What is pollution? The dictionary defines it as “the presence in or introduction into the environment of a substance or thing that has harmful or poisonous effects,” or “the action or process of making land, water, air, etc., dirty and not safe or suitable to use.”

Toxins from pollution affect almost a quarter billion people worldwide. In some of the worst polluted areas, babies are born with birth defects, children’s IQs are lower, and life expectancy can be as little as 45 years.

There are three primary mediums affected by pollution: land, water and air.

Land can be poisoned by trying to get too much from too little. Case in point is the overuse of fertilizer and/or not letting the soil regenerate itself by rotating crops. More traditional farming methods can be very efficient and non-polluting, converting waste products, like manure, into useful food. The fast-growth, high-yield factory-farming methods used extensively in this country can produce large quantities of food, but they overuse a substantial amount of chemicals. The crops from these “super farms” often receive huge quantities of pesticides and nitrogen/phosphorus rich fertilizers to boost crop yield. Excess amounts of these chemicals run off, polluting the environment, and sometimes producing food of questionable quality.

Land can also be polluted by household garbage and industrial waste. Americans produce about 250 million tons of garbage a year, consisting of stuff like plastics, grass clippings, glass, food scraps, newspapers, tires, paint and batteries. That’s more than 4 pounds of waste per person per day, according to the Environmental Protection Agency. Just over half the waste, some hazardous, ends up in landfills, some of it having a decay-life of thousands of years. Only about 34 percent is recycled.

A recent article in The Sylva Herald reported that lead, which is toxic to humans and animals, was leaching into land and water near Southwestern Community College’s firing range.

Water pollution occurs when foreign substances are introduced into streams, rivers, estuaries and oceans. Much of it comes from sewage, agricultural runoff, and/or heavy metals like lead or mercury from industrial waste. According to the EPA, 44 percent of streams, 64 percent of lakes and 30 percent of bays and estuarine areas in the United States are contaminated and not fit for fishing or swimming. Fish and shellfish concentrate mercury, which is highly toxic to humans, in their bodies.

When agricultural nutrients such as nitrogen and phosphorus flow into bodies of water (called eutrophication), they work just like fertilizer and make algae grow at excessive rates. The algae then blocks sunlight from other plants, which die, and their decomposition leads to even less oxygen in the water. This, of course, kills fish and other aquatic animals. The National Oceanic and Atmospheric Administration says 80 percent of ocean pollution comes from land runoff, which can severely affect marine life.

According to the United Nations, almost 800 million people worldwide do not have access to clean water, and about 2.5 billion don’t have adequate sanitation. Sewage and other contaminants get into the surface and underground aquifers. Untreated sewage causes pathogens to grow, and organic and inorganic compounds in bodies of water can actually change its composition, resulting in low levels of dissolved oxygen, necessary for fish.

Warming water, known as thermal pollution, is also a problem. It happens when a factory or power plant uses water to cool its operations and discharges hot water. This can cause the water to hold less oxygen, and the temperature change can also kill marine life. According to some studies, it is estimated that in the United States, almost half of the water withdrawn from water systems is used for cooling electric power plants.

We all breathe air composed of 99 percent nitrogen, oxygen, water vapor and inert gases. Air pollution occurs when other gases are added to the mix. Auto and diesel exhaust release smoke and soot containing millions of particles and hazardous gases, like oxides of sulfur, carbon and nitrogen. This can create acid rain and smog. Indoors, secondhand tobacco smoke can be hazardous to your health.

Air pollution can also be in the form of gases like methane, which warm the planet through the greenhouse effect. This gas is 20 times as potent as carbon dioxide in causing atmospheric warming. It is produced naturally, such as in wetlands by the fermentation of organic matter in the absence of oxygen. Livestock (there are 1.5 billion cows on the Earth), leaks from oil refineries, fracking and landfills all further contribute methane to the air.

Pollution is all around us all the time and affects us in many ways, known and unknown, causing mild discomfort at a minimum and illness as a worst case. Efforts at reducing or eliminating it are hampered by governments and industries more concerned about the present than the future.

Those who would like to ask me questions about any other science topic may e-mail inquiries to lynn@thesylvaherald.com.

Marcus Goodkind of Tuckasegee, a retired aerospace engineer, worked with the National Aeronautics and Space Administration as a manager at Kennedy Space Center on all the manned programs from Mercury to Shuttle, including Apollo 11, the first manned lunar landing.