Until well into the twentieth century, the components of pollution were thought to be
primarily smoke and soot (suspended particulate matter) and sulfur dioxide. These are all
waste products from industrial facilities, home heating and utility power plants. With
growing industrialization and the popular use of the automobile, we have identified more
air pollutants from a broad range of sources. The "dirty six" are
internationally defined as "primary pollutants." All six of these pollutants are
commonly found in the Puget Sound region:
In addition to the "dirty six," there are other toxic air pollution components in our air. Arsenic, asbestos, benzene, vinyl chloride, mercury and beryllium are all examples of toxic pollutants.
PM10 consists of small, discrete solid or aerosol particles in the air. Particulate matter with a diameter of less than or equal to10 micrometers is referred to as PM car spares 10. A PM10 particle is roughly 1/8 the diameter of a human hair, so it is invisible to the naked eye. Motor vehicles, wood burning and industrial activity are major sources of particulate matter. Particulate matter in the respiratory tract may produce injury by itself, or it may act with gases to increase the effect on the body. The elderly, those suffering from respiratory illness, and young children are especially prone to the harmful effects of particulates. Particulate matter also makes our long-distance views appear hazy.
PM10 enters the air from automobile, bus and truck exhaust, fuel burning (including wood stoves and fireplaces), industry, construction, and other sources. These emissions change daily depending on how much and when people are driving and heating their homes and industrial operations, equipment upset or breakdown.
Currently, PM10 data in the Puget Sound region is collected at 15 locations. There are two federal standards for particulate matter: a 24-hour average of 150 micrograms per cubic meter (or 100 on the Pollutant Standard Index) and an annual average of 50 micrograms per cubic meter. Since adoption of the PM10 standards in 1987, none of the PM10 locations have exceeded the PM10 standards. The Puget Sound region has not violated the 24-hour standard since 1989. This means the Puget Sound region is in compliance with the PM10 standards.
Research has suggested that a significant amount of particulate pollution may be smaller than PM10. Particles as small as 2.5 micrometers or smaller may, in fact, be a more serious health danger as these particles have the ability to penetrate deeper into lung tissue. The U.S. EPA established new federal standards for PM2.5 in 1997. The annual standard is 15 ug/m3 (3 year average), while the 24-hour standard is 65 ug/m3 (98th percentile). Our agency is currently working with the Washington State Department of Ecology to establish a network of PM2.5 monitoring sites throughout the Puget Sound area.
Our data indicates that we will meet the 24-hour standard for PM2.5, but we are close to exceeding the annual standard. These measurements were made using different instruments than those EPA requires for future monitoring (EPA Federal Reference Method). However, comparison studies show that the data from the instruments we used (DICHOTS) are comparable to Federal Reference Method data.
Sulfur dioxide is a colorless, corrosive gas that has a bitter taste, but no smell at low levels. Industrial sites such as smelters, paper mills, power plants and steel manufacturing plants are the main sources of sulfur dioxide pollution. Sulfur dioxide has been associated with a variety of respiratory diseases and increased mortality rates. Inhalation of sulfur dioxide can cause increased airway resistance by constricting lung passages.
Sulfur dioxide is a common air pollutant regulated by a national standard. Local sulfur dioxide standards have been in effect since 1968. Sulfur dioxide enters the air mainly from industrial processes and from the combustion of sulfur-containing fuels such as coal and oil. In the Puget Sound region, the four main industrial areas with sulfur dioxide point sources are in the Everett Port area, Seattle Harbor Island-Duwamish Valley area, Tacoma Port area, and the Bremerton Naval Shipyard.
The EPA standard for sulfur dioxide is a one-hour average of 0.40 ppm. The Puget Sound region complies with federal sulfur dioxide standards.
Carbon monoxide is a colorless, odorless, toxic gas commonly formed when carbon-containing fuel is not burned completely. Carbon monoxide chemically combines with the hemoglobin in red blood cells to decrease the oxygen-carrying capacity of the blood. It also weakens the contractions of the heart, reducing the amount of blood pumped throughout the body. It can also affect the functioning of the lungs and brain. People with heart disease and pregnant women are especially at risk of the effects of carbon monoxide.
Carbon monoxide is emitted by motor vehicles more than any other source. For Puget Sound region cities, motor vehicles contribute significantly in all cases of high carbon monoxide levels.
The occasions with high ambient levels of carbon monoxide occur mainly during autumn and winter months near congested areas. Traffic congestion mostly occurs with afternoon commuting and increased shopping during the holidays. Levels are often higher when the weather is stable and winds are light. This kind of weather temporarily hampers dispersion of everyday carbon monoxide.
The two federal standards for carbon monoxide are a 35 parts per million (ppm) 1-hour standard and a 9 ppm 8-hour standard. The Puget Sound area meets both federal standards. Monitoring for carbon monoxide is conducted by the Washington State Department of Ecology.
Nitrogen dioxide is a poisonous, brownish gas that when combined with oxygen, quickly reacts with water vapor to form corrosive nitric acid, a major component in acid rain. Nitrogen dioxide is formed as the result of high temperature fuel combustion and atmospheric reactions. The presence of nitrogen dioxide in the air has been connected with a range of respiratory diseases. Nitrogen dioxide plays an essential role in the photochemical reactions that produce ozone, the major component in smog.
The Puget Sound region meets federal nitrogen dioxide standards. The Washington State Department of Ecology is responsible for monitoring of nitrogen dioxide in the Puget Sound area.
Ozone is a pungent-smelling, colorless gas produced in the atmosphere when nitrogen oxides and volatile organic compounds (VOC) chemically react under sunlight.
Ozone is a pulmonary irritant that affects lung tissues and respiratory functions. Ozone impairs the normal function of the lungs and at higher concentrations (between 0.15 and 0. 25 ppm), causes lung tightness, coughing and wheezing. People with chronic respiratory problems, such as asthma, seem most sensitive to ozone. Studies show that ozone also damages forests, particularly since ozone levels tend to be higher at the mountain elevations.
The highest ozone levels occur on hot summer afternoons, since ozone forms as the sun heats up during the day. Strong sunlight alone is not the cause of ozone. Even with high temperatures and sunlight, ozone levels would be low without the nitrogen oxides and VOC pollutants emitted from activities like driving and using gas-powered lawn and garden equipment.
The federal ozone standard is a eight-hour average value of 0.08 ppm or 100 on the Pollution Standard Index (PSI). This standard was recently revised by the U.S. Environmental Protection Agency after extensive research on the health effects of ozone pollution. U.S. EPA established the new standard in September 1997.
The Puget Sound area currently complies with ozone standard, though by a slim margin. If a monitoring site registers an exceedence more than three times in a three-year period, the region is considered in violation of the federal standard. None of the Puget Sound ozone monitoring sites has measured more than two exceedences in the last two years. Ozone monitoring is conducted by the Washington State Department of Ecology.
Particles of lead or its compounds enter the air from vehicle exhaust and from industries that smelt or process metal. Lead affects blood formation and nervous systems and kidneys. Young children from one to five years old are particularly sensitive to lead exposure.
Lead emissions come from automobile exhaust and stationary industrial sources such as primary and secondary nonferrous smelters. The Puget Sound region fully complies with the ambient air quality standard for lead. In the past, urban area lead levels violated the standard near high traffic roadways due to the high lead content of automobile exhaust. Today, ambient lead levels near roadways are virtually non-existent as a result of the elimination of lead from gasoline.
Updated July 21, 1999
