Chesapeake Bay Journal: Particulates

Particulates

By Karl Blankenship

Particulate matter is the term used for a mixture of solid particles and liquid droplets found in the air. Course particles (larger than 2.5 microns) come from windblown dust, grinding operations, etc. Fine particles, (less than 2.5 microns) come from fuel combustion, agricultural burning, wood stoves, etc. These fine particles are so small that several thousand of them could fit on the period at the end of a sentence. They are a health concern because they easily lodge in the deepest recesses of the lungs. On a smoggy day, a million tiny particles can be inhaled into one's mouth and nose in a single breath.

Present standard

The particulate standard regulates particles 10 microns in diameter or less (a human hair is about 70 microns thick), to no more than 150 micrograms per cubic meter of air measured daily and an annual average of no more than 50 micrograms per cubic meter.

Proposed standard

Particles of 2.5 microns or less would be limited to concentration of 50 micrograms per cubic meter daily, and an average of no more than 15 micrograms per cubic meter annually.

Particulates & the Environment

The same fine particles linked to serious health effects are also a major cause of visibility impairment in many parts of the United States. In many parts of the county, the visual range has been cut by more than 70 percent. In the East, the current range is only 14-24 miles, versus a natural range of 90 miles. In the West, the current range is 33-90 miles, versus a natural range of 140 miles.
Fine particles can remain suspended in the air and travel long distances. For example, emissions from a Los Angeles oil refinery can form particles that in a few days will affect the visibility in Rocky Mountain National Park in Colorado.

Particulates & Health

Recent scientific studies have linked particulate matter, especially fine particles (alone or in combination with other air pollutants), with:

Premature death
Respiratory-related hospital admissions and emergency room visits
Aggravated asthma
Acute respiratory symptoms, including severe chest pain, gasping and aggravated coughing; chronic bronchitis; and decreased lung function such as shortness of breath
Work and school absences.

Particulates & the Bay

Particulates are thought to be a source of toxics to the Chesapeake, as fine, soft particles readily absorb toxics that are released during fossil fuel combustion. Also, nitrogen oxides can form into small nitrate particles, adding to the amount of nutrients entering the Bay.