Particulate matter (also called PM or particle pollution), one of the EPA criteria pollutants, is a complex airborne mixture of solid particles and liquid droplets. Though PM ranges widely in size, it has been divided into two categories based on diameter.
- PM2.5: Particles with a diameter smaller than 2.5 micrometers (µm, or microns)
- Also called fine particles
- PM10: Particles with a diameter between 2.5 µm and 10 µm
- Also called inhalable coarse particles
- Particles larger than 10 µm (e.g., sand and large dust) are not regulated by EPA (EPA, 2013i)
Both regulated classes of PM (PM2.5 and PM10) are extremely small; the average human hair is approximately 70 µm in diameter, nearly 30 times larger than the largest PM2.5 particle (Figure 1).
Figure 1: Sizes of particulate matter
Health Effects | Top
Exposure to both ‘fine’ (PM2.5) and ‘coarse’ (PM10) particles is associated with a number of harmful health effects, particularly those involving the heart and lungs. In general, the size of the particles is directly linked to their potential for causing health problems.
- Smaller particles (e.g., PM2.5) are most dangerous as they can easily get deep into the lungs.
- They can enter the circulatory system or remain embedded for long periods.
- People with preexisting heart conditions, including:
- People with preexisting lung conditions, including:
- Older adults, who may have undiagnosed heart or lung conditions
- Children, whose hearts and lungs are still developing
Symptoms of exposure to particulate matter
People with heart conditions may experience:
- Chest pain
- Irregular heartbeat
- Shortness of breath
- Heart attacks
- Coronary artery disease (CAD) is the most common heart problem related to long term exposure to PM2.5 (CDC, 2013a)
- However, CAD is largely linked to risky lifestyle habits like poor diet, smoking, and lack of exercise
People with lung conditions may experience:
- Shortness of breath
- Decreased ability to breathe deeply or vigorously
- Increased susceptibility to respiratory infections
- Aggravation of existing lung conditions like asthma and chronic bronchitis
Healthy people may experience temporary symptoms like:
- Eye, nose, and throat irritation
- Chest tightness
- Shortness of breath
These cardiovascular and respiratory health effects can increase doctor and emergency room visits, hospital stays, absences from school and work, and deaths. Nationwide, studies have shown a 15% decrease in the risk of heart disease deaths with every PM2.5 decrease of 10 micrograms per cubic meter of air (µg/m3). Particle pollution has also been associated with lung cancer and adverse birth outcomes, such as low birth weight and preterm birth (CDC, 2013; Shah et al., 2011; UDOH, 2014a).
Ways to Reduce Exposure | Top
The likelihood of being affected by PM increases as more time is spent outdoors during periods with high PM levels, and as more strenuous activities are performed.
Protect your health when PM levels are high
- Monitor PM levels in your area
- Since exercise is good for health, it is important to both stay active as well as know when to make changes
- Reduce the amount of time spent on high exertion activities
- Substitute a less strenuous activity (e.g., take a walk instead of jogging or running)
- Plan outdoor activities for days when PM levels are low
- Spend less time in areas likely to have higher PM levels, such as near busy roads
PM levels can also be elevated indoors, particularly when outdoor levels are high (EPA, 2014f).
Reduce indoor PM
- Do not smoke indoors
- Reduce the use of particle sources like candles, wood burning stoves, and fireplaces
- Certain air filters can help reduce indoor PM. See the EPA's Guide to Air Cleaners for more information.
Sources | Top
PM is composed of many different compounds and chemicals, including soil, dust, salts, acids, soot, metals, and organic chemicals. When thinking about where PM comes from, it is again divided into two categories.
- Primary Particles: Released directly from a source.
- Some of the most common sources include smoke and soot from fires, fuel combustion (both industrial and residential), industrial processes, and dust from many different places.
- Secondary Particles: Formed in complex reactions involving other atmospheric pollutants like nitrogen dioxide and sulfur dioxide.
Over 30% of primary PM2.5 particle emissions in Utah also came from dust in 2011 (Figure 2) (EPA, 2016a). Fires contributed over 15%, while fuel combustion and mobile sources emitted 15% and 12.5% of the total primary PM2.5 particles, respectively. Remember that this graph shows only primary particles, those release as particles directly from a source. Most PM2.5 is made of secondary particles, those formed in the atmosphere from other pollutants.
Figure 2: 2014 primary PM2.5 particle emissions in Utah by source sector
In 2014, 67% of the primary PM10 particles in Utah came from dust, largely from unpaved roads (Figure 3) (EPA, 2016b). The next highest source categories, agriculture and industrial processes, contributed approximately 17% and 5%, respectively, of the total primary PM10 particles. Remember that this graph shows only primary particles, those release as particles directly from a source.
Figure 3: 2014 primary PM10 particle emissions in Utah by source sector
Standards and Trends | Top
There are three primary National Ambient Air Quality Standards (NAAQS) for particulate matter, which were most recently revised in 2012. There is an annual primary standard for PM2.5 of 12 µg/m3, and PM2.5 and PM10 have 24-hour primary standards of 35 µg/m3 and 150 µg/m3, respectively. Since weather conditions play such a large role in the data collected year to year, each of the three standards are evaluated over rolling three year periods. The PM2.5 24-hour primary standard is the 98th percentile averaged over three years, while the PM10 24-hour primary standard is not to be exceeded more than once per year on average over a three year period (EPA, 2013j).
Nationally, both PM2.5 and PM10 levels have shown steady reductions between 2000 and 2015, decreasing by 37% (Figure 4) and 36% (Figure 5), respectively.
Figure 4: Average national PM2.5 concentration, 2000 - 2015
Figure 5: Average national PM10 concentration, 2000 - 2015
The Southwest region states of Arizona, Colorado, New Mexico, and Utah have shown less improvement over the same time period, with a 24% decrease in PM2.5 levels (Figure 6) and a 16% dcrease in PM10 levels (Figure 7). However, part of this trend is due to a spike in PM10 levels among some Southwest monitoring sites in 2011 – 2012, and regional PM2.5 levels already being below the national average in the early 2000s.
Figure 6: Average PM2.5 concentration in the Southwest, 2000 – 2015
Figure 7: Average PM10 concentration in the Southwest, 2000 – 2015
The PM2.5 level averaged across 18 air quality monitors throughout the Wasatch Front (including Brigham City and Logan) is shown in Figure 8. The average 24-hour PM2.5 concentration consistently exceeded the current 24-hour NAAQS (first enacted in 2006). The average concentrations from most individual monitors were also consistently above the 24-hour NAAQS (data available from UDAQ).
Figure 8: 3-year average of the 98th percentile of the 24-hour PM2.5 concentration
By contrast, the annual mean PM2.5 concentration averaged across the same 18 air quality monitors has consistently been below the annual NAAQS of 12 µg/m3 since at least the 2002 – 2004 three year period (Figure 9). The annual mean concentrations from most individual monitors were also consistently below the annual NAAQS (data available from UDAQ).
Figure 9: 3-year average of the annual mean PM2.5 concentration
There are a number of areas in Utah that have been designated as nonattainment for PM by EPA under the most recent NAAQS. All areas in Utah were attaining the 1997 PM2.5 24-hour primary standard of 65 µg/m3. However, when this standard was lowered to 35 µg/m3 in 2006, the urban areas along the Wasatch Front were unable to comply and were re-designated as nonattainment (Figure 10).
Figure 10: PM2.5 nonattainment areas in Utah
For PM10, Salt Lake and Utah Counties have been designated as nonattainment for the 24-hour primary standard of 150 µg/m3 (Figure 11). In general, both areas have been in compliance with the NAAQS since 1996, but disagreements regarding the classification of exceedances due to windborne dust during high wind events have prevented re-designation to attainment or maintenance (EPA, 2009; UDAQ, 2014f).
Figure 11: PM10 nonattainment areas in Utah
Data and Indicators | Top
The Utah Environmental Public Health Tracking Program (EPHT) has created a number of indicators exploring data on particulate matter in Utah. An indicator is a fact or trend that indicates the level or condition of something. Well known indicators include gross national product, unemployment rates, and presidential approval ratings. In a public health context, indicators show trends like cancer rates, drinking water contamination levels, and blood lead levels in children. Visit the EPHT frequently asked questions page for more information.