For the most part, the air we breathe in the United States is characterized by a handful of regulated National Ambient Air Quality (NAAQ) pollutants:  oxides of nitrogen (NOx); sulfur dioxide (SO2); carbon monoxide (CO); lead (Pb); ozone (O3); and particulate matter (PM).  The relationships among them are complex; this article focuses on the newest development in regulating particulate matter for health care. In September 2006 the U.S. Environmental Protection Agency (EPA) issued the most protective suite of NAAQ standards for particulate air pollution ever.  “Fine” PM is a mixture of very small (solid) particles and liquid droplets that reach deep into the lungs, and link to a variety of significant societal health problems.

PM-2.5, (a subset of PM known as “fine” particulates) refers to particles less than 2.5 microns in diameter (a micron is 1/1000^th of a millimeter).  By comparison, human hair diameters range from 40 to 120 microns. The new regulation strengthens the PM-2.5 standard by lowering the 24-hour standard (i.e., air samples collected over a 24-hour period every third day) from 65 to 35 micrograms per cubic meter (ug/m3).

Other PM-2.5 and PM-10 standards remain the same except for the annual PM-10 standard that has been revoked because available evidence does not suggest a link to health problems.  Studies for PM-2.5, however, correlate to aggravated asthma, chronic bronchitis, reduced lung function, irregular heartbeat, heart attack, and premature death in people with heart or lung disease.

Recent research at the Keck School of Medicine of the University of Southern California (USC) found that children who lived within 500 meters of a freeway, or approximately a third of a mile, since age 10 had substantial deficits in lung function by the age of 18 years, compared to children living at least 1,500 meters, or approximately one mile, away.

As recent as February 1, 2007 the Wall St reet Journal reported on a study of over 58,000 post-menopausal women, which found that the added risk of cardiovascular death from living in the most polluted areas of ‘fine particles of soot’ – including Cincinnati ,  and Riverside (CA) – was 150%, close to the impact of being an active smoker!  This is in contrast to the prevailing thinking of only 40%, roughly like living with a smoker and brea thing in second-hand smoke.

PM-2.5 is made up of a number of components, including acids, nitrate and sulfate salts, organic chemicals, metals, and soil and dust particles.   “Condensibles” found in emissions from petroleum combustion devices exhaust as vapors (i.e., non-particulate) and once emitted may slowly transform into PM-2.5 via chemical reactions in the atmosphere that take place over hundreds of miles. These conversion chemistries add another layer of complexity beyond the tough enough questions of PM-2.5.

Fine particles measured in the air may be carried in from out-of-state winds long distances from their source. Events such as wildfires or volcanic eruptions can raise fine particle concentrations hundreds of miles away.  Compounding this, there are no EPA promulgated (i.e., approved by regulation) reference analytical methods for measuring PM-2.5 emitting from sources. Methodologies used to evaluate atmospheres are very different from those that measure stack emissions from a source (e.g., boiler or engine).

Outdoor fine particles arise primarily from mobile sources such as auto, truck, bus and off-road vehicle exhausts, as well as the burning of fuel or vegetation.  In addition, inefficient coal and petroleum combustion from utilities and industry contribute significant quantities of fine particles.  PM-2.5 is also produced by common indoor activities, including tobacco smoke, cooking (frying, sautéing, broiling), burning candles or oil lamps, and operating fireplaces and fuel-burning space heaters.

This more stringent PM-2.5 air standard results in many more areas of the United St ates being considered in non-attainment (i.e., non-compliance) of this new regulatory limit; that is, these locations have ambient air that exceeds the new concentration limit.  It is the responsibility of each affected State to provide EPA with a plan (called a State Implementation Pl an, SIP) to deal with this.  The entire New York City Metropolitan Area (all counties: Nassau , Suffolk , all five NYC boroughs, Rockland , Westchester and Oran ge ), as well as several counties in neighboring New Jersey , Pennsylvania and Conn ecticut , now all fall into PM-2.5 non-attainment.

Because of the inherent nature of these extremely small particles, there is no reasonably available control technology uniquely suitable to mitigate just this particular problem, so the current trend and regulatory guidance is to minimize the precursor chemicals that lead to PM-2.5. These measures will be discussed in Part 2 to this series, and include using alternate, cleaner and region-wide available fuels, and newer, more efficient technologies like combined heat and power, or cogeneration.