“Particulate matter (PM) is a complex mixture of substances ranging from dry solid fragments, solid-cores fragments with liquid coatings, and small droplets of liquid,” the California Environmental Protection Agency Air Resources Board (ARB) in: “Facts About Particulate Matter Mortality: New data revealing greater dangers from PM2.5,” expressed. “These particles vary in shape, size and chemical composition and may include metals, soot, soil and dust.”1
That, suffice it to say, covers but a small part of the complex story that PM is. There is more – much more.
Diane Bailey, who is a senior scientist with the Natural Resources Defense Council, in an email adds: “Particulate matter as a broader class of pollutants in solid form encompasses all kinds of soot particles including diesel soot, and other types of particles like crustal dust (minerals), ash, etc.,” and further clarifies, “The soot particles themselves contain toxic constituents – you can think of each particle like a micro-honeycomb of carbon filled with other minerals, condensed hydrocarbons, metals, etc.”2
“[D]iesel exhaust contains soot particles and other gaseous pollutants like acetaldehyde and benzene – some 400 chemical constituents in total,” Bailey continues, providing even greater perspective.
Noted, too, according to ARB is that particulate matter is identified and categorized in general according to size: PM 10 (or coarse particulates) ranges in size – between 2.5 and 10 micrometers in diameter while PM 2.5 (or fine particulates) is smaller than 2.5 microns in size.
Moreover, particulates of both sizes prompt cause for concern from a health-impacts or implications standpoint because they can lodge deep in the lung.
Furthermore, the ARB relates: “There are two categories of PM sources. Primary PM is released directly into the atmosphere, such as dust or soot, while secondary PM is formed in the atmosphere by the chemical reactions of gases, such as nitrogen oxides, sulfur oxides, ammonia and volatile organic compounds. Both primary and secondary sources must be controlled in order to reduce ambient PM.”3
Meanwhile, the ARB lists major contributing PM sources:
- Passenger cars
- Off-road equipment
- Residential wood-burning
- Forest and agricultural burning
- Electric power generation and industrial sources4
“Dust from paved and unpaved roads, and construction, mining, and agricultural activities also contribute to PM2.5,” the ARB pointed out.5
Add to this ammonia produced via livestock operations not to mention that which comes from motor vehicles and through fertilizer applications, according to the ARB.6
Due to the public health danger PM poses, mitigating this pollutant is job 1 in my view, and that’s putting things tamely.
Regarding particulate-matter matters and although covered here many times before, today’s is a much, much more in-depth discussion.
- California Environmental Protection Agency Air Resources Board, “Facts About Particulate Matter Mortality: New data revealing greater dangers from PM2.5,” May 30, 2008, p. 1, http://www.ncuaqmd.org/files/Particulate%20Matter%20Mortality%20Fact%20Sheet.pdf
- Diane Bailey, Senior Scientist, Natural Resources Defense Council, personal communication, Apr. 29, 2014.
- California Environmental Protection Agency Air Resources Board, “Facts About Particulate Matter Mortality: New data revealing greater dangers from PM2.5,” May 30, 2008, p. 1.
- Ibid. p. 2.
- Ibid. p. 2
- Ibid. p. 2