71. Intro to Air Pollution, 7.4 Atmospheric CO2 and Particulates. 7.5

Clean Air Act (1970)

Identified 6 criteria air pollutants that the EPA is required to set acceptable limits for, monitor, and enforce

6 Criteria air pollutants

Sulfur dioxide (SO2), Nitrogen Oxides (NO and NO2), Carbon Monoxide (CO), Particulate Matter (PM), Ozone (tropospheric)( O3), lead (Pb)

Sulfur Dioxides (SO2)

Causes: Coal combustion (electricity)

Effects: Respiratory irritant, smog, acid precipitation

Nitrogen Oxides (NO and NO2)

Causes: All fossil fuel combustion (gas especially)

Effects: Ozone, photochem smog, acid precipitation

Carbon Monoxide (CO)

Causes: Incomplete combustion

Effects: Ozone, Lethal to humans

Particulate Matter (PM)

Causes: Fossil fuel/ biomass combustion

Ozone (O3)(Tropospheric)

Causes: Photochemical oxidation of NO2

Effects: Respiratory irritant, smog, plant damage

Lead (Pb)

Causes: Metal plants, waste incineration
Effects: Neurotoxicant

CO2

Not one of the 6 criteria pollutants in the Clean Air Act; doesn’t directly lower air quality; a greenhouse gas; leads to earth warming, thus environmental and human health consequences

Coal Combustion

releases more air pollutants than other fossil fuels, ~35% of global electricity; releases CO, CO2, SO2, NOx

Nitrogen Oxides (NOx and SOx)

Released by combustion of anything, especially fossil fuels and biomass

Nitrogen Oxides

environmental and human health impacts: resp. irr. trophospheric ozone formation > photochemical smog, combines with water and O2 in atm. to form nitric acid > acid precipitation

Primary air pollutants

emitted directly from sources such as vehicles, power plants, factories, or natural sources; NOx, CO, CO2, VOCs, SO2, PM, hydrocarbons

Secondary air pollutants

primary pollutants that have transformed in presence of sunlight, water, O2; occurs more during the day (sunlight drivers formation); tropospheric ozone; sulfuric acid (H2SO4) and sulfate (SO4); Nitric acid (HNO3) and nitrate (NO3)

Lead

common gasoline additive

natural sources of air pollutants

lightning strikes, plants. forest fires, volcanoes

lightning strikes

converts N2 in atm. to NOx

plants

plants emit VOCs

forest fires

CO, PM, SOx, NOx; combustion of biomass also releases CO2 and H2O vapor (GHG)

Volcanoes

SO2, PM, CO, NOx

natural sources of CO2 and PM

Respiration, aerobic decomp., natural PM sources, anaerobic decomp.

respiration

All living things (plants included) release CO₂ through respiration

Natural PM Sources

Sea salt, pollen, ash from forest fires & volcanoes, dust (windborne soil); Leads to haze (scattering of sunlight & reduced visibility)

Aerobic Decomposition

Decomposition of organic matter by bacteria & decomposers in the presence of oxygen → releases CO₂

Anaerobic Decomposition

Decomposition of organic matter by bacteria & decomposers in low or oxygen-free conditions → releases CH₄ (methane)

Particulate Matter

 solid or liquid particles suspended in air (also referred to as “particulates”)

PM (<10 micrometers

• Particles or droplets like dust, pollen, ash, or mold

• Too small to be filtered out by nose hairs and trachea cilia; can irritate respiratory tract & cause inflammation

PM_2.5  ( <2.5 micrometers)

• Particles from combustion (especially vehicles) smaller dust particles

• More likely to travel deep into the lungs due to smaller size

• Associated with chronic bronchitis and increased risk of lung cancer

Developing nations

uses more subsistence fuels (wood, manure, charcoal (biomass)); releases CO, PM, NOx, VOCs; can cause deforestation; leads to high concentrations when combustion done indoors, results in est. 3.5-4.3 mil deaths annually

Developed nations

uses more commercial fuels (coal, oil, natural gas) supplied by utilities; typically burned in closed, well ventilated furnaces, stoves, etc.; comes from chemicals in products :adhesives in furniture, cleaning supplies, insulation, lead paint

particulates (PM)

common indoor air pollutant (ex. smoke, dust, asbestos)

asbestos

long, silicate particle previously used in insulation (since been linked to lung cancer and asbestosis)

Carbon Monoxide (CO)

produced by incomplete combustion of any fuel due to low O2 or temp; an asphyxiant: causes suffocation due to CO binding to hemogoblin in blood; developed: malfunctioning natural gas furnace ventilation; developing: indoor biomass combustion for heating/cooking

Volatile Organic Compounds (VOCs)

chemicals used in variety of home products that easily vaporize, enter air, and irritate eyes, lungs, bronchioles

Hydrocarbons

high vapor pressure > commonly evaporates at room temp. ; ranges from harmless to toxic (aldehydes)

Examples of VOCs

cleaners, plastics and fabrics, adhesives/sealants

radon gas

radioactive gas released by decay of uranium naturally found in rocks underground (granite especially); 2nd leading cause of lung cancer

dust and mold

natural indoor air pollutants that can worsen asthma, bronchitis, COPD, emphysema

lead

found in paint in old homes, also found in lead water pipes which contaminates drinking water sources, damages central nervous system