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Health Risks to People Swimming Near Storm Drains

Illnesses listed below generally are associated with swimming in water contaminated with urban runoff:
  • Earaches
  • Sinus Problems
  • Diarrhea
  • Fever
  • Rashes

Study findings revealed that individuals who swim in front of flowing storm drains are 50 percent more likely to develop a variety of symptoms than those who swim 400 yards away from the same drains.

Photo courtesy of Dr. Rachel Noble

What are they?

Microorganisms (including bacteria, viruses, and protozoans) are essential to all forms of life. There are billions of types of micro-organisms that serve as building blocks for all kinds of ecosystems around the world. Most microorganisms are beneficial; they fill important miss such as helping humans digest food, aiding in the proper treatment of wastewater, and carrying out functions necessary to sustain the food chain. These helpful microorganisms are known as antigenic.

Electron micrograph of bacteria (large spheres) and marine viruses (small spheres) from water collected from near a flowing beach storm drain.

Most of these are natural marine viruses, but some may cause illnesses in swimmers.

The microorganisms that can cause harmful diseases are called pathogenic. Listed below are the three common microorganisms associated with polluted water:

Bacteria – these tiny (13,000 individuals = one inch) single-celled organisms are present in the bodies of all living creatures, including humans. Bacteria play a vital role in processes such as decomposition and digestion. Bacteria can be found in large numbers in raw sewage, effluents, and in natural waters. Some well-known diseases mused by pathogenic bacteria include cholera, dysentery, shigellosis, and typhoid fever.

Viruses – too small to be recognized by ordinary light microscopes, viruses am generally recognized by the symptoms that they produce in the host. All viruses are parasites and must grow on living tissue. Many viruses are associated with feces, and are expected to be found in domestic wastes. Because many viruses can survive for extended periods of time in natural waters and can occasionally withstand the treatment process, they pose a public health concern. Viruses of concern that are transported in water include hepatitis A, Norwalk-type virus, rotavirus, and adenovirus.

Protozoans – these single-celled organisms can grow up to 5 millimeters long, and are found almost entirely in aquatic environments. Pathogenic protozoans compose approximately one-third of the entire class, and can muse serious health problems such as gastrointestinal disease, dysentery, and ulceration of the liver and intestines.

It is important to keep in mind that seawater typically contains about 1 billion bacteria and 1 trillion viruses that are not pathogenic to humans.

Where do they come from?

Pathogens may enter waters through point and non-point sources, while others may occur naturally in the environment. Some point sources are wastewater treatment facilities and combined sewer overflows. Non-point sources include land and road runoff, human sewage from recreational boats, and septic systems.

The Hyperion Sewage Treatment Plant has greatly reduced the number of pathogens that are released into the environment through the disinfectant processes. However, treatment is not always 100% effective and breakdowns in facilities sometimes occur. During heavy rains, there is too much water for the sewage treatment plant to handle, and some untreated or partially treated water maybe disposed into the Santa Monica Bay.

Wildlife, domestic animals and birds may also contribute pathogens to the environment.

Some Symptoms and Illness
Gastroenteritis (includes diarrhea and abdominal pain), salmonellosis, and cholera.
Fever, common mid, gastroenteritis, diarrhea, respiratory infections, and hepatitis.
Gastroenteritis, giardiasis (including diarrhea and abdominal cramps), and dysentery.

Protecting Yourself

There are measures you can take to reduce the chances of becoming ill when swimming in ocean waters. Children, the elderly and people with chronic illnesses should be extra careful.

  1. Swim in areas with good water circulation rather than in protected inlets
  2. Don’t put your head underwater
  3. Stay out of the ocean for up to 72 hours after a rainstorm

In 1992, the Santa Monica Restoration Bay Project published a finding titled, An Epidermiological Study of Possible Adverse Health Effects of Swimming in Santa Monica Bay which concluded that recreational activity (e.g. swimming, surfing, etc.) near storm drain flows caused illnesses.

Thanks to the Narragansett Bay University of Rhode Island, Office of Marine Programs for the information on bacteria contained on this page.