Carbon monoxide from motor vehicles

The carbon monoxide in the atmosphere originates to a large extent from motor vehicles and is almost completely due to them in the vicinity of streets. 

Yes, at least the levels of COj, or carbon monoxide have been reduced from motor vehicles. Some scientists say that it would be hard to asphyxiate oneself with a new, well-tuned vehicle. 

The amounts of carbon monoxide emitted from industrial processes, from the use of fuel for generating electric power and for heating homes, offices, and commercial and industrial structures, and from burning wood waste and debris from logging operations are eadi small in comparison with emissions from transportation, but they are nevertheless important. For example, the concentrated emissions of carbon monoxide from home heating with firewood, although less than 6 percent of total national emissions, are a concern quite distinct from carbon monoxide emissions from motor vehicles, and the potential health effects should not be imderestimated. 

Air pollution is principally a problem in urban and heavily industrialized areas, where the flow of clean air from surrounding areas is insufficient to disperse the accumulation. Motor vehicles account for more than 50% of the man-made emissions of carbon monoxide, hydrocarbons, and nitrogen oxides (4). More than half of the U.S. annual trillion vehicle miles are driven in urban areas (5). Nature produces much more pollutants than all man-made sources, but natural emissions are widely dispersed and do not contribute heavily to urban pollution problems (6, 7). 

Carbon monoxide (CO) Is one of the most widely distributed air pollutants. It Is formed by natural biological and oxidation processes, the Incomplete combustion of carbon-containing fuels and various Industrial processes. However, the largest Individual source of man-made emissions Is motor vehicle exhausts which account for virtually all CO emitted In some urban environments. It has been estimated that global man-made emissions range from 300-1600 million tons per year, which Is approximately 60% of the total global CO emissions (22-23). 

Carbon monoxide is produced by the incomplete combustion of fossil fuels, and in major urban areas of developed nations a major source is the exhaust from light-duty motor vehicles (LDMV). Figure 2.7 shows the distribution of sources within the United States in 1996. A total of 89 X 106 short tons, or 81 Tg, of CO were emitted, about 60% of which comes from highway vehicles (EPA, 1997). 

At the present moment, almost of methanol has been produced from natural gas through steam reforming followed by synthesis from hydrogen and carbon monoxide. Methanol is a promising fuel in future, because it is easily handled as liquid fuel, compatible with the existing infrastructure of motor vehicles, and wide application for direct burning and fuels for fuel cells. Furthermore, it is widely used for bulk chemicals. 

Carbon monoxide (CO) poisoning remains the single most common cause of fatal poisoning in developed, Western countries and most probably in the rest of the world as well. Motor vehicle exhausts, defective heating systems and smoke from all types of fires are common sources. Some 40% of an absorbed dose of dichloro-methane is also metabolized to CO. 

With the rapid expansion of the number of motor vehicles based on combustion engines, in certain parts of some countries the problem of the air pollution is even reaching catastrophe levels. One car produces approximately I t of harmful gases annually, containing 700 kg of carbon monoxide, 100 kg of hydrocarbons, 35 kg of nitrogen oxides and uncertain amounts of other highly toxic substances such as benzo[a]pyrene or lead. A striking illustration of the scale of the problem comes from the USA a child is born every 12 s a car is produced every 5 s. It has been considered that... 

Of the total amounts of hydrocarbons entering the atmosphere during motor vehicle operation, 60-70% come from exhaust gases, a further 15-30% from the crankcase, the remaining portion being evaporated from the carburettor and petrol tank. The number of different hydrocarbons in exhaust gases is estimated to be about 200. All the processes leading to carbon monoxide production also lead to the release of non-combusted hydrocarbons. 

A number of studies on motor-vehicle emissions have been realised for the preparation of directives and have been formalised by different Community Directives- Other studies on motor-vehicles are destined to Lead to a further stage in the reduction of emissions- It must be stated that these studies concern not only the problems of hydrocarbon emissions but also the whole spectrum of emissions one cannot distinguish between different pollutants and, apart from hydrocarbons, one must simuItaneoulsy consider nitrogen oxides, carbon monoxides as well as taking into account economic aspects of energy consumption and prices- In these studies no real distinction is made between the different types of hydrocarbons, one considers total hydrocarbons. 

Most of today s motor vehicles contain a catalytic converter to rednce the toxicity of emissions from their internal comhnstion engines. These catalytic converters have been nsed for many years as a means to comply with ERA emission standards. Since 1981 most vehicles have nsed three-way converters. They convert emissions to safer prodncts in three ways. Exhansts, before they reach the catalytic converter, contain nitrogen oxides, carbon monoxide, and some amonnt of noncombnsted hydrocarbons from gasoline. In the catalytic converter they are converted to less toxic prodncts, as shown in the following examples ... 

Carbon Monoxide (CO) Colorless, odorless gas resulting from the incomplete combustion of hydrocarbon fuels. CO interferes witb tbe blood s ability to carry oxygen to the body s tissues and results in numerous adverse health effects. More than 80 percent of the CO emitted in urban areas is contributed by motor vehicles. 

The most important natural source of atmospheric carbon monoxide is the combination of oxygen with methane (CH4), which is a product of the anaerobic decay of vegetation. (Anaerobic decay takes place in the absence of oxygen.) At the same time, however, carbon monoxide is removed from the atmosphere by the activities of certain soil microorganisms, so the net result is a harmless average concentration that is less than 0.12 to 15 ppm in the Northern Hemisphere. Because stationary source combustion facilities are under much tighter environmental control than are mobile sources, the principal source of carbon monoxide that is caused by human activities is motor vehicle exhaust, which contributes to about 70% of all CO emissions in the United States. 

Carbon monoxide, emitted by motor vehicles, is toxic because it diminishes the blood s ability to carry oxygen, in high concentrations, carbon monoxide is lethal, in lower concentrations, it causes the heart and respiratory system to work harder. The adverse health effects related to carbon monoxide exposure include impairment of visual perception, decreased work capacity, decreased manual dexterity, and lower learning ability. Those who suffer from cardiovascular disease, especially those with angina or peripheral vascular disease, are most sensitive. 

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