Outdoor Air Pollution

1. Outdoor Air Pollution

2. 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

3. 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

4. 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

5. 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

6. 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)

7. Local air pollution

8. 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

9. 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)

10. 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

11. Photochemical smog / LA smog LA Santiago Las Vegas

12. 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

13. 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)

14. 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

15. 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

16. 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

17. 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

18. 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