CARS AND POLLUTION Emissions from an individual car are generally low, relative to the smokestack image many people associate with air pollution. But in numerous cities across the country, the personal automobile is the single greatest polluter, as emissions from millions of vehicles on the road add up. Driving a private car is probably a typical citizen’s most “polluting” daily activity. SOURCES OF AUTO EMISSIONS The power to move a car comes from burning fuel in an engine. Pollution from cars comes from by-products of this combustion process (exhaust) and from evaporation of the fuel itself.
THE COMBUSTION PROCESS Gasoline and diesel fuels are mixtures of hydrocarbons, compounds which contain hydrogen and carbon atoms. In a “perfect” engine, oxygen in the air would convert all the hydrogen in the fuel to water and all the carbon in the fuel to carbon dioxide. Nitrogen in the air would remain unaffected. In reality, the combustion process cannot be “perfect,” and automotive engines emit several TYPES OF POLLUTANTS. Automobile Emissions: An Overview “Perfect” Combustion FUEL (hydrocarbons) + AIR (oxygen and nitrogen) CARBON DIOXIDE + water + unaffected nitrogen TYPICAL ENGINE COMBUSTION FUEL + AIR UNBURNED HYDROCARBONS + NITROGEN OXIDES + CARBON MONOXIDE + CARBON DIOXIDE + water
Type of air pollutant by vehicle emission Amount produced by transportation (in millions of short tons) Amount of pollutant produced by highway travel Amount of pollutant produced by non-highway travel Amount of total emissions pollutant produced by petrol vehicles Amount of total emissions pollutant produced by diesel vehicles CO74.0353.80%23.80%98%1.60% NOx10.6236.20%22.10%55.90%44.10% VOCs6.1722.10%13.30%5.90%4.10% PM-100.481%1.60%48.60%51.40% PM-2.50.412.80%6.10%36.70%63.30%
the formation of which can lead to risk of damage to the human respiratory system. Though beneficial in the upper atmosphere, at the ground level this gas irritates the respiratory system, causing coughing, choking, and reduced lung capacity. In addition, some kinds of HCs are also indirect greenhouse gases, and can cause liver damage and even cancer.
the main effects of these types of exposures are drowsiness, dizziness, and headaches. Leukemia (cancer of the tissues that form the white blood cells) and subsequent death from cancer have occurred in some workers exposed to benzene for periods of less than 5 and up to 30 years
NOx are pollutants that cause lung irritation and weaken the body's defenses against respiratory infections such as pneumonia and influenza, can cause shortness of breath and chest pains and increase a person's susceptibility to asthma.
O reduces the blood's oxygen carrying capacity, and, when inhaled, blocks the transport of oxygen to the brain, heart, and other vital organs in the body. Extreme levels of exposure, such as might occur due to blockages in tailpipes, can be fatal. Fetuses, newborn children, and people with chronic illnesses are especially susceptible to the effects of CO. In addition, carbon monoxide is directly linked to visual impairment, reduced work capacity and mental dexterity, poor learning ability, nausea, headaches, dizziness, and even death
Acrolein is a colorless or yellow liquid with a disagreeable odor. It dissolves in water very easily and quickly changes to a vapor when heated and also burns easily. Small amounts of acrolein can be formed and can enter the air when trees, tobacco, other plants, gasoline, and oil are burned. Breathing large amounts can damage lungs and can cause death. Animal studies show that breathing acrolein causes irritation to the nasal cavity, lowered breathing rate, and damage to the lining of the lungs.