Fine particulate matter in the air: Health-impacting at any concentration?

I discovered a really interesting article about the Air Quality Index (AQI) titled: “Air Quality Index – time for a rethink?” written by Clive Stott in the Dec. 2017 issue of the Woodsmoke Climate Change News newsletter on pages 14 and 15.

In it, Stott, in effect, asserts PM 2.5 is unsafe regardless of air concentration or level of such. I take that to mean that no matter the concentration in the air, if breathed in, fine particulate matter is unhealthy, period.

So, let’s think about this for a moment.

What we know is, fine particulate matter is released in the air as a result of fossil-fuel combustion or from the burning of wood, for example. But, it can also form in the air when certain chemicals combine and, in addition to being a solid (often referred to as soot) can take liquid form as well.

Speaking to this, and in “Particulates uncovered: Diesel, soot get closer look,” the California Environmental Protection Agency Air Resources Board states: “‘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.’”

As to size, the particles are less than 2.5 micrometers in diameter (20 to 30 can be placed side-by-side across the width of a human hair) and they can become lodged deep in lung tissue and/or enter the bloodstream.

According to information presented on the “Air Quality Guide for Particle Pollution” page presented on the U.S. Environmental Protection Agency’s (EPA) Web site inhalation of PM 2.5 is linked to: coughing and wheezing; reduced lung function; heart and asthma attacks; strokes and early death.

So, understanding this, the question on the table is: If PM 2.5 is unhealthy or unsafe at any concentration, then why have it listed on the Air Quality Index at all?

Okay, but, wait a minute. What about the National Ambient Air Quality Standards (here in the U.S.) for such – both 24-hour and annual which are 35 and 12 micrograms per cubic meter of air, respectively?

So as to provide a bit more detail, I wrote in the “Making sense of air quality data – PM 2.5” post on Oct. 11, 2014: “For instance, the U.S. Environmental Protection Agency (EPA) assigned a health standard for PM 2.5 of 35 micrograms per cubic meter (35 μg/m3 set by the EPA on Oct. 17, 2006). This particular threshold is in reference to daily ambient PM 2.5 or over a period of 24 hours. So, for every cubic meter of air, if the fine particulate matter concentration is greater than 35 micrograms, the standard is exceeded. This corresponds to an Air Quality Index (AQI) of 101 and places air at the unhealthy-for-sensitive-individuals or populations level.

“Then there is the U.S. EPA annual fine particulate matter standard. This is set at 12 μg/m3 of air and became effective on Dec. 14, 2012.”

So, take PM 2.5 measured over a 24-hour period. In establishing or setting standards, by doing such, does this not suggest that daily air concentration with less than 35 micrograms per cubic meter of PM 2.5 mean air quality is considered good or is in the good range given this standard being in effect? But, if PM 2.5 is unsafe regardless of air concentration or level, then to set or establish a standard or limit for such, would this not be a moot point? In other words, what would be the point? I believe this is Stott’s point exactly.

Speaking of which, Stott does have a point.

So I now turn the matter over to you: I am interested in knowing what you think as I am certain others would be as well.

Article updated on Nov. 25, 2017 at 11:09 a.m. Pacific Standard Time.

3 thoughts on “Fine particulate matter in the air: Health-impacting at any concentration?

  1. Much more dangerous are nanoparticles from “cleantech” 100+ times smaller than PM2.5. These are getting in our brains and attack our nerve systems. The method of micrograms per cubic meter is long overdue. We need to start measuring surface area. The same weight comparing a 1 microgram particle with nanoparticles. The nanoparticles can have a surface area of a football field.

  2. Clive Stott may have something here.

    Okay, so looking at this subject in the broader context, if we think about the words “Air,” “Quality” and “Index,” “Index” to me suggests a scale. “Air,” meanwhile, is self-explanatory. “Quality,” as it relates to air to me is a construct which refers to its condition. Air is either clean or it’s not. It’s either good or it’s not. It’s either healthy or it’s not. This is how I see it.

    The whole purpose of having an “Air Quality Index” is to provide the public with a useful tool to gauge the quality of the air in a designated area. But, what good is such if it is confusing to too many people?

    When I tune in to watch the weather and air-quality reporting on the local broadcast news on television, I typically hear just a cursory reference related to the quality of the air in my area and see on screen an accompanying illustration that displays a color (green, yellow, orange, red, etc.) and, along with that, the corresponding words and/or a corresponding number, such as “good,” “moderate,” “unhealthy for sensitive individuals,” and so on and so forth, “good” being in the zero to 50 range, “moderate” being in the 51 to 100 range – you get the idea.

    But, the real question: Is all this really necessary?

    Why not just a two-color illustration? “Green” for “good” or “healthy,” and “red” for “bad” or “unhealthy”?

    Or, maybe even do away with the Air Quality Index entirely and have something on the order of a Pollutant Standards Index or PSI, which would directly correlate with pollutant standards – hence the name.

    At times said standards are met, then such could have a “pass” designation and at other times when said standards are exceeded, then such could have a “fail” designation attached.

    Meanwhile, in the San Joaquin Valley in the fall and winter, there are typically wood-burning restrictions that go into effect when fine particulate matter levels exceed designated thresholds. For purposes of burning wood, if a certified clean wood-burning appliance is being used, and a permit has been acquired for its use, then as long as the concentration of fine particulates in the air is between 20 and 65 micrograms per cubic meter, then in these devices it is permissible to burn wood during these times. For non-certified, non-permitted older wood-stoves and fireplaces, then as I understand things, wood-burning is prohibited for fine particulate air concentrations at 20 micrograms and above.

    However, if concentrations of such above 35 micrograms per cubic meter are considered either unhealthy or unsafe, how any wood-burning is allowed is beyond me. But, this is a story for a different time.

    Anyway, my two cents.

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