outdoor air pollution. history: local problem since use of fire regional problem since industrial...
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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
LA
Santiago
Las Vegas
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