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Air Pollution

Explore the different types of air pollutants, their sources, and impact on the environment and human health. Learn about primary vs. secondary pollutants, conventional pollutants, acid rain, and indoor air pollution. Discover how human activities contribute to air pollution and steps for a cleaner future.

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Air Pollution

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  1. Air Pollution Chapter 16

  2. Outline • Types of Air Pollutants: Primary vs. Secondary • Natural and Human-Caused Sources of Air Pollution • Primary and Secondary Pollutants • Conventional Pollutants • Acid Rain • Ozone: the Global Sunscreen • Stratospheric Ozone Versus Tropospheric ozone • Stratospheric Ozone Depletion • Indoor Air Pollution • Current Conditions & Future Prospects

  3. How much air pollution can be confusing? I thought I saw a blue jay this morning. But the smog was so bad that it turned out to be a cardinal holding its breath. Michael J. Cohen

  4. INTROUCTION: THE AIR AROUND US • Air pollution is generally the most widespread & obvious environmental problem • Forms of air pollution: smoke, haze, dust, odors, noise, toxic and corrosive gases • Over the past 20 years, developed countries have been improving air quality, while air quality in developing world is getting worse • E.g.: in China & Pakistan: air pollutants are 10x higher than the threshold of health safety

  5. Types of Air Pollutants • Primary Pollutants: • Released directly from the source (e.g., NO, NO2, SO2…) • Secondary Pollutants: • Formed from the reactions of primary pollutants with each other, or with other components of the atmosphere • Photochemical oxidants  photochemical smog • Acids  acid rains

  6. – 2 SO4 Primary Pollutants NO3 – CO CO2 Secondary Pollutants SO2 NO NO2 SO3 Most hydrocarbons HNO3 H2SO4 Most suspended particles H2O2 O3 PANs Most and salts Natural Stationary Sources Mobile Primary vs. Secondary Pollutants

  7. NATURAL SOURCES OF AIR POLLUTION • Natural Fires: smoke • Volcanoes: ash, acids, hydrogen sulfide • Sea Spray: sulfur • Vegetation: volatile organic compounds (e.g., terpenes) • Bacterial metabolism in swamps & cellulose decay in guts of termites & ruminants: methane (2/3 of methane in the air) • Airborne particles: dust, pollen, viruses, & bacteria

  8. HUMAN-CAUSED AIR POLLUTION • Human-caused (anthropogenic) pollutants can be: • Different from natural pollutants (e.g., CFCs, PCBs…) • Identical to natural pollutants, doing harm by overloading natural cycles (C, S, N… cycles) • Carbon cycle disruption: Burning fossil fuels & Forest clearing   CO2 to the atmosphere  Global warming  Alteration of food production & ecosystems

  9. HUMAN-CAUSED AIR POLLUTION • N & S cycles disruption Burning fossil fuels Petroleum refining Use of Nitrogen fertilizers Burning of coal  ↑ [NOx] troposphere ↑ [SOx]troposphere Acid Deposition  Harm Plants, Animals & Materials

  10. CLASSIFICATION OF AIR AIR POLLUTANTS • Conventional or criteria pollutants: US Clean Air Act (1970) designated seven major pollutants for which maximum ambient air levels are mandated • Unconventional or non-criteria pollutants: pollutants that are considered by the EPA as especially toxic or hazardous => Emissions standards are set by EPA • E.g.: Asbestos, benzene, formaldehyde, mercury, Polychlorinated Biphenyls (PCBs) • Are mostly anthropogenic in origin

  11. The Seven Conventional Pollutants • Sulfur Compounds • Nitrogen Oxides • Carbon Monoxide • Particulates • Hydrocarbons • Lead • Photochemical Oxidants

  12. Conventional Pollutants - Sulfur Compounds • Natural sources: • Evaporation of sea spray • Erosion of sulfate-containing dust from arid soils • Fumes from volcanoes • Biogenic emissions (H2S) • Anthropogenic sources (predominant form is SO2): • Fossil fuel combustion • Purification of sulfur-containing natural gas or oil • Industrial processes • Sulfur dioxide (SO2): • Colorless, corrosive gas (damages plants & animals) • Reacts with H2O  H2SO4 (1st component of acid rain) • Sulfate particles & droplets => reduce visibility • Health effects: 2nd to smoking (constriction of the airways)

  13. Conventional Pollutants - Nitrogen Compounds • Sources of NOx: • Burning of N-containing fuel in vehicles and power plants • Heating fuel above 650o C in the presence of O2 • Oxidation of N-containing compounds by bacteria in soil or water • Nitrogen dioxide (NO2) • Reacts with H2O  HNO3 (2nd component of acid rain) • Reacts with VOCs under the action of solar UV  components of photochemical smog • NO2 is a reddish brown gas  distinctive color of the photochemical smog • Health effects: lung irritation & respiratory diseases

  14. Conventional Pollutants - Carbon Oxides • Carbon Monoxide (CO) • Colorless, odorless, toxic gas • Produced by incomplete combustion of fuel, biomass, or solid wastes • Inhibits oxygen transport by binding to hemoglobin  impairment of perception & thinking, headaches, drowsiness, dizziness, coma & even death • Carbon dioxide (CO2) • Predominant form of carbon in the air • Incineration of solid wastes • Increasing levels (0.5% / year) due to human activities (fossil fuel combustion, & forest & grassland fires)  global warming

  15. Conventional Pollutants – Particulate Material • Atmospheric aerosols • Solid particles or liquid droplets suspended in the air • E.g.: dust, ash, soot, smoke, pollen, spores, … • Most apparent form of air pollution (reduce visibility & leave dirty deposits on windows, painted surface, textiles…) • Health effects : aggravation of lung diseases; chronic respiratory diseases; & lung cancer. • Respirable particles which are less than 2.5 micrometers are among most dangerous (e.g., asbestos fibers & cigarette smoke)

  16. Conventional Pollutants - VOCs • Volatile Organic Compounds (VOCs): • Organic chemicals that exist as gases in the air • VOCs are generally oxidized to CO & CO2. • VOCs play an important role in the formation of photochemical oxidants (components of photochemical smog) • Sources of VOCs: • Natural: emitted by plants (e.g, terpenes, isoprenes) and some bacteria (methane) • Human-caused: unburned/partially burned hydrocarbons from fossil fuel combustion , & petroleum refineries (e.g., benzene, formaldehyde, chloroform, phenols…) • Health effects: mutations; reproductive problems; lung cancer

  17. Conventional Pollutants – Metals • Metals • Many toxic metals are mined & used in manufacturing processes, or occur as trace elements in fuel (coal) • Released into the air from fuel combustion, ore smelting, or waste disposal • Lead • Released from combustion of leaded gasoline • Binds to & inactivate enzymes => metabolic poison & neurotoxin(20% of city children in polluted area suffer from mental retardation) • Mercury • Released from coal-burning power plants & waste incinerators • Neurotoxin • Long-range transport of lead & mercury through the air bioaccumulation in aquatic ecosystems far from the emission sources (dangerous to eat fish from polluted lakes)

  18. Secondary Pollutants- Photochemical Oxidants Smog

  19. Conventional Pollutants – Photochemical Oxidants • Secondary pollutants (esp. ozone & PANs): products of atmospheric reactions driven by solar energy (esp. UV radiations) • Ozone (O3): formed by splitting nitrogen dioxide (NO2) to give NO & singlet (free) oxygen: NO2 NO + O; then: O + O2  O3 • Ozone in ambient air is a strong oxidizing agent => damages vegetation, building material (paint, rubber, plastics), & sensitive tissues (eyes & lungs) • Ozone has chocking, biting odor distinctive of photochemical smog • PANs (peroxyacetyl nitrates): damaging (esp. to the eyes) photochemical oxidant generated by the interaction of VOCs with nitrogen dioxide in the atmosphere

  20. Acid Deposition • pH & Atmospheric Acidity: pH scale ranges from 0-14. • 7 = Neutral; <7 = Acidic; >7 = Basic • Unpolluted natural rain generally has pH of 5.6 due to carbonic acid created by CO2 in air. • Any rain with a pH < 5.6 is acid rain. • The deposition of wet acidic solutions or dry acidic particles from the air. NO2 + H2O  HNO3 (Nitric acid) SO2 + H2O  H2SO4 (Sulfuric acid) Acid deposition is commonly called acid rain. • Acid deposition occurs on a regional basis rather than a global one

  21. Effects of acid rains and air pollutants on plants and forests • Acid rains & air pollutants can directly damage plants, or indirectly by disrupting normal growth & development patterns • Damage the waxy coating (helps prevent excessive water loss & damage from pests, diseases, drought & frost) • interfere with photosynthesis & plant growth • Reduces nutrient uptake • Causes leaves to turn yellow or brown & drop off

  22. Effects of acid deposition on aquatic life • Acidification  disrupt aquatic food chain • Eggs & the young of many species are killed when the pH drops to about 5 • At pH levels below 5 adult fish may die • Acid deposition & runoff into lakes & streams may release from soil toxic aluminum ions (Al3+) & methyl mercury => fish death

  23. Indoor Air Pollution • EPA (Environmental Protection Agency): • [Pollutants]indoors > [Pollutants]outdoors • Health risks from indoor pollution are magnified (people generally spend more time indoors or inside vehicles) • The four most dangerous indoor air pollutants are: • Cigarette smoke • Formaldehyde • Asbestos • Radioactive Radon

  24. Para-dichlorobenzene Tetrachloroethylene Chloroform 1, 1, 1- Trichloroethane Formaldehyde Benzo-a-pyrene Nitrogen Oxides Styrene Tobacco Smoke Asbestos Radon-222 Methylene Chloride Carbon Monoxide Indoor Air Pollution

  25. Major Indoor air Pollutants • Tobacco smoke (cigarettes) • The most important air pollutant in terms of human health in the US • Causes early deaths & other smoking-related illnesses (lung cancer, respiratory ailments, cardiovascular diseases) • 400,000 die annually in the US from a disease related to smoking

  26. Major Indoor air Pollutants • Formaldehyde (Colorless & extremely irritating gas) • Health effects • Headache, nausea, dizziness • Irritation of eyes, throat, skin, and lungs • Sources • Building material (plywood, particleboard, high-gloss wood…) • Furniture & furniture stuffing (upholstery) • Adhesives in carpeting & wallpaper • Formaldehyde containing insulation • Fingernail hardener

  27. Major Indoor Air Pollutants • Asbestos (fibers of silicate minerals) • Asbestos is strong, flexible, & cheap => used as a building material in: • Water pipelines • Insulation of heaters & pipes • Floor, walls, & ceiling tiles • Cement, car brakes… • If asbestos is completely sealed within a product => not hazardous; however, • Asbestos can easily crumble into tiny & suspended dust • Prolonged exposure to asbestos dust: • Asbestosis: difficulty in breathing (can cause death) • Lung cancer

  28. Major Indoor Air Pollutants in developing countries • Less Developed Countries also suffer from indoor air pollution • Organic fuels (firewood, charcoal, agricultural wastes) make up majority of household energy • Often burned in smoky, poorly ventilated heating and cooking fires => release of: • Carbon monoxide  headaches, drowsiness, irregular heartbeat… • Nitrogen oxides  headaches, lungs irritation, colds…

  29. Health Effects of Indoor Pollution • Respiratory and cardiovascular diseases • Sick building syndrome (dizziness, headaches, coughing, sneezing, burning eyes, chronic fatigue, & flue-like symptoms) • New buildings are more commonly “sick” than old ones: • Efficient insulation in new building => reduced air exchange => pollutants from new carpeting & furniture build up to high levels • Population at greatest risks: • Smokers, infants & children, the old &/or sick, pregnant women, factory workers

  30. Effects of air pollution on human health • Exposure to air pollutants (in particular cigarette smoke) can overload or break down natural defenses of the respiratory system causing respiratory illnesses such as lung cancer, asthma, bronchitis & emphysema. • Groups at risk: elderly people, infants, pregnant women, & people with heart or respiratory diseases.

  31. Effects of air pollution on human health • Bronchitis • Persistent inflammation of airways in the lung that causes mucus build-up, a painful cough, & muscle spasms constricting airways. • Severe bronchitis can lead to emphysema– an irreversible obstructive lung disease in which airways become permanently constricted & alveoli are damaged or destroyed.

  32. Reducing Indoor Air Pollution • Cover ceiling, tiles, and lining of AC ducts to prevent release of mineral fibers (asbestos) • Ban smoking or limit it to well ventilated areas • Set stricter formaldehyde emissions standards for carpet furniture and building materials • Use exhaust hoods for stoves and appliances burning gas • Install efficient chimneys for wood-burning stoves • Increase intake of outside air

  33. Effects of air pollution on materials • Air pollution damages buildings & structures. • Steel in reinforced concrete corrodes, which weakens buildings, roads, & bridges • Paint & rubber deteriorate due to oxidization • Limestone, marble & some kinds of sandstone deteriorate & fall to pieces

  34. CURRENT & FUTURE CONDITIONS • In developed countries, air quality has improved dramatically in the last decade in terms of major large-volume pollutants • Cities where pollution is largely from traffic still have serious air quality problems • Major metropolitan areas of many developing countries are growing at explosive rates, and environmental quality is very poor

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