New Jersey Environmental Public Health Tracking Program

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Particulate Matter in Outdoor Air

What is Particulate Matter?

The tiny particles suspended in air are known as Particulate Matter (PM). Particulate matter can occur naturally in the air, originating from wildfires, volcanic eruptions, dust storms and other sources.  Man-made sources of PM include the burning of fossil fuels in vehicles, power plant emissions, and various industrial processes.

Particles are classified according to their size.  Particles greater than 10 microns in diameter (one micron is one-millionth of a meter) are filtered by the nose and throat, and do not enter the lungs.  Particles less than 10 microns in size (PM10) are small enough to enter the lungs, but do not penetrate deeply. Fine particles, those less than 2.5 microns in size (PM2.5), are respirable, meaning that these particles can penetrate deep into the lungs.  Even smaller particles, known as ultrafine particles, may pass through the lungs into the blood and affect other organ systems.

How Does Particulate Matter Affect Human Health?

The health impact of breathing in PM has been widely studied in humans and animals.  The adverse effects from exposure to PM on human health may include asthma, cough, difficult breathing, altered lung function, bronchitis, cardiovascular disease, lung cancer, and premature death.  Fine particles (PM2.5) are of greatest health concern because they can be carried deep into the lungs.

What is Being Done to Protect Human Health?

The Clean Air Act was enacted by Congress to direct the U.S. Environmental Protection Agency (USEPA) to set National Ambient Air Quality Standards for several pollutants, including PM.  The current standards for PM2.5 are 35 micrograms per cubic meter (µg/m3) averaged over 24 hours, and 15 µg/m3 as an annual average. 

The USEPA has developed the Air Quality Index (AQI) to explain to the public how the level of PM and other air pollutants may impact human health.  The color-coded index has the following values: "Good", "Moderate", "Unhealthy for Sensitive Groups", "Unhealthy", "Very Unhealthy", and "Hazardous". The AQI is publicized through radio, television, newspapers and the internet.  Depending on the measured or forecast AQI level, some people may be advised to limit or avoid strenuous outdoor exercise.

 The NJDEP and USEPA have established a variety of programs to meet the health-based National Ambient Air Quality Standards.  For PM, these efforts include reduction of emissions from industrial facilities (refineries, power plants, mills), vehicles (gasoline and diesel), and other combustion sources.

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