2-­‐5-­‐3: Air Pollution   A"er this lecture, you should be able to:   Dis5nguish between various types of atmospheric pollu5on, their characteris5cs, and their effects on environmental and biological systems.   Explain how and why urban areas face unique challenges with respect to air pollu5on.   Evaluate components of the Clean Air Act and how they have or intend to improve overall air quality.   Analyze the factors that lead to upper atmospheric ozone deple5on and how ozone can be both essen5al and a pollutant.   Iden5fy sources of indoor air pollu5on and how they affect biological systems. Air Pollution in Lower Atmosphere  
A brief history  
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The atmosphere has long been a sink for waste disposal Long history of recogni5on of the existence of atmospheric pollutants Sta5onary sources -­‐ those that have a rela5vely fixed loca5on  
Point sources  
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Natural photochemical smog recognized in 1550   Acid rain first described in 17th century   Word smog introduced in 1905   Mixture of smoke and fog  
Fugi5ve sources  
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generate air pollutants from open areas exposed to wind processes Area sources  
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emit pollutants from controllable sites well defined areas within which are several sources of air pollutants Mobile source -­‐ move from place to place while emiUng pollutants  
Automobiles, trucks, buses, aircra", ships, and trains. General Effects of Air Pollution   Affects many aspects of our environment including visual quali5es, vegeta5on, animals, soil, water quality, natural and ar5ficial structures, and human health.   Affect human health in several ways Toxic poisoning, cancer, birth defects, eye irrita5on, and irrita5on of respiratory system   Increased suscep5bility to viral infec5ons, causing pneumonia and bronchi5s   Increased suscep5bility to heart disease   Aggrava5on of chronic diseases, such as asthma and emphysema  
  Many air pollutants have synergis5c effects  
Do greater damage to the lungs than a combina5on of the two pollutants would be expected to do based on their separate effect Air Pollutants  
200 air pollutants recognized and assessed by US EP and listed in Clean Water Act  
Primary pollutants  
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Secondary pollutants  
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EmiXed directly into the air Carbon monoxide (58%), vola5le organic compounds (11%), nitrogen oxides (15%), sulfur oxides (13%), and par5culates (3%) Produced through reac5ons between primary pollutants and normal atmospheric compounds Natural pollutant exceed anthropogenic pollutants (other than sulfur and nitrogen oxides)  
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Release of sulfur dioxide from volcanic erup5ons. Release of hydrogen sulfide  
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Geysers and hot springs Biological decay in bogs and marshes Release of ozone in the lower atmosphere as a result of unstable meteorological condi5ons Emission of par5cles from wildfires and windstorms Natural hydrocarbon seeps Air Toxics   Known/suspected to cause cancer or other serious health problems.   Associated with long-­‐term and short-­‐term exposures   Gases, metals, and organic chemicals that are emiXed in rela5vely small volumes   Cause respiratory, neurological, reproduc5ve, or immune diseases   Standards have been set for more than 150 air toxics   Ex: hydrogen sulfide, hydrogen fluoride, chlorine gases, benzene, methanol, ammonia   EPA es5mates that the average risk for cancer from exposure to air toxics is about 1 in 21,000 Urban Air Pollution  
Smog  
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Term first used in 1905 as mixture of smoke and fog that produced unhealthy air Photochemical smog (LA type smog or brown air) Sulfurous smog (London type smog, gray air, or industrial smog)  
Whether air pollu5on develops depends on topography and meteorological condi5ons  
Primary adverse effect  
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Damage to green plants and aggrava5on of chronic disease Usually low-­‐level over long period of 5me In the lower atmosphere, restricted circula5on associated with inversion layers may lead to pollu5on event  
Occurs when warmer air is found above cooler air Potential for Urban Air Pollution   Determined by the following factors:  
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Rate of emission of pollutants per unit area Downwind distance that a mass of air moves through an urban area Average speed of the wind   Eleva5on to which poten5al pollutants can be thoroughly mixed by naturally moving air in the lower atmosphere  
  The most reasonable strategies: Reduce   Collect  
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Capture  
Retain   Reduc5on of emissions through energy efficiency and conserva5on measures is preferred Clean Air Act Amendments of 1990   Regula5ons enacted by the U.S. Congress that address   Acid rain   Toxic emissions   Ozone deple5on   Automobile exhaust   Buying and selling of sulfur dioxide emissions   Nitrogen dioxides-­‐ reduced by 10 million tons   Toxins-­‐ especially those causing cancer Air Quality Index   Used to describe air pollu5on on a given day   Determined from measurements of the concentra5on of five major pollutants:   Par5culate maXer, sulfur dioxide, carbon monoxide, ozone, and nitrogen dioxide. Ozone Depletion and CFCs  
The major features of the hypothesis:  
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CFCs emiXed in the lower atmosphere are extremely stable and therefore have a very long residence 5me (about 100 years) CFCs eventually wander upward and enter the stratosphere Once above the stratospheric ozone, they may be destroyed by UV radia5on, releasing chlorine, a highly reac5ve atom The chlorine released then depletes the ozone Deple5on increases the amount of UVB radia5on that reaches Earth s surface Damage to food chain on land and in oceans (loss of primary produc5on ) UVB is a cause of human skin cancers and is also thought to be harmful to the human immune system Sources of Indoor Air Pollution   Common indoor air pollutants are o"en highly concentrated compared with outdoor levels   Many poten5al indoor sources of pollutants.   Effec5veness of the steps we have taken to conserve energy in buildings has led to the trapping of pollutants inside Pathways, Processes, and Driving Forces  
Many air pollutants originate within buildings and may be concentrated there because of lack of proper ven5la5on  
Other air pollutants may enter by infiltra5on,  
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Through cracks and other openings in the founda5ons and walls Or by way of ven5la5on systems  
Systems are designed to provide a comfortable indoor environment for people  
Design depends on a number of variables  
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Including the ac5vity of people in the building, air temperature and humidity, and air quality. If designed correctly, the system will  
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Provide thermal comfort for people inhabi5ng the building Provide the necessary ven5la5on (u5lizing outdoor air) Remove common air pollutants via exhaust fans and filters Control of Indoor Air Pollution  
Strong financial incen5ves to provide workers with a clean air environment  
Meet minimum indoor air quality standards  
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Including increase in the inflow of fresh air through ven5la5on One of the principal means for controlling quality is by dilu5on  
Fresh outdoor air mixed  
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Ven5la5ng air-­‐condi5oning system Windows that can be opened Various types of air-­‐cleaning systems reduce poten5al pollutants  
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Par5cles, vapors, and gases Can be installed as part of the hea5ng, ven5la5on, and AC system or as stand-­‐alone appliances   Educa5on also plays an important role  
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May involve deciding not to install unvented or poorly vented appliances. Educated people are more aware of their legal rights with respect to product liability and safety. Educa5on provides people with the informa5on necessary to make decisions concerning exposure, and strategies to avoid poten5ally hazardous condi5ons in the home and workplace. End of Lecture Objectives  
Dis5nguish between various types of atmospheric pollu5on, their characteris5cs, and their effects on environmental and biological systems.  
Explain how and why urban areas face unique challenges with respect to air pollu5on.  
Evaluate components of the Clean Air Act and how they have or intend to improve overall air quality.  
Analyze the factors that lead to upper atmospheric ozone deple5on and how ozone can be both essen5al and a pollutant.  
Iden5fy sources of indoor air pollu5on and how they affect biological systems.