20150218 - particulate matter

Particulate Matter (PM) Research

What is Particulate Matter?

Particulate matter (PM) is an air pollution term for a mixture of solid particles and liquid droplets found in the air. The pollutant comes in a variety of sizes and can be composed of many types of materials and chemicals. Particles that are small enough to be inhaled have the potential to cause health effects. Of particular concern is a class of particles known as fine particulate matter or PM2.5 that gets deep into the lung.
There are many sources of PM. The air pollutant can originate from natural processes, like forest fires and wind erosion, and from human activities, like agricultural practices, smokestacks, car emissions, and construction. Examples include dust, dirt, soot, soil, and smoke.

Types of PM

Although it can be categorized in a number of ways, PM has traditionally been classified by size. In general, the smaller the particle, the stronger its potential impact on human health because it can be more easily inhaled. For this reason, EPA monitors and regulates particles in two size categories depending on their predicted penetration into the lung. These categories are:

Coarse particles (PM10)

Inhalable particles less than 10 micrometers (μm) in diameter used as a nominal surrogate for particles between 2.5 and 10μm in diameter; found near roadways and dusty industries

Fine particles (PM2.5)

Inhalable particles less than 2.5μm in diameter; generally found in smoke and haze, emitted from natural sources like forest fires and industrial combustion sources, or formed when gases react in the air. Ultrafine particles (PM0.1) are a subset of inhalable PM2.5 particles less than 0.1μm in diameter. They are not specifically regulated but have a strong link to combustion and therefore are garnering special attention.
PM can also be classified by its source:

• Primary particles: directly emitted from a natural or human source
• Secondary particles: produced when chemicals from natural and human sources react in the atmosphere often energized by sunlight

Human Health Effects

Inhalable particles, particularly fine particles, have the greatest demonstrated impact on human health. Their small size allows them to get deep into the lungs and from there they can reach or trigger inflammation in the lung, blood vessels or the heart, and perhaps other organs. Studies have linked PM exposure to health problems such as:

• Irritation of the airways, coughing, and difficulty breathing
• Reduced lung function
• Aggravated asthma
• Chronic bronchitis
• Irregular heartbeat
• Nonfatal heart attacks
• Some cancers

Research has found that certain populations are more vulnerable to these health effects, such as people with pre-existing heart or lung diseases, children, and older adults.


 http://www.epa.gov/airscience/air-particulatematter.htm