Notes on Air Pollution and Its Effects

7.1 Introduction to Air Pollution (Pollutants)

  • Objective: Identify the sources and effects of air pollutants.

  • Essential Knowledge:

    • STB-2.A.1: Coal combustion releases major pollutants such as carbon dioxide, sulfur dioxide, toxic metals, and particulates.

    • STB-2.A.2: Fossil fuel combustion emits nitrogen oxides, contributing to ozone formation and photochemical smog.

    • STB-2.A.3: Sulfur dioxide from burning fossil fuels affects air quality.

    • STB-2.A.4: The Clean Air Act regulates pollutants, notably lead in fuels, decreasing atmospheric lead.

    • STB-2.A.5: Air pollutants can be classified as primary (directly emitted) or secondary (formed by reactions in the atmosphere).

Air Pollution Basics

  • Common Pollutants:

    • Coal Combustion: Major source of CO, CO2, SO2, NOx, toxic metals (mercury, arsenic, lead), particulates.

    • Health Effects: Respiratory irritations, smog formation, acid precipitation.

    • Criteria Air Pollutants (Clean Air Act identifies 6): SO2, NOx, O3, CO, PM, Pb.

Air Pollutants vs. Greenhouse Gases

  • CO2 Discussion:

    • Not a criteria pollutant; does not directly harm air quality but contributes to greenhouse effect.

    • Gained regulatory power in 2007 (EPA can regulate greenhouse gases).

Effects of Coal Combustion

  • Coal is a major electricity source (~35% globally) but releases significant pollutants (SO2, NOx, toxic metals).

  • SO2 Impacts: Respiratory irritant, causes acid precipitation, contributes to smog by forming sulfurous aerosols.

Nitrogen Oxides (NOx)

  • Sources: Released from combustion of fossil fuels and biomass; formed during high-temperature combustion.

  • Health Effects: Respiratory irritant, contributes to ozone formation (tropospheric O3), acid precipitation.

Regulatory Successes: Lead Phasing Out

  • Before Clean Air Act: Lead widely used in gasoline; phased out starting in 1974 due to its neurotoxic effects.

Primary vs. Secondary Pollutants

  • Primary Pollutants: Directly emitted (e.g., NOx, CO, particulate matter).

  • Secondary Pollutants: Formed by reactions (e.g., Ozone, sulfuric acid).

Photochemical Smog (7.2)

  • Formation: Occurs in urban areas, primarily due to vehicle emissions of NOx and VOCs under sunlight.

  • Health Effects: Respiratory problems, eye irritation.

  • Reduction Strategies: Reducing NOx and VOC emissions.

Understanding Thermal Inversion (7.3)

  • Concept: Inversion traps cooler air and pollutants near the ground, exacerbating air quality issues.

  • Urban Heat Island Effect: Urban areas are warmer due to absorption of heat by materials like concrete.

Natural Sources of CO2 and Particulates (7.4)

  • CO2 Sources: Natural respiration, decomposition, and volcanic eruptions contribute to atmospheric CO2.

  • Particulate Matter Sources: Natural (dust, pollen) and anthropogenic (combustion, biomass burning).

Indoor Air Pollutants (7.5)

  • Types: Carbon monoxide (asphyxiant), particulates (dust, mold, asbestos), VOCs from household products.

  • Radon: Naturally occurring radioactive gas linked to lung cancer; homes should be tested for radon levels.

Reducing Air Pollutants (7.6)

  • Methods: Regulatory practices (Clean Air Act), conservation, use of alternative fuels, scrubbers for industrial exhaust.

Acid Rain (7.7)

  • Causes: Primarily due to SO2 and NOx from combustion, leading to environmental harm through acidification of soils and water sources.

Noise Pollution (7.8)

  • Effects: Physiological stress, hearing loss, disrupted animal communication, and migratory routes due to urban noise sources.