Introduction to Particulate Matter
particulate-matter

Particulate matter (PM) is airborne particles and droplets, that can be inhaled. Some PM is formed through physical motion, like pulverized dust getting wind swept, and other PM is formed through gaseous chemical reactions in the atmosphere. Particulate matter is [regulated](/wiki/pm-monitoring-regulations) because it has negative health consequences, especially when it is small enough to travel deep into the lungs, and be [respired.](https://publiclab.org/wiki/pm#Respirable+Particles) ####Pages in this research area: [Questions and notes shared on PM](/pm#Questions) [Understanding Particulate Matter](https://publiclab.org/wiki/pm#Background+Information) [Collecting Data on Particulate Matter](https://publiclab.org/wiki/pm-monitoring) [Choosing a PM monitoring Method - Overview](https://publiclab.org/wiki/choosing-a-method-for-particulate-matter-monitoring) In depth: - [Visual monitoring](/wiki/visual-pm)- monitoring with your eyes - [Filter-based monitoring](/wiki/filter-pm) - monitoring with lab analysis - [Optical monitoring](/wiki/optical-pm) - monitoring with sensors - [Passive monitoring](/wiki/passive-pm) - monitoring with other sample collection tools - [Sticky Pad monitoring](https://publiclab.org/notes/mathew/06-05-2014/the-development-of-stickypad-monitoring) - using tape and other materials to monitor for particulates - [Public Lab PM monitoring tool development](/wiki/pm-dev) - [Passive Monitoring tool](https://publiclab.org/wiki/SEM-stub-pm) - [Silica Monitoring](/wiki/silica-monitoring) [Regulations on PM Monitoring](https://publiclab.org/wiki/pm-monitoring-regulations) _________________________________ ###Questions [questions:pm] ###Notes [notes:pm] ###Background Information Particulate Matter (PM) is airborne dust and particle pollution that settles onto surfaces and into lungs. As a [regulated pollutant PM](/wiki/pm-monitoring-regulations) is shorthand for inhalable and respirable particulate matter, or [particulate matter that can stick in the lungs.](https://publiclab.org/wiki/pm#Respirable+Particles) Based on size alone, small airborne particles can become lodged in the lungs or even enter the bloodstream. At this size, some non-toxic materials, such as [silica](/wiki/silica), can be carcinogenic. Historically, most dust was naturally occurring, but at present natural sources of particles such as wind erosion, volcanoes, pollen, and forest fires have been overtaken by human-generated particles from combustion, roads, agriculture, construction, and mining (citation:[EPA/600/R-95/115](http://ofmpub.epa.gov/eims/eimscomm.getfile?p_download_id=4608)). [Monitoring sources of particle pollution](/wiki/pm-monitoring) and [advocating for their reduction](/wiki/frac-sand-action-oriented-resources) can have positive public health impacts. [According to the CDC](http://ephtracking.cdc.gov/showAirHIA.action), a 10% reduction in fine particles could prevent 13,000 deaths annually in the U.S. ###Airborne particles we can see [![visible-particles.png](//i.publiclab.org/system/images/photos/000/014/328/medium/visible-particles.png)](//i.publiclab.org/system/images/photos/000/014/328/original/visible-particles.png) The smallest particles we can see with a naked eye are visible only because they diffract light to make a haze, usually with a reddish-purple tint. We cannot see haze particles directly, however, haze can be [monitored as a proxy for small particles](/wiki/visual-pm). Mold spores, lint, and household dust particles can be seen individually only when reflecting light, as in the rays coming through window into a dark room. Particles of fine sand and soil that are visible can get airborne for short periods of time. Fog are small raindrops falling slowly, and are just barely visible. Of visible particles, only haze-sized particles pose a significant health risk, [see Respirable Particles below](https://publiclab.org/wiki/pm#Respirable+Particles). ###Dust, droplets, & particle size Almost all airborne particles are either dust (solid particles broken from larger solids) or droplets (liquid particles which grow as they condense gases out of the air). A third category of nanometer-sized particles, ultrafines, are short-lived emissions from combustion. These three modes, ultrafines, droplets, and dust, are each clustered around a specific size range, such that the sizes of particles in the air are not evenly distributed. Ultrafines are short-lived, forming the center of droplets quickly. Large dust particles are also short lived, settling out. In the middle are mature droplets and fine dust that make up both the bulk of long-lived atmospheric particles and the most worrisome particles because of their [respirability](https://publiclab.org/wiki/pm#Respirable+Particles). [![CORRECTillustrative3-peak-ultradropdust.png](//i.publiclab.org/system/images/photos/000/014/317/medium/CORRECTillustrative3-peak-ultradropdust.png)](//i.publiclab.org/system/images/photos/000/014/317/original/CORRECTillustrative3-peak-ultradropdust.png) ###Dust While some dust comes from biological sources (skin, bacteria, mold, pollen), most comes from dirt and rocks crushed small enough to get airborne. Only dust less than 10 μm can stay airborne for days, and dust less than 5 μm dust can travel for years. Larger dust settles out (called sedimentation), while smaller dust is removed by being washed away in rain or by running into objects (impaction). [![CORRECTillustrative3-peak-dust.png](//i.publiclab.org/system/images/photos/000/014/318/medium/CORRECTillustrative3-peak-dust.png)](//i.publiclab.org/system/images/photos/000/014/318/original/CORRECTillustrative3-peak-dust.png) ###Droplets Droplets are formed as gases cool and condense. Atmospheric droplets condense from combustion gases, especially industrial and transportation emissions like sulfur dioxide and nitrogen dioxide, and also water. Atmospheric water dominates the droplet formation process. ####Droplet Formation [![droplet-formation.png](//i.publiclab.org/system/images/photos/000/014/329/medium/droplet-formation.png)](//i.publiclab.org/system/images/photos/000/014/329/original/droplet-formation.png) Cooling gases quickly condense into droplets in what is called the ‘accumulation mode’ of droplets. Accumulating droplets are sometimes called ‘cloud scavenging’ for the way they grow by collecting gases and mixing with other droplets. Droplets gain and lose water as the humidity changes. Condensing water often brings multiple droplets together, and this ‘wetting’ and ‘drying’ of droplets can aid in droplet accumulation. [![CORRECTillustrative3-peak-droplet.png](//i.publiclab.org/system/images/photos/000/014/320/medium/CORRECTillustrative3-peak-droplet.png)](//i.publiclab.org/system/images/photos/000/014/320/original/CORRECTillustrative3-peak-droplet.png) [![CORRECTillustrative3-peak-droplet-humidity.png](//i.publiclab.org/system/images/photos/000/014/319/medium/CORRECTillustrative3-peak-droplet-humidity.png)](//i.publiclab.org/system/images/photos/000/014/319/original/CORRECTillustrative3-peak-droplet-humidity.png) ####Droplets’ Beginnings: Ultrafine nulceotoids While dust can only be ground to about 0.5 μm minimum, and most dust particles are much bigger, smaller solid particles can be formed under intense heat and pressure, such as in a fire or engine. These ultrafine, or nanoparticles, are less than 0.1 μm and last only as long as their rapidly dissipating energy can keep them from bonding. With only a dozen to a few hundred molecules making up each ultrafine particle, the properties and behavior of ultrafines are poorly understood. Ultrafine material, especially elemental carbon nanoparticles from transportation and diesel, are a growing field of study. [![6.jpg](//i.publiclab.org/system/images/photos/000/013/922/medium/6.jpg)](//i.publiclab.org/system/images/photos/000/013/922/original/6.jpg) As ultrafine particles lose energy, cooling gases condense around them, ‘nucleating’ (forming the center, or nucleus, of) a new droplet. Often the gases condensing onto ultrafines are in the same emissions stream from combustion, including sulfur dioxide, nitrogen oxides, and volatile organic compounds (VOCs). The droplets formed around ultrafines may also nucleate other droplets, especially ‘wet’ droplets of water. ###Respirable Particles The body removes objects from the lungs in two ways, by coughing (“expectorating”), or by absorption and removal by the blood stream. In order to enter the bloodstream, particles must pass the last branching passageways in the lungs: the terminal bronchioles. Particles above the terminal bronchioles are the “thoracic fraction” (thoracic means in the chest), and below the terminal bronchioles particles are considered respired particles. Respired particles may, however, still be removed by coughing. [![inhalable-respirable.png](//i.publiclab.org/system/images/photos/000/014/334/medium/inhalable-respirable.png)](//i.publiclab.org/system/images/photos/000/014/334/original/inhalable-respirable.png) The most particles in the respiratory system average around 2.5 μm, while most in the thoracic fraction are are around 10 μm. The fate of short-lived ultrafine particles in the lungs is still being studied. [![CORRECTillustrative3-peak-respirable.png](//i.publiclab.org/system/images/photos/000/014/321/medium/CORRECTillustrative3-peak-respirable.png)](//i.publiclab.org/system/images/photos/000/014/321/original/CORRECTillustrative3-peak-respirable.png) ###Regulation Particulate Matter is one of six ‘criteria pollutants’ determining National Ambient Air Quality Standards ([NAAQS](/wiki/frac-sand-legislation#National+Ambient+Air+Quality+Standards)). All of the EPA’s [technology-based particle regulations](https://publiclab.org/wiki/pm-monitoring-regulations#The+Federal+Reference+Methods:) share features in common with the [PM10 standard](https://publiclab.org/wiki/frac-sand-legislation#Particulate+Matter), and a deep look at the PM10 standard is illustrative. ####PM10 PM10 is the US EPA’s first attempt to capture a standardized indicator of respirable particles. “PM10” stands for Particulate Matter less than or equal to 10 μm in diameter. Established in 1987, PM10 is now a global benchmark. PM10 is a technology-based standard-- all PM10 tools and measurements are related back to the original reference [filter-based PM Monitors](/wiki/filter-pm) instrument. Similar measurement tools with a tight correlation with this original [Federal Reference Method (FRM)](https://publiclab.org/wiki/pm-monitoring-regulations#The+Federal+Reference+Methods:) now share the FRM designation. Tools that use different processes and have a somewhat less tight correlation are designated [Federal Equivalent Methods (FEMs)](/wiki/pm-monitoring-regulations#Federal+Equivalent+Methods). You can read about the FRM PM10 monitor [in the Code of Federal Regulations](https://www.gpo.gov/fdsys/granule/CFR-2012-title40-vol2/CFR-2012-title40-vol2-sec50-6/content-detail.html): [![er18jy97.022.png](//i.publiclab.org/system/images/photos/000/014/332/medium/er18jy97.022.png)](//i.publiclab.org/system/images/photos/000/014/332/original/er18jy97.022.png) The goal of the FRM is to generate a 24 hour average of the concentration of respirable particles in the air. It does this by pumping a precise volume of air inside, selecting the particles smaller than 10 μm, and depositing them on a filter, and measuring their accumulated mass. Note that the FRM concentration is determine in "mass per volume" and not "number of particles per volume," and thus requires a gravimetric rather than a particle-counting technique. The particles are selected for size with a device called an impactor (o cyclone). The function of an FRM impactor is written into the regulation and legally defines what is and isn’t PM10. [![PM10-FRM.png](//i.publiclab.org/system/images/photos/000/014/333/medium/PM10-FRM.png)](//i.publiclab.org/system/images/photos/000/014/333/original/PM10-FRM.png) An impactor sorts particles by momentum. As air is drawn into the instrument, an impactor plate interrupts the air’s linear flow. Light particles stay in the air stream and pass around the plate. Due to inertia, more massive particles can’t make the turn and hit the plate, thereby crashing out of the sample airstream: [![impactor.png](//i.publiclab.org/system/images/photos/000/014/330/medium/impactor.png)](//i.publiclab.org/system/images/photos/000/014/330/original/impactor.png) The _cutoff_ size where particles either hit the plate or pass beyond it is not an absolute cutoff; there is a distribution of particle sizes that impact the plate or stay airborne. Different impactor designs are described by the 'sharpness' by which they select particles. [![cutpoint_vs_sharpness.png](//i.publiclab.org/system/images/photos/000/014/326/medium/cutpoint_vs_sharpness.png)](//i.publiclab.org/system/images/photos/000/014/326/original/cutpoint_vs_sharpness.png) For a PM10 cutoff, 50% of particles that are 10 μm in diameter are passed by the impactor, and 50% crash. The distribution is not even, and the rate at which the impactor cuts off particles above 10 μm is the ‘sharpness’ of the cutoff. Other categories of regulation include PM2.5 and PM10-2.5, read more in [PM Monitoring Regulations](/wiki/pm-monitoring-regulations). [![CORRECTillustrative3-peak-pm10.png](//i.publiclab.org/system/images/photos/000/014/322/medium/CORRECTillustrative3-peak-pm10.png)](//i.publiclab.org/system/images/photos/000/014/322/original/CORRECTillustrative3-peak-pm10.png) The PM2.5 FRM monitor is identical to the PM10 monitor, except for a second impactor for PM2.5 after the impactor for PM10. [![CORRECTillustrative3-peak-pm2.5.png](//i.publiclab.org/system/images/photos/000/014/323/medium/CORRECTillustrative3-peak-pm2.5.png)](//i.publiclab.org/system/images/photos/000/014/323/original/CORRECTillustrative3-peak-pm2.5.png) [![CORRECTillustrative3-peak-pm10-25.png](//i.publiclab.org/system/images/photos/000/014/324/medium/CORRECTillustrative3-peak-pm10-25.png)](//i.publiclab.org/system/images/photos/000/014/324/original/CORRECTillustrative3-peak-pm10-25.png) Note that neither category directly aligns with the size fraction that can travel into the bronchial region of the lungs, particles of approximately 5 μm. Also note that the FRMs collect particulate matter without determining the composition of that particulate matter, which can vary widely based on location and pollution sources. Inhaled silica is known to be especially damaging to human health, so **silica-specific exposure is [regulated in occupational settings, and in ambient settings in six states](/wiki/silica-monitoring).**...


Author Comment Last activity Moderation
jess_morgan_236 "Air quality cannot be fixed in one day. We all need to be involved in protecting nature in order to breathe cleaner air. " | Read more » about 2 years ago
lalegitimate "Are you looking for Finance? Are you looking for fast cash to enlarge your business Interested people should please contact us reply to us (Whats ..." | Read more » about 2 years ago
stevie " @stevie has marked @caitlion as a co-author. " | Read more » over 2 years ago
PeterBella "@fongvania @stevie Thank you for the EPA Colocation Instruction Guide slide deck. @TravisLondon The info linked above in the slide deck does a grea..." | Read more » over 2 years ago
stevie "Great info! thank you! " | Read more » over 2 years ago
fongvania "From this Guidebook for Developing a Community Air Monitoring Network: If possible, permanently install a community monitor at the colocation site..." | Read more » over 2 years ago
eustatic "I think it all depends on the sampling rate and whether the data converge, ha. For electronic monitors sampling every few seconds, two weeks isn't..." | Read more » over 2 years ago
Ag8n "We were in an medical environment, usually class 100,000. These instruments are different from the ones used by public lab, but based on the same ..." | Read more » over 2 years ago
wu_ming2 "@bhamster I just became aware of this thread. My profile has notifications settings on but received none. Who knows why. For the record my soluti..." | Read more » over 2 years ago
kimberlystephanie241 "Firearms being shipped to Colorado, Connecticut, Maryland, Massachusetts, New Jersey or Vermont may have the magazine(s) removed before shipment if..." | Read more » over 2 years ago
ferian084 "residence inn breakfast hours " | Read more » over 2 years ago
stevie " @stevie has marked @travislondon as a co-author. " | Read more » over 2 years ago
stevie " @stevie has marked @travislondon as a co-author. " | Read more » over 2 years ago
stevie " @stevie has marked @travislondon as a co-author. " | Read more » over 2 years ago
stevie " @stevie has marked @TravisLondon as a co-author. " | Read more » over 2 years ago
hackeronrent "Yes it is. " | Read more » over 2 years ago
jeffalk "@Sara, I believe your question specifically refers to indoor air quality, specifically particulates, and humidity and because @Warren 's comments..." | Read more » over 2 years ago
warren "Hi Sara! Yes, in two broad ways that I've seen -- both in being able to distinguish particulates /from/ humidity, and potentially in humidity affe..." | Read more » over 2 years ago
seankmcginnis "@denissebn_06 - Kriging is a type of spatial interpolation that can estimate values for unknown locations based on known values/locations. This is..." | Read more » almost 3 years ago
amocorro "Here's some introductory information that might be helpful: https://desktop.arcgis.com/en/arcmap/10.3/tools/3d-analyst-toolbox/how-kriging-works.ht..." | Read more » almost 3 years ago
denissebn_06 " @denissebn_06 has marked @sarasage as a co-author. " | Read more » almost 3 years ago
seankmcginnis "@eustatic & @amocorro - I was able to create a scheduled Python script that calls the API and returns the data on 10 minute intervals (PurpleA..." | Read more » almost 3 years ago
amocorro "@seankmcginnis also shared these helpful links today - how to get the data for Purple Air. API for PurpleAir https://api.purpleair.com/ Looks lik..." | Read more » almost 3 years ago
amocorro "@lesbreathe Mary Jo asked a similar question today! " | Read more » almost 3 years ago