In the 1970s, the first regulations on air pollutants were implemented in the United States. Since that time, we have made many significant reductions on all types of air pollutants. However, bad air quality, smog, and acid rain continue to threaten our health and environment. In this chapter, we discuss certain key air pollutants and ways that you can monitor these air pollutants in your area. Air pollution is a global problem but it requires participation from international leaders to amateurs scientists like you.
Here is a list of criteria air pollutants:
Skip to the Air Quality Monitoring Section.
The EPA has identified six criteria air pollutants that they regulate across the country. Below are brief descriptions of each and its effects on human health.
In the upper atmosphere, ozone is a gas that forms a protective ozone layer that protects us from harmful UV rays. However, in the lower atmosphere, this gas can reduce lung functions and is especially harmful for people with asthma, lung disease, or other respiratory problems. Ozone, which is made of three oxygen atoms (chemical symbol O3) is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC) with the addition of sunlight. It is the primary component of smog and is more prevalent on hot and sunny days.
This image shows the smog, caused primarily by ozone, over the city of Los Angeles.
Nitrogen Oxides (NOx)
Nitrogen Oxides are not necessarily unsafe as isolated gases; however, they act as precursors to more harmful chemicals. A common form is nitrogen dioxide (NO2) which can form a reddish-brown layer over urban areas. Nitrogen Dioxide, unlike Ozone, is more prevalent in the winter months and the reddish-brown layer over cities becomes worse in the winter. Along with other chemicals, NOx can cause the creation of ozone, acid rain, and toxic chemicals, nutrient loading in water systems, and contribution to global warming. Due to EPA regulations, nitrogen oxide emissions have fallen from 27 million tons to 19 million tons from 1970 to 2006. Although this is a significant improvement, there is still much that needs to be done.
|The figure above show the process of acid rain formation from nitrogen dioxide and sulfur dioxide. ||This picture shows a forest devastated by acid rain in the Jizera mountains of the Czeck Repulic. |
Sulfur Dioxide (SO2)
Sulfur, which is present in coal and other raw materials, transforms to sulfur gas in the form of SO2 when fuel such as oil and coal are burned. SO2, like ozone, can aggravate lung functions especially for people with pre-existing conditions. It also causes acid rain, which makes soils and water more acidic and therefore harms plants, trees, and people, through both respiratory-aggravating acid fogs and by increasing the solubility of heavy metals in natural waters. Since the 1970s, the EPA has worked to reduce SO2 emissions across the United States from 31 to 15 million tons from 1970 to 2006.
This chart shows the progess to date for reductions in SO2 across the United States.
As an elemental metal, lead can be found in natural and manufactured goods. In small quantities, lead is not hazardous, but it can be harmful when ingested through the air, water, or accidentally through soil. In the past, automobiles were the main emission source for lead in the air, but EPA standards have drastically reduced this amount. Currently, metal processing plants emit the most lead into the environment. When distributed through the body, lead can cause serious neurological, kidney, immune, developmental, and cardiovascular systems. Children are especially sensitive to lead, and even small amounts of lead can lead to developmental problems. Because lead is so harmful to humans, the EPA placed strict regulations on lead. causing lead emissions to fall by over 98% from 1970 to 2006.
This diagram shows the areas with the highest lead concentrations (black) and lowest (white) concentrations in the United States. Notice that the areas of highest concentrations tend to correlate with areas of heavy coal burning.
Carbon Monoxide (CO)
Being an odorless and colorless gas, carbon monoxide is undetectable to human senses. It is mainly emitted from automobile exhaust, but industrial processes and biomass burning also contribute to CO emissions. Carbon monoxide is poisonous if ingested at high levels. It affects cardiovascular functioning and the nervous system by reducing the amount of oxygen to the rest of the body. The carbon monoxide emissions in the United States have fallen from 197 million tons to 89 million tons.
Particulate Matter (PM)
Particulate matter is a mixture of small solid and liquid particles suspended in the air. Although it is slightly counterintuitive, smaller particles actually cause more damage to humans than larger particles because they can enter more freely into the respiratory system. ‘Inhalable coarse particles’ are those smaller than 10 micrometers in diameter but larger than 2.5 micrometers. These are generally due to roadways or dusty industries. ‘Fine particles’ are smaller than 2.5 micrometers in diameter. They are found in smoke and haze. The main sources of emissions are from industrial power plants, automobiles, or even wildfires. Particulate matter can affect respiratory functions and cause irregular heartbeats. Those with heart and lung disease are especially vulnerable. Although particulate matter concentrations are still high in the United States, particulate matter has fallen by 80% from 1970 to 2006.
This graph displays the annual fine particulate matter concentrations at locations in the western US and Hawaii. We can see that particulate matter is still an important issue that many regions have yet to control.
Although mercury is not classified as one of the six criteria air pollutants, the EPA still regards mercury as a harmful air pollutant and began regulations in 2005. As a natural element, mercury is found in many rocks on the Earth’s surface, including coal deposits. Mercury is released into the air when coal is burned within power plants. Mercury can also be released from burning hazardous products, producing chlorine, and from mercury spills. Mercury is most potent when deposited into the water and soil rather than directly from the air. When mercury enters the water and soil, microorganisms transform the mercury into methylmercury, which is highly toxic. This chemical can build up in fish, shellfish, and animals that eat the fish and shellfish. When humans consume fish, they are exposed to this harmful toxin. Health risks include harm to the brain, lungs, kidneys, and immune system to people of all ages. For children and developing fetuses, methylmercury can cause neurological damage. Although it is not common, mercury vapor in the air, usually in poorly-ventilated or warm indoor spaces, can cause health problems. These include respiratory problems, neuromuscular changes such as tremors and weakness, emotional changes such as mood swings, and headaches.
This diagram represents the cycle of mercury in water sources. Some mercury settles to the bottom while some is released into the air. However, the large amount is converted through methylation and ingested by fish. The biomagnification process through the food cycle intensifies the mercury in the larger fish. When we eat these large fish, we are exposed to heavy doses of mercury which can harm us.
Now that we know the main air pollutants, let's look at ways to monitor these pollutants as amateur scientists.
As a student in middle or high school, you might want to ask your school to look into the Group Against Smog Pollution (GASP) initiative for middle and high schools. Although primarily offered for middle and high schools, GASP encourages anyone interested to contact the group. Through a grant, this non-profit group loans schools a sophisticated air quality monitor for a two-week period. The GASPer Air Quality Monitor is supplied at no charge to the school although a $30 donation fee for delivery is requested.
The GASPer is a suitcase-sized portable monitor that can run on battery power. It is equipped with physical sensors, the necessary software, and even a laptop (if necessary) to display the data. It can measure:
- Carbon monoxide
- Carbon dioxide
- Sulfur dioxide
- Ultraviolet radiation
- Extremely low frequency radiation
- Ionizing radiation
- Barometric pressure
- Wind speed and direction
It can display data up to every second and also provide average, maximum, and minimum concentrations. In addition, it can provide data on concentrations that exceed EPA standards.
A guidance manual as well as in-person training and technical assistance are provided to participants. GASP also encourages groups to present their findings to the annual GASPer Air Congress. The contact information for this group is provided below:
http://www.gasp-pgh.org/ | email@example.com | 412-325-7382
Wightman School Community Building
5604 Solway Street, #204, Pittsburgh, PA 15217
This group is located in Pennsylvania, but other groups are doing similar projects across the country.
Like the GASPer, AIR (Area’s Immediate Reading) is a device that can be obtained through a non-profit group, Preemptive Media Project, to measure air quality. The project began in New York City in 2006 but has expanded to Long Beach, CA; Pittsburgh, PA; Australia; Belo Horizonte, Brazil; and San Francisco, CA. The projects are centered on city air pollution, and the devices should not be from each city.
AIR is a hand-held device that you can carry around your neighborhood to measure air quality. The device detects carbon monoxide (CO,) nitrogen oxides (NOx,) and ground-level ozone (O3.) It provides real-time data and shows previous data from other locations on the device. Your data is transmitted to the AIR website, which has an online visualization of the data collected since 2006. In addition, the device maps out polluters in the area and your distance from the point source.
Because the project is a social experiment as well as an environmental monitoring program, this might not be the best for long-term intensive air quality testing. As specified by the Preemptive Media Project, one person should only carry the device for one day and then pass it on to another participant.
The group’s contact information is provided below:
http://www.pm-air.net/index.php | firstname.lastname@example.org
125 Maiden Lane
New York, NY 10038
Environmental Home Test Kits
If you are looking for a low-scale, low-cost alternative, do-it-yourself kits are also available. These kits can provide sample kits to measure gas concentrations in the atmosphere. Most kits include air quality measurements of:
- Nitrogen Dioxide (NO2)
- Carbon Monoxide (CO)
- Carbon Dioxide (CO2)
- Methane (CH4)
- Lead (Pb)
- Ozone (O3)
- Sulfur Dioxide (SO2)
These kits can run from $20 to $100. They provide preliminary information on air quality near you. However, you should remember that one sample is not a complete evaluation of air quality in your area. Air pollutants can transport large distances in fairly quick time periods. Therefore, continual monitoring is the only way to obtain significant results.
Examples of Air Quality Kits: EcoBadge
The EPA provides results on air quality at many stations throughout the United States. It measures ozone levels by the hour across the United States. Compare your ozone levels measured from your kit to the EPA estimates.
- Go to the AirNow website
- Underneath the Air Quality Map, click Ozone Now
This will provide two maps: one shows the current ozone level for the hour and the second shows an 8-hour loop for the past 8-hour period.
To find the closest air quality monitor to you, click ‘Ozone Monitoring Locations’ at the top of the map.
The EPA measures six air pollutants – Carbon Monoxide, Lead, Ground-Level Ozone Precursor: Nitrogen Oxide (NOx,) Ground-level Ozone Precursor: Volatile Organic Compounds (VOC,) Particulate Matter (PM,) and Sulfur Dioxide (SO2) – down to the county level across the United States. It outlines the major source of each pollutant and total amount of annual emissions by county. You can also look up this information to see if your air pollution data matches these sources.
The AIRNOW Ozone Monitor Visualization for July 30, 2008.
A sun photometer is a hand-held device that measures the intensity of the sunlight. When the sun’s rays travel through the atmosphere, aerosols scatter and absorb the light, which dissipates the energy. By knowing the amount of sunlight entering the atmosphere, the thickness of the atmosphere, and the amount of sunlight reaching the earth (from your photometer) you can measure the amount of aerosols in the atmosphere.
You should only calculate the sun’s intensity on clear cloud-free days. The sun photometer will provide a two voltage calculations: a light sunlight voltage and a dark voltage. The actual voltage measurement is equal to the sunlight voltage minus the dark voltage. The sun photometer can measure at two wavelengths – 508nm (green) and 625nm (red.) You should measure the voltage for both channels.
By measuring both the red and green channels, you can find out the size of aerosol particles. Smaller particles scatter more green light whereas large particles scatter red and green light equally. Therefore, by comparing the results of Aerosol Optical Depth from the two wavelengths, you can figure out whether there are more large or small particles.
When keeping records, make sure to include:
- Sunlight and dark voltages for green band
- Sunlight and dark voltages for red band
- Exact time of day
- Angle of the sun
- Cloud cover
A virtual photometer can be found on the NASA Calipso Sunphotometer website. It explains how a photometer works and provides a virtual photometer that shows how conditions such as haze, pressure, and particle size can influence your reading.
From the voltage, you can correlate your results with NASA satellites using the steps below. In addition, you can correlate your results with the ground-based AERONET photometer readings in your area.
The equation for conversion is:
aa = [ ln (Vo(ro/r)2) – ln(V) – aR(p/po)m ]/m
aa = absorption due to aerosols (Aerosol Optical Depth)
Vo = voltage outside the atmosphere. This value is calculated by the GLOBE science team
ro/r = is a ratio of distances between the sun and the Earth and is based on the time of observation.
V = voltage calculated by your photometer. It is the solar voltage minus the dark voltage.
aR = is the fraction of absorption due to scattering of sun beam by molecules in the atmosphere (rather than aerosols.)
p/po = the pressure at your height above sea level divided by the pressure at sea level.
m = mass of the air above the photometer. If the sun is directly above the observer, the mass is equal to 1. If the sun is at angle, the mass is equal to m * sec(z) where z is the angle of the sun.
To find the reasoning behind this calculation, go the website: http://www.cs.drexel.edu/~dbrooks/globe/aot_eq.html
Photometer readings, like the ones you have completed, were some of the most crucial steps for correlating MODIS satellite data to true aerosol data. NASA scientists used photometer readings from students across the world to improve satellite data through Global Learning Observations to Benefit the Environment (GLOBE). For more information on this program, visit the GLOBE sunphometer website.
To correlate your data to satellite:
- Go to the MODIS Terra and Aqua, Daily Instance.
- Enter your location coordinates or use the map to zoom to your area.
- Choose the Aerosol Optical Depth at 550nm
- Compare your aerosol optical depth calculations to the satellite data.
In addition to satellite data, AERONET is a system of sophisticated ground-based aerosol detectors. You can also compare your Aerosol Optical Depth calculation to AERONET data.
- Go to the AERONET website.
- Use the map to navigate to the nearest station in your area.
- Choose the year and day of your experiment. (Not all stations are operational so you might have to choose sites that are farther from your location to find data)
- Look at the monthly and daily data. You can find the hour where you took your sample and correlate your results with AERONET data by choosing the wavelength closest to 508nm and 625nm.
Another way to test air quality is to measure the health of biological organisms at various sites in a forest. This work is best to do near point sources such as industrial factories and power plants. In addition, bio-monitoring must be performed where organisms can actually grow and are not directly affected by human interactions. One of the best air quality organisms is lichen. These are fairly abundant organisms that are formed by fungus, green algae, and bacterium. Lichen perform gas exchange directly over their surface, which makes them strongly affected by atmospheric influences. Through lichen, you can monitor sulfur, nitrogen, metal concentrations, and other parameters over a long period of time. There are two basic approaches. The first is to measure the total species presence and cover. If you expect to find lichen in a certain area but are unable, this could mean that the air quality is harmful in the area. However, in this case, you must account for other changes that might affect the lichen concentrations besides air pollution. The second approach is to perform elemental analysis on samples taken from the area. This is more sophisticated and can show which pollutants are prevalent in the area.
For more information on the experimental procedure, refer to the paper: ‘Manual for Monitoring Air Quality Using Lichen in National Forests of the Pacific Northwest.’
Air Quality (Haze) Webcams
Particulate and ozone pollution creates haze. Many areas, particularly national parks like the Great Smoky Mountains National Park (despite its name) and the Grand Canyon National Park, have experienced a long-term trend of increasing haze levels and decreasing visibility, resulting in less pristine views. Webcams are in place that provide regularly updated images of haze conditions. In some cases, these Webcams have shown the ground-level effects wildfires, and even of dust aerosols transported from China’s Gobi Desert over the Pacific Ocean to the western United States.
These are two images of the same Boston location from the HazeCam website. As you can see, conditions can vary tremendously depending on the season. The reddish-brown fog in January is probably due to
nitrogen dioxide concentrations rather than ozone because nitrogen dioxide is more prevalent in the winter.
Understanding Air Pollution (California Environmental Protection Agency Air Resources Board)
Air Pollution: Understanding the Problem and Ways to Help Solve It (Air & Water Inc.)*
* Links to a commercial Web site do not constitute endorsement of services or products from the site owner by the National Aeronautics and Space Administration.
Top of Page