Pollution nitrous oxide

Nitrous oxide (N O), commonly known as laughing gas is also known to cause environment pollution. Nitrous oxide is obtained as a by-product during the manufacture of adipic acid as follows ... 

In densely populated areas, traffic is responsible for massive exhausts of nitrous oxides, soot, polyaromatic hydrocarbons, and carbon monoxide. Traffic emissions also markedly contribute to the formation of ozone in the lower parts of the atmosphere. In large cities, fine particle exposure causes excess mortality which varies between one and five percent in the general population. Contamination of the ground water reservoirs with organic solvents has caused concern in many countries due to the persistent nature of the pollution. A total exposure assessment that takes into consideration all exposures via all routes is a relatively new concept, the significance of which is rapidly increasing. 

Public concerns about air quality led to the passage of the Clean Air Act in 1970 to amendments to that act in 1977 and 1990. The 1990 amendments contained seven separate titles covering different regula-toiy programs and include requirements to install more advanced pollution control equipment and make other changes in industrial operations to reduce emissions of air pollutants. The 1990 amendments address sulfur dioxide emissions and acid rain deposition, nitrous oxide emissions, ground-level ozone, carbon monoxide emissions, particulate emissions, tail pipe emissions, evaporative emissions, reformulated gasoline, clean-fueled vehicles and fleets, hazardous air pollutants, solid waste incineration, and accidental chemical releases. 

The carbonic acid produced in Equation (6.5) is a proton donor, so the solution contains more solvated protons than hydroxide ions, resulting in rain that is (overall) an acid. To make the risk of pollution worse, acid rain in fact contains a mixture of several water-borne acids, principally nitric acid, HNO3 (from nitrous oxide in water), and sulphurous acid, H2SO3 (an aqueous solution of sulphur dioxide). 

Most models of gas uptake in the respiratory tract have been concerned with carbon dioxide, carbon monoxide, oxygen, and anesthetic gases like chloroform, ether, nitrous oxide, benzene, and carbon disulfide (e.g., see Lin and Gumming and Papper and Kitz ). Unfortunately, there are only a few preliminary models of pollutant-gas transport and uptake in the respiratory tract. 

The chemical structures of the currently available inhaled anesthetics are shown in Figure 25-2. The most commonly used inhaled anesthetics are isoflurane, desflurane, and sevoflurane. These compounds are volatile liquids that are aerosolized in specialized vaporizer delivery systems. Nitrous oxide, a gas at ambient temperature and pressure, continues to be an important adjuvant to the volatile agents. However, concerns about environmental pollution and its ability to increase the incidence of postoperative nausea and vomiting (PONV) have resulted in a significant decrease in its use. 

Nitrous oxide is nontoxic—it used as the propellant in whipped-cream spray cans—and so might seem to be an unlikely pollutant. However, as noted earlier, it may contribute significantly to greenhouse warming. Furthermore, on diffusing to the stratosphere, N20 becomes involved in the ozone cycle (reactions 8.2, 8.3, and 8.6) following its conversion to nitric oxide (NO) ... 

The nitrogen atoms are then oxidized to NO by reaction with OH (R116), or they can be converted to N2 by reaction with NO (R114b). At lower temperatures the oxidation mechanism for HCN is more complicated, involving formation and consumption of a number of pollutant species including oxicyanides, amines (NH,), and nitrous oxide (N20). 

Nitrous oxide should not be confused with nitric oxide, or NO, another gas that dilates the blood vessels (but is an air pollutant). 

A number of compressed and liquified gases are used as refrigerants and aerosol propellants. These include nitrous oxide, nitrogen, carbon dioxide, propane, and butane. The use of chlorofluorocarbons (CFCs) is restricted because of environmental pollution leading to health hazards. These have been replaced by hydrogenated fluorocarbons (HFCs), which are less likely to cause environmental pollution. 

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