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2.1.3 Volatile Organic Compounds

These volatile organic compounds (VOCs) make up the lower boiling fractions of fuels and lubricants, and partially combusted fuels. These VOCs are emitted during refueling, leakage in the engine, and tailpipe.

VOCs are complex compounds of aliphatics, olefins, aldehydes, hetones and aromatics. Many these compounds are known to be potentially hazardous to human health. But in general these compounds are found in such low quantities there are no fears of having direct effects on human health. Rather these compounds have a direct effect on photochemical smog.

2.1.3.1 Effects of Benzene

Prolonged exposure to benzene especially in the respiratory tract or cutaneous contact can result in aplastic anemia or acute myelogenous leukemia. Bone marrow is also affected. When the bone marrow is affected it decreases circulation in the erythrocyte, platelets and leukocytes. Benzene related leukemia usually affects workers exposed to it for periods of forty years.

2.1.3.2 Effects of Aromatics

Aromatics have been added in modern day fuels which contain high levels of benzene. The total benzene emission increase is directly proportional to the amount of aromatics found in fuels. For about every 1% of aromatics there is 4% of benzene. It was also found that the amount of non-benzene aromatics in fuels also results in a n increase in tailpipe emissions of benzene.

2.1.3.3 Effects of Hydro Carbons

Aliphatic hydrocarbons upon inhalation may be harmful, because in high concentrations, they depress the central nervous system causing dizziness and incoordination. It is generally accepted that low level exposures have no or little effects on the human body. But they do play an important role in photochemical smog.

2.1.3.4 Effects of Alcohol

With the additions of methanol and ethanol as fuel additives was implemented to reducing emissions. But the problem is that these additives are very volatile hence they will contribute to the overall VOC load. The problem with additives such as methanol tends to emit formaldehyde. And formaldehyde is a carcinogen and a key component to photochemical smog.

2.2 PHOHEMICAL SMOG

There are two types of smog. The first, which has been known for a long time, is when there is an incomplete combustion of coal. This phenomena produces sulfur dioxide and smoke and in combination with fog forms smog. The second type is when automobiles exhaust produces oxidative pollutants, which leads to photochemical smog. Photochemical smog results from the atmospheric reaction between certain hydrocarbons and oxides of 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

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