what Is Pollution and Where Does It Come From?

What Is Pollution, and Where Does It Come From?

Any addition to air, water, soil, or food that threatens humans' health, survival, or activities, or other living organisms. The particular chemical or form of energy that causes such harm is called a pollutant. Most pollutants are solid, liquid, or gaseous by-products or wastes produced when a resource is extracted, processed, made into products, or used. Pollution can also take the form of unwanted energy emissions, such as excessive heat, noise, or radiation.

In other words, a pollutant is a chemical or form of energy in the wrong place in the wrong concentration. For example, the ozone is a natural and important component of the stratosphere (the second layer). It shields the earth from most of the life-destroying ultraviolet radiation emitted by the sun. However, in the troposphere (the layer of the atmosphere closest to the earth), ozone is a dangerous air pollutant. Pollutants can enter the environment naturally (for example, from volcanic eruptions) or through human (anthropogenic) activities (for example, from burning coal). Most pollution from human activities Occurs in or near urban and industrial areas, where pollutants are concentrated. Industrialized agriculture 1s also a major source of pollution. Some pollutants contaminate the areas produced; others are carried by winds or flowing water to other areas. Pollution does not respect local, state, or national boundaries.

Some pollutants come from single, identifiable sources, such as the smokestack of a power plant, the drainpipe of a meat-packing plant, or the exhaust pipe of an automobile. These are called point sources. Other pollutants come from dispersed (and often difficult to identify) nonpoint sources. Examples are the runoff of fertilizers and pesticides (from farmlands, golf courses, and suburban lawns and gardens) into streams and lakes and pesticides sprayed into the air or blown by the wind into the atmosphere. It is much easier and cheaper to identify and control pollution from point sources than from widely dispersed non-point sources.

What Types of Harm Are Caused by Pollutants?

Disruption of life-support systems for humans and other species.
Damage to wildlife.
Damage to human health.
Damage to property and nuisances such as noise and unpleasant smells, tastes, and sights.

Three factors determine how severe the harmful effects of a pollutant will be. One is its chemical nature how active and harmful it is to living organisms. Another is its concentration, the amount per unit of volume or weight of air water, soil, or body weight.

A concentration of one part per million (1 ppm) corresponds to one part pollutant per one million parts of the gas, liquid, or solid mixture in which the pollutant is found; one part per billion (1 Ppb) refers to one part of the pollutant per one billion parts of the medium it is found in, and one part per trillion (1 ppt) means that one part of pollutant is found in one trillion parts of its medium. In a gas mixture, the reference is usually ppm, ppb, or ppt by volume; in liquids and solids, the reference is generally ppm, ppb, or ppt by weight. Parts per million, billion, or trillion may seem like negligible amounts of pollution. Nevertheless, concentrations of some pollutants at such low levels can seriously affect people, other animals, and plants. One way to lower the concentration of a pollutant is to dilute it in a large volume of air or water. Until we started overwhelming the air and waterways with pollutants, dilution was the solution to pollution. Now it is only a partial solution. The third factor is a pollutant's persistence-how long it stays in the air, water, soil, or body.

Degrad- able or nonpersistent pollutants are broken down completely or reduced to acceptable levels by natural physical, chemical, and biological processes. Complex chemical pollutants broken down (metabolized) into simpler chemicals by living organisms (usually by specialized bacteria) are called biodegradable pollutants. Human sewage in a river, for example, is biodegraded fairly quickly by bacteria. If the sewage is not added faster, then it can be broken down.

Many of the substances we introduce into the environment take decades or longer to degrade. Examples of these slowly degradable or persistent pollutants include the insecticide DDT and most plastics. Nondegradable pollutants cannot be broken down by natural processes. Examples include the toxic elements lead and mercury. The best ways to deal with non-degradable pollutants (and slowly degradable pollutants) are to not release them into the environment at all or to recycle or reuse them. Removing them from contaminated air, water, or soil is an expensive and sometimes impossible process. We know little about the possible harmful effects of 90% of the 72,000 synthetic chemicals now in commercial use and the roughly 1,000 new ones added each year. Our knowledge about the effects of the other 10% of these chemicals is limited, mostly because it is quite difficult, time-consuming, and expensive to get this information. Even if we determine the main health and other environmental risks associated with a particular chemical, we know little about its possible interactions with other chemicals or about the effects of such interactions on human health, other organisms, and life-support processes. A major problem in dealing with pollution and its effects is that people differ on the definition of a pollutant and acceptable levels of pollution-especially if they must choose between pollution control and their jobs. As the philosopher Hegel pointed out nearly two centuries ago, tragedy 1s not the conflict between right and wrong, but the conflict between right and right.

What can we do about pollution?

There are two basic approaches to dealing with pollution: prevent it from reaching the environment or clean it up if it does. Pollution prevention or input pollution control is a throughput solution. It slows or eliminates the production of pollutants, often by switching to less harmful chemicals or processes. Pollution can be prevented (or reduced) by the three Rs of resource use: Reduce, Reuse, Recycle.

Pollution cleanup or output pollution control involves cleaning up pollutants after they have been produced. This is an important approach, but environmentalists have identified several problems with relying primarily on pollution cleanup. First, it is often only a temporary bandage as long as population and consumption levels continue to grow without corresponding im- improvements in pollution control technology. For example, adding catalytic converters to cars has reduced air pollution, but increases in the number of cars and the total distance each travels (increased throughput) have reduced the effectiveness of this cleanup approach.

Second, pollution cleanup often removes a pollutant From one part of the environment only to cause pollution 1

another part. We can collect garbage, but the garbage is then typically either burned (perhaps causing air pollution and leaving toxic ash that must be put some- were); dumped into streams, lakes, and oceans (per- haps causing water pollution); or buried (perhaps causing soil and groundwater pollution). Third, 01ce pollutants have entered and become dispersed in the air and water (and in some cases, the soil) at harmful levels; it usually costs too much to reduce them to acceptable concentrations. Both pollution prevention and pollution cleanup are needed, but environmental scientists and some economists urge us to emphasize prevention because it works better and is cheaper. Prevention also helps eliminate some of the high costs and political difficulties of the government-mandated command-and-control regulatory approach. For widely dispersed and difficult-to-identify nonpoint pollution, hazardous wastes, and slowly degradable and nondegradable pollutants, pollution prevention is the most effective (perhaps only) approach. As Benjamin Franklin re- minded us long ago, "An ounce of prevention is worth a pound of cure."

An increasing number of businesses have found that pollution prevention pays. So far, however, about 99% of environmental spending in the United States is devoted to pollution cleanup, and only 1% to pollution prevention-a situation that environmental scientists and some economists believe must be reversed as soon as possible.

Both pollution prevention and pollution cleanup can be encouraged either by the carrot approach of using incentives such as various subsidies and tax write-offs or by the stick approach of regulations and taxes. A mix of both approaches is probably best, for excessive regulation and too much taxation can incite resistance and cause a political backlash. Achieving8 the right balance is a challenging task.

The countries of the former soviet union, many eastern European countries, China, most developing countries

are far behind in pollution control and prevention. Consider some of the environmental horrors found in various parts of the former Soviet Union: Of every 10 barrels of oil produced each day, about 1 is spilled-equivalent to one huge oil tanker spill every six hours. Indiscriminate use of pesticides has led to severe contamination of soil and water in many regions. The once-huge Aral Sea is disappearing because most of its water has been diverted for agri- culture. Severe erosion has depleted large tracts of farmland.

Past abuses and rapid and unpredictable political and economic changes are also taking an increasing toll on the incredible biodiversity found in these countries. Deposits of long-lived radioactive materials from the explosion of the Chernobyl nuclear power plant in 1986 have left large areas uninhabitable. There are thousands of unregulated dump Sites containing nuclear and toxic wastes. Some 14-16% of all territory in Russia has been designated as ecological disaster zones. As these countries struggle to transform their economies, little money is available for repairing such ecological damage. Even with adequate resources, it would take decades to clean up such widespread ecological devastation.