Why Outdoor Air Quality Monitoring Is Important

As of October 19, 2021, 17 wildfires are burning in California, Idaho, Montana, Oregon, and Washington. Only two of these are contained, and all 17 have collectively burned more than 2.2 million acres (about 3,400 square miles). So far this year, over 47,000 fires have burned about 6.5 million acres (just over 10,000 square miles) in the U.S. (1)

The yearly prevalence of wildfires often leads to a larger conversation about outdoor air quality monitoring generally, including concerns about smoke, smog, ozone, carbon monoxide, and other air pollutants that negatively affect the health of living things. (1, 2)

The Environmental Protection Agency (EPA) monitors and regulates both ambient air pollution and stationary sources of pollution in the U.S. However, there is much you can do to help improve air quality, as well. Taking even a few of the suggested measures can improve the air quality in your home and environment over time, which can lead to improved overall health for you and your family.

Air Pollutants

The following are the major contributors to air pollution and constitute serious threats to human health:

  • Wildfire smoke. Wildfire smoke contains thousands of chemicals that can cause severe respiratory issues, chest pain, and a fast heart rate. Children, the elderly, first responders, and pregnant women are particularly at risk for serious consequences from inhalation. Compounding the risk is the fact that wildfire smoke ages - meaning that the sun acts on it and other chemicals in the air - as it travels, increasing its toxicity. Large particles like ash typically do not travel far from the fire, but aerosolized smaller particles can travel across continents. These smaller particles, which are less than 2.5 micrometers in diameter (50 times smaller than a grain of rice), are collectively called particulate matter. They are small enough to bypass the body's natural defenses, enter the lungs, and cause respiratory problems like lung inflammation. (3, 4)
  • Smog. Comprising many chemicals, smog is air pollution that reduces visibility. The term comes from the Industrial Revolution when smoke from burning coal mixed with fog relatively close to the ground and created a yellowish-brown haze. There are two types of smog: normal and photochemical. Normal smog results from burning high-sulfur coal, whereas photochemical smog is formed when sunlight reacts with nitrogen oxides (NOx) and volatile organic compounds (VOCs) in the atmosphere. (5, 6) VOCs are compounds that have a high vapor pressure and low water solubility. Many VOCs are human-made chemicals used and produced in the manufacture of paints, pharmaceuticals, and refrigerants. (7)

Both wildfire smoke and smog can contain any combination of the following six:

  1. Carbon monoxide (CO). CO is a poisonous, colorless, odorless, tasteless gas that is deadly in high concentrations. CO is released from burning materials containing carbon, like gasoline, propane, and natural gas. By displacing oxygen in the blood, CO deprives vital organs of oxygen. Exposure to large amounts or high concentrations of CO can cause death in minutes. Even if a person with CO poisoning is rescued and survives, he or she may have permanent neurological and heart damage. Age and general health also play a role in a survivor's prognosis. (8, 9)
  2. Nitrogen oxides (NOx). A mixture of gases containing nitrogen and oxygen, nitrogen oxides are released to the air mainly from motor vehicle exhaust, as well as burning coal and natural gas. Nitrogen oxides are used in the production of rocket fuel and explosives, among other things. (10)
  3. Ground-level ozone (O3). Tropospheric or ground-level ozone forms when the pollutants from motor vehicles, oil refineries, power plants, and chemical plants react with sunlight. Ground-level ozone contains NOx and VOCs. (11, 12)
  4. Particulate matter (PM). PM refers to solid and liquid particles in the air, some of which can be seen with the naked eye. Others can only be detected with an electron microscope. Some come directly from certain sources, such as construction sites, unpaved roads, fields, or fires, but most are the result of complex chemical reactions of power plant, industrial, and automobile pollutants. (13)
  5. Sulfur dioxide (SO2). Sulfur dioxide is a colorless gas with a pungent, rotten-egg odor. In nature, it is released into the atmosphere from volcanic eruptions. It also enters the atmosphere through burning coal and oil and from copper smelting. (14)
  6. Lead (Pb). A bluish-gray metal found in all parts of the environment, lead comes from burning fossil fuels, manufacturing, battery production, and devices that shield people from X-rays. Though its prevalence has been drastically reduced due to health concerns, lead is still present in the air and therefore still a danger. (15)

The Negative Health Effects of Air Pollutants

There are many other harmful chemicals in the air, but the above six are the ones that the EPA monitors most closely because they are the most widespread in the U.S. Exposure to these chemicals can cause a number of serious health issues for anyone. However, numerous studies on children, pregnant women, and the elderly show that these groups are the most susceptible to illnesses that air pollution induces. For example (16, 17):

- In children:

  • Respiratory infections
  • Asthma
  • Bronchitis
  • Lung damage
- In pregnant women:
  • Altered fetal brain size, leading to cognitive impairments like ADHD and autism
  • High blood pressure
  • Low fetal birth weight
  • Preterm delivery
- In the elderly:
  • Increased risk of Alzheimer's disease and dementia
  • Worsening of physical disabilities

How the EPA Performs Outdoor Air Quality Monitoring

The EPA monitors air quality in two ways: ambient air quality monitoring and stationary source emissions monitoring. Both monitor air quality according to stipulations set forth by the Clean Air Act (CAA) of 1970, which authorized state and federal regulations to limit pollution from both mobile and stationary sources. At about the same time, the EPA was established to implement these regulations. In 1990, President George H. W. Bush signed revisions to the CAA into law. These revisions included expanded air pollution research programs and increased authority to enforce the CAA. (18, 19)

Ambient Air Quality Monitoring

Ambient air quality monitoring collects and measures samples of the following ambient air pollutants to evaluate the status of the atmosphere: CO, oxides of nitrogen (NO2 and NO3), O3, lead (Pb), PM (both particulates with aerodynamic diameters below 10 micrometers [PM-10] and those aerodynamic diameters below 2.5 micrometers [PM-2.5]), SO2, and VOCs. (20)

Stationary Source Emissions Monitoring

Monitoring of stationary facilities and manufacturing plants involves collecting emissions data to demonstrate compliance with certain regulatory requirements. The facility operator also uses this data to take corrective action if necessary. There are three types of stationary source emissions monitoring systems (20):

  1. Continuous emission monitoring system (CEMS): continuously measures a pollutant of concern, such as CO or NOx.

  2. Continuous opacity monitoring system (COMS): measures the amount of sunlight that particulate matter blocks out in outgoing emissions. For example, if all light is blocked out, the substance blocking the light is said to have 100% opacity. Continuous parametric monitoring system (CPMS): measures a given parameter that is a key indicator of system performance. For example, a CPMS could monitor temperature, pressure, or flow rate. If called for, the CPMS can measure multiple parameters at once.

EPA Programs

The EPA has many programs that carry out ambient air quality monitoring and stationary source emissions monitoring. One of these is the PAMS network. PAMS stands for "photochemical assessment monitoring station," and there are 45 of them across the country. This network was started in the 1990s to meet the standards of the CAA, and its primary objectives are (21):

  • To develop a database of pollutants that create ground-level ozone, like carbon monoxide and nitrogen oxides.

  • To track ozone pollutant concentrations. On an hourly basis, each PAMS site measures such things as VOCs and NOx (ozone precursors), ambient temperature, humidity, precipitation, and ultraviolet radiation. (21)

Another program is the National Air Toxics Trends Station (NATTS) network, developed to fulfill the need for consistent, long-term monitoring data. The NATTS network assesses trends and emission-reduction program effectiveness, among other things. Initiated in 2003, the current NATTS network configuration includes 26 sites (21 urban and five rural) across the United States. Typically, the EPA monitors over 100 pollutants at each NATTS, although only 19 of those are formally required. Target pollutants include VOCs, carbonyls, PM-10 metals, and polycyclic aromatic hydrocarbons (PAHs), a class of chemicals that occur naturally in coal, crude oil, and gasoline. PAHs are produced when coal, oil, gas, wood, garbage, and tobacco are burned. (22, 23)

What You Can Do to Combat Air Pollution

The EPA has many other programs that provide outdoor air quality monitoring, as required by the CAA and its amendments; however, there are some things you can do to help improve air quality, as well (24, 25):

  • Conserve electricity. Set your thermostat a little higher in the summer and lower in winter. Participate in local energy-conservation programs.

  • Look for the ENERGY STAR label when buying home or office equipment. The ENERGY STAR is the trusted symbol for energy-efficient products and practices. The ENERGY STAR label was established to:

    • Reduce greenhouse gas emissions and other pollutants caused by the inefficient use of energy.

    • Make it easy for consumers to identify and purchase energy-efficient products that offer savings on energy bills without sacrificing performance, features, and comfort.

    • Keep vehicle engines properly tuned.
    • Carpool, use public transportation, bike, or walk when possible.
    • Combine errands to reduce the "cold starts" of your car.
    • Burn only dry, seasoned wood, or better yet, use gas logs. If you use a wood-burning stove or fireplace insert, make sure it meets EPA design specifications.
    • Compost leaves and yard waste rather than burning.

While the EPA is tasked with monitoring air quality for the nation, everyone can help by taking even a few of the measures listed above. Doing so can improve the air quality in your home and environment over time, which can lead to improved overall health for you and your loved ones.

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