Particulate Matter Fact SheetWhat is particulate matter?
PM10 refers to particles with a diameter of ten microns or smaller. (One thousand particles of this size could fit into the period at the end of this sentence.) PM10 is a mixture of substances that can include elements such as carbon, lead, and nickel; compounds such as nitrates, organic compounds, and sulfates; and complex mixtures such as diesel exhaust and soil. These substances may occur as solid particles or liquid droplets.
Particles from natural and manmade, and indoor and outdoor sources can become airborne. Some particles are emitted directly into the atmosphere while others, referred to as "secondary" particles, result from gases that are transformed into particles through physical and chemical processes in the atmosphere.
PM10 includes a subgroup of finer particles called PM2.5. These fine particles have a diameter of 2.5 microns or smaller. Like PM10, PM2.5 can be a mixture of substances coming from different sources.
PM10 is California's most complex air pollution problem because it is not a single substance, but rather a mixture of different types of particles and liquid droplets. The chemical make-up of ambient PM10 and the sources of PM10 vary widely from one area to another. For example, in some areas, wind-blown dust may be a major contributor, while in other areas, secondary particles resulting from combustion sources may dominate. In addition, there is not a single PM10 season. Some areas experience the worst PM10 air quality in the fall, while others record highest levels in the winter. The sources contributing to PM10 air pollution can vary from season to season.
Should I be concerned about exposure to particulate matter?
Particles larger than 10 microns tend to be filtered out in the nose and therefore do not enter the respiratory tract. As such, they probably do not pose a health problem. Breathing PM10 at some concentrations, however, may impact health. For example, it can increase the frequency and severity of asthma attacks and bronchitis. For people whose health is already compromised by respiratory or cardiac disease, breathing particulate matter has also been associated with premature death.
The subgroup of fine particles (known as PM2.5) may pose an increased health risk relative to PM10 because these particles can reach deeper into the lungs and be deposited there. They are also more likely to contain substances that are particularly harmful to human health than PM10.
Who is at risk from exposure to particulate matter?
Children. Active children may receive more particulate matter exposure because they are likely to be outdoors, and their breathing rates are higher than adults. Children are also more likely to have asthma or other respiratory illnesses that may be aggravated by exposure to particulates.
Adults who are active outdoors. Healthy adults of all ages who exercise or work vigorously outdoors are considered a "sensitive group" because they have a higher level of exposure to particulates than people who are less active outdoors.
People with respiratory diseases, such as asthma. These diseases make the lungs more vulnerable to the effects of particulates. Thus, individuals with these conditions will generally experience the effects of particulates earlier and at lower levels than less sensitive individuals.
Why is it important that the Valley meet the federal particulate matter standards?
The Environmental Protection Agency has set a federal standard for particulate matter to protect public health, so attaining that standard means everyone breathes easier. Not attaining the standard may result in increase health problems, lost school and work time, change the chemical balance in soil and water, degrade visibility, and lower our overall quality of life in the Valley.
Source: Adapted from the California Air Resources Board
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