Air Pollution 101
According to the World Health Organization, nearly two million people die prematurely from the health effects of air pollution every year. Defined as the contamination of air by smoke and harmful gases, air pollution is a critical environmental concern that affects all of us.
As one of the top-ranked areas for ozone and particle pollution, the St. Louis region is no stranger to poor air quality conditions. In fact, summertime ozone levels have exceeded federal-based health standards every year since the passage of the Clean Air Act. But, how does this pollution form? What causes it? And, how does it affect our health?
Ozone is a molecule that serves both good and bad functions. In the lower atmosphere, the troposphere, ozone is a major component of smog. This is what people call "bad" ozone because of its harmful effects on people, materials and ecosystems.
Ozone is created when heat and sunlight react with nitrogen oxides and Volatile Organic Compounds (VOCs) that are emitted from motor vehicles, industrial facilities, gasoline vapors, chemical solvents and dozens of other sources. Ozone levels tend to rise in mid-morning, several hours after the rush-hour and onset of emissions-generating business operations, and peak in the late afternoon. The concentration of ozone in the air strongly correlates to many meteorological characteristics including temperature, wind speed and atmospheric stability.
Ground level ozone should not be confused with the protective ozone layer in the upper atmosphere, the stratosphere, which shields the Earth from the harmful ultraviolet rays of the sun. This is what is known as "good" ozone. Chemically, "good" and "bad" ozone are identical. Location is the only difference between the two.
The sources of VOCs can be split into four main categories:
- Point sources are large stationary sources (e.g., power plants, chemical plants, major manufacturing sites).
- Area sources are sources which, when viewed individually, do not have large enough emissions to warrant individual tracking, but in the aggregate may significantly contribute to emissions (e.g., small businesses such as dry cleaners or printers, vehicle refueling operations, open burning, lighter fluid, painting).
- Mobile sources are vehicles traveling on public roads.
- Off-road or non-road mobile sources are aircraft, rail, marine vessels, farm and construction equipment, lawn and garden equipment and other such machinery.
High concentrations of ground-level ozone can cause shortness of breath, coughing, wheezing, headaches, nausea, and eye and throat irritation.
Even in healthy adults, studies have shown that exposure to various levels of ozone pollution can cause decreased lung function. But, children, older adults and those who suffer from lung diseases like emphysema, bronchitis, pneumonia and asthma are especially vulnerable to ozone pollution.
For children whose lungs are still developing, high ozone smog levels pose an increased risk of respiratory issues because kids breathe more rapidly and inhale more air pollution per pound of body weight than adults. Children also breathe more through their mouths, which means that pollution bypasses the body’s first line of defense: the nose.
High levels of pollution can also be harmful to exercising adults. During exercise or strenuous work, individuals breathe more often and draw air more deeply into the lungs, often increasing their air intake by as much as 10 times. While exercising, individuals also breathe more through their mouths, bypassing the nose, the body’s natural air filter.
For more information about the health effects of ozone, visit the American Lung Association’s website.
Particle pollution refers to a mixture of solid particles and liquid droplets found in the air. Some particles such as dust, dirt, soot or smoke are large or dark enough to be seen with the naked eye, while other fine particles, such as acids, organic chemicals, metals, soil and dust particles and allergens, are so small they can only be detected by using an electron microscope.
With diameters of 2.5 micrometers and smaller, the particles are a size nearly 30 times smaller than a single strand of human hair.
Fine airborne particles come from a variety of sources including:
- Motor vehicles
- Power plants
- Wood burning stoves and fireplaces
- Forest fires
- Some industrial processes
Because of their minuscule size, fine particles can travel deep into the lungs, and in some cases, the bloodstream, causing serious health problems. Scientific studies have linked particle pollution exposure to a variety of health conditions including:
- Irritation of the airways, coughing or difficulty breathing
- Decreased lung function
- Aggravated asthma
- Development of chronic bronchitis
- Irregular heartbeat
- Heart attacks
- Premature death in people with heart or lung disease
As is the case with high ozone days, individuals are encouraged to modify their schedules to reduce time outdoors and avoid strenuous outdoor activities on days when elevated PM levels are expected.