Area IV: Pollution

IVA1: Air Pollution

20-2 Outdoor Air Pollution

Outdoor air pollution comes mostly from natural sources and burning fossil fuels air pollution: chemicals in the atmosphere

in concentrations high enough to affect climate, materials, and health

natural sources rarely reach harmful levels increased use of fossil fuels has greatly

increased the amount of air pollution two categories

primary pollutants: directly enter air secondary pollutants: form from primary

Fig. 20-4 Sources, types of air pollutants

20-2 Outdoor Air Pollution air pollution, cont.

cities generally have higher pollution levels than rural areas; winds can carry pollutants to other areas

can infiltrate indoor air high-risk human health problem most people exposed to poor air live in

developing countries six conventional air pollutants have maximum

standards of allowable concentrations set by governments of developed countries

Table 20-1 Major classes of air pollutantsClass

Carbon oxides

Sulfur oxides

Nitrogen oxides

Volatile organic compounds (VOCs)

Suspended particulate matter (SPM)

Photochemical oxidants

Radioactive substances

Hazardous air pollutants (HAPs), which cause health effects such as cancer, birth defects, and nervous system problems

Examples

Carbon monoxide (CO) and carbon dioxide (CO2)

Sulfur dioxide (SO2) and sulfur trioxide (SO3)

Nitric oxide (NO), nitrogen dioxide (NO2), nitrous oxide (N2O) (NO and NO2 often are lumped together and labeled NOx)

Methane (CH4), propane (C3H8), chlorofluorocarbons (CFCs)

Solid particles (dust, soot, asbestos, lead, nitrate, and sulfate salts), liquid droplets (sulfuric acid, PCBs, dioxins, and pesticides)

Ozone (O3), peroxyacyl nitrates (PANs), hydrogen peroxide (H2O2), aldehydes

Radon-222, iodine-131, strontium-90, plutonium-239 (Table 3-1, p. 49)

Carbon tetrachloride (CCl4), methyl chloride (CH3Cl), chloroform (CHCl3), benzene (C6H6), ethylene dibromide (C2H2Br2), formaldehyde (CH2O2)

20-2 Outdoor Air Pollution

Carbon dioxide can be classified as an air pollutant three reasons carbon dioxide can be

considered a pollutant: in high concentrations any chemical can

become a pollutant CO2 concentration in the troposphere has

increased due to fossil fuel burning and clearing trees that absorb CO2 (?)

troposphere is warming global warming can change global climate

patterns

Table 20-2 Major Outdoor Air PollutantsCARBON MONOXIDE (CO)

Description: Colorless, odorless gas that is poisonous to air-breathing animals; forms during the incomplete combustion of carbon-containing fuels (2 C + O2 2 CO).

Major human sources: Cigarette smoking (p. 409), incomplete burning of fossil fuels. About 77% (95% in cities)comes from motor vehicle exhaust.

Health effects: Reacts with hemoglobin in red blood cells and reduces the ability of blood to bring oxygen to body cells and tissues. This impairs perception and thinking; slows reflexes; causes headaches, drowsiness, dizziness, and nausea; can trigger heart attacks and angina; damages the development of fetuses and young children; and aggravates chronic bronchitis, emphysema, and anemia. At high levels it causes collapse, coma, irreversible brain cell damage, and death.

Table 20-2 Major Outdoor Air PollutantsNITROGEN DIOXIDE (NO2)

Description: Reddish-brown irritating gas that gives photochemical smog its brownish color; in the atmosphere can be converted to nitric acid (HNO3), a major component of acid deposition.

Major human sources: Fossil fuel burning in motor vehicles (49%) and power and industrial plants (49%).

Health effects: Lung irritation and damage; aggravates asthma and chronic bronchitis; increases susceptibility to respiratory infections such as the flu and common colds (especially in young children and older adults).

Environmental effects: Reduces visibility; acid deposition of HNO3 can damage trees, soils, and aquatic life in lakes.

Property damage: HNO3 can corrode metals and eat away stone on buildings, statues, and monuments; NO2 can damage fabrics.

Table 20-2 Major Outdoor Air PollutantsSULFUR DIOXIDE (SO2)

Description: Colorless, irritating; forms mostly from the combustion of sulfur containing fossil fuels such as coal and oil (S + O2 SO2); in the atmosphere can be converted to sulfuric acid (H2SO4), a major component of acid deposition.

Major human sources: Coal burning in power plants (88%) and industrial processes (10%).

Health effects: Breathing problems for healthy people; restriction of airways in people with asthma; chronic exposure can cause a permanent condition similar to bronchitis. According to the WHO, at least 625 million people are exposed to unsafe levels of sulfur dioxide from fossil fuel burning.

Environmental effects: Reduces visibility; acid deposition of H2SO4 can damage trees, soils, and aquatic life in lakes.

Property damage: SO2 and H2SO4 can corrode metals and eat away stone on buildings, statues, and monuments; SO2 can damage paint, paper, and leather.

Table 20-2 Major Outdoor Air PollutantsSUSPENDED PARTICULATE MATTER (SPM)

Description: Variety of particles and droplets (aerosols) small and light enough to remain suspended in atmosphere for short periods (large particles) to long periods (small particles; Figure 20-6, p. 441); cause smoke, dust, and haze.

Major human sources: Burning coal in power and industrial plants (40%), burning diesel and other fuels in vehicles (17%), agriculture (plowing, burning off fields), unpaved roads, construction.

Health effects: Nose and throat irritation, lung damage, and bronchitis; aggravates bronchitis and asthma; shortens life; toxic particulates (such as lead, cadmium, PCBs, and dioxins) can cause mutations, reproductive problems, cancer.

Environmental effects: Reduces visibility; acid deposition of H2SO4 droplets can damage trees, soils, and aquatic life in lakes.

Property damage: Corrodes metal; soils and discolors buildings, clothes, fabrics, and paints.

Table 20-2 Major Outdoor Air PollutantsOZONE (O3)

Description: Highly reactive, irritating gas with an unpleasant odor that forms in the troposphere as a major component of photochemical smog (Figures 20-3 and 20-5).

Major human sources: Chemical reaction with volatile organic compounds (VOCs, emitted mostly by cars and industries) and nitrogen oxides to form photochemical smog (Figure 20-5).

Health effects: Breathing problems; coughing; eye, nose, and throat irritation; aggravates chronic diseases such as asthma, bronchitis, emphysema, and heart disease; reduces resistance to colds and pneumonia; may speed up lung tissue aging.

Environmental effects: Ozone can damage plants and trees; smog can reduce visibility.

Property damage: Damages rubber, fabrics, and paints.

Table 20-2 Major Outdoor Air PollutantsLEAD

Description: Solid toxic metal and its compounds, emitted into the atmosphere as particulate matter.

Major human sources: Paint (old houses), smelters (metal refineries), lead manufacture, storage batteries, leaded gasoline (being phased out in developed countries).

Health effects: Accumulates in the body; brain and other nervous system damage and mental retardation (especially in children); digestive and other health problems; some lead-containing chemicals cause cancer in test animals.

Environmental effects: Can harm wildlife.

20-3 Photochemical and Industrial Smog

photochemical smog is formed by the reaction of N-oxides and volatile hydrocarbons with energy from sunlight photochemical reaction: any chemical

reaction activated by light photochemical smog contains more than

100 primary and secondary pollutants NO2 found in smog is a yellow-brown gas some NO2 reacts with hydrocarbons to

produce O3, nitric acid, aldehydes, peroxyacyl nitrates (PANs), and others

Fig. 20-5 Formation of photochemical smog

20-3 Photochemical and Industrial Smog photochemical smog, cont.

these substances are photochemical oxidants and can irritate the respiratory tract and damage crops and trees

photochemical smog is more common in cities in warm, dry, sunny areas

some hydrocarbon-emitting tree species can contribute to formation of smog

emit volatile organic compounds only a factor when forests are close to

urban areas with large sources of NOx

20-3 Photochemical and Industrial Smog industrial smog is a mixture of sulfur

dioxide, droplets of sulfuric acid, and a variety of suspended solid particles emitted by burning coal and oil

coal burning CO2, CO, and C particles (soot) coal and oil also contain sulfur that is then

converted to SO2 SO2 + H2O H2SO4 in several steps H2SO4 + NH3 (NH4)2SO4; gives air a gray

color

Fig. 20-6 Suspended particulate matter

20-3 Photochemical and Industrial Smog industrial smog, cont.

most countries have adopted pollution controls, but several countries with industrialized urban areas have serious smog problems

China has a serious gray-smog problem in many areas, causing premature death

20-3 Photochemical and Industrial Smog natural factors affecting air pollution

reducing outdoor air pollution: rain and snow salty sea spray winds

increasing outdoor air pollution: urban buildings hills and mountains high temperatures grasshopper effect: movement from tropical

or temperate areas to the poles

20-3 Photochemical and Industrial Smog a layer of warm air sitting on top of a layer

of cool air near the ground can prevent outdoor pollutants from rising and dispersing

turbulence disperses air pollutants a temperature inversion, where a layer of

warm air sits over a layer of cold air, prevents mixing, and dense, colder air becomes stagnant and accumulates more pollutants

Fig. 20-7 Temperature inversions

20-3 Photochemical and Industrial Smog temperature inversions, cont.

two areas are particularly susceptible to inversions:

a city located in a valley surrounded by mountains that experiences cloudy, cold weather part of the year

a sunny climate with light winds and mountains on three sides and several million people and vehicles (Los Angeles basin)

20-4 Acid Deposition

Acid rain results from air pollution SO2, NOx, and particulates react in the

atmosphere to produce acidic chemicals that travel long distances before coming back to the earth

tall smokestacks reduce local pollution, but can increase regional pollution

acidic particles remain in the atmosphere for 2–14 days (and can end up in other countries); factors:

prevailing winds precipitation other weather patterns

Fig. 20-8 Acid deposition

20-4 Acid Deposition acid deposition, cont.

acidic substances return to the earth in one of two forms:

wet deposition as acidic rain, snow, fog, and cold vapor with a pH less than 5.6

dry deposition as acidic particles mainly a problem in areas downwind from coal-

burning facilities and urban areas some areas have basic compounds in the soil

that act to buffer or neutralize some acidic deposits

Fig. 20-9 Acid deposition in the U.S.

20-4 Acid Deposition harmful effects of acid deposition

contributes to human respiratory diseases such as bronchitis and asthma

damages metallic objects, which can leach toxic metals

damages limestone, marble, and sandstone large amounts of money are spent each

year to clean and repair damaged monuments and statues

decreases atmospheric visibility kills fish in lakes, especially when pH < 4.5

aluminum ions are released into the water many lakes in northern Europe and eastern

U.S. have few fish due to decreased pH

Fig. 20-10 Acid deposition worldwide

20-4 Acid Deposition harmful effects of acid deposition, cont.

depletes some soil nutrients, releases toxic ions into soil, and weakens plants that become susceptible to other stresses

effects on plants are caused partly by chemical interaction in the soils

may be initial growth stimulus from N and S continued deposition leaches Mg and Ca

salts from soil and lowers plant productivity herbivores that eat these plants can also

develop calcium deficiencies synergistic effects may occur when the

plants are exposed to several pollutants simultaneously

20-4 Acid Deposition harmful effects of acid deposition, cont.

acid can also dissolve Al, Cd, and Hg ions from the soil, which are toxic to plants and animals

acid-loving mosses may be stimulated to grow and harm trees by holding quantities of water and killing mycorrhizal fungi needed by the trees

weakened trees are more susceptible to diseases

the mountaintop trees are those that are most harmed by acidic rain because they are also growing in thin soils

Fig. 20-11 Effects on soil and plants

20-4 Acid Deposition progress has been made in reducing acid

deposition in the U.S. the 1990 amendments to the Clean Air Act

have lead to significant reductions in SO2 and NOx emissions from coal-fired power and industrial plants

it is predicted that an additional 80% reduction in SO2 emissions would be needed to allow northeastern streams and lakes to recover from the effects of acid deposition

20-4 Acid Deposition prevention and control methods can reduce

acid deposition best approaches: those that reduce/eliminate

emissions of SO2, NOx, and particulates can use low-sulfur coal

+: lowers the amount of SO2 released -: emits more mercury, CO2, and radioactive

particles can neutralize acid lakes by adding limestone,

lime, or a small amount of phosphate fertilizer controlling acid deposition is controversial

inclusion of environmental and health costs of coal would give a more realistic picture

20-5 Indoor Air Pollution indoor air pollution is usually a greater

threat to health than outdoor air pollution EPA studies have shown that:

levels of 11 common pollutants are 2–5 times greater inside than outside

inside cars may have pollution 18 times higher than outside

people usually spend 70–98% of their time indoors or in vehicles

sick-building syndrome has been linked to various air pollutants; new buildings apt to be more prone due to less air exchange

20-5 Indoor Air Pollution indoor air pollution, cont.

EPA 4 most dangerous indoor air pollutants: cigarette smoke fine and ultrafine particles

in developing countries, as many as 2.8 million people die each year from breathing elevated levels of indoor smoke and particulates

formaldehyde causes the most people in developed

countries difficulty used to manufacture common household

materials

20-5 Indoor Air Pollution indoor air pollution, cont.

EPA 4 most dangerous indoor pollutants, cont. radioactive radon-222 gas

produced by the decay of uranium-238 tends to be pulled into homes because of

slightly lower air pressure inside homes thought to be the 2nd leading cause of

lung cancer deaths each year in the U.S. the EPA and the Surgeon General’s

Office recommended that everyone living in a detached home, a townhouse, or the first three levels of an apartment building test for radon

20-5 Indoor Air Pollution indoor air pollution, cont.

EPA 4 most dangerous indoor pollutants, cont. radioactive radon-222 gas, cont.

remedies include sealing cracks in foundation and walls, increasing ventilation, and using a fan for cross ventilation

20-7 Preventing, Reducing Air Pollution Clean Air Acts in the U.S. have greatly

reduced outdoor air pollution from six major pollutants

U.S. Congress passed Clean Air Acts in 1970, 1977, and 1990

national air quality standards (NAAQS) were established for six outdoor criteria pollutants

primary standard to protect human health secondary standard to prevent

environmental and property damage

20-7 Preventing, Reducing Air Pollution Clean Air Acts, cont.

the six criteria air pollutants decreased 48% between 1983 and 2002

93% for Pb 41% for CO 40% for volatile organics 34% for suspended particulate matter 33% for SO2

15% for NOx

the EPA has established national emission standards for 188 hazardous air pollutants (HAPs) that may cause serious health and ecological effects

20-7 Preventing, Reducing Air Pollution Clean Air Acts, cont.

release of two HAPs—mercury and dioxins has increased in recent years; EPA estimates that about 100 million Americans live in areas where the risk of cancer from HAPs is 10 times higher than the accepted standard

smog levels did not drop any between 1993 and 2003 after dropping in the 1980s (except L.A. ?)

20-7 Preventing, Reducing Air Pollution Clean Air Act deficiencies

we rely more on cleanup than prevention Congress has not increased fuel-efficiency

standards for cars oceangoing ships have little or no air pollution

regulations the Clean Air Acts have not done much to

reduce greenhouse gas emissions little has been done to deal seriously with

indoor air pollution inadequate enforcement

20-7 Preventing, Reducing Air Pollution allowing producers of air pollutants to buy

and sell government air pollution allotments in the marketplace can help reduce emissions

the Clean Air Act of 1990 allows a cap-and-trade approach that permits companies to buy and sell SO2 pollution rights

allows “hot spots” to continue to exist between 1990 and 2002, this scheme reduced

SO2 emissions by 40% in the U.S

20-7 Preventing, Reducing Air Pollution cap-and-trade approach, cont.

emissions trading has been expanded to include NOx, particulates, and volatile organics, and for the combined emissions of SO2, NOx, and Hg from coal-burning plants

in 2002, the EPA reported that the largest and oldest cap-and-trade program produced less emissions reductions than projected or that could be expected

20-7 Preventing, Reducing Air Pollution plants already in existence in 1970 were

not required to meet the new Clean Air Act standards

a 1977 rule (New Resource Review) requires older plants to upgrade pollution control equipment when they expand or modernize the facilities

this has been circumvented by calling these expansions maintenance

the Bush administration eased the NRR restrictions for older facilities

20-7 Preventing, Reducing Air Pollution there are a number of ways to prevent and

control air pollution from motor vehicles get older, more polluting vehicles off the road use zeolites to remove pollutants from fuels use hybrid-electric vehicles and zero-emission

vehicles developing countries are increasing their air

pollution with more vehicles on the road that are over 10 years old and are without pollution controls

20-7 Preventing, Reducing Air Pollution there is controversy over reducing

emissions of ultrafine particles that pose a serious threat to human health

fine particles (less than 10 microns) and ultrafine particles (less than 2.5 microns) are generally not captured by most air pollution control equipment

penetrate natural defenses of resp. system estimated to kill 65–200 k Americans/year;

higher in developing countries (300–700 k) costs to implement stricter standards are

estimated at $7 billion/year with health and other benefits of $120 billion/year

20-7 Preventing, Reducing Air Pollution little effort has been spent on reducing

indoor air pollution in developing countries, indoor air pollution can

be reduced by use of clay or metal stoves and venting to the outside, and by use of solar cookers in sunny areas; would also reduce deforestation

there is a need to focus on preventing air pollution of all types in developing countries

at present, there is an output approach to controlling pollution

we need to shift focus to preventing air pollution