Particulates

Particulates is the term given to the tiny particles of solid or semi-solid material found in the atmosphere. It is this "dirt" in the air that is visible as a "Brown Cloud", haze or smog. The sources of particulates are many: wind-blown dust and sand from roadways, fields, and construction; coal dust, fly ash, and carbon black from various combustion sources; and automobile exhaust, to name a few. Particulates that range in size from less than 0.1 micrometer up to approximately 45 micrometers are called "total suspended particulates (TSP)". Larger particles tend to settle out of the air and not remain suspended, except in high winds. Smaller size particles fall into the PM10 category consisting of particles in the 0-10 micron range and/or the PM2.5 category of particles in the 0-2.5 micron range.

The human nose filters out 99 percent of the large and medium-sized particles. The rest enter the windpipe and lungs, where some, known as inhalable particulates, cling to the protective mucous and are removed. Some of the smallest, called respirable particulates, are deposited in the lungs' tiny air sacs (alveoli).

In the lungs particulates slow down the exchange of oxygen with carbon dioxide in the blood, causing shortness of breath. The heart may be strained because it must work harder to compensate for oxygen loss. Usually the people most sensitive to these conditions have respiratory diseases like emphysema, bronchitis, asthma, or heart problems. The elderly and children are also sensitive.

Particles themselves may be poisonous if inhaled or absorbed, damaging remote organs like the kidneys or liver. Swallowed mucous that is laden with poisonous particulate matter may damage the stomach.

In addition, particulates may be carriers of poisonous liquid or gaseous substances. Sulfur dioxide, a major air pollutant in its own right, is frequently absorbed by particulates and can react with them to form sulfates. Sulfates react with moisture in the air or in the respiratory tract to form a corrosive liquid (sulfuric acid) that irritates delicate membranes and slows down the cleansing action of mucous. This effect can reduce the body's ability to remove harmful bacteria, increasing the possibility of infection.

Adverse health effects from particulate matter aren't always seen immediately. Particulates can accumulate in the lungs after repeated, long-term exposure, causing respiratory distress and other health problems that may be manifested later.

Particulates in the air block out and scatter sunlight, reducing visibility. Particulates soil and corrode metals, masonry, and textiles. Irritating odors are often associated with particulates, also.

History of the various particulate standards (pdf file).

The current standards that are in effect for particulates are a 24 hour PM10 standard of 150 micrograms per cubic meter, a 24 hour PM2.5 standard of 35 micrograms per cubic meter and an annual PM2.5 standard of 15 micrograms per cubic meter.

Total Suspended Particulates have not been routinely monitored in Maine since 2000. TSP monitors are used on occasion to document nuisance conditions or to obtain lead data.

Hi-Vols operate on the same principle as a vacuum cleaner in that the air is drawn through a filter to "catch the dust". The difference is that a Hi-Vol draws a calibrated volume of air through a pre-weighed filter pad (rather than a bag) for a twenty-four hour period. The change in weight of the filter pad is recorded as total suspended particulate or TSP in micrograms of particulates per cubic meter of air.

PM10 size particles are currently being monitored at seven different sites for varying time periods using modified low volume particulate samplers. Sites are located in Augusta , Bangor , Lewiston , Madawaska, Portland , Presque Isle and Van Buren. The sampling is conducted with size-selective inlets and flow-controlling devices designed to meet EPA's monitor specifications. Data collected using a continuous monitor at one site in Presque Isle is currently available on the air quality web site . Data from the other sites is collected using filter media and is typically not available for several weeks. PM10 data and long term trends in this data can be viewed in the latest annual air quality report .

Monitoring for the PM2.5 program began in 1999 with additional funding provided by EPA. The initial program was to require three years of data at a number of sites around the state to determine compliance with the new standards using the newly developed federal register method (FRM) integrated samplers. Maine was initially required to have twelve sites in operation for the first year of the program and an additional three sites added for the second year. Maine also received funding for three continuous monitors in the second year of the program.

After reviewing the data collected during the first few years of the monitoring program the monitoring sites were reduced in number and some new sites were added. Maine is currently collecting PM2.5 data in Augusta , Bangor , Bar Harbor, Greenville , Lewiston , Madawaska, Portland , Presque Isle and Rumford. Four of these sites are also collecting continuous PM2.5 data which can be viewed on the air quality web site . All of the sites are collecting data using the filter based method. Past data collected using the filter based method can be viewed in the latest annual air quality report .

 

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