Benton Clean Air Agency

Air Pollutants - Frequently Asked Questions

Current levels of PM in the Tri-Cities?

The BCAA currently measures air pollution with a rating called PM2.5, and PM10. The “PM” refers to Particulate Matter. The number after the “PM” refers to the size of the particle in micro-meters; PM10 is about 1/7th the diameter of a human hair and PM2.5 is about 1/28th the diameter of a human hair.

Particulate Matter

The Air Quality Index (AQI) is a way to simplify the impacts of air pollution through the use of a color chart. If you want to know the actual concentration of the pollution, it is given above the charts with the units of “ug/m3” or micrograms per cubic meter. For most people, the color chart is easier to understand.

The pollutant with the highest AQI is the pollutant that is most responsible for the health impacts. Since PM10 is a larger particle, it is more often associated with dust and has a higher AQI during windstorms and during the summer and fall. PM10 can trigger asthma and allergy symptoms. PM2.5 is a much smaller particle and is associated with smoke and vehicle exhaust. It usually has a higher AQI due to smoke from wildfires, stagnant air, and the winter when woodstoves are in use.

PM2.5 particles are generally associated with smoke and combustion sources. Because of the smaller particles, PM2.5 can have greater health effects than larger particles such as dust and ash.

How does Benton County’s Air Quality compare with other areas?

Compared to other urban areas in Washington State, Benton County has some of the cleanest air over the majority of the year. Our average pollution levels are well below the national average. However, on occasion, Benton County does have problems with a pollutant called “particulate matter”. Particulate matter is a federally regulated pollutant; in high concentrations, it poses a health risk to both sensitive populations and to healthy, active people as well.

What is particulate matter?

Particulate matter, or “PM”, is a form of pollution composed of very small particles of dust, smoke, soot, and other materials. PM comes in many shapes, sizes, and compositions. However, the Environmental Protection Agency (EPA) has identified through many years of scientific study, that two sizes of PM have identifiable health risks.

These two types of PM are called PM10 and PM2.5. The number refers to how small the particles are. PM10 is composed of particles that are 10 microns or smaller in diameter; this is about 1/ 7-th the diameter of a human hair. PM2.5 is even smaller, being only 2.5 microns across or 1/28th the diameter of a human hair.

The severity of the health effects from breathing these particles depends upon the concentration, or “how much” of the PM is in the air. The EPA has set health standards, called National Ambient Air Quality Standards (NAAQS), for these and other air pollutants, called “criteria pollutants”. The criteria pollutants are considered to have the greatest adverse effect on the people. Each NAAQS has an associated concentration and duration that areas cannot exceed.

How is PM harmful of health?

PM10 and PM2.5 are among the most harmful of all air pollutants. When inhaled these particles evade the respiratory system’s natural defenses and lodge deep in the lungs.

Health problems begin as the body reacts to these foreign particles. PM can increase the number and severity of asthma attacks, cause or aggravate bronchitis and other lung diseases, and reduce the body’s ability to fight infections.

Although particulate matter can cause health problems for everyone, certain people are especially vulnerable to the adverse health effects of PM. These “sensitive populations” include children, the elderly, exercising adults, and those suffering from asthma or bronchitis. The important thing to consider is that healthily, active people are also at risk because those individuals are often outside and are breathing more air during exercise, thus increasing their exposure.

Of greatest concern are recent studies that link PM exposure to the premature death of people who already have heart and lung disease, especially the elderly.

Where does PM come from?

In the western United States, there are sources of PM in both urban and rural areas, major sources include:

  • Activity-related and wind blown dust from construction and agriculture

  • Wind blown dust from open lands.

  • Outdoor and agricultural burning.

  • Wood burning stoves and fireplaces.

  • Wildfires.

  • Industrial sources.

  • Motor vehicles.

PM is a mixture of materials that can include smoke, soot, dust, salt, acids, and metals. Particulate matter also forms when gases emitted from motor vehicles and industry undergo chemical reactions in the atmosphere.

What can I do to reduce PM in Benton County?

  • Here are a few things individuals, business, and other organizations can do immediately to reduce the threat of PM:

  • Reduce travel on days with poor air quality.

  • Avoid using your wood stove and fireplace on days that have poor air quality.

  • Drive slowly on unpaved roads and other dirt surfaces

  • Get involved with air quality improvement programs in your community

  • If you own or operate an industrial source of PM, comply with local rules that apply to your operation. Work with local agencies to develop strategies that will further reduce PM emissions.

Other Questions?

If you have any questions about Particulate Matter, PM10, PM2.5, blowing dust, or smoke impacts from agriculture, forest burning, or wildfires, please contact BCAA.

Thanks to the California Air Resources Board for their information on Particulate Matter.