Unit 7: Pollution

Air Pollution

• Air quality concerns pre-Clean Air Act

  • 1966 NYC smog crisis: 3 day event killed hundreds and hurt thousands

  • 1948 Donora PA smog: Killed 20 people and caused respiratory problems in over half the citizens of Donora

• EPA & Clean Air Act

  • Regulates air quality and helps fund and set up projects for cleaning air pollution

  • Sets minimum requirements for 6 “criteria pollutants” based on human health and environmental-based criteria

  • Reducing outdoor (ambient) concentrations of air pollution that can lead to smog, haze, or acid rain

  • Setting limits and reducing toxic pollutants (ones known or suspected to cause cancer, death, or other disease)

  • Phasing out production and use of chemicals that deplete the ozone layer

• Air Quality Index

  • Measure of air pollution/quality that uses a scale from 0 to 500

    • High AQI is worse, with the line for unhealthy air quality generally around 100

  • Based on National Ambient Air Quality Standards

• Primary v Secondary Air Pollutants

  • Primary: Emitted directly from sources such as vehicles, power plants, factories, or natural sources (volcanoes, forest fires)

    • NO2, CO, CO2, VOCs, SO2, PM, hydrocarbons

  • Secondary: Primary pollutants that have transformed in presence of sunlight, water, O2

    • Occur more during the day (since sunlight often drives formation)

    • Tropospheric O3 (Ozone)

    • Sulfuric acid and sulfate

    • Nitric acid and nitrate

• EPA & Lead 

  • Since early 1920s, lead was a common gasoline additive -> ethyl 

    • Largest source of atmospheric is lead pollution (non fuel sources are mainly industrial, i.e. lead smelting)

    • It reduced engine knock by improving quality of gas and was cheap

  • The dangers of lead poisoning (first noticed in Ancient Greece) came to the forefront in the US in the 1960s and 70s

  • Severely damage the brain and central nervous system

    • In kids, reduces IQ and attention span, increases antisocial behavior can cause comas

    • In adults, memory loss, mental illness, hallucinations and craziness, negative effects on reproductive systems, impaired kidney function

• Particulate Matter

  • Solid or liquid particles suspended in the air, can be primary or secondary pollutants

    • PM 2.5 = smaller than 2.5 microns in diameter

    • PM 10 = smaller than 10 microns in diameter

  • Natural sources: Sea salt, pollen, ash from forest fires, volcanoes dust (windborne soil)

  • Human sources: 

    • Combustion (power plants, cars, fires, etc.) 

    • Wind swept dust (farming, construction)

    • Handling and processing of industrial materials

    • Reaction of gasses (SO2, NO2, VOCs) in atmosphere

  • Ecological effects

    • Can cause haze and impair visibility

    • Depending on what they’re made of, can acidify soil and bodies of water, affect nutrient availability

  • Health effects

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

    • Associated with chronic bronchitis and increased risk of lung cancer

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

• Nitrogen Oxides

  • Mostly exists naturally and high in the atmosphere because of lightning

  • Approximately 75% of surface level nitrogen oxide is from fossil fuel combustion, with most of it being from cars

  • Nitrogen oxide forms when N₂ combines with O₂ (especially during combustion, but also lightning)

    • Typically not a problem at ambient concentration, can cause lung, eye, skin irritation at really high levels

  • NO2 can be both a primary and secondary pollutant

    • Worse for lung irritation, asthma, lung disease, respiratory infections, fluid buildup in lungs

    • Much more chemically reactive 

• Ground level ozone (O3)

  • Can oxidize plant tissues leading to inhibited ability to photosynthesize and grow, as well as increasing risk of harm due to disease or pests 

  • Health effects: 

    • More difficult to breathe deeply and vigorously; chest pain

    • Destroy lung tissue, causing coughing and sore/scratchy throat

    • Inflame and damage airways

    • Make the lungs more susceptible to infection

    • Aggravate lung diseases such as asthma and bronchitis

• Normal O3 formation

1. Sunlight breaks NO2 into NO + O

2. O bonds with O2 to form O3

3. At night, O3 reacts with NO to form NO2 and O2 once again

4. O3 levels drop overnight

5. O3 formation typically peaks in afternoon when sunlight is most direct and NO2 emissions from morning traffic have peaked

6. Morning commute leads to high NO2 levels from car exhaust

• Volatile Organic Compounds (VOCs)

  • Carbon-based compounds that volatilize (evaporate easily)

  • Sources: gasoline, formaldehyde, cleaning fluids, oil-based paints, trees (pine smell, isoprene as sunscreen, etc.)

    • Great Smoky Mountains

    • Blue Ride Mountains

• Photochemical Smog

1. NO2 into ozone

2. Without NO to react with O3 builds up instead of returning to O2 and NO2 overnight

3. O3 combines with photochemical oxidants (NO + VOCs) to form photochemical smog

4. Add VOCs to form photochemical oxidants

• Impacts and Reduction of Smog

  • Environmental

    • Reduces sunlight, limiting photosynthesis

    • O3 damages plant stomata and irritates animal respiratory tracts

  • Humans

    • Respiratory irritant, worsens asthma, bronchitis, obstruct airways, irritates eyes

  • Economic

    • Increased health care costs to treat asthma, bronchitis, etc.

    • Lost productivity due to sick workers missing work or dying

    • Decreased agricultural yields due to less sunlight reaching crops and damage to plant stomata

  • Reduction

    • Vehicles

      • Decreasing the number of vehicles on the road decreases NO2 emissions

      • Fewer vehicles means less gas, fewer VOCs

        • Carpooling, public transport, biking, walking, working from home

    • Energy

      • Increased electricity production from renewable sources  that don’t emit nitrogen oxides (solar, wind, hydro)

      • Natural gas power plants release for less nitrogen oxides than coal

• Sulfur Dioxide 

  • Mainly burning of coal and oil, also burning of diesel fuels

  • Health effects

    • Lung irritation

    • Impaired respiratory immune system

    • Cause bronchitis and exacerbate existing conditions

  • Negative effects

    • Corrosive to human infrastructure

    • Destroy chlorophyll and plant tissue

    • Cause acid rain

• NO2 + HNO3 -> nitrate ion + hydrogen ions + sulfate ion

• SO2 + H2SO4 -> nitrate ion + hydrogen ions + sulfate ion

  • NO and SO2 react with O2 and H2O in the atmosphere, forming nitric and sulfuric acid

  • Sulfuric acid and nitric acid dissociate in the presence of water into sulfate and nitrate ions, and hydrogen ions (H+)

  • Acidic rain water (higher H+ concentration) decreases soil and water pH; can limit tree growth in forests down wind from major SO2 and NO sources

• Environmental effects of acid rain

  • Acidity means higher H+ ion concentration and lower pH

    • Range of tolerance

  • H+ ions displace or leech other positively charged nutrients (Ca²⁺, K⁺) from soil

  • H+ ions also make metals like aluminum and mercury more soluble in soil and water

    • Slow growth or kill plants and animals living in the soil or water

• Limiting acid rain

  • Reducing NO and SO2 emissions reduces acid deposition

    • Higher CAFE standards

    • More public transport

    • Renewable energy sources

    • More efficient electricity use

  • Since passage of Clean Air Act, acid deposition has decreased significantly

  • Limestone (calcium carbonate) is a natural base that can neutralize acidic soil/water

  • Calcium carbonate reacts with H+ ions, forming HCO₃ and giving off Ca²⁺

    • This neutralizes acidic water/soil, moving it closer to pH of 7

  • Regions with limestone bedrock have some natural buffering of acid rain

    • Humans can also add crushed limestone to soils and waters to neutralize

• Air Toxins

  • Known to cause or are suspected of causing cancer, birth defects, reproduction problems, other serious illnesses and even death

  • Main sources include industrial outputs (manufacturing), vehicle emissions, commercial outputs (dry cleaners and auto shops) and spills

  • Most regulation is for “major sources” with some regulation on “area sources” (smaller outputs)

  • Examples: 

    • Heavy metals like cadmium or mercury

    • Persistent organic pollutants like DDT

    • Benzene

    • Asbestos

  • East Palestine Train Derailment

• Urban Heat Island Effect

  • Urban areas tend to have higher surface and air temperature than surrounding suburban and rural areas due to: 

    • Lower albedo

    • Concrete and asphalt absorb more of sun’s energy than areas with more vegetation

    • Absorbed sunlight is given off as IR radiation - heat

  • Less evapotranspiration:

    • Water evaporating from surfaces and transpiration from plants carries heat from surface into the atmosphere

    • This cools off rural and suburban areas which have more vegetation

• Thermal Inversion

  • Normally the atmosphere is warmest at earth’s surface and cools as altitude risks

  • Because cold air at the surface is trapped beneath the warmer mass above, convection doesn’t carry pollutants up and away

  • During a thermal inversion, a cooler air mass becomes trapped near earth’s surface (inverting normal gradient)

    • Due to a warm front moving in over it

    • Or due to hot urban surfaces cooling overnight (long nights and clear skies exacerbate this)

  • Because warm air rises, air convection carries air pollutants away from earth’s surface and distributes them higher into the atmosphere

• Effects of Thermal Inversion

  • Air pollutants (smog, particulate matter, ozone, SO2, NO3) trapped closer to earth

  • Respiratory irritation: asthma flare ups leading to hospitalization, worsened blocking lungs

  • Decreased tourism revenue

  • Decreased photosynthetic rate

• Air Pollution Basics

  • Write about air pollutants (specific molecules/particles) 

  • Clean Air Act (1970) identified 6 criteria air pollutants that the EPA is required to set acceptable limits for, monitor, and enforce

    • CO2 is not one of the 6 criteria air pollutants in Clean Air Act (even though Supreme Court ruling found that EPA could regulate greenhouse gases, which it started doing in 2009)

      • Does not directly lower air quality from a human health standpoint, since it’s not toxic to organisms to breathe, not damaging to lungs and eyes, does not lead to smog or decreased visibility

      • CO2 is a greenhouse gas that leads to global warming 

• Reducing Emissions

  • Reducing emissions will reduce air pollutants

    • Drive less, walk/bike/bus more

    • Conserve electricity (smart appliances)

    • Eat more plants, less meat

    • Renewable, non-pollution emitting energy (solar, wind, hydro)

  • Laws and Regulations

    • Clean Air Act: Allows EPA to set acceptable levels for criteria air pollutants

      • Monitor emission levels from power plants and other facilities

      • Tax/sue/fine corporations that release emissions above levels

    • CAFE Vehicle Standards: Corporate Average Fuel Economy standards require the US fleet of vehicles to meet certain average fuel

      • Requires vehicle manufacturers to work to make more efficient vehicles

      • More efficient vehicles burn less gasoline and release less NO, PM, CO, CO2

    • Pollution Credits: Companies that reduce emissions well below EPA set levels earn pollution credits

      • They can sell these to companies that release more than acceptable levels

• Reducing Vehicle Air Pollutants

  • Vapor Recovery Nozzle

    • Capture hydrocarbon VOCs released from gasoline fumes during refueling

      • Separate tube inside nozzle captures vapors and returns them to underground storage tank beneath the gas station

      • Reduces VOCs, which contribute to smog and irritate respiratory tracts

      • Also reduces benzene (carcinogen) released from gasoline vapors

  • Catalytic Converter

    • Requires on all vehicles after 1975

    • Contains metals (platinum and palladium) that bind to NO and CO

      • Converts NO, CO, other hydrocarbons into CO2, N2, O2, H2O

• Reducing SO and NO

  • Crushed Limestone (SO₂)

    • Used to reduce SO₂ from coal power plants

    • Crushed coal mixed with limestone (calcium carbonate) before being burned in boiler

    • Calcium carbonate in limestone combines with SO2 to produce calcium sulfate, reducing SO2 being emitted

    • Calcium sulfate can be used to make gypsum wallboard or sheetrock for home foundations

  • Fluidized Bed Combustion (NO)

    • Fluidizing jets of air pumped into combustion bed

    • Jets of air bring more O2 into rxn, making combustion more efficient and bringing SO2 into more contact with calcium carbonate in limestone

    • Also allows coal to be combusted at lower temperatures, which emits less NO

• Wet and Dry Scrubbers

  • Dry Scrubbers (NO, SO, VOCs)

    • Large column/tube/pipe filled with chemicals that absorb or neutralize oxides from exhaust streams (emissions)

    • Calcium oxide is a common dry scrubber additive which reacts with SO2 to form calcium sulfite

  • Wet Scrubbers (NO, SO, VOCs, PM)

    • May involve chemical agents that absorb or neutralize NO, SO, VOCs but also include mist nozzles that trap PM in water droplets as well

      • Mist droplets with pollutants and PM trapped in them fall to bottom of scrubber or get trapped at top by mist eliminator

      • Sludge collection systems traps polluted water for disposal

• Reducing Particulate Matter

  • Electrostatic Precipitator

    • Power plant/factory emissions passed through device with a negatively charged electrode, giving particles a negative charge

    • Negatively charged particles stick to positively charged collection plates, trapping them

    • Plates discharged occasionally so particles fall down into collection hopper for disposal in landfills

  • Baghouse Filter (PM)

    • Large fabric bag filters that trap PM as air from combustion/industrial process passes through

    • Shaker device knocks trapped particles loose into collection hopper below

    • PM collected and taken to landfill

Indoor Air Pollution

• Indoor air quality is more important for the average person

  • Average Americans spend 90% of their time indoors 

  • Lack of ventilation and a smaller space can lead to higher concentrations of pollutants

  • Excessive amounts of pollutants can lead to “sick building syndrome” 

  • Poor air quality in buildings can lead to sluggish behavior, frequent headaches, lowered resistance to viruses and colds, difficulty concentrating and increased absenteeism in common occupants

• Especially important for kids with less developed immune systems and lungs, who also breathe more rapidly than adults

• Developing v Developed Countries

  • Developing nations use more subsistence fuels such as wood, manure, charcoal (biomass)

    • These biomass fuels release CO, PM, NO_x, VOCs 

      • Can also cause deforestation

    • Often combusted indoors with poor ventilation, leading to high concentrations

    • Estimated 3 billion people globally cook with subsistence fuels, resulting in estimated 3.5 - 4.3 million deaths annually

  • Developed nations use more commercial fuels (coal, oil, natural gas) supplied by utilities

    • Typically burned in closed, well ventilated furnaces, stoves, etc.

    • Major indoor air pollutants in developed nations come from chemicals in products: adhesives in furniture, cleaning supplies, insulation, lead paint

• Some indoor air pollutants aren’t really a concern outdoors

  • Some air pollutants can’t reach a critical concentration to cause harm outdoors, but can when they build up indoors

    • Radon

    • Carbon monoxide

• Carbon Monoxide (CO)

  • CO is produced by incomplete combustion of basically any fuel

    • Not all fuel is combusted due to low O₂ or temperature

  • CO is an asphyxiant: causes suffocation due to CO binding to hemoglobin in blood, displacing O₂

    • Hydrocarbon + not enough O₂ → (burn) carbon monoxide fine particles

  • Lethal to humans in high concentrations, especially with poor ventilation (odorless and colorless - hard to detect) 

    • Hemoglobin carries oxygen and carbon dioxide; carbon monoxide binds very tightly to hemoglobin + oxygen and carbon dioxide can no longer be carried

    • Developed nations: CO is released into home by malfunctioning natural gas furnace ventilation

      • Can be detected by carbon monoxide detectors (similar to smoke detectors) 

    • Developing nations: CO emitted from indoor biomass combustion for heating/cooking

• Radon Gas

  • Radioactive gas released by decay of uranium naturally found in rocks underground (granite especially)

    • Usually enters homes through cracks in the foundation and then disperses up from the basement/foundation through home

      • Uranium in the foundation rocks -> radium -> radon -> home

      • Can also seep into groundwater sources and enter body through drinking water

    • 2nd leading cause of lung cancer after smoking

      • EPA recommends testing homes with airborne radon monitor

      • Sealing cracks in foundation can prevent it from entering and increasing ventilation in the home can disperse if it’s detected

• Indoor PM

  • Indoor sources of particulate matter include pet dander, mold, asbestos, combustion/cooking, smoking, dust, cockroaches and dust mites

• Indoor VOCs

  • Health effects 

    • Short term: Dizziness, nausea, headaches, eye, nose, throat irritation

    • Long term: Kidney, liver, respiratory disease, cancer

  • Sources

    • Copiers + printers, correction fluids, carbonless copy paper, glues + adhesives, permanent markers, hobby supplies

    • Photographic solutions and dry-cleaned clothing

    • Aerosol sprays, varnish, and perfume

    • Moth repellents and air fresheners

    • Building materials and furnishings

    • Detergents, cleaners, and disinfectants

    • Paints, paint remover, and other solvents; wood preservatives

    • Stored fuels and automotive products; pesticides 

    • Detergents, cleansers, and disinfectants

• Lead

  • Found in paint in old times (EPA banned lead paint in 78) 

    • Paint chips off walls/windows and is eaten by small children (due to curiosity and sweet taste) or inhaled as dust

    • Lead water pipes can also release lead into drinking water sources (as in Flint) but it’s less common than lead paint

      • Damages central nervous system of children due to smaller size and still developing brain

    • Can be removed from home by stripping lead paint and replacing with non-lead based paint

    • Lead water pipes can be replaced by cities with copper pipes

• Indoor Ozone

  • Not really a problem unless your ventilation is terrible or you use an ozone generator

• NO2 and SO2

  • Potential sources include kerosene heaters; gas or wood stoves and furnaces; tobacco smoke

• Reducing indoor air pollution

  • Source control

    • Examples include controlling humidity to decrease mold

    • Sealing pollution sources (like asbestos) away

    • Adjusting gas stoves to reduce emissions

    • Properly storing chemicals

  • Improved ventilation

  • Air cleaners and filtration  

Noise & Light Pollution

• Ranking by loudness

  • Conversations

  • Blender

  • Road

  • Construction 

  • Rock concert

  • Bomb

• Noise pollution: Sound at levels high enough to cause physiological stress and hearing loss

• Sources

  • Domestic and industrial activity

  • Transportation

  • Construction

• Loudest sound in recorded history

  • Krakatoa Volcanic Eruption in 1883

  • Ruptured eardrums of people 40 miles away

• Harmful effects 

  • Tinnitus

  • Hearing loss

  • Stress & physiological symptoms of stress

• Effects of noise exposure on children

  • Cognitive: Difficulty in speech development, impaired language comprehension, poor memory and reading ability

  • Physical: Hearing loss, raised blood pressure, endocrine imbalance

  • Behavioral: Stress & anxiety, lack of motivation, hyperactivity

• Harmful effects on other organisms

  • Stress

  • Masking of sounds used to communicate or hunt

  • Damaged hearing

  • Changes to migratory routes

• Marine mammals are especially affected

  • Use of sonar

  • Sound carries further through water

• Reducing noise pollution

  • Turn it down (on average headphones can play higher than 100 db)

  • Avoid noisy situations or use proper equipment

  • Keep large sources of noise away from residential and ecologically important areas

  • Install barriers

• Light pollution

  • Human-made alteration of outdoor light levels from those occurring naturally

  • Glare: Excessive brightness

  • Light trespass: Light falling where not intended

  • Sky glow: Brightening of light sky

• Human health effects

  • Glare can affect ability to see at night

  • Affects circadian rhythm and sleeping which can lead to: 

    • Depression

    • Obesity

    • Diabetes

    • Heart disease

    • Cancer

• Environmental effects

  • Can affect nocturnal animals’ sleep vs waking cycles and ability to hunt or hide

  • Can negatively affect reproductive strategies of certain species

  • Can misdirect species that use the moon/stars to navigate

  • Can throw off timing of life events (migration, flowering) for species that use light as an indicator

• 80% of world lives under sky glow, 99% of US and Europe

• Stratospheric Ozone & life on Earth

  • Ozone in the stratosphere absorbs UV-C and much of UV-B radiation

    • Without ozone layer, life on land would not be possible since UV-B & C radiation causes significant tissue damage & mutates DNA

    • Human health benefits of stratospheric ozone: 

      • Prevention of skin cancer & cataracts

      • UV-B & C mutate DNA (skin cancer) and cause oxidative stress in eyes (cataracts)

  • Remember: tropospheric = respiratory irritant, damaging to plant tissue and precursor to photochemical smog

• Anthropogenic Ozone Depletion

  • CFCs (chlorofluorocarbons) aka “freon” are a primary anthropogenic (human) cause of O₃ breakdown

    • Used as refrigerant chemicals and propellants in aerosol containers (hair spray, febreeze, etc)

  • UV radiation causes free chlorine atom to separate from CFCs

    • Highly electronegative chlorine atom bonds to one of the oxygen atoms of ozone (O₃) converting it into oxygen (O₂) 

    • Free O atom then bonds to O from chlorine monoxide to form O₂ and free Cl atom to go break down more O₃

  • One single Cl atom persists in atmosphere for 50 - 100 years and can destroy up to 100,00 ozone molecules

• Natural Ozone Depletion

  • Antarctica spring melt forms polar stratospheric clouds (PSC)

    • Clouds made of water and nitric acid (HNO₃) that can only from in consistent -100 deg F temperature range found above Antarctica

    • In presence of PSCs, chlorine nitrate (CLONO₂) and hydrochloric acid (HCl) react and give off Cl₂

      • Cl₂ is photolyzed (broken by sun) into 2 free Cl atoms

  • Remember what Cl atoms due to ozone from CFCs (break O₃ down into O₂ over and over)

• Reducing Ozone Depletion

  • Main way to reduce anthropogenic O₃ depletion in phasing out and replacing CFCs

    • Montreal Protocol (87’) was a global agreement to phase CFCs out of production in refrigerators, aerosols, and other uses

      • Replaced with HCFCs (CFCs with hydrogen added)

      • HCFCs can still deplete O₃ and acts as GHGs, but to lesser degree 

      • Not a permanent solution, but temporary transition option (phase out in developed nations after 2020, developing nations have until 2030)

    • Replacement for HCFCs is HFCs (still GHGs, but not O₃ depleting since they don’t contain Cl) 

      • Replacements for HFCs and HFOs (just hFCs with C-C double bonds that shorten atmospheric lifetime & GWP)