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.

Additional Resource:

• Learn more about carbon monoxide in outdoor and indoor air | CO in outdoor air > | CO in indoor air >

What is Ground-Level Ozone?

Ozone is often described as good up high, bad nearby. While high-altitude ozone protects us from UV rays, ground-level ozone is harmful when inhaled. It is not emitted directly but forms through chemical reactions in the atmosphere. The term “ozone” is not to be confused with “smog,” another type of air pollution that consists of ground-level ozone, particulate matter and other gaseous pollutants.

Sources of Ground-Level Ozone

Ground-level ozone is created when nitrogen oxides (NO_x) and volatile organic compounds (VOCs) react in the presence of sunlight. Major sources of ozone precursors (NO_x and VOCs) include vehicle exhaust, factory emissions, and chemical solvents.

Health and Welfare Effects

Breathing ozone can trigger chest pain, coughing, and throat irritation. It can reduce lung function and inflame the linings of the lungs, especially in children and active outdoor workers.

Ground-level ozone can also damage vegetation and ecosystems. The pollutant can cause mass die-off in crops, reducing growth and increasing disease.

Arizona Air Quality Planning

Ground-level ozone remains a persistent air quality challenge in Arizona. Although the Yuma area was previously designated as marginal nonattainment for the 2015 8-hour ozone standard, it has since been successfully redesignated to attainment. Additionally, while the Phoenix area has achieved attainment status for the 1979 1-hour and 1997 8-hour revoked ozone standards, the Phoenix-Mesa area remains in nonattainment for the 2008 and 2015 8-hour ozone standards. 

Additional Resources:

• Ozone Fact Sheet | English > | Spanish >
• Learn more about ozone | View EPA Ozone >

What is Particulate Matter?

Particulate matter (PM) is a complex mixture of extremely small solid particles and liquid droplets suspended in the air and are categorized by size:

• Particulate Matter 10 (PM₁₀): Inhalable particles with diameters 10 micrometers or smaller (about ¹/₇th the width of a human hair).
• Particulate Matter 2.5 (PM_2.5): Fine particles with diameters 2.5 micrometers or smaller.

Sources of Particulate Matter

PM₁₀ often comes from mechanical sources like crushing or grinding operations, dust from unpaved roads, and agricultural activities. PM_2.5 is primarily a byproduct of combustion, such as motor vehicle exhaust, power plants, and wood burning. Both PM₁₀ and PM_2.5 can be directly emitted from sources (primary particles) or formed in the atmosphere through chemical reactions of gases (secondary particles).

Health and Welfare Effects

Larger inhalable particles, such as PM₁₀, primarily irritate the upper airways and aggravate asthma, whereas fine particles, such as PM_2.5, penetrate deep into the lungs and bloodstream, where they can trigger heart attacks, decrease lung function, and cause premature death in vulnerable populations. Beyond public health, fine particles impair visibility by causing haze in national parks and settled PM damages ecosystems by acidifying water bodies, and altering soil nutrients.

Arizona Air Quality Planning

PM₁₀

Several areas previously designated as an NAA for PM₁₀ have achieved attainment status, specifically Payson, Ajo, and Bullhead City. Despite this progress, PM₁₀ remains a persistent challenge across Arizona. The following areas are currently designated as NAAs for the PM₁₀ standard: Paul Spur/Douglas, Miami, Yuma, Hayden, Phoenix, Rillito and West Pinal. Additionally, ADEQ is currently drafting SIPs to address PM₁₀ levels in the Yuma, Hayden, Rillito and Miami NAAs. The Nogales NAA is attaining the NAAQS for PM₁₀, but for international emissions sources. 

PM_2.5

The Nogales and West Central Pinal areas were previously designated as NAAs for the 2006 24-hour PM_2.5 standard. Nogales has since been successfully redesignated to attainment status, while West Central Pinal remains classified as a moderate NAA for the 2006 24-hour PM_2.5 standard. 

Additional Resources:

• Particulate Matter Fact Sheet | English > | Spanish >
• Learn more about particulate matter | View EPA Particulate Matter >

What is Lead?

Lead is a naturally occurring metal that can be toxic when inhaled or ingested.

Sources of Lead

While lead was historically common in gasoline and paint, today outdoor exposure in ambient air primarily stems from industrial activities, such as metal smelting and mining.

Health and Welfare Effects

Lead is especially dangerous for children, as it can cause irreversible damage to the nervous system, leading to learning disabilities and lower IQ.

Reducing exposure is the best way to protect oneself. The Arizona Department of Health Services (ADHS) provides information on lead health effects, common sources of lead exposure in Arizona, ways to reduce exposure in the home, and nutrition tips that may help reduce the body's absorption of lead at the ADHS Lead Poisoning Parent Portal | View >

Arizona Air Quality Planning

Lead planning in Arizona is concentrated on the Hayden area, the state’s only lead NAA. The area was designated an NAA for the 2008 lead NAAQS primarily due to copper smelting operations. ADEQ has since developed a SIP revision for Hayden to provide for attainment of the NAAQS through permanent and enforceable control measures. 

Additional Resources:

• Learn more about lead | View EPA Lead >

What is Nitrogen Dioxide?

Nitrogen dioxide is a highly reactive gas and part of a larger group of nitrogen oxides. It is used as an indicator for the entire group of nitrogen-oxide pollutants.

Sources of Nitrogen Dioxide

Nitrogen dioxide primarily forms from the burning of fuel in motor vehicles, power plants, and off-road equipment.

Health and Welfare Effects

Nitrogen dioxide can irritate the airways and aggravate respiratory diseases, particularly asthma. It also contributes to the formation of both ground-level ozone and fine particulate matter (PM_2.5).

Arizona Air Quality Planning

All areas in the United States currently meet the federal standards for nitrogen dioxide. To ensure continued compliance, Arizona submitted the required infrastructure SIP for the 2010 nitrogen oxide standards.

Additional Resources:

• Learn more about nitrogen dioxide | View EPA Nitrogen Dioxide >

What is Sulfur Dioxide?

Sulfur dioxide is a colorless, reactive gas with a sharp, pungent odor similar to a struck match.

Sources of Sulfur Dioxide

The largest source of sulfur dioxide in the outdoor (ambient) air is the burning of fossil fuels by power plants and other industrial facilities. In Arizona, copper smelting is also a significant contributor.

Health and Welfare Effects

Sulfur dioxide can cause respiratory distress within minutes of exposure, leading to coughing and wheezing. It is also a precursor to the formation of fine particulate matter (PM_2.5).

Arizona Air Quality Planning

With the exception of Hayden, all areas in Arizona previously designated as an NAA for the revoked 1971 sulfur dioxide standard - Ajo, Douglas, Miami, Morenci, and San Manual - have been redesignated to attainment. Currently, Hayden remains designated as an NAA for both the 1971 and 2010 sulfur dioxide standards, and Miami remains an NAA for the 2010 sulfur dioxide standard; both designations are attributed to emissions from copper smelting operations. ADEQ has implemented control strategies through SIP revisions to achieve compliance with the NAAQS. 

Additional Resources:

• Learn more about sulfur dioxide | View EPA Sulfur Dioxide >