Types of Pollution: Air Pollution and Water Pollution

pollution picture showing smoke from a smokestack

The types of pollution problems confronting people in the United States get described in general terms related to either the ecosystem, such as air pollution or ocean pollution, or to a human sense, such as noise pollution or light pollution.

Scientists studying these different types of pollution tend to focus on two separate but interrelated questions:

  • What is the source of the pollution?
  • What types of pollution comes from those sources?
Identifying the types of pollution of concern to people and communities can be as easy as testing samples of air soil and water for chemicals such as carbon dioxide or mercury. Identifying the source of the pollution can be more difficult, depending on the pollutant in question because air and water, along with the pollutants they carry, naturally move across boundaries.

Sometimes scientists address the sources of pollution question by dividing it between point source and non-point sources. Point source pollution usually refers to specific, identifiable sources of a specific pollution concern, such as an oil spill or coal ash spill that directly discharge material into the water. Non-point source pollution refers to cases of pollution that can not be traced to one definitive source, or pollution that comes from multiple sources, making the problem more difficult to solve. Urban smog problems for example, result because of contributions from many individual transportation and industrial sources.

What is Smog?

The term smog, first used by H.A. Des Voex in 1905, described the foggy conditions in urban areas resulting from the sulfur dioxide emissions coming from the newly created smokestacks of the industrial revolution.

Today's urban smog problems, primarily photochemical smog, result when sunlight breaks down chemicals such as volatile organic compounds (VOCs) and nitrogen oxides (NOX) into their constituent parts. Once broken down, the now free oxygen molecules can link up with the oxygen in the air (O2) and create ozone 3, a variation of oxygen, with one additional oxygen molecule attached to it. While VOCs and NOx occur naturally, anthropogenic (human initiated) sources remain the focal point of policy analysis.

Volatile Organic Compounds (VOCs), a group of chemical compounds, share some common characteristics. First, the organic designation means that the compound is almost always composed of carbon (C) and hydrogen (H) molecules. Volatility refers to the evaporative quality of the compound. Anyone pumping their own gasoline and immediately notices the smell of gas experiences a quick lesson regarding gasoline's high degree of volatility.

Motor vehicle emissions represent the primary source of VOC emissions. However, evaporation of gasoline, solvents, oil-based paints, and hydrocarbons from the petrochemical industry are also significant sources. NOx result from the combustion of fossil fuels such as oil and gas, with motor vehicles the primary primary source, followed by fuel burning in homes, businesses, factories and power plants.

Water Pollution

Descriptions and discussions of types of water pollution often mirror those of air pollution, with researchers attempting to identify the types of pollutants and sources of pollutants in the water that can cause harm to human health.

Water pollution issues also easily divides into fresh water and salt water categories. Fresh water from rivers and lakes, for example, provides drinking water for large populations. The recent example of a harmful blue-green algal bloom in Lake Erie closing down Toledo's water system exemplifies the dangers associated with the management of fresh water resources.

Algal blooms also threaten salt water environments, causing concern for both human health and economics. Red Tide in the Gulf of Mexico, for example, can cause paralytic shellfish poisoning and consequently halt the local shell fish industry.

Coastal Dead Zones

Coastal dead zones, areas of oxygen depleted waters incapable of supporting marine life, occur seasonally, and they often are situated along areas where river mouths intersect with coastal waters. Nutrients from agriculture runoff collect and flow down river to the ocean, creating a super supply of food for the local phytoplankton, single-celled plants, that grow into large groups called algae blooms. When the blooms die and fall to the ocean floor, the decomposition process depletes the area of oxygen.

The Gulf of Mexico dead zone, the largest in the United States, results from agriculture run off from the farm belt around the Mississippi River. The run off flows to the Gulf of Mexico causing a seasonal dead zone.

Since it was first discovered in 1972, researchers from the National Oceanic and Atmospheric Administration (NOAA) studied the Gulf dead zone causes and effects. The forty year dead zone history shows that, despite attempts to reduce agriculture run off levels, the dead zone maintains itself and occasionally reaches record levels.

Natural causes serve as the primary triggers for the second type of dead zone. For example, irregular northerly summer winds along the Oregon Coast cause coastal waters to upwell, or turn over. The colder water that is pushed to the surface contains sufficient nutrients to support the algae bloom and decomposition process.

The 2006 dead zone episode lasted close to four months and covered the northern half of the Oregon coast with probable intrusion into the southern Washington coast. Dead crabs, sea cucumbers and other marine organisms were documented along the length of the dead zone.

Because the ocean animals associated with dead zone episodes suffer losses, area coastal communities economically dependent on their offshore waters also suffer losses.

Other Types of Pollution

Separating types of pollution into air and water pollution represents an idealized approach to the topic. Various issues such as Mining and the Environment and Trade and the Environment create a variety of air and water pollution problems, depending on the specific issue under consideration. The links in the boxes on the right hand side of the column point to articles that examine a variety of common air and water pollution issues.

© 2011-2014 Patricia A. Michaels