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Frequently Asked Questions about Air Toxics

Air toxics 101: What are they and where do they come from?

Air pollutants from a variety of sources impact the health of people every day. Air toxics are pollutants in the air that are bad for your health and our environment. Air toxics can also be referred to as harmful air pollutants and air toxic contaminants. Examples of air toxics include diesel soot and benzene from vehicles, small particles from smoke, and metals like nickel from metal plating.

Exposure to air toxics may increase your chances of experiencing health issues. For example, inhaling the benzene in the fumes from car and truck exhaust can increase your chances of experiencing respiratory irritation and, over time, cancer. Many air toxics, such as heavy metals, may last a long time or build up in people who breathe them over a long time. ​

There are many sources of air toxics. Some are naturally occurring like wildfire smoke, but most are produced by human activity such as emissions from industrial facilities; exhaust from cars, trucks, farming equipment, and construction equipment; and burning wood in fireplaces and woodstoves.​

​Since there are many sources of air toxics, generally everyone is exposed to them at different levels. However, there are recognized locations that have higher levels of air toxics. These include areas near busy roadways and highways; near industrial facilities; near high levels of smoke from wood burning or wildfires.

In addition to location, preexisting health conditions may increase a person's risk of health effects from air toxics.  People who have health conditions such as asthma and other respiratory or heart conditions may be more affected. Children can also be at greater risk to air toxics because they are still growing, and because they breathe more air per pound of body weight than adults.​

DEQ's work on air toxics includes finding and measuring levels of air toxics, controlling emissions of air toxics through regulations and permits, and reducing the health risks posed by air toxics through programs and policies.​

DEQ uses air monitors, models, and emissions to find the amount and type of air toxics and other pollutants.

  • Find - DEQ uses air monitors, pollutant inventories and modeling to identify sources of air toxics emissions and assess levels of pollution in the environment.

  • Control - DEQ controls emissions with permits and compliance mechanisms through programs like Cleaner Air Oregon and the Vehicle Inspection Program.

  • Reduce - DEQ develops and implements other programs and regulations that have the co-benefit of reducing air toxics. These programs include woodstove regulations, clean fuel regulations, electric vehicle rebates, and grants for diesel mitigation.

For more information on monitoring and modeling, see the FAQ section, “Identifying Air Toxics".​

Health and air toxics: Are they harmful and what do we know?

Breathing air containing air toxics can increase the risk of breathing problems, heart disease, impaired brain development, infertility, birth defects, and various types of cancer.

Health effects can happen due to either short-term or long-term exposure to air toxics. Whether a person experiences health problems from air toxics depends on many factors, such as

  • How long the contact lasted,

  • The type and amounts of contaminants in the air,

  • How often a person breathes them,

  • A person's general health,

  • And inherited (genetic) factors.

For example, DEQ, in collaboration with Oregon Health Authority, uses information about

  • How harmful air toxics are to human health (toxicity information)​

  • How much and in what ways a person comes into contact with air toxics (exposure information) 


​Certain chemicals harm our health at very low doses, and these are considered more toxic than others. Knowing how toxic a chemical is means understanding how much of the chemical (the dose) it takes to harm health. Scientists do studies to learn how toxic the chemical is. We don't know everything about toxic chemicals. Our understanding of  which air toxics are harmful and how is increasing as new studies are completed.

Risk is defined as the probability and degree of harm arising from a given situation or activity. If you roller skate down a hill, you will likely get to the bottom of the hill just fine, but there is a risk that you could get hurt, resulting in a broken bone or a skinned knee.

Cancer risk refers to the number of people who may get cancer for every 1 million people who have the same exposure to air toxics. For example, a 1-in-1 million risk means that one person may develop cancer for every 1 million people exposed to the same air. A 10-in-1 million risk means 10 people may develop cancer per 1 million exposed, etc. Air toxics are not the only thing that can increase a person's cancer risk.

The American Cancer Society estimates that one in three women and one in two men will develop some type of cancer during their lifetime. These background cancers are from a combination of all possible causes including age, genetics, random chance, lifestyle factors like tobacco use, and environmental exposures. On average, about 400,000 people per million will get cancer at some point in their lifetime. This is called the background rate of cancer. Exposure to air toxic contaminants may increase cancer risk. ​

​Non-cancer risks are not discussed as a probability of an individual suffering an adverse effect, but as a hazard quotient (HQ). A hazard quotient is the ratio between an individual's potential exposure to an air toxic and the amount at which that air toxic would cause a bad health effect. If there are exposures to multiple chemicals, you add up all the HQs of potential air toxics, say from a facility, and get a Hazard Index for the whole site and all the pollutants emitted from it.

When the HI is less than 1, non-cancer health effects are not expected for people exposed to those air toxics.  When the number is greater than 1, non-cancer health effects are possible, but not certain and more information is needed to understand the health effects of a toxic air contaminant in a specific situation.

HIs are not an estimate of the likelihood that an effect will occur, but rather an indication of whether there is potential cause for concern for adverse health effects.

Learn more about noncancer risk in the CAO program from our fact sheet, Cleaner Air Oregon: Non-Cancer Health Risk​.

Both federal and state governments set health-protective limits and benchmarks for air toxics for various air quality programs. Different programs use different names for these limits and benchmarks, but they all have a similar purpose. They are set such that a person could breathe air with air toxics at those amounts for a lifetime without a posing a high risk of health effects.

Some examples of health-protective, chemical-specific limits and benchmarks include:

  • EPA sets National Ambient Air Quality Standards (NAAQS)to regulate air quality for a group of six air toxics that this EPA program calls “criteria pollutants." These NAAQS indicate the amount of each pollutant that are safe for the public, including people more sensitive to outdoor air pollutants such as the very young, the elderly and those with respiratory issues. These levels are set in terms of the concentration of these pollutants in the air.

  • Toxicity reference values that DEQ's Cleaner Air Oregon program uses to evaluate health risks to nearby neighbors of industrial emitters of wide range of air toxics (250+ chemicals).

The U.S. Agency for Toxic Substances and Disease Registry has fact sheets for many chemicals, including air toxics, that answer the most frequently asked health questions. You can find these fact sheets on the Center for Disease Control and Prevention website. The Oregon Health Authority also has information on environmental health.  ​

Identifying air toxics: How do we know where and what they are?

 There are three main ways we know about air toxics. 


  • Monitors and does source testing for air toxics.
  • Collaborates with the EPA to create emissions inventories of air toxics.
  • Employs modeling software to learn more about how toxics move in the air.​
For more information:

​DEQ monitors for 109 hazardous air pollutants at air toxics sampling sites. Monitoring involves placing equipment at a site that will provide important information about the concentration of air toxics in specific locations. Two of those sites are permanent and the rest are called trend sites that rotate to different places in the state every year. Air toxics monitoring provides important, concrete information about air pollutants that are known to cause cancer and other serious health problems also monitors for what is called criteria pollutants including ozone and fine particulate matter (PM2.5). More about air monitoring and the latest annual air toxics report can be found on our air monitoring page.

For industrial and commercial sources of air toxics source testing, using EPA test methods is a way to identify and quantify air pollution from a source. Source testing is used in two different ways. First, for sources or source types with limited available data, source testing is used to develop information for modeling risk, known as emission factors, for different air pollutants so that emissions can be estimated on an hourly, daily or annual basis. Second, source testing is used for compliance purposes to show that a source is not exceeding an emission limit or an emission factor.​

An Emissions Inventory is a list of air pollution sources and the amount of air pollution from each source. Sources can include industrial facilities, cars and trucks, and wildfires. The amount of air pollution is calculated using the best available information. They do not predict or measure the amount of pollution in the air at any given place or time. Measured air pollution at certain sites is available on the DEQ's Air Quality Index webpage. Check the links below for more information and to view DEQs Emissions Inventories.​

​​The air toxics emissions inventory, or ATEI, is an accounting of toxic emissions discharged into the atmosphere by equipment or activities from industrial facilities over the course of one year. The ATEI covers all large and permitted industrial facilities in Oregon and is reported once every three years.

DEQ collects this emissions information from facilities who hold specific permits such as a Title V, ACDP Standard or Simple permits. Each facility must estimate their own emissions. The data is then reviewed by DEQ's technical experts, corrected or revised as needed, and made publicly available through the DEQ AQ Permits Online web page.

The available reports provide a snapshot of estimated facility emissions. This periodic, state-wide ATEI is a separate reporting requirement than an Emissions Inventory submitted as part of the Cleaner Air Oregon risk assessment process. ​

To understand the health risk from air toxics to the people living, working, going to school, or recreating in Oregon, you must first determine how much pollution is in the air. You can do this in one of two ways: modeling or monitoring.

Monitoring involves setting up a piece of equipment and directly measuring the pollution in the air at a specific location. Modeling involves collecting information on the emissions and the local weather patterns. For example, emissions from a facility are informed by the reported air toxics, source testing and monitoring. This information is run through computer models to estimate where the pollution will go over time.

The Portland Air Toxics Solutions study is an example of modeling for all sources of air toxics: mobile, area, and stationary sources.

The main benefit of monitoring is its accuracy because it directly measures the amount of pollution in the air. However, monitoring can only determine health risks at a single location – where the monitor is set up. Monitoring is also expensive and must be measured over a period of months to years to understand the changes that can happen under different weather conditions.

The main benefit of modeling is the ability to estimate the amount of pollution in areas all around, including at specific locations and facilities. Additionally, modeling can estimate pollution under a wide range of weather conditions and identify situations that may lead to higher amounts of pollution impacting people nearby. However, modeling can over- or underestimate the amount of pollution in the air. This depends on several factors, including how accurate the emissions inventory is and how the much is known about how the pollution leaves the site, including information such as facility stack height.

There are pros and cons to both modeling and monitoring. DEQ uses both techniques depending on the circumstances. For facilities going through Cleaner Air Oregon, DEQ uses modeling to understand how the facility impacts the community, including at homes, schools, business and parks. DEQ also sets up air toxics monitors to look at areas where many different sources of toxic air pollution may impact people's health.​

The Air Toxics Screening Assessment (AirToxScreen) is a screening tool developed by the Environmental Protection Agency to understand outdoor air toxics in the United States. This tool takes data from monitors and the emissions inventory data and then runs computer models to help understand risk. The main page about the tool can be found on EPA's AirToxScreen web page. The purpose of the tool is for state, local and tribal air agencies to identify which pollutants, emission sources and places they may wish to study further to better understand any risks to public health from air toxics. To learn more about this tool and how this tool compares to past tools and similar tools, visit EPA's AirToxScreen Overview. The tool is based on modeled data. 

For more information, please visit National-scale Air Toxics Assessment webpage​

It is important to note that Oregon uses different levels for some toxics than EPA uses. However, this screening tool still tells us which areas have higher cancer and non-cancer risk than other areas, just not at Oregon specific air toxic risk levels. AirToxScreen is a reviewed, consistently updated, and publicly accessible tool. Oregon does not currently have a state-based tool that models Oregon's air toxics. 

Controlling air toxics: Federal and state regulations

​Regulation simply means how something is controlled by law. For air toxics, there are both federal and state regulations. Regulations can be levels of chemicals that are allowable, or they can be programs that reduce risk for air toxics. Terms you may have heard to control the levels of air toxics might include criteria pollutants, Toxic Air Contaminants or TAC, and Hazardous Air Pollutants or HAPs. ​

​To your lungs, there is no difference between these terms. They are different labels for potentially harmful chemicals that can be found in the air. Different government entities and programs categorize, label, and regulate them in different ways based on where they come from, so they have different names.

Please see these resources if you want to learn more about these terms:

How air toxics are controlled depends on the source of the pollution. Cleaner Air Oregon and DEQ's permitting system control toxics coming from facilities. There are many ways to control air toxics from facilities including technology such as scrubbers or filter systems. Using alternative materials that have lower levels of air toxics is another way to reduce emissions.

There are numerous approaches to reduce air toxics from mobile sources by addressing both fuels and vehicles.  Air toxics emissions from vehicles can be reduced by adding tail pipe filters or using newer, more efficient vehicles, including electric vehicles. Find more information about DEQ's programs on the Clean Vehicles page.  ​

​The effects of lead are the same whether it enters the body through breathing or swallowing. The main target for lead toxicity is the nervous system, both in adults and children. Children are more sensitive to the health effects of lead than adults. Exposure to lead in the womb, in infancy, or in early childhood may slow mental development and cause lower intelligence later in childhood. It appears that some of these effects, particularly changes in the levels of certain blood enzymes and in aspects of children's neurobehavioral development, may occur at blood lead levels near zero. Therefore there may be no safe level.

After lead was removed from gasoline many years ago, lead levels in Oregon's air dropped dramatically. Oregon has been in compliance with the federal lead standard since 1976. Based on DEQ's past monitoring, all areas in Oregon are below the recently tightened federal lead standard. Part of the new lead standard requires new monitoring near industries reporting over a ton of lead emitted per year and in metropolitan areas with population greater than 500,000. Under these criteria, EPA requires lead monitoring at Cascade Steel in McMinnville and in the City of Portland.

Different tools are used to understand health risks and health outcomes. For the Cleaner Air Oregon program, regulations and requirements are based on health risk rather than health outcomes. This is because CAO regulations are intended to be proactive and prevent people from experiencing health issues. DEQ and OHA do not want to wait until people have health issues to require action from industrial facilities.​​

Reducing air toxics

While CAO is the only program that directly reduces air toxics, there are many other programs at DEQ that reduce air toxics as a co-benefit. These include:

  • Clean Vehicle Programs such as electric vehicle rebates, and diesel mitigation grants
  • Clean Fuels program which promotes use of alternative fuels that have lower GHGs and other air toxics
  • Replacing old woodstoves with cleaner heating equipment
  • Wildfire protection
  • Open burning restrictions ​

You can do many things to improve air quality. There is a detailed list on ways you can help improve air quality, including:

  • Driving less (reducing trips, using public transportation, carpooling and telecommuting) or purchasing an electric vehicle.

  • Choose products that emit fewer volatile organic compounds, which are usually air toxics as well. Many paints and other products are now available in low toxicity formulations.

  • Reduce woodstove use, tuning up vehicles and equipment, and using cleaner engines or electric alternatives.

Additionally, you can get involved by advocating for clean air with community-based organizations, being a part of DEQ's rule making, or volunteering with organizations that work to reduce air pollution. ​