Automobile Emissions Essay Research Paper ABSTRACTPollution from — страница 3

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nitrogen in the presence of sunlight. The most common effects on the human body by photochemical smog are eye irritation, potential effects on the respiratory system, reduced visibility and plant damage. During intense smog periods, ozone levels tend to reach hazardous levels. Hence these levels will also have an adverse effect on human health. Studies have been done in determining the effects of ozone on animals and humans. Exposures to 6 ppm of ozone for a period of four hours will have about a 50% mortality rate among rats and mice. At levels of (ozone) about 1 ppm will have adverse effects (permanent damage) on the respiratory tracts of small animals. Some animals also developed some form of immunity to low levels of ozone. Studies done on humans were done using low levels of

ozone for relatively short periods of time. Hence long term effects are unknown. For short-term effects to ozone exposure humans expressed similar patterns to those of animals. It was found that humans obtain some form of immunization. Other research showed that asthmatics did not suffer more effects from ozone exposure than did other individuals with or without light exercise, there was irritation at 0.12 ppm with high exercise levels and the effect at high exercise levels was a product of ozone concentration, ventilation rate and exposure time. 2.3 PARTICULATE EMISSIONS 2.3.1 Lead Because of high compression ratios built automobiles (generally American built cars), these automobiles use to require high-octane (90-100) octane gasoline for high performance. To obtain such levels

at the time either tetraethyl lead or other organometallic compounds, or by increasing the aromatic content of the gasoline. But through environmental awareness advanced countries have reduced or cut out lead in gasoline products. The removal of lead was also necessary for catalyst equipped cars to function properly. The effects of lead were very important for the removal from gasoline powered automobiles. High lead concentrations have adverse effects on human heath such as neurotic, renal, and reproductive effects. At lower levels of lead exposure it may cause hyperactivity, auditory deficiencies, reduction in intelligence, and reduced nerve conduction. Also by measuring blood lead levels in humans it was found by lowering the lead emission lower the lead blood levels. 2.3.2

Diesel Emissions Diesel engine powered automobiles are very similar to powered by petrol with the exception that diesel engines produce a lot more particulate emissions. As discussed earlier particulate emissions are believed to be carcinogenic. High exposures to diesel particulate resulted in lung inflammation, accumulations of soot and chronic lung disease in rats. Lung tumors also increased at high concentrations but none were found at low levels. 2.3.3 Manganese Methylcyclopentadienyl manganese tricarbon (MMT) is another metal containing anti lock additive. This additive has been used in petrol cars since the phase out of leaded fuels to increase compression. The concentration of MMT is very low in petrol fuels. Hence there has been little or no effect in the rise of

manganese emissions. Chronic exposure to high levels of manganese (in occupational settings) has resulted in maganism. Maganism is a disease, which produces psychotic behavior with hallucinations, delusions and compulsions. Also it may result in a condition resembling Parkinson and eventually death may occur in a severe case. 3. EMISSION CONTROL 3.1 EXHAUST EMISSIONS CONTROL LEGISLATION Legislation requiring the control of emissions from motor vehicles was first introduced in America in the 1600’s and has been progressively revised by incorporating reduced emissions requirements. An important step in emission control was taken in the 1970 amendment to the United States Clean Air Act which required a 90 % reduction in carbon monoxide, hydrocarbon, and nitrogen oxide emissions.

Figure 3.1 illustrates the percentage of these pollutant resulting from automobile emissions. POLLUTANT TOTAL AMOUNT VEHICLE EMISSIONS Amount Percentage NITROGEN OXIDES 36 019 17 012 47 HYDROCARBONS 33 869 13 239 39 CARBON MONOXIDE 119 148 78 227 66 Table 3-1 Pollution Accounted by Automobile Emissions in 1989 (1000 tons) The 1970 amendment requirements were so stringent for that period that they could not be met with available engine technology. New technology has since been developed and the requirements have been met. However, more rigid standards are continuously being proposed to improve emissions. While significant improvements to fuel economy, power output, and emissions have been made in recent years by modification and control, none of them have resulted in an engine