Particulate Matter (PM), Total Suspended Particulate
(TSP), PM10 and PM2.5
Particulate matter, or PM, is the term for particles found in the air, including dust, dirt, soot, smoke, and liquid droplets. Particles can be suspended in the air for long periods of time. Some particles are large or dark enough to be seen as soot or smoke. Others are so small that individually they can only be detected with an electron microscope. Total suspended particulate (TSP) includes particles of various sizes. Some proportion of TSP consists of particles too large to enter the human respiratory tract; therefore, TSP is not a good indicator of health-related exposure. Fine particulates are the main factor accounting for this health damage. The particles most likely to cause adverse health effects are the fine particulates PM10 and PM2.5 - particles smaller than 10 microns and 2.5 microns in aerodynamic diameter, respectively.
Almost all fine particulates are generated as a result of combustion processes, diesel fuelled engine combustion, and various industrial processes, including incineration. Emissions from these anthropogenic sources tend to be PM10 and/or PM2.5. Course particles are generally emitted from sources such as vehicles travelling on unpaved roads, materials handling and crushing/grinding operations as well as wind blown dust.Particulates from natural sources (such as evaporated sea spray, wind borne pollen, dust, and volcanic or other geothermal eruptions) tend to be coarse. Some particles are emitted directly from their sources, such as smoke stacks and cars. In Other cases, gases, such as Sulphur oxide and sulphur dioxide (SO2), Nitrogen oxides (NOx) and Volatile Organic Compounds (VOC’S), interact with other compounds in the air to form PM. Their chemical and physical composition, vary depending on location, time of the year and meteorology.
Short-term exposure to PM10 can irritate the lungs and perhaps cause immune responses; lung constriction, producing shortness of breath and cough may result. The materials dissolving from the particles can also damage cells. Larger particles deposit in the upper respiratory tract, while smaller inhalable particulates travel deeper into the lungs and are retained for longer periods of time. Long-term, lower level PM10 exposure may cause cancer and premature deaths. Those with a known history of asthma or chronic lung disease are especially sensitive to these effects. The elderly or those with pre-existing heart conditions may also have severe reactions, since the resulting lack of oxygen may strain the heart.
Both PM10 and PM2.5 can accumulate in the respiratory system and are associated with numerous health effects. PM10 primarily aggravate respiratory conditions such as asthma. Exposure to PM2.5 is associated with several serious health effects like premature death, respiratory related hospital admissions and emergency room visits and aggravated asthma. PM2.5 exposure is also responsible for acute respiratory symptoms, including aggravated coughing and difficult or painful breathing; chronic bronchitis; decreased lung function that can be experienced as shortness of breath; and work and school absences. Adverse health effects have been associated with exposures to PM over both short periods (such as a day) and longer periods (a year or more).
- The South African Department of Environmental Affairs and Tourism’s (DEAT) guideline values for Particulate matter are as follows:
o Total Suspended Particulates (TSP) are :
§ 24 Hour Average = 300 micrograms per cubic meter (ug/m3)
§ Annual Average = 100 ug/m3
o Fine InhalableParticulate Matter (PM10)
§ 24 Hour Average = 180 ug/m3
§ Annual Average = 60 ug/m3
- United States EPA’s National Ambient Air Quality Standards (US NAAQS) has set an air quality standard of 50 ug/m3 for long-term 1-year average concentrations of PM10, short-term, 24-hour PM10 concentrations should not exceed 150 ug/m3 more than once a year. Long term (annual) PM2.5 concentrations should not exceed 15 ug/m3 more than once a year and the short term (daily) PM2.5 concentrations should not exceed 65 ug/m3 more than once a year.
- The WHO has a 50 ug/m3 annual average guideline limit.
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