What Causes Salt Lake’s Air Pollution—and Why You Should Care
Perhaps, during the 27 red- or orange-air quality days Salt Lake City experienced throughout last winter’s inversion season, your eyes did not smart; your throat and chest did not burn; your breath did not whistle in and out. Perhaps your lungs didn’t struggle to transfer the oxygen from your breath into your bloodstream. If so, you were luckier than the estimated 86,078 children and adults in Salt Lake City with asthma, or the 188,795 people with cardiovascular disease, or the 92,845 adults over 64.
Perhaps your luck will hold this winter. However, if you are young, old, asthmatic, diabetic, have heart disease, or are a longtime outdoor athlete, chances are you, too, will at some point suffer the effects of our dirty air.
Unless, of course, we get it before it gets you.
Winter bad guys: PM2.5 and PM10
The Clean Air Act of 1970 identifies six common air pollutants found throughout the US. Besides affecting people, they can damage the environment and personal property. The EPA calls them “criteria air pollutants” because they are so harmful to health that the EPA has developed standards for allowable levels. PM2.5 and ozone are criteria pollutants (carbon monoxide, nitrogen oxides, sulfur dioxide and lead are the others) and, along with PM10, are the most worrisome components of the dirty air we breathe in SLC.
“PM” simply stands for “particulate matter.” Some particles, such as dust, dirt, pollen, soot and smoke, are emitted directly —think tailpipes; others, such as ozone, are formed in the atmosphere when gases react to airborne pollutants. These particles and gases can remain suspended in the air for long periods of time. Some, such as soot or smoke, are large enough to see. Others are so small they can only be detected with an electron microscope.
Particles between 2.5 and 10 micrometers in diameter (PM10, or “coarse” particles) are smaller than the width of a single human hair. When you inhale these particles, they stick to the sides of your airway and/or lodge into narrow passageways in your lungs. Your lungs respond by producing mucous to trap the particles, and tiny vibrating hairs do their best to move the mucous out of the lungs via coughing or swallowing. Although this process helps cleanse the lungs of PM10, some particles may remain trapped and cause irritation and even scarring of the delicate lung tissue.
Local sources of coarse particles include crushing or grinding operations (e.g. Kennecott, gravel pits), ash (from forest fires, wood-burning stoves and fireplaces), and dust stirred up by wind or vehicles. PM10 particles can stay in the air for minutes or hours, and they can travel up to 30 miles—so you can still inhale it even if you aren’t right next to a PM10 source.
Have you ever taken a nice full breath of air, only to feel that the breath is not satisfying—that the air has somehow not reached your body? PM2.5 (fine particles) may be the culprit. These particles measure 2.5 micrometers or less in diameter; you need an electron microscope to see these guys.
Because of their minute size, they are much more dangerous to health. PM2.5 particles travel down the smaller airways in the lungs and find their way to the alveoli, the tiniest crevices of the lungs. Special cells trap the particles in such a way that they can’t escape, which inhibits the alveoli from feeding oxygen into the bloodstream and scrubbing away carbon dioxide. This toxic presence can result not only in shortness of breath and irreversible lung damage, but can lead to diseases such as asthma, chronic obstructive pulmonary disease (COPD, which includes emphysema and chronic bronchitis), heart disease and lung cancer.
Sources of fine particles include all types of combustion, including motor vehicles, power plants, residential wood burning, forest fires, agricultural burning, and some industrial processes. These smaller particles are lighter than coarse particles and stay in the air longer—days or weeks. They can travel hundreds, if not thousands, of miles.
Outdoor enthusiasts, children and boomers at risk
In general, risk varies throughout a lifetime. It is high in early childhood, lower in healthy adolescents and young adults, and increases in middle through old age. Factors that increase your risk of heart attack, such as high blood pressure or elevated cholesterol levels, as well as lung disease and diabetes, also increase risk from particles.
PM2.5 and PM10 are especially dangerous to active children as they tend to spend a lot of time playing outdoors and their organs are still developing; and outdoor athletes, as the rapid and deep breathing that accompanies aerobic or other physical activity sends the particles deeper into the lungs.
Roughly one out of every three people in the US is at a higher risk of experiencing PM2.5-related health effects.
In the past few years, science has discovered that air pollution is also toxic to the brain, impairing intellectual development in children and accelerating the normal cognitive decline that accompanies aging. But air pollution’s greatest impact on public health is likely its adverse impact on the most critical stage of human development, the first three months after conception. Components of air pollution can cross the placenta, compromising critical organ development. Virtually every adverse pregnancy outcome, including low birth weight, pre-term deliveries, and fetal and infant deaths, occurs at increased rates among mothers exposed to higher than average levels of air pollution. Because of pollution’s effect on genetic integrity, a person’s lifelong propensity for chronic diseases can be affected by the air pollution breathed by his mother while he was in the womb.
Location, location: the good and bad of ozone
Although the nasty yellow-gray air in the valley in winter is generally a function of PM2.5s and PM10s being trapped near the valley floor by a stable mass of cold air, much of our summer air pollution comes in the form of ground level ozone. Ozone is a gas made up of three atoms of oxygen, and occurs both in the stratosphere and troposphere. When it is in the Earth’s upper atmosphere—the stratosphere, six to 30 miles above the Earth’s surface—it forms a protective layer that shields us from the sun’s harmful ultraviolet rays.
But in the Earth’s lower atmosphere (the troposphere), ozone reacts chemically with oxides of nitrogen (NOx) and volatile organic compounds (VOC) to form a harmful air pollutant. Major sources of NOx and VOC are motor vehicle exhaust; gasoline vapors from gas-powered residential and commercial equipment and filling stations; and emissions from power plants, refineries, chemical plants and other industrial processes. Add sunlight and water vapor to this mix and you get a toxic gas: On hot sunny days, ozone levels can rise above the level of 75 parts per billion (.075 ppm) the EPA has deemed acceptable. These levels fluctuate throughout the day, generally peaking in mid- to late afternoon when temperatures are at their highest.
High ozone concentrations have also been observed in cold months; a few high elevation areas in the West with high levels of local VOC and NOx emissions, such as the Uintah Basin, have formed ozone when temperatures are near or below freezing. A 2012 study in the Uintah Basin, led by the Utah Department of Environmental Quality, found that oil and gas operations were responsible for 98-99% of VOC emissions and 57-61% of NOx emissions occurring in cold weather.
It’s easy to overlook ozone pollution because, unlike winter smog, ozone can be clear and odorless (although it also shows up in summer smog). But like PM2.5, this oxidant gas burrows into the tiny crevices of the lungs and affects the transport of oxygen to the bloodstream, affecting everyone from fetuses to seniors.
The American Lung Association’s most recent “State of the Air” report gave Utah an “F” for high ozone, ranking our state 51st for high ozone days out of 277 metropolitan areas. Recent studies by the Utah Division of Air Quality have shown ozone levels that exceed the EPA’s standards even in previously pristine locations such as Antelope Island—possibly as a result of drifting polluted air. Some conjecture that toxic air is making its way across the ocean from heavy polluters such as China, raising a whole other set of issues.
Our fair city also received an “F” for 24-hour PM2.5 from the Lung Association; Salt Lake was 6th out of 277 US cities in this category. Three Utah regions—Salt Lake City, Provo and the Cache Valley—are currently in nonattainment for 24-hour PM2.5 standards set by the EPA in 2006: 35 micrograms per cubic meter (ug/m3). However, no area in Utah exceeds the EPA’s annual standard for PM2.5, which is measured by taking an average of PM2.5 levels throughout the year; outside of inversions, our PM2.5 levels are considered average.
You would be forgiven if you think that when pollutant levels fall below the maximum allowable ones set by the EPA (green air days), the air is safe. But you would be wrong. Medical science has shown that there is no safe level of PM, and likely no safe level of ozone. The standards set by the EPA are rather arbitrary—more in line with what the political forces will accept. The American Lung Association grades pollutants on a different and more stringent scale. Medical societies and clean air advocates are continually asking the EPA to tighten standards; it has responded at times, but rarely to the extent requested by medical science.
Still, bringing Salt Lake City, Provo and the Cache Valley into EPA attainment is a start. These nonattainment areas have been designated as such since 2009. Under current law, once a city has received an EPA nonattainment designation, state and local governments must develop plans outlining how areas will reach and maintain the legal standards within a 10-year period. This past September 3, the Utah Department of Environmental Quality submitted a plan to the Air Quality Board that it claims will cut PM2.5 pollution levels to “acceptable” standards by 2019 (the latest allowable date to achieve compliance). The proposal was passed by the Board and was out for public comment in October.
Making this a battle of good guys versus bad guys or industry versus private citizens misses the point. The wheels of industry purport to turn on our behalf. Do we want to wait six years for the cogs of government to grind their way to better air, or do we want to be proactive and attend to issues, lobby local officials and—most important because it is within an individual’s control—make changes to our own habits that work toward improving our air?
Marjorie McCloy is a former editor of Rock and Ice and Women’s Sports and Fitness, and freelances for many national publications. She lives in Salt Lake City.