Air Pollution Notes

Air Pollution Overview

• Air pollution includes smoke, haze, dust, odors, corrosive gases, and toxic compounds.

• Air pollution emissions amount to billions of metric tons per year.

• The impact of air pollution depends on the specific toxin, exposure time, and concentration.

• Health Effects:

  • Asthma

  • Bronchitis

  • Emphysema

  • Heart disease

  • Stroke

  • Neurological damage

  • Other health problems

• Air pollution:

  • Impairs human health.

  • Damages crops and ecosystems.

  • Corrodes buildings and infrastructure.

  • Affects the climate.

  • Odors and loss of visibility impact our quality of life.

• Air pollution is especially dangerous for children.

Population Exposure to Air Pollution

• In 2017, a significant portion of the global population was exposed to air pollution levels exceeding WHO guidelines.

• The WHO guideline value for particulate matter (PM2.5) is 10 micrograms per cubic meter per year ($10µg/m^3$).

• This value represents the lower range of WHO recommendations, above which adverse health effects are observed.

Air Pollution Severity and Mortality

• In many Indian cities, air pollution is 20 times higher than levels considered safe for human health.

• Health Impact:

  • Respiratory ailments

  • Cardiovascular diseases

  • Lung cancer

  • Infant mortality

  • Miscarriages are up to 50% higher in countries with high pollution levels.

• Approximately 6.5 million people worldwide die from air pollution annually.

• 92% of these deaths occur in low-income countries.

• Reasons for High Mortality in Low-Income Countries:

  • Weak pollution control policies

  • Uncertain healthcare

• 95% of the human population is exposed to air quality that does not meet WHO guidelines over the course of a year.

• WHO guidelines: 5 ug/m3 annually

Primary and Secondary Pollutants

• Primary pollutants are harmful when released directly into the air.

• Secondary pollutants become harmful after reacting with other gases or substances in the air.

• Photochemical oxidants are compounds created by reactions driven by sunlight.

• Atmospheric acids are formed when pollutants such as $NO<em>2$ and $SO</em>2$ dissolve in water.

Air Quality Index (AQI)

• The US AQI levels and associated health recommendations are as follows:

  • Good: 0-50 (PM2.5: 0-9.0 $μg/m^3$) - Air quality is satisfactory.

  • Moderate: 51-100 (PM2.5: 9.1-35.4 $μg/m^3$) - Sensitive individuals should avoid outdoor activity.

  • Unhealthy for Sensitive Groups: 101-150 (PM2.5: 35.5-55.4 $μg/m^3$) - General public and sensitive individuals are at risk.

  • Unhealthy: 151-200 (PM2.5: 55.5-125.4 $μg/m^3$) - Increased likelihood of adverse effects for the general public.

  • Very Unhealthy: 201-300 (PM2.5: 125.5-225.4 $μg/m^3$) - General public will be noticeably affected; sensitive groups should restrict outdoor activities.

  • Hazardous: 301+ (PM2.5: 225.5+ $μg/m^3$) - General public at high risk; outdoor activities should be avoided.

• WHO PM2.5 recommended guidelines as of 2024: 0-5.0 $μg/m^3$

Air Quality Index Statistics

• In 2023, Maricopa County had good air quality (AQI of 0-50) for 23.63% of the days.

• Bernalillo County had good air quality for 100.00% of the days.

EPA AirNow Website

• The EPA AirNow website (https://www.airnow.gov/) provides information on air quality.

Air Pollution Control

• Legal enforcements are used to control air pollution.

• Bad air quality is often found in major port cities, oil and gas extraction areas, and industrial cities.

• Primary standards are set to protect human health.

• Secondary standards are set to protect crops, materials, climate, visibility, and personal comfort.

US Clean Air Act of 1963

• The first national legislation in the US aimed at air quality.

• Amended in 1970 to be applied equally across the country.

• Addresses six major pollutants (Conventional or criteria pollutants):

  • Sulfur dioxide

  • Nitrogen oxides

  • Carbon monoxide

  • Ozone

  • Lead

  • Particulate matter

• Major sources of these pollutants are transportation and power plants.

• Also regulates unconventional pollutants which are produced in less volume but are especially toxic or hazardous such as:

  • Asbestos

  • Benzene

  • Mercury

  • PCBs

  • Vinyl chloride

New Source Reviews 1977

• Industries argued it would be too expensive to retrofit new pollution-control equipment on old factories.

• Existing equipment was “grandfathered” from new pollution limits, but rules would apply when equipment was upgraded or replaced.

• Plant owners were incentivized to keep old facilities operating due to exemptions.

• Resulting in old facilities being among the biggest contributors to smog and acid rain.

Cap and Trade System

• The EPA sets maximum emission levels for pollutants.

• Facilities can buy and sell emission “credits”.

• Companies decide whether to install pollution control equipment or buy credits, depending on cost.

Supreme Court Ruling of 2007

• The EPA has the responsibility to limit greenhouse gases because they endanger public health and welfare and thus fall under the Clean Air Act.

• The 2014 Clean Power Plan (Obama) was blocked.

• In 2017, this law was replaced with a new rule that supported the coal industry by encouraging efficiency rather than emission controls.

• The Inflation Reduction Act of 2022 amended the Clean Air Act, reinforcing $CO_2$ as an air pollutant and affirming the EPA's authority and responsibility to regulate it.

• It includes hundreds of billions of dollars in tax incentives and grants to reduce the cost of meeting emission standards.

Air Pollutants

• Particulate Matter:

  • Coarse PM: PM 2.5-10 $μm$

  • Fine PM: PM < 2.5 $μm$

  • Ultrafine PM: PM < 0.1 $μm$

• Gases:

  • Ground-level ozone ($O_3$)

  • Nitrogen dioxide ($NO_2$)

  • Sulfur dioxide ($SO_2$)

  • Carbon monoxide (CO)

  • Volatile organic compounds (VOCs)

Sulfur Dioxide ($SO_2$)

• Colorless, corrosive gas.

• Damages both plants and animals.

• Reacts with water vapor to create sulfuric acid (acid rain).

• Minute droplets can penetrate deep into lungs, causing permanent damage, irritates eyes and corrodes buildings.

• Destroys chlorophyll in plants.

Nitrogen Oxides ($NO_x$)

• Highly reactive gases.

• Combine with water to form nitric acid (acid rain).

• Excess nitrogen in water causes eutrophication.

Carbon Monoxide (CO)

• Colorless, odorless, highly toxic gas.

• Produced by incomplete combustion of fuel, land-clearing fires, and cooking fires.

• Internal combustion engines are a major source of CO.

• Inhibits respiration in animals.

Ozone ($O_3$)

• Ground-level ozone is a highly reactive oxidizing agent that damages eyes, lungs, and plant tissues.

• Interacts with a variety of volatile organic compounds (VOCs) to produce photochemical oxidants.

Tropospheric Ozone ($O_3$)

• Tropospheric ozone is a powerful greenhouse gas and air pollutant that is harmful to human health, agricultural crops, and ecosystems.

• Sources: Tropospheric ozone does not have any direct emissions sources, rather it is formed when sunlight interacts with different pollutants such as:

  • Methane

  • Carbon Monoxide

  • Non-methane volatile organic compounds

  • Nitrogen oxides

• Reducing the pollutants that form tropospheric ozone would generate rapid benefits for the climate and human health.

• Climate Impacts: Contributes to global warming

• Health Impacts: Causes 1+ million pollution-related deaths every year and millions more chronic diseases

• Agriculture & Ecosystems: Toxic to many plants and causes up to 15% in annual yield losses of soy, wheat, rice, and maize

• Tropospheric ozone damages plants and their ability to sequester $CO_2$, which doubles its climate impact.

Best & Worst Cities for Ozone Pollution

• Cleanest Cities by Ozone (examples):

  • Albany-Schenectady, NY

  • Augusta-Richmond County, GA-SC

  • Bangor, ME

• Worst Cities by Ozone (examples):

  • Los Angeles-Long Beach, CA

  • Visalia, CA

  • Bakersfield, CA

What is Ozone Pollution?

• Bad or ground-level ozone pollution is created when vehicle and other emissions mix with pollutants and are heated by the sun.

• Warmer weather increases ground-level ozone pollution.

• The Air Quality Index (AQI) grades air quality based on ground-level ozone, particle pollution, carbon monoxide, sulfur dioxide, or nitrogen dioxide levels.

• Visit airnow.gov or watch local alerts.

• Recommendations:

  • Watch local air quality advisories.

  • Ozone levels are always lower in the morning, so plan outdoor activities accordingly.

  • The elderly, the very young, and those with lung disease are at the highest risk from severe ozone pollution and should limit afternoon outdoor time during poor ozone days.

  • Keep windows closed.

  • Take medications exactly as prescribed.

  • Use the circulate setting on your home thermostat to keep polluted air out.

  • Call your doctor if symptoms increase or if you need more medication.

  • Facemasks are highly encouraged to limit COVID-19 infection but provide no protection against ozone pollution.

Lead

• Impairs nerve and brain function.

• Industrial and mining processes produce lead, especially smelting of metal ores, mining, and burning coal.

• Leaded gasoline was banned in the 1980s.

• One of the most successful pollution-control measures in American history.

Particulate Material

• Includes dust, ash, soot, lint, smoke, pollen, spores, algal cells, and other suspended materials.

• Aerosols are extremely minute particles or liquid droplets suspended in the air.

• Often most apparent form as they reduce visibility and leave deposits.

• Fine particles less than 2.5 micrometers penetrate deep into lungs and damage fragile lung tissue, leading to scarring and decreased lung function and can even enter the bloodstream.

Estimated Fluxes of Pollutants to the Atmosphere Annually (Millions of metric tons per year)

Improvement in U.S. Air Pollution (1990-2020)

• 73% decrease in carbon monoxide

• 86% decrease in lead (since 2010 only)

• 61% decrease in nitrogen dioxide

• 25% decrease in ground-level ozone

• 26% decrease in coarse particulate matter

• 91% decrease in sulfur dioxide

• Source: https://www.epa.gov/clean-air-act-overview/progress-cleaning-air-and-improving-peoples-health

Hazardous Air Pollutants (HAPs)

• Special category of pollutants that are particularly dangerous even in low concentrations.

• Cause cancer and nerve damage, and disrupt hormone functions and fetal development.

• Persistent substances remain in ecosystems for long periods of time and bioaccumulate.

• Examples include metals, chlorinated hydrocarbons, and volatile organic compounds such as:

  • Gasoline vapors

  • Solvents

  • Components of plastics

• Emitted by chemical-processing factories that produce gasoline, plastics, solvents, pharmaceuticals, and other organic compounds.

• Examples: Benzene, toluene, xylene, dioxins.

• The EPA reports that 100 million Americans live in areas where the cancer rate from HAPs is 10x the accepted standard.

• Can check Toxic Release Inventory (TRI).

Toxic Release Inventory for Evansville

• https://enviro.epa.gov/triexplorer/tri_factsheet.factsheet?pzip=&pstate=IN&pcity=EVANSVILLE&pcounty=&pyear=2023&pParent=TRI&pDataSet=TRIQ1

• Indiana ranks 2 out of 56 states/territories nationwide based on total releases per square mile (Rank 1 = highest releases)

• Evansville, IN vs. United States:

  • Number of TRI Facilities: 17 vs 21,661

  • Total Production-Related Waste Managed: 6.3 million lbs vs 34.6 billion lbs

  • Total On-site and Off-site Disposal or Other Releases: 89.2 thousand lbs vs 3.3 billion lbs

  • Total On-site: 85.1 thousand lbs vs 2.9 billion lbs

    • Air: 85.1 thousand lbs vs 520.7 million lbs

    • Water: 53 lbs vs 184.8 million lbs

    • Land: 0 lbs vs 2.2 billion lbs

  • Total Off-Site: 4.0 thousand lbs vs 396.1 million lbs

Airborne Mercury

• Widespread and persistent neurotoxin.

• Minute doses cause nerve damage and other impairments, especially in young children and fetuses.

• 70% of airborne mercury is released by coal-burning power plants.

• Aquatic bacteria convert airborne mercury into a form that accumulates in living animal tissues.

• 80% of human exposure to mercury comes from eating fish.

• Mercury levels in the Pacific Ocean have risen 30% in 20 years due to increased coal burning in China.

• Regulated by the Clean Air Act in 2000, leading to an 80% decrease in mercury emissions from power plants through metal capture before it leaves the smokestack.

• Minamata Convention of Mercury (2017) is an international treaty to reduce mercury globally.

Indoor Air Pollution

• Indoor air can be worse than outdoor air due to the use of volatile organic compounds in carpets, furniture, cleaning products, paints, etc.

• Many homes have concentrations that would be illegal in the workplace.

• Cigarette smoke:

  • 400,000 people in the US die from diseases caused by smoking every year.

  • Total costs: $100 billion per year.

• Radon:

  • 15,000-20,000 deaths each year in the US.

  • Nearly 1 out of every 15 homes in the US has elevated radon levels.

Pollutants and Climate Change

• Pollutants that cause climate change include carbon dioxide, methane, nitrous oxide, and halogen gases.

• Atmospheric circulation distributes pollutants around the globe.

• Antarctica even has heavy metals, pesticides, and radioactive elements in its air.

• Soot, smoke, ash, and particulates settle on arctic snowfields and absorb the sun’s heat, rather than reflecting it like the snow does; this is known as “black carbon.”

• These particles also block sunlight to inhibit photosynthesis.

• Contaminants transport toward the poles.

• The Inuit people of Broughton Island above the Arctic Circle have higher levels of PCBs in their blood than any other known population except victims of industrial accidents, which come from PCBs bioaccumulated from fish, caribou, and other animals they eat.

Ozone “Hole”

• Reduced concentration of ozone in the stratosphere.

• It measures 8 million square miles over Antarctica.

• Caused by chlorine-based aerosols, such as chlorofluorocarbons (CFCs).

• CFCs are nontoxic, nonflammable, chemically inert, long-lasting, and cheaply produced.

• Used in refrigerators, air conditioners, Styrofoam insulation, and aerosol cans.

• Lightweight so diffuse into the stratosphere and remain in circulation for years.

• Ozone is important in absorbing UV radiation, which damages plant and animal cells.

Montreal Protocol 1987

• International agreement to phase out CFCs by 1996.

• $500 million fund to assist poorer countries in switching to alternatives.

• Numerous alternatives already existed.

• The CFC ban had a strong effect.

• CFC production fell sharply.

• CFCs are being removed from the atmosphere more rapidly than being added.

• Stratospheric ozone layers are recovering rapidly.

• Also helped reduce climate change.

Health Effects of Air Pollution

• Bronchitis and emphysema

• 250,000 people suffer from pollution-related conditions in the US

• 50,000 deaths

• Irritate and damage delicate tissues in the eyes and lungs

• Fine, suspended particulate materials penetrate deep into the lungs, causing irritation, scarring, and tumor growth.

• Carbon monoxide reduces oxygen flow to the brain

Environmental Effects of Air Pollution

• Acid rain from sulfur dioxide, sulfate, and nitrogen oxides.

• Sulfuric acid deposits destroy vegetation.

• Damage lake ecosystems.

• Reduce nutrient availability in soils.

• Mobilize toxic concentrations of metals in soils.

• Emissions of $SO<em>2$ and $NO</em>x$ have decreased dramatically over 30 years.

Pollution Trapped Over Cities

• Temperature inversion: Stable, cold air rests near the ground with warm layers above (reverse of normal conditions).

• Normally, when warm air rises, it mixes in the atmosphere to help disperse pollution.

• In a temperature inversion, cool air below, air remains stable and still, and pollutants accumulate near the ground.

• Created by rapid nighttime cooling.

• Occur often in valleys (Los Angeles).

• Cities have low albedo and absorb large amounts of solar energy.

US Pollution

• Air quality hazardous levels days down 93% from a decade ago in 23 of the largest US cities

• 80% of US meets National Ambient Air Quality Standards

• Improvements largely due to filters, scrubbers, and precipitators on power plants, and catalytic converters on vehicles.

• Controlling methane and hazardous pollutants is still a major challenge.

Pollution in Developing Areas

• China and India

• 21 of the world’s 30 worst cities (PM2.5 levels) were in India in 2019

• Factories burn low-quality coal, very few pollution controls, farmers burn crop residues, and a rising number of vehicles.

“Asian Brown Cloud”

• A 2-mile thick cloud of ash, aerosols, dust, and smog covering the entire Indian subcontinent for much of the year.

• A product of forest fires, burning agricultural wastes, and overuse of fossil fuels.

• Blocks up to 15% of solar energy reaching the earth.

• Affects agriculture.

• 80% human-made.

• Predicted to disrupt weather patterns and decrease rainfall in the area by up to 40%.

• Cools sea temperatures leading to more changes in weather patterns.

• Could travel halfway around the globe in a week.

Delhi, India

• Worst air quality of any major city on earth.

• 2.5 million people die every year in India from diseases related to air pollution.

• 20 million residents.

• Caused by motor vehicles, burning crop residues, and industrial facilities.

• Visibility is limited to a few hundred meters.

“Valley of Death”

• Cubatao, Brazil in the 1980s.

• One of the most dangerously polluted places in the world.

• Steel plant + oil refinery + chemical factories: pollutants trapped between onshore winds and uplifted plateau nearby.

• The end of military rule and restoration of democracy allowed citizens voices to be heard to changes to be made.

• $300 million effort.

• Result:

  • Particulate pollution down 75%,

  • Ammonia down 97%,

  • Hydrocarbons down 86%,

  • Sulfur dioxide down 84%.

Air Pollution Control Strategies

• Most effective: conservation!

• Particulate removal: Filtering air emissions by trapping particulates.

• Sulfur removal: Switch to low-sulfur coal.

• Catalytic converters to oxidize or reduce sulfur, and remove nitrates, hydrocarbons, and carbon monoxide.

• Control hydrocarbons by complete combustion or control of evaporation.

Economic Costs of Air Pollution

• Cost of air pollution regulation: $50 billion.

• Economic benefits of reduced illness, property damage, and increased productivity: $1.3 trillion.

COVID-19 and Air Quality

• Lockdown led to significant improvements in air quality, with fine particulates reduced by up to 60% and nitrogen oxides reduced by 20%.

• If all human-made sources of pollution were shut down, the air would clear up in a few days.

• 90-mile visibility nearly everywhere compared to the current 10-mile.

Take-Away Points

• Air pollution is the most obvious and widespread type of pollution also it spreads to every crevice on earth.

• Release 2 billion metric tons of pollutants worldwide.

• Health effects:

  • Respiratory diseases

  • Birth defects

  • Heart attacks

  • Cancer

  • Developmental disabilities in children

• Environmental impacts:

  • Destruction of stratospheric ozone

  • Poisoning of forests and waters by acid rain

  • Corrosion of building materials

• The economic cost of pollution greatly outweighs the costs of pollution prevention.

• Progress has been made:

  • Montreal Protocol

  • Clean Air Act

Our Nation's Air

• Between 1970 and 2022, the combined emissions of the six common pollutants (PM, and PM, $SO<em>2$, $NO</em>X$, VOCs, CO and Pb) dropped by 78 percent. This progress occurred while the U.S. economy continued to grow, Americans drove more miles and population and energy use increased.

• Air Quality Trends Show Clean Air Progress:

  • While some pollutants continue to pose serious air quality problems in areas of the U.S., nationally, criteria air pollutant concentrations have dropped significantly since 1990 improving quality of life for many Americans. Air quality improves as America grows.

  • Declining National Air Pollutant Concentration Averages Percent Change(1990-2020):

    • CO -81%

    • Pb (from 2010) -88%

    • $NO_2$ annual -60%

    • $NO_2$ 1-hour -54%

    • $O_3$ -22%

    • $PM_{10}$ -34%

    • $PM_{2.5}$ annual (from 2000) -42%

    • $PM_{2.5}$ 24-hour (from 2000) -42%

• Air Pollutant Emissions Decreasing

• Emissions of key air pollutants continue to decline from 1990 levels. These reductions are driven by federal and state implementation of stationary and mobile source regulations.

  • $SO_2$ Emissions

    • -92%

  • Direct $PM_{10}$ Emissions

    • -27%

  • $NO_x$ Emissions

    • -71%

  • VOC Emissions

    • -48%

• Unhealthy Air Days Show Long-Term Improvement

  • The Air Quality Index (AQI) is a color-coded index EPA uses to communicate daily air pollution for ozone. particle pollution, $NO<em>2$, CO, and $SO</em>2$. A value in the unhealthy range, above national air quality standard for any pollutant, is of concern first for sensitive groups, then for everyone as the AQI value increases.

  • Fewer unhealthy air quality days means better health, longevity, and quality of life for all of us.