Air Pollution
Learning Objectives
Pollutants in the atmosphere can be anthropomorphic (man-made) or natural.
Air pollution is defined as chemical or physical changes that result in air quality degradation.
Pollutant Classification:
Primary: chemicals released in a harmful state.
Secondary: chemicals that are not harmful at release but are altered by sunlight into a harmful state.
Fugitive: substances that are harmful and released by accident.
The EPA recognizes seven substances in the Clean Air Act as the most serious threats to air quality:
1) Sulfur Compounds:
Source: combustion of coal is the primary source.
Effects/Problems: sulfur compounds are released as particulates and can be transported long distances by wind. The particulates combine with water producing acid precipitation.
2) Nitrogen Compounds:
Source: high temperature combustion by power generating and transportation industries. Also from bacterial activity in soils and water, fertilizers and organic matter.
Effect/Problems: combine with atmospheric water to produce acid precipitation.
3) Carbon Oxides:
Source: burning of fossil fuels, organic decay.
Effects/Problems: Greenhouse Effect? also carbon monoxide is poisonous and in large enough concentrations is lethal.
4) Particulate Matter:
Source: Industrial processes, mining, transportation.
Effects/Problems: Most visible form of air pollution, reduces visibility, acts as an absorbant for other pollutants. Respirable particles can cause lung damage.
5) Volatile Organic Compounds:
Source: Plants are the largest source. Also produced by fermentation and digestion processes. Synthetic organic compounds also contribute.
Effects/Problems: Substances can irritate mucous membranes, methane is a greenhouse gas (Greenhouse Theory?). Most synthetic organic compounds are hazardous and can contribute to photochemical oxidant concentration.
6) Photochemical Oxidants:
Source: produced from secondary chemical reactions in the presence of sunlight.
Effects/Problems: produce ozone that at altitude is beneficial, is harmful at the surface. Ozone acts as an oxidant that irritates mucous membranes and lung tissue.
7) Metals:
Source: leaded gasoline, mining and smelting industries.
Effects/Problems: many metals are toxic and bioaccumulate.
Effects of Acid Deposition:
Acid deposition includes acidic rain, ice, snow and fog as well as the deposition of fine particulates in a dry form. Acid deposition has the greatest effects on lakes and streams. As pH increases (~5.0) the eggs and fry of fish species will be harmed. At pH levels less than ~5.0 many adult fish will be killed. Lower pH acts to solubilize metals which can be toxic. At lower pH nutrient cations become less available. Acid deposition is also harmful to vegetation. Acid deposition has also had a detrimental affect on monuments and buildings. Marble will be etched and pitted with increased acidity.
Health Problems caused by Air Pollution:
Air pollution tends to produce inflammation in lung and respiratory tissues. Mucous membranes and eye tissues are also affected. Cardiovascular stress increases with increased air pollution. The sick and elderly are most at risk from the affect of air pollution.
Emission Reduction Strategies:
1) Reduction through conservation and efficiency: is the best solution.
2) Filters: remove particulates from emissions.
3) Cyclone collectors: gravitational separation of particulates from emission.
4) Electrostatic Precipitators: electrostatic charges attract fine particulates from emissions.
5) Scrubbers: emission stream is mixed with an alkali solution (either fluidized or dry) to neutralize sulfur laden emissions.
6) Staged Burners: allows more complete combustion which reduced the amount of nitrogen oxides released.
Indoor Air Pollution:
Modern buildings are sealed very tightly for energy saving and air in the buildings is filtered. If the filter is not properly maintained then pollution inside the building can be 5 - 100 times more polluted than outdoors.
Indoor air pollutants recognized by the EPA as threatening to human health:
1) Carbon Monoxide: produced from burning of ANY organic material: wood stoves, fireplaces, oil and gas furnaces. If exhaust system is not properly working carbon monoxide may be released to the interior of the building. It is FATAL. If you have any organic combustion in your home you should RUN to the nearest home store and buy a
CARBON MONOXIDE DETECTOR!!!! IT COULD SAVE YOUR LIFE!!!!
2) PAH (Polycyclic aromatic hydrocarbons): from flooring, padding, carpeting. Causes irritation of eyes and mucous membranes.
3) Radon: colorless and odorless. A natural radioactive gas formed from the weathering of granitic rocks. Causes lung cancer but easily detected.
4) Formaldehyde: from building materials, insulation, foam products, paneling. Can trigger asthma attacks and irritate eyes.
5) Asbestos: can cause lung cancer, previously discussed.
6) Tobacco Smoke: CANCERS!!!
Proper ventilation is the key to preventing indoor air pollution.
"Sick Building Syndrome": The World Health Organization (WHO) estimates that 30% of all US buildings exceed recommended pollution levels and are considered "sick".
