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Introduction to Particulate Matter

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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 because it has negative health consequences, especially when it is small enough to travel deep into the lungs, and be respired.

Pages in this research area:

Questions and notes shared on PM
Understanding Particulate Matter
Collecting Data on Particulate Matter
Choosing a PM monitoring Method - Overview

In depth:


Questions

Title Author Updated Likes Comments
Is the Purple Air sensor an EPA-validated tool? @kgradow1 7 months ago 4
Can we use a Purple Air through a VPN? @stevie 7 months ago 5
Where can I find good low-cost air quality sensors? @mgoodwin 8 months ago 5
Can you blur the location of a Purple Air device? @stevie 9 months ago 3
Do you really need a special filter to filter out ultrafine particulates in the air? @BostonFern 10 months ago 3
What are ways to make dense CSV data more readable? @warren about 1 year ago 7
SPS30 instead of PlanTower units? @subir about 1 year ago 4
What do the different colors mean on the Simple Air Sensor? @stevie over 1 year ago 5
What are best practices and tools to help clean up data sets? @stevie over 1 year ago 26
What is the correct AQI measure ? @sagarpreet over 1 year ago 22
Sanity check for air sensors @Ag8n about 2 years ago 13
Low-cost air quality sensors to measure PM2.5, PM10? @bigmit37 over 2 years ago 9
What information should be posted with images taken with a microscope? @stevie over 2 years ago 3
What is a good way to track vehicular traffic? @stevie over 2 years ago 14
How do I find out who is responsible for maintaining the roadway by my house? @stevie over 2 years ago 3
What are ways to visualize particulate matter pollution that comes from vehicular traffic? @stevie over 2 years ago 2
How are gravel and asphalt companies regulated? @stevie over 2 years ago 1
What type of permits are required for gravel and asphalt processing facilities? @stevie over 2 years ago 1
What's the best material for observing dust (PM) accumulation? @stevie over 2 years ago 9
Is there someone who can help pull and analyze Purple Air data? @stevie over 2 years ago 9
Can collecting dust on a sticky pad result in EPA review? @liz over 2 years ago 1
Can MiniVol (TAS Particulate Matter Monitor) measure Black Carbon or Elemental Carbon? @stevie over 2 years ago 2
Hey @matthew I am trying to build same PPM kit you guys have here. Where did you guys get the sampler stub? @Matej over 2 years ago 2
Measuring pollen @Yeipi over 2 years ago 9
The difference between medical particle monitoring and your particle monitoring? @Ag8n over 2 years ago 4
What do respirable silica particles (frac sand pollution) look like? @warren almost 3 years ago 5
Anyone in Ontario working on ultrafine particle pollution? @liz almost 3 years ago 0
What are different ways to collect respirable dust samples for analysis? @warren almost 3 years ago 3
What kind of Framework for Participatory PM2.5 can be used for creating monitoring cities? @stevie almost 3 years ago 0
What are some ways to collect dust or particulate samples for analysis? @warren almost 3 years ago 4
What is the scenario under which you would use an optical vs. a passive monitor to measure dust? @kgradow1 about 3 years ago 1
How does the EPA measure things, especially the size of dust particles? @kgradow1 about 3 years ago 3
Is it possible to accurately size inhalable and respirable particles using a DIY microscope? @gretchengehrke about 3 years ago 4
Is it possible to discern jagged from rounded particles using a DIY microscope? @gretchengehrke about 3 years ago 4
How big are silica particles, in microns? @warren about 3 years ago 2
How big are smoke particles, in microns? @warren about 3 years ago 4
Are there any methods to distinguish where particulate matter in the air comes from? @stevie over 3 years ago 4
What are the health effects related to fine particles of calcium carbonate? @stevie over 3 years ago 8
What procedure is best to determine background airborne silica levels? @mathew almost 4 years ago 1
calibration calculations don't match MiniVol manual @mathew almost 4 years ago 6
DustDuino available for sale @Najat about 4 years ago 1
Can a passive dust monitoring housing be made from a cheaper/easier material? @warren about 4 years ago 2
lightweight air quality sensors for a weather balloon @glenc about 4 years ago 2
Question: Could this be used to monitor a construction site? @DustinBlock over 5 years ago 1
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Ask a question  or help answer future questions on this topic

Notes

Title Author Updated Likes Comments
Looking at Dust (and other things) @partsandcrafts 5 months ago 2
Is the Purple Air sensor an EPA-validated tool? @kgradow1 7 months ago 4
Can we use a Purple Air through a VPN? @stevie 7 months ago 5
Where can I find good low-cost air quality sensors? @mgoodwin 8 months ago 5
CANCELED Event: Sand Sentinel Training, Bloomer WI @stevie 9 months ago 3
Can you blur the location of a Purple Air device? @stevie 9 months ago 3
Upcoming OpenHour on Particulate Matter Monitoring @stevie 9 months ago 12
Do you really need a special filter to filter out ultrafine particulates in the air? @BostonFern 10 months ago 3
Log Simple Air Sensor data to SD card @imvec 11 months ago 2
Simple air sensor assembly notes @natevw about 1 year ago 0
Event: Wisconsin Sand Sentinel Training @stevie over 1 year ago 0
Opencv.js for blob detection in microscopic images @aashnaaashna over 1 year ago 2
What do I do next, after using a low-cost or DIY air sensor? @warren over 1 year ago 7
Exploring with the Simple Air Sensor @stevie over 1 year ago 8
What happens to the simple air sensor when the battery pack runs low? @stevie over 1 year ago 11
What are the advantages to using 2 particle sensors at the same time? @warren over 1 year ago 11
Draft Sand Sentinel Program @stevie over 1 year ago 1
What are some activities for using the Simple Air Sensor as part of a broader air quality project? @warren over 1 year ago 15
What is the correct AQI measure ? @sagarpreet over 1 year ago 22
Assembling the Simple Air Sensor @warren over 1 year ago 5
Is there a predictive relationship between the number of PM 2.5 and smaller airborne particulates compared to the mass of the same ug per cubic meter? @Tomp over 1 year ago 5
Event: Frac Sand Mining Health Research Public Forum @stevie over 1 year ago 1
What constitutes transit violations in Wisconsin? @kamau19 over 1 year ago 2
What constitutes an air quality violation in Wisconsin? @stevie over 1 year ago 3
Download & Analyze Purple Air data @jiteovien almost 2 years ago 15
Air Sensor Project @johnb1003 almost 2 years ago 4
Should the Purple Air be co-located with a weather station? @stevie almost 2 years ago 3
Frac Sand Sentinel Fellowship @stevie almost 2 years ago 0
Particulate sensor using a STBM271 @david_uwi almost 2 years ago 8
AIR-QUALITY & BALLOON LAUNCH: SUMMER 2019 QUEENSBRIDGE TECH LAB COMMUNITY SCIENCE PROJECT @SadiePrego almost 2 years ago 5
Notes from Tuesday’s frac sand call @stevie about 2 years ago 6
Recent conversations on the frac sand issue @stevie about 2 years ago 15
Sanity check for air sensors @Ag8n about 2 years ago 13
How to evaluate low cost air quality sensors @jiteovien about 2 years ago 4
PM 2.5 Air Quality Index for Keller, Texas @jiteovien about 2 years ago 13
Public Lab Providence has a PurpleAir @jiteovien about 2 years ago 13
Calibrating low cost air quality sensor part 2 @jiteovien over 2 years ago 1
Pharmaceutical class 100000 particulate as compared to pm2.5 @Ag8n over 2 years ago 2
The fight to get out of Pascagoula @stevie over 2 years ago 6
What's the best material for observing dust (PM) accumulation? @stevie over 2 years ago 9
Overview: Hackteria Remix: Building a Basic Microscope with Raspberry Pi @partsandcrafts over 2 years ago 14
MACA - Open AQ monitor - Second prototype @nanocastro over 2 years ago 19
Can collecting dust on a sticky pad result in EPA review? @liz over 2 years ago 1
Hand-cut or lasercut a simple DIY microscope stage @warren over 2 years ago 1
Measuring pollen @Yeipi over 2 years ago 9
Report: Particle Visualization Event @stevie over 2 years ago 0
How to Make a Simple Smartphone Microscope #citizenscience #science #DIY #3dprinting @zengirl2 over 2 years ago 4
What do respirable silica particles (frac sand pollution) look like? @warren almost 3 years ago 5
Particle Visualization Event in Hixton, WI @gretchengehrke almost 3 years ago 5
Have you used the particle atlas? @Ag8n almost 3 years ago 15
What different electronic particulate pollution sensors are available and at what cost? @warren almost 3 years ago 4
Visualize live sensor data with p5js and an Arduino @warren almost 3 years ago 10
What are different ways to collect respirable dust samples for analysis? @warren almost 3 years ago 3
Python and openCV to analyze microscope slide images of airborne particles @amirberAgain almost 3 years ago 41
Thoughts on Low Cost air quality sensors @guolivar almost 3 years ago 14
How good is the PurpleAir sensor and what does it detect? @warren almost 3 years ago 11
What are some ways to collect dust or particulate samples for analysis? @warren almost 3 years ago 4
Changes in factory pollution and asthma emergency department visits @DrJessie about 3 years ago 0
How do DIY microscopes compare (cost, ease of use, resolution) to commercial options? @warren about 3 years ago 3
What is the scenario under which you would use an optical vs. a passive monitor to measure dust? @kgradow1 about 3 years ago 1
How does the EPA measure things, especially the size of dust particles? @kgradow1 about 3 years ago 3
How big are silica particles, in microns? @warren about 3 years ago 2
How big are smoke particles, in microns? @warren about 3 years ago 4
Re-posting 2016 Dustduino report @liz over 3 years ago 0
Issue briefing: ultrafine particle pollution from dehydrated biosolids @liz over 3 years ago 2
Are there any methods to distinguish where particulate matter in the air comes from? @stevie over 3 years ago 4
Changing filters on the pDR-1500 @mathew over 3 years ago 0
Practicing a PM hotspot survey in New Auburn, WI @mathew over 3 years ago 6
MiniVol pre-deployment preparation, Updated @mathew over 3 years ago 0
UWEC air quality monitoring @bkleist over 3 years ago 3
Site Survey for a Minivol @mathew over 3 years ago 0
Troubleshooting leaks on the MiniVol @mathew over 3 years ago 0
Frac sand hotspot testing and site survey @stevie over 3 years ago 0
Can the New Auburn, WI Recreation Area be used to identify downwind dust from Great Northern Sand? @mathew over 3 years ago 2
EPA Method 22: Visual Determination of Fugitive Emissions @gretchengehrke almost 4 years ago 0
EPA Method 9: Visual Determination of the Opacity of Emissions from Stationary Sources @gretchengehrke almost 4 years ago 2
Can PM4 be monitored with the MiniVol? @mathew almost 4 years ago 1
What procedure is best to determine background airborne silica levels? @mathew almost 4 years ago 1
Air Quality Monitoring at UWEC @bkleist almost 4 years ago 10
MiniVol pre-deployment preparation, with images @mathew almost 4 years ago 0
Routine maintenance and calibration of the MiniVol, with images @mathew almost 4 years ago 0
Routine maintenance and calibration of the MiniVol @mathew almost 4 years ago 0
Minivol PM monitoring deployment @mathew almost 4 years ago 0
MiniVol pre-deployment preparation @mathew almost 4 years ago 0
Identifying a PM monitoring site for deploying a MiniVol @mathew almost 4 years ago 0
calibration calculations don't match MiniVol manual @mathew almost 4 years ago 6
ShenangoChannel.org - a dashboard for monitoring and sharing @liz almost 4 years ago 5
Overview: MiniVol PM monitor @mathew almost 4 years ago 1
Measuring Air Quality (PM) @ new years eve during fireworks @GreenFrogg almost 4 years ago 19
Dustduino potentiometer testing @imvec almost 4 years ago 9
Microscope from Tablet Computer @MicroscopesAreCool almost 4 years ago 1
What fuels a movement? @stevie almost 4 years ago 0
Barnraising 2016 at LUMCON: Resources for Landfill Researchers @sarasage about 4 years ago 0
Can a passive dust monitoring housing be made from a cheaper/easier material? @warren about 4 years ago 2
Thoughts on Method 9 and its utility @gretchengehrke about 4 years ago 3
Sizing particles in microscope images at Portland Science Hackday @mathew about 4 years ago 4
DIY microscope resources @liz about 4 years ago 1
Is CALPUFF a good air quality modeling tool @marlokeno about 4 years ago 4
Calibrating a Microscope @mathew over 4 years ago 2
OpenFlexure Microscope: high-resolution assembly @mathew over 4 years ago 7
Automating ImageJ for particle image analysis @SimonPyle over 4 years ago 8
Mapping dust hotspots with low-cost monitors @mathew over 4 years ago 0
Automating Passive Particle Monitor Analysis @mathew over 4 years ago 3
Pm 2.5 network in Taiwan @liz over 4 years ago 0
DIY: Wi-Fi Streaming Weatherproof PM2.5 Monitor (Dylos-based) @kevinvivergy almost 5 years ago 18
Raspberry Pi based microscope @Holger about 5 years ago 8
Aquarium Pump modifications for Durability & Flexibility @mathew about 5 years ago 0
Dustduino Build for the AMP project @LauraChipley about 5 years ago 2
Deploying UNC passive sampler on South Side of Chicago @AmberWise about 5 years ago 4
Using ImageJ to process passive particle monitor samples @mathew about 5 years ago 2
analyzing passive monitors @mathew about 5 years ago 8
Optical Imaging of Passive Particle Monitors @mathew about 5 years ago 3
Replicating a Passive Dust Monitor & Method @mathew about 5 years ago 4
Plan for recording Shinyei optical sensors using Open Pipe Kit @mathew over 5 years ago 15
Testing the Mobile DustDuino @willie about 6 years ago 10
Low-cost passive aerosol monitors @mathew over 6 years ago 4
Global Community Monitor work on Silica Dust from Coal Terminals in Seward, AK @eustatic over 6 years ago 0
Broadcast dust readings from a smartphone @Schroyer over 6 years ago 12
Dissecting Humidity from Particle Count in Frac Sand Sampling @Jdahlen over 6 years ago 17
a first look at dust with consumer scanners @mathew over 6 years ago 7
The development of stickypad monitoring @mathew over 6 years ago 5
Midwestern Frac Sand Deposits, Aquifers, & Rivers @mathew over 6 years ago 3
How do we measure particulate stuff in the air? @donblair over 6 years ago 10
Preliminary PCBs for Particulates @donblair over 6 years ago 7
Frac Sand mining- polar light microscopy? @mathew over 6 years ago 5
Field Testing the Shenyei PM sensor @willie over 6 years ago 8
Measure coarse and fine air particulates with a DustDuino @Schroyer about 7 years ago 33
Sketches for airborne particulate sensor for camera phones @warren over 8 years ago 1
Show more

Background Information

Particulate Matter (PM) is airborne dust and particle pollution that settles onto surfaces and into lungs. As a regulated pollutant PM is shorthand for inhalable and respirable particulate matter, or particulate matter that can stick in the lungs.

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, 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).

Monitoring sources of particle pollution and advocating for their reduction can have positive public health impacts. According to the CDC, a 10% reduction in fine particles could prevent 13,000 deaths annually in the U.S.

Airborne particles we can see

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. 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.

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.

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

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

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

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

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

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

Regulation

Particulate Matter is one of six ‘criteria pollutants’ determining National Ambient Air Quality Standards (NAAQS). All of the EPA’s technology-based particle regulations share features in common with the PM10 standard, 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 instrument. Similar measurement tools with a tight correlation with this original Federal Reference Method (FRM) now share the FRM designation. Tools that use different processes and have a somewhat less tight correlation are designated Federal Equivalent Methods (FEMs).

You can read about the FRM PM10 monitor in the Code of Federal Regulations:

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

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

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

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.

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

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.