Primary Pollutants Definition

Describing a primary pollutant, the Environmental Protection Agency (EPA) states it is "emitted into the atmosphere directly from the source of the pollutant and retains the same chemical form." The secondary variety forms as a result of chemical reactions that take place after a substance is released into the air. Understanding the characteristics of pollutants as well as how they get into the environment is crucial to understanding the effects.

Particulate Matter (PM)

Encompassing things as varied as dust, ash, smoke, sand and mist, PM or particulates occur both naturally and as the result of human actions. Natural sources include volcanic eruptions, wind-blown dust and wildfires. Anthropogenic source examples are automobiles, industrial processes, wood burning stoves and dust kicked up by construction projects. PM size is measured in microns. The most problematic are particulates 10 microns or less (PM10). These are small enough to be inhaled deep into the lungs, causing and aggravating asthma and other breathing disorders.

Sulfur Dioxide (SO2)

Introduced to the air mainly from the burning of coal, sulfur dioxide is a primary pollutant and the cause of acid rain. Normal water has a pH of about 5.5; SO2 can reduce this to as low as 4.0. The phenomenon was one of the first recognized primary regional pollutants, as the effects go beyond the cities where the industrial polluting processes are taking place. Acid rain acidifies lakes and streams, and damages trees and soils, among other negative consequences. Direct health effects also include eye, nose and throat irritation as well as headaches, nausea and dizziness.

Nitrogen Oxides (NOx)

Burning of fossil fuels is a big contributor to nitrogen oxide pollution. Automobiles and industrial smelting processes are also major culprits. Nitrogen dioxide is common and can at times be seen over cities as a reddish brown gas. The EPA points out that NOx "reacts with ammonia, moisture, and other compounds to form nitric acid and related particles." These particles contribute to all sorts of respiratory illnesses. Nitrogen is a nutrient, which when introduced in high quantities to water bodies, contributes to increased biochemical oxygen demand (BOD) and eutrophication, described as the enrichment of water by plant nutrients. Nitrous oxide (N2O) is a greenhouse gas.

Volatile Organic Compounds (VOCs)

VOCs are extremely reactive organic compounds. Harmful ground-level ozone is made from a reaction between NOx and VOCs when exposed to sunlight. Other health and environmental problems like VOCs entering aquifers are also a concern. Automobiles, industrial processes, cleaning solvents and paints are some of the leading VOC emitters.

Carbon Monoxide (CO)

Being odorless, colorless and tasteless makes the highly toxic gas CO extremely dangerous. Sources include incomplete combustion, malfunctioning furnaces, space heaters and fireplaces. According to the University of Virginia Health System, CO not only prevents your body from using oxygen properly, but damages the central nervous system.

Warning

Carbon monoxide detectors are essential for every building, considering the multitude of potential sources and the inherently dangerous nature of the gas if undetected.

Resources

• USGS: VOCs in Ground and Drinking Water