It became a serious threat to vegetation, wild life, and human health. Air pollution has been the cause of numerous health problems including asthma and cancer. It is estimated that over 60,000 people in the united states alone die each year due to heart and lung diseases related to air pollution.
Hundreds of elements and compounds such as benzene and formaldehyde are known to be emitted during the combustion of coal, oil, natural gas, and wood in electric power plants. Engines of vehicles, furnaces, and even fire plaees. Some compounds are added to liquid fuels for various reasons (such as MTBE to raise the oetane number of the fuel and also to oxygenate the fuel in winter months to reducc urban smog). The largest source of air pollution si the motor vehicles, and the pollutants released by the vehicles are usually grouped as hydrocarbons (HC), nitrogen oxides (〖NO〗_X), and carbon
Monoxide ( CO) (Fig. 2-63). The HC emissions are a large component of volatile organic compounds (VOCs) emissions, and the two terms are generally used interchangeably for motor vehicle emissions. A significant portion of the VOC or HC emissions are caused by the evaporation of fuels during refueling or spillage during spitback or by evaporation from gas tanks with faulty caps that do not close tightly. The solvents, Propellants, and household cleaning products that contain benzene, butane, or other HC products are also significant sources of HC emissions.
The increase of environmental pollution at alarming rates and the rising awareness of its dangers made it necessary to control it by legislation and international treaties. In the united states, the clean air act of 1970 (whose passage was aided by the 14-day smog alert in Washington that year) set limits on pollutants emitted by large plants and vehicles. These early standards focused on emissions of hydrocarbons, nitrogen oxides, and carbon monoxide. The new cars were required to have catalytic converters in their exhaust systems to reduce HC and CO emissions. AS a side benefit, the removal of lead from gasoline to permit the use of catalytic converters led to a significant reduction in toxic lead emissions.
Emission limits for HC, 〖NO〗_X, and CO form cars have been declining steadily since 1970. The clean air act of 1990 made the requirements on emissions even tougher, primarily for ozone, CO, nitrogen dioxide, and particulate matter (PM). As a result, today’s industrial facilities and vehicles emit a fraction og the pollutants they used to emit a few decades ago. The HC emissions of cars, for example, decreased from about 5 g/km (grams perkm) in 1970 to 0.25 g/km in 1980 and about 0.06 g/km in 1999. This is a significant reduction since many of the gaseous toxics from motor vehicles and liquid fuels are hydrocarbons.
Children are most susceptible to the damages caused by air pollutants since their organs are still developing. They are also exposed to more pollution since they are more active, and thus they breathe faster. People with heart and lung problems, especially those with asthma, are most affected by air pollutants. This becomes apparent when the air pollution levels in their neighborhoods rise to high levels.
OZONE AND SMOG
If you live in a metropolitan area such as los angeles, you are probably familiar with urban smog-the dark yellow or brown haze that build up in a large stagnant air mass and hangs over populated areas on calm hot
Summer days. Smog is made up mostly of ground - level ozone (o_3), but it also contains numerous other chemicals, including carbon monoxide (CO), particulate matter such as soot and dust, volatile organic compounds (VOCs) such as benzene, butane, and other hydrocarbons. The harmful ground level ozone should not be confused with the useful ozone layer high in the stratosphere that protects the earth from the sun’s harmful ultraviolet rays. Ozone at ground level is a pollutant with several adverse health effects.
The primary source of both nitrogen oxides and. Hydrocarbons is the motor vehixles. Hydrocarbons and nitrogen oxides react in the presence of sunlight on hot calm days to form ground-level ozone. Which is the primary component of smog (Fig. 2-64) the smog formation usually peaks in tate afternoons when the temperatures are highest and there is plenty of sunlight. Although ground-level smog and ozone form in urban areas with beavy traffic or industry, the prevailing winds can transport them several hundred miles to other cities.this shows that pollution knows of no boundarics, and it is a global problem.
O:one irritates eyes and damages the air sacs in the lungs where oxygen and carbon dioxide are exchanged, causing eventual hardening of this soft and spongy tissue. It also causes shortness of breath, wheezing, fatigue, headaches, and nausea, and aggravates respiratory problems such as asthma. Ever exposure to ozone does a little damage to the lungs, just like cigarette smoke, eventually reducing the individual’s lung capacity. Staying indoors and minimizing physical activity during heavy smog minimizes damage. Ozone also harms vegetation by damaging leaf tissues. To improve the air quality in areas with the worst ozone problems, reformulated gasoline (RFG) that contains at least 2 percent oxygen was introduced. The use of RFG has resulted in significant reduction in the emission of ozone and other pollutants, and its use is mandatory in many smog-prone areas.
The other serious pollutant in smog is carbon monoxide, which is a colorless, odorless, poisonous gas. It is mostly emitted b motor vehicles, and it can build to dangerous levels in areas with heavy congested traffic. It deprives the body’s organs from getting enough oxygen by binding with the red blood cells that would otherwise carry oxygen. At low levels, carbon monoxide decreases the amount of oxygen supplied to the brain and other organs and muscles, slows body reactions and reflexes, and impairs judgment. It poses a serious threat to people with heart disease because of the fragile condition of the circulatory system and to fetuses because of the oxygen needs of the developing brain. At high levels, it can be fatal, as evidenced by numerous deaths caused y cars that are warmed up in closed garages or by exhaust gases leaking into the cars.
Srnog also contains suspended particulate matter such as dust and soot emitted by vehicles and industrial facilities. Such particles irritate the eyes and the lungs since they may carry compounds such as acids and metals.
ACID RAIN
Fossil fuels are mixtures of various chemicals, including small amounts of sulfur. The sulfur in the fuel reacts with oxygen to form sulfur dioxide (SO_2), which is an air pollutant. The main source of SO_2 is the electrie power plants that burn high-sulfur coal. The clean air act of 1970 has limited the SO_2 emissions severely, which forced he plants to install SO_2