes, cigarette smoke, synthetic materials and household chemicals, and include benzene, formaldehyde and polynuclear aromatic hydrocarbons (PAH).
VOCs are involved in the formation of ground level ozone and in the depletion of the ozone layer. They also contribute to the greenhouse effect, photochemical oxidants produced from the use of VOCs are greenhouse gases. Only the most important VOCs are included below.
The most abundant aromatic hydrocarbons in urban atmospheres are benzene, toluene and xylenes, and trimethylbenzenes.
Benzene; the chemical formula for benzene is C6H6, and it has a molecular weight of 78.11 g/mol. (US EPA, 2002). Benzene occurs as a volatile, colorless, highly flammable liquid, it has a sweet odor with an odor threshold of 1.5 ppm (5 mg/m3).
It is a VOC that is a minor constituent of petrol. The main sources of benzene in the atmosphere in Europe are the distribution and combustion of petrol. Of these, combustion by petrol vehicles is the single biggest source (70% of total emissions).
Benzene is present in petrol but not diesel. Hydrocarbons including benzene are emitted during refueling, by evaporating from fuel tanks and exhausts and as unburnt hydrocarbons in exhausts. Benzene is also present in cigarette smoke and in some glues and cleaning products. Acute (short-term) inhalation exposure of humans to benzene may cause drowsiness, dizziness, headaches, as well as eye, skin, and respiratory tract irritation, and, at high levels, unconsciousness. Chronic (long-term) inhalation exposure has caused various disorders in the blood, including reduced numbers of red blood cells and aplastic anemia, in occupational settings. Reproductive effects have been reported for women exposed by inhalation to high levels, and adverse effects on the developing fetus have been observed in animal tests. Increased incidences of leukemia (cancer of the tissues that form white blood cells) have been observed in humans occupationally exposed to benzene.
Xylene, m-, o-, and p-Xylene are the three isomers of xylene; commercial or mixed xylene usually contains about 40-65% m-xylene and up to 20% each of o- and p-xylene and ethylbenzene. Mixed xylenes are colorless liquids that are practically insoluble in water and have a sweet odor. The odor threshold for m-xylene is 1.1 ppm. The chemical formula for mixed xylenes is C8H10 (http://www.epa.gov/ttn/atw/hlthef/).
Xylenes are released into the atmosphere as fugitive emissions from industrial sources, from auto exhaust, and through volatilization from their use as solvents. Acute (short-term) inhalation exposure to mixed xylenes in humans results in irritation of the eyes, nose, and throat, gastrointestinal effects, eye irritation, and neurological effects. Chronic (long-term) inhalation exposure of humans to mixed xylenes results primarily in central nervous system (CNS) effects, such as headache, dizziness, fatigue, tremors, and incoordination; respiratory, cardiovascular, and kidney effects have also been reported.
Toluene, the chemical formula is C6H5CH3, and its molecular weight is 92.15 g/mol. Toluene occurs as a colorless, flammable, refractive liquid, that is slightly soluble in water. Toluene has a sweet, pungent odor, with an odor threshold of 2.9 parts per million (ppm).
Toluene’s major use is to be added to gasoline to improve octane ratings, it is also used to produce benzene and as a solvent in paints, coatings, adhesives, inks, and cleaning agents. It has a minor importance in the production of polymers used to make nylon, plastic soda bottles, polyurethanes and for pharmaceuticals, dyes, cosmetic nail products, and the synthesis of organic chemicals.
Exposure to toluene may occur from breathing ambient or indoor air. The central nervous system (CNS) is the primary target organ for toluene toxicity in both humans and animals for acute (short-term) and chronic (long-term) exposures. CNS dysfunction and narcosis have been frequently observed in humans acutely exposed to toluene by inhalation; symptoms include fatigue, sleepiness, headaches, and nausea. CNS depression has been reported to occur in chronic abusers exposed to high levels of toluene. Chronic inhalation exposure of humans to toluene also causes irritation of the upper respiratory tract and eyes, sore throat, dizziness, and headache. Human studies have reported developmental effects, such as CNS dysfunction, attention deficits, and minor craniofacial and limb anomalies, in the children of pregnant women exposed to toluene or mixed solvents by inhalation. Reproductive effects, including an association between exposure to toluene and an increased incidence of spontaneous abortions, have also been noted. However, these studies are not conclusive due to many confounding variables. (http://www.epa.gov/ttn/atw/hlthef/toluene.html)
Methanogenic bacteria (lithotrophic autotrophs)
Natural gas leaks during fossil-fuel mining
Transfer to soils and ice caps
Methanotrophic bacteria (conventional
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