Pollutants in the air threaten the lives of everything living on earth. They cause acid rain and smog, weaken the ozone layer, increase the chances of cancer and contribute to changing the climate of the world. Pollutants can be invisible and often we don’t even realize that we’re making them.
Polluted air travels with the wind, affecting all of us, whether or not we are responsible for it. Smog aggravates heart and respiratory diseases. Acid rain erodes buildings, hurts plants and trees and kills marine life by poisoning lakes.Metal particles and vapors from fuel, called air toxins, cause lung and respiratory problems. Chemicals like methane and carbon dioxide are found in refrigerators and air conditioners. These chemicals last a long time in the atmosphere and make holes in the ozone layer and contribute to global warming. Some of the causes of these pollutants are more obvious than others.
While automobiles, chemical plants and industrial factories are commonly known culprits, paints, dry cleaners, farm equipment, lawn mowers and various household products are also contributing to the problem. Pollutants:-An air pollutant is known as a substance in the air that can cause harm to humans and the environment. Pollutants can be in the form of solid particles, liquid droplets, or gases. In addition, they may be natural or man-made.
Pollutants can be classified as primary or secondary. Usually, primary pollutants are directly emitted from a process, such as ash from a volcanic eruption, the carbon monoxide gas from a motor vehicle exhaust or sulfur dioxide released from factories. Secondary pollutants are not emitted directly.Rather, they form in the air when primary pollutants react or interact. An important example of a secondary pollutant is ground level ozone — one of the many secondary pollutants that make up photochemical smog. Some pollutants may be both primary and secondary: that is, they are both emitted directly and formed from other primary pollutants. About 4 percent of deaths in the United States can be attributed to air pollution, according to the Environmental Science Engineering Program at the Harvard School of Public Health. Major primary pollutants produced by human activity include:- * Sulfur oxides (SOx),Nitrogen oxides (NOx),Carbon dioxide (CO2),Volatile organic compounds ,Chlorofluorocarbons (CFCs),Ammonia (NH3), Radioactive pollutants Health effects:-The World Health Organization states that 2.
4 million people die each year from causes directly attributable to air pollution, with 1.5 million of these deaths attributable to indoor air pollution. “Epidemiological studies suggest that more than 500,000 Americans die each year from cardiopulmonary disease linked to breathing fine particle air pollution. . .” A study by the University of Birmingham has shown a strong correlation between pneumonia related deaths and air pollution from motor vehicles. Worldwide more deaths per year are linked to air pollution than to automobile accidents.
Published in 2005 suggests that 310,000 Europeans die from air pollution annually.Causes of deaths include aggravated asthma, emphysema, lung and heart diseases, and respiratory allergy. The US EPA estimates that a proposed set of changes in diesel engine technology (Tier 2) could result in 12,000 fewer premature mortalities, 15,000 fewer heart attacks, 6,000 fewer emergency room visits by children with asthma, and 8,900 fewer respiratory-related hospital admissions each year in the United States. Diesel exhaust (DE) is a major contributor to combustion derived particulate matter air pollution.
In several human experimental studies, using a well validated exposure chamber setup, DE has been linked to acute vascular dysfunction and increased thrombus formation. This serves as a plausible mechanistic link between the previously described association between particulate matter air pollution and increased cardiovascular morbidity and mortality.Control devicesThe following items are commonly used as pollution control devices by industry or transportation devices. They can either destroy contaminants or remove them from an exhaust stream before it is emitted into the atmosphere.Particulate control & conclusion:-* Mechanical collectors (dust cyclones, multicyclones) * Electrostatic precipitators an electrostatic precipitator (ESP), or electrostatic air cleaner is a particulate collection device that removes particles from a flowing gas (such as air) using the force of an induced electrostatic charge. Electrostatic precipitators are highly efficient filtration devices that minimally impede the flow of gases through the device, and can easily remove fine particulate matter such as dust and smoke from the air stream.* Scrubbers* Baffle spray scrubber* Cyclonic spray scrubber* Ejector venturi scrubber* Mechanically aided scrubber* Spray tower* Wet scrubber* NOx control* Low NOx burners* Selective catalytic reduction (SCR)* Selective non-catalytic reduction (SNCR)* NOmmx scrubbers* Exhaust gas recirculation* Catalytic converter (also for VOC control)Particulate scrubbers Wet scrubber is a form of pollution control technology.
The term describes a variety of devices that use pollutants from a furnace flue gas or from other gas streams. In a wet scrubber, the polluted gas stream is brought into contact with the scrubbing liquid, by spraying it with the liquid, by forcing it through a pool of liquid, or by some other contact method, so as to remove the pollutants.