More than 360,000 boaters use North Carolina’s waterways, and their numbers -- both commercial and recreational -- are increasing each year.

Clean water is important to all of us. Yet many of us who depend on water for our activities are sources of water pollution. People throw trash over the sides of boats; they spill gasoline while refueling; and they dump boat sewage into the water.

Polluted water is a health risk, and it can wreck a water-based economy. We need to protect our coastal waters from pollution. One way is to properly dispose of sewage from work boats and pleasure craft.

Untreated marine sewage poses risks to public health and the coastal environment. And some chemicals used to treat sewage may be toxic to marine life.

You can help keep our waters clean -- whether you own a large fishing boat with onboard toilets, or whether you own a small sailboat with a port-a-potty. Don’t dump your waste into the water. Use pumpout and dump stations instead.

Last year, the Division of Coastal Management and other organizations launched the Clean Marina program to further encourage marinas to be proactive in their approach to protecting the environment.

What is marine sewage?

Marine sewage is sewage discharged from installed toilets or portable toilets on boats. It is different from other types of sewage:

• It usually is more concentrated

• It often contains chemicals not found in other sewage

• All too often, it is released directly into
  our waters

Why is marine sewage a problem?

Marine sewage poses a number of threats to public health and the coastal environment:

Health risks

When you pump or dump marine sewage directly into the water, you can introduce disease-carrying microorganisms into that water. The bacteria and viruses found in raw or partially treated sewage can cause diseases such as gastroenteritis, hepatitis, typhoid and cholera. You may be at risk for these diseases if you swim in waters contaminated by marine sewage. Disease-causing organisms in the water can build up in the bodies of shellfish. You may at risk if you eat raw or partially cooked shellfish from sewage-contaminated waters.

Environmental hazards

Marine sewage can cause a host of problems for water and marine life:

• Sewage and Oxygen: Sewage in water decays. As bacteria and other microorganisms in water break sewage down, they use up oxygen. That's oxygen that fish and other marine life need to breathe.

• Nutrients: Marine sewage is high in nutrients, such as nitrogen and phosphorus. The nutrients can cause algal blooms -- large, fast-growing colonies of floating algae. These blooms can block light from other plants growing on the bottom. Once the nutrients that support the blooms are used up, the algae begins to die. As the algae decays, it uses up oxygen, reducing that available for fish and other marine life.

• Sewage Chemicals: Many boaters use chemical additives, such as chlorine and formaldehyde, to disinfect or control sewage odors on board. Most chemicals on the market today are biodegradable and are believed to be safe if used as directed by the manufacturer. But if you use the wrong type of additives or use more than recommended, those chemicals can be toxic to marine life.

Where is the risk greatest?

Problems associated with marine sewage are greatest in enclosed marinas and harbors, or other areas where water circulation is poor. Without good circulation, marine sewage is not dispersed and dissipated quickly. This allows sewage to build up and remain in an area for long periods of time. The larger the amount of sewage and the longer it is present, the greater a threat it is to human health and the environment.

Areas valued for their natural or recreational importance are at particular risk. North Carolina is home to several such areas, including the nationally recognized Albemarle-Pamlico estuarine system, the Atlantic Intracoastal Waterway, and the Cape Hatteras and Cape Lookout national seashores. Shellfish waters, nature preserves and beaches also are of economic importance to our state.