OUTDOOR AIR POLLUTION

HISTORY:

• Local problem since use of fire• Regional problem since industrial revolution• Now a global issue (acid deposition, ozone

depletion)• Landmark events: Donora, PA 1948. London,

England 1952

ENVIRONMENTAL EFFECTS:

• Affects plant growth (productivity), crop yields and disrupts food web • Acidification of aquatic ecosystems,

eutrophication • Amphibians and lichens are especially sensitive

(good indicator species)• Decreases visibility and clarity

HUMAN HEALTH EFFECTS

• Acute: irritation of eyes, skin, and respiratory system• Aggravates asthma and emphysema (COPD),

contributes to CV disease• Increases susceptibility to respiratory infection

(pneumonia, bronchitis)• Chronic: permanently decreases lung function,

raises risk of lung cancer • Children are especially affected• Synergistic effects especially affect urban dwellers,

some occupations like miners and textile workers

HUMAN RESPIRATORY SYSTEM:

• Major function is to exchange gases with environment. Major organs: lungs• expansion of lungs done by diaphragm and rib

muscles • epiglottis –closes off trachea during swallowing• alveoli increase surface area for gas exchange• actual exchange of gases occurs through diffusion• Respiratory problems affected by air pollution:• asthma, chronic bronchitis, lung cancer,

emphysema

SOURCES OF AIR POLLUTANTS

Natural sources: volcanoes, pollen, microorganisms, dust storms, wildfires

•  Anthropogenic sources (in order): transportation, power plants, industry

• Stationary (fixed) or mobile (cars, planes, ships)• Point sources (power plants) or non-point area

sources (cities)• Fugitive sources- do not go through pipe or

smokestack • Primary pollutants- released directly into the air• Secondary pollutants- modified after emission

(smog, acid deposition)• (photochemical reaction – activated by UV light)

LOCAL AIR POLLUTION

VARIABILITY AND TRENDS IN AIR POLLUTION:

•worse in urban and industrialized areas • influenced by topography, meteorology, seasons (temperature

inversions)  • Air quality is better in US; EPA estimates since 1970• PM 78% CO 23% NOx 14% Pb 98% SO2 32%

• Air quality worse in developing countries:• Mexico City, Beijing: air exceeds WHO standards 350 days/year • Eastern Europe (Soviet Block countries) burned high S coal• resulted in forest decline due to acid rain, major human health

problems

SPECIFIC POLLUTANTS:

• Know sources, human health effects, environmental effects, methods of control for each.

• Sulfur dioxide• Nitrogen oxides• Carbon monoxide• Ozone, smog• Particulate matter (PM)• Lead (Pb)• VOCs (Volatile Organic Compounds)

SMOG (SMOKE +FOG) • 2 types:

• 1. Photochemical smog (LA type)-from car emissions reacting with sunlight

• strong oxidants; harm respiratory system, damage crops and trees•  N2 + O2 2 NO

• burning forms nitric oxide

• 2NO + O2 2NO2 • nitric oxide combines with O2 to form nitrogen dioxide

• NO2 + UV radiation NO + O • nitrogen oxide breaks down

• O2 + O O3• ozone produced

PHOTOCHEMICAL SMOG / LA SMOG

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2. SULFUROUS SMOG (LONDON TYPE, GRAY AIR, INDUSTRIAL) FROM BURNING COAL, OIL

• Burning releases sulfur oxides (SOx), mostly sulfur dioxide (SO2)• Mostly in stagnant air, cloud cover, high humidity• Worse in less developed countries with inadequate

pollution control

CONTROL OF AIR POLLUTION

• Cars (produce NOx, CO, previously Pb. Diesel source of PM) • reduce automobile numbers and use• Stricter emissions standards and enforcement• Low emissions cars, improve gasoline, modify fuel • Public transportation, car pools• Catalytic converters, remove CO, NOx (cars only)

INDUSTRY: (SOURCE OF SOX, NOX, PM)

• PM: use bag filters, electrostatic precipitators, ash must be landfilled• SOx: Use low sulfur, alternative energy, improve

conservation, efficiency• Technologies: Ca reacts with sulfur to form

calcium sulfate (CaSO3)• Limestone injection: mix coal with limestone before

burning• Flue gas scrubbing: lime injected into exhaust • Trade allowances - market based system to encourage

reduction in SO2 • NOx: burn at lower temperatures

CLEAN AIR LEGISLATION

• 1970 Clean Air Act established NAAQS and AQI• 1990 amendments added provisions for acid rain, urban smog, HAPs,

Ozone protection, and CFCs, and trade allowances for SOx

• New Source Review required older industries and refineries to upgrade their pollution controls if they are modify their facilities • Further revisions have been challenged by industries and

environmentalists:• Bush administration has relaxed rules

NATIONAL AMBIENT AIR QUALITY STANDARDS (NAAQS):

• sets acceptable concentrations for 6 “criteria” pollutants that • Threaten public health/ the environment over

broad areas (nonpoint)• Are emitted in large quantities • CO, Pb, Nitrogen oxides NOx, Ozone, Particulate

matter, SOx

• ambient = surrounding, criteria = based on scientific research

AIR QUALITY INDEX (AQI)

• Measures levels of 5 criteria pollutants (not Pb – why?)• Forecast of daily air pollution levels• Purpose to educate and protect public – focuses

on health effects• Limitations - doesn’t cover chronic or synergistic

effects• Categories: green = good, yellow = moderate,

orange=unhealthy for sensitive groups, red = unhealthy, purple = very unhealthy

NATIONAL EMISSIONS STANDARDS FOR HAZARDOUS AIR POLLUTANTS

• – regulates emissions (from point sources)• for specific substances (air toxics or HAPs with

known or suspected serious health effects (mutagens, carcinogens, neurotoxins, teratogens)• Tend to be localized, from point sources• Examples: Ammonia, chlorine, asbestos,

arsenic, mercury, benzene