What is carbon monoxide?
Carbon monoxide is a colorless, odorless, and tasteless gas formed when carbon-based fuels do not burn completely.
Sources of Carbon Monoxide
Carbon monoxide is produced during the combustion processes involving fuels. The largest source of carbon monoxide in outdoor air is motor vehicle exhaust. Other sources include wood stoves, lanterns, gas ranges, and industrial processes.
Health and Welfare Effects
Carbon monoxide reduces the amount of oxygen that can be transported in the bloodstream to critical organs. At high concentrations, it can cause dizziness, upset stomach, vomiting, confusion, and even death.
Learn more about protecting your family and yourself from carbon monoxide poisoning | EPA Carbon Monoxide Guide >
Arizona Air Quality Planning
All areas in Arizona currently meet federal carbon monoxide standards. Previously, Maricopa and Pima counties were designated as an NAA due largely to motor vehicle emissions. However, following successful implementation of permanent and enforceable control measures, both of these areas are now maintaining the standards and have been redesignated to attainment.
Learn more about carbon monoxide in outdoor and indoor air | CO in outdoor air > | CO in indoor air >
There are two kinds of ozone:
- High-altitude ozone or the good ozone that is high up in the atmosphere and forms a protective barrier around the Earth from the sun’s harmful ultraviolet rays.
- Ground-level ozone or the bad ozone that forms closer to the Earth in the air we breathe. This ozone is not usually emitted directly, but rather forms from chemical reactions between oxides of nitrogen (NOx ) and volatile organic compounds (VOCs) in sunlight. The term ozone should not be confused with smog, another type of pollution that consists of ground-level ozone and other gaseous and particulate pollution.
Ground-level ozone (O3 ) is regulated by EPA. Ground-level ozone comes from pollution emitted from cars, power plants, industrial boilers, refineries, and chemical plants. Ozone pollution can even come from paints, cleaners, solvents, and motorized lawn equipment. For this reason, levels of ground-level ozone tend to be the highest near urban centers as opposed to rural areas. In Arizona, ground-level ozone is primarily concentrated in Maricopa County, where most urban centers are located. However, ozone pollution can easily be transported or carried over rural areas outside cities.
Health and Welfare Effects
Ozone can be particularly dangerous and abundant on hot days in an urban area. Exposure to ozone can make it very difficult to breathe and cause coughing and shortness of breath. It can lead to worse conditions like damaged airways, chronic bronchitis, asthma, and emphysema. Even if symptoms have disappeared, ozone can continue to damage the lungs.
Ground-level ozone can also damage vegetation and ecosystems. The pollutant can cause mass die-off in crops, reducing growth and increasing disease.
Historically, Arizona’s ozone levels have decreased thanks to pollution controls outlined in SIPs and enforced by state and federal air quality departments.
Ozone Plans
EPA established new ozone standards in 2015. The Yuma and Phoenix-Mesa areas are currently designated nonattainment and classified as marginal for the 2015 8-hour ozone standard. The Phoenix-Mesa area is also designated nonattainment and classified as moderate for the 2008 8-hour ozone standard. See our eMap for the Ground-level Ozone nonattainment and maintenance areas | View eMap >
Maricopa/Pinal County
2017 Maricopa 8-Hour Ozone Moderate Nonattainment Area Plan (Phoenix-Mesa 2008 Ozone Area) | View >
Maricopa/Pinal/Gila County
2025 Gila County, Arizona RACT Analysis and Negative Declarations for the 2015 Ozone NAAQS | View >
2020 Maricopa Eight-Hour Ozone Marginal Nonattainment Area Plan (Phoenix-Mesa 2015 Ozone Area) | View >
Yuma County
2020 Yuma Eight-Hour Ozone Marginal Nonattainment Area Plan (Yuma 2015 Ozone Area) | View >
To learn more about ground-level ozone, please visit EPA’s webpage | Learn More >
What is Lead?
Lead is a bluish-gray, naturally occurring element/metal found deep within the ground. Lead is widely used in a variety of applications and products, including batteries, pipes, construction materials, X-ray shields, and more. It is toxic to both humans and animals when inhaled or ingested.
Where does lead pollution come from?
Lead becomes a pollution when it enters the air, water, soil and buildings. In the past, a major source of lead pollution came from leaded gasoline. After the adoption of unleaded gasoline, lead pollution now mostly comes from industrial sources like smelters, mining and refining. Once in the air, lead can attach to airborne particles to form particulate matter. Lead can also settle into the soil and then be kicked up again by human activity or wind. Indoor lead pollution is most common in older homes (pre-1978) that were constructed using lead-based paint and water pipes.
How does lead affect my health?
When suspended in the air, lead can be inhaled and distributed to the airways and the bloodstream. Exposure can cause the build-up of lead in the bones. Lead can cause irreversible damage to the human body, especially in children. In a young child’s immune system, lead can cause behavioral deficiencies, learning deficits, lowered IQ and slowed growth.
Pregnant women are also more at risk due to the accumulation of lead in the bones during and after exposure. The accumulated lead in the bones is released during pregnancy into the fetus. Lead can also enter the placenta, exposing the fetus to lead and causing premature birth and reduced growth.
In adults, lead exposure can cause heart problems, increased blood pressure, decreased kidney function, reproductive issues and difficulties with memory or concentration.
For more information, visit the Environmental Protection Agency (EPA) Lead webpage about lead and how it may affect your health | View >
How can I protect myself?
Reducing exposure is the best way to protect oneself. Arizona Department of Health Services (ADHS) has information about reducing exposure at the ADHS Lead Poisoning Parent Portal | View >
Forecast and historical monitored lead levels in Arizona
ADEQ issues a daily lead forecast for the Hayden/Winkelman area based on forecast wind speeds and direction. High levels of lead in the ambient air are due to mineral processing activities at the ASARCO Hayden Operations | Forecast >
Historical Hayden/Winkelman Lead Data | View >
Lead Plans
Lead Pollution (Pb) Nonattainment Area eMap | View >
2017 Hayden Lead State Implementation Plan (SIP) | View >
To learn more about Lead pollution, please visit EPA’s webpage | Learn More >
Nitrogen oxides (NOx ) is a group of highly reactive gasses, including nitrogen dioxide, nitrous acid, and nitric acid. For standards-setting, EPA uses nitrogen dioxide (NO2 ) as an indicator pollutant, meaning, if nitrogen dioxide pollution exists in the air, so do other nitrogen oxides.
In particular, nitrogen dioxide commonly comes from fuel combustion, such as mobiles, power plants, and off-road equipment. The nitrogen oxides that form from these sources combine with volatile organic compounds (VOCs) to form ground-level ozone, the bad kind of ozone. The smallest, most harmful particulate pollution, known as PM2.5 , is also formed from nitrogen oxides in combination with VOCs, sulfur oxides, ammonia, and particulates.
Ultimately, nitrogen oxides pollution impacts visibility, breathing abilities, water quality, acid rain, and the Earth’s temperature.
Health and Welfare Effects
Nitrogen dioxide itself has been shown to lead to adverse respiratory effects including airway inflammation and asthma. Those living near major roadways are at high risk, considering NO2 emissions are approximately 30-100 percent higher than areas away from roadways.
The nitrogen oxides family can react with ammonia, VOCs, and other compounds to form PM2.5 pollution that easily penetrates into sensitive and deep parts of the lung causing respiratory diseases like emphysema and bronchitis. NOx also can aggravate a pre-existing heart disease, leading to premature death.
The bad type of ozone, ground-level, is formed from when NOx and VOCs react with sunlight and heat. Ground-level ozone acts as a dense barrier blocking pollution from escaping the higher atmosphere. This pollution grows closer to Earth and traps heat and decreases visibility. Certain groups like children, the elderly, and people with lung diseases are especially at risk of ground-level ozone, which can cause poor breathing and other respiratory issues.
Nitrogen Oxides Plans
There are no nonattainment areas in the country for the 2010 NOx standards. Since all areas in the country are attaining the standards, Arizona has submitted the required infrastructure-SIP.
2010 NO2 Infrastructure SIP | View >
To learn more about NO2 & NOx, please visit EPA’s webpage | Learn More >
Particulate matter, sometimes referred to as particle pollution or PM, is a complex mix of very small particles, water vapor, and gases. Common small particles can include lead, dust, dirt, and sand. When these components combine, air pollution forms.
EPA regulates two categories of particulate matter for health and welfare reasons:
- PM10: Inhalable coarse particles are between 2.5 and 10 micrometers in diameter
- PM2.5: Fine particles are smaller than 2.5 micrometers in diameter
For a size comparison, a single strand of human hair on average is 70 micrometers in diameter, making it 30 times larger than the largest fine particle.
Keep in mind, particle pollution can come from many different types of particles, gasses, and liquids. Particle pollution can be sourced from construction sites, unpaved roads, fields, smokestacks, and fires. But they can also come from atmospheric reactions between gasses like sulfur dioxides and nitrogen oxides that are emitted from power plants, other industries, and cars.
Health and Welfare Effects
These fine particles pose more health risks than larger particles like gravel because they can settle deeper into the lungs and even into the bloodstream. Like other air pollution, particles can cause premature death in people with heart or lung disease, nonfatal heart attacks, irregular heartbeat, aggravated asthma, decreased lung function, and respiratory issues like inflamed airways and difficulty breathing.
Particulate Matter Plans
Arizona has a unique mix of urban and agricultural sources of particulate matter. Several areas of the state have historically exceeded the PM10 and PM2.5 air quality standards. See our eMap for the Particulate Matter (PM) nonattainment and maintenance areas | View eMap >
Gila County
2012 Limited Maintenance Plan Update for Payson PM10 Maintenance Area | View >
Maricopa County
2012 Maricopa Association of Government Five Percent Plan for PM10 for Maricopa County Nonattainment Area | View >
Mohave County
2012 Limited Maintenance Plan Update for Bullhead City PM10 Nonattainment Area | View >
Pinal County
2012 Five Percent Plan for PM10 for Pinal County Township 1 North, Range 8 East Nonattainment Area | View >
2015 West Pinal Moderate PM10 Nonattainment Area Plan | View >
Pima County
2008 Rillito Moderate Area PM10 Limited Maintenance Plan and Request for Redesignation | View >
2019 Ajo PM10 Redesignation Request and Maintenance Plan | View >
Santa Cruz County
2012 Nogales PM10 Nonattainment Area Plan | View >
2013 Nogales PM2.5 Nonattainment Area Plan | View >
Yuma County
2006 Yuma PM10 Maintenance Plan | View >
To learn more about particulate matter, please visit EPA’s webpage | Learn More >
What is sulfur dioxide?
Sulfur dioxide (SO2) is a toxic, colorless gas that has a pungent odor, much like that of a just-struck match. Chemically, it is a compound made up of one sulfur atom and two oxygen atoms. SO2 is also part of a larger group of compounds found in the atmosphere called sulfur oxides (SOx). Since SO2 is the predominant sulfur oxide in the atmosphere, and therefore of greatest concern, the Environmental Protection Agency (EPA) has established a National Ambient Air Quality Standard (NAAQS) for SO2. In general, the regulation of SO2 is assumed to cover all other sulfur oxides as well.
For more information about SO2, NAAQS and areas in Arizona that do not meet standards, visit:
EPA SO2 NAAQS | View >
Hayden SO2 Nonattainment Area | View >
Miami SO2 Nonattainment Area | View >
Where does SO2 come from?
The majority of SO2 in the atmosphere comes from the burning of fossil fuels (for example, coal and oil) by power plants and other industrial facilities. Other sources include: industrial processes, such as metal extraction (smelting); non-road vehicles, such as large ships, locomotives, etc.; and natural sources, such as volcanoes.
How does SO2 affect my health?
Breathing SO2 can irritate the nose, throat and airways within 10 to 15 minutes of exposure. Coughing, wheezing, shortness of breath or a tight feeling around the chest may be experienced. Children, elderly and those who suffer from asthma or other lung diseases are particularly sensitive to the effects of SO2. Chronic exposure can increase the susceptibility of the effects of SO2.
Moreover, SO2 and other sulfur oxides can react with other compounds in the air and form small particles, or fine particulate matter (PM2.5). Fine particulates are small enough to penetrate into the lungs and even the bloodstream, which may cause additional health problems.
For more information visit:
EPA Sulfur Dioxide (SO2) Pollution| View >
Air Quality Guide for Particle Pollution | View >
How can I protect myself?
The EPA has recommendations for 1-hour SO2 average concentrations | Learn More >
Current and historical monitored SO2 levels in Arizona
Hayden SO2 Data (2018) | View >
Miami SO2 Data (2018) | View >
Sulfur Dioxide Plans
Currently, Arizona has several nonattainment and maintenance areas for the 1971 and 2010 SO2 standards. See our eMap for the Sulfur Dioxide (SO2 ) nonattainment and maintenance areas | View >
Gila and Pinal Counties
2002 Hayden SO2 Nonattainment Maintenance Plan | View >
2017 Hayden SO2 State Implementation Plan (SIP) | View >
Gila County
2002 Miami SO2 Nonattainment and Maintenance Plan | View >
2017 Miami SO2 State Implementation Plan (SIP) | View >
Greenlee County
2014 Morenci SO2 Maintenance Plan | View >
Pima County
2013 Ajo SO2 Maintenance Plan Renewal | View >
Pinal County
2007 San Manuel SO2 Nonattainment Area Plan | View >
To learn more about SO2, please visit EPA’s webpage | Learn More >
Unfamiliar with some of the acronyms or technical terms used on this page?
Visit our glossary | View >