A Threat to Biscayne Bay

Effects of Sewage - Contaminated Water on Human Health

Q and A with Helena Solo-Gabriele



Water Quality Monitoring

Water Quality Standards

CDC's Division of Parasitic Diseases: FAQ about Recreational Waterborne Diseases

Keeping Marine Sewage Out of Our Waters

Haile, R.W., Witte, J.S., Gold, M., Cressey, R., McGee, C., Millikan, R.C., Glasser, A., Harawa, N., Ervin, C., Harmon, P., Harper, J., Dermand, J., Alamillo, J., Barrett, K., Nides, M., and Wang, G. (1999). The health effects of swimming in ocean water contaminated by storm drain runoff. Epidemiology 10: 355-363.

Pruss, A. (1998). Review of epidemiological studies on health effects from exposure to recreational water. International Journal of Epidemiology 27(1): 1-9.

Effects of Sewage-Contaminated Water on Human Health

What is sewage and how does it get into marine recreational water?
Sewage is used water that often contains human waste (feces and urine). It is usually pumped through a network of pipes from homes and businesses to a sewage treatment plant. Sometimes large sewage lines break and the contents leak into marine recreational waters and beaches.

What organisms can live in sewage-contaminated water?
A variety of organisms live in the human gastrointestinal tract. These organisms, including bacteria, viruses, and parasites, end up in human waste. Many of these organisms can be transmitted to other humans and animals, including marine organisms like shellfish, through contact with sewage-contaminated water.

For more information, visit CDC's Division of Parasitic Diseases: Waterborne Diseases or the National Academy Press: Microbial Pathogens in Coastal Waters.

What are the possible routes of exposure?
There are many routes of human exposure to the organisms in sewage-contaminated water:

oral - drinking contaminated water or eating contaminated seafood
dermal - getting contaminated water on your skin and in open cuts or rashes
aerosol - inhaling water droplets such as those from breaking waves.

What are the possible diseases caused by exposure to sewage-contaminated water?
The most commonly reported illness associated with oral exposure to contaminated water is generally called gastro-enteritis. Gastro-enteritis is an infection of the gastrointestinal tract. It can result from aerosol exposure to contaminated water, too. Oral exposure to sewage-contaminated water can also cause hepatitis, an infection of the liver. Dermal exposure to sewage-contaminated water often results in the infection of open cuts or rashes.

What are the symptoms of diseases caused by exposure to sewage-contaminated water?
Gastro-enteritis can affect different parts or the whole of the gastro-intestinal tract. Symptoms of gastro-enteritis include vomiting, pain in the abdomen, and/or diarrhea. Sometimes gastro-enteritis is accompanied by a fever. The illness can cause severe dehydration (loss of water and electrolytes) due to the vomiting and/or diarrhea. This is especially common in little children or persons who are already sick with other conditions.

Hepatitis can look exactly like gastro-enteritis. Severe cases cause people's skin to become yellow, or jaundiced, because the liver is not able to clear out its own bile. Bile contains the liver's waste products.

Infected cuts or rashes look swollen, red, and may have a thick yellowish discharge called pus. There is usually a lot of pain at the site of the rash or cut. Sometimes the infection causes a fever. Of note, eyes and ears can be infected in the same way.

For more information, visit Working with Sewage.

What is the risk to people from using sewage-contaminated recreational waters?
Pruss (1998) reviewed all significant existing studies of the effects of exposure to sewage-contaminated recreational water on human health. She found that most of these studies reported a dose-related increase of health risk in swimmers with an increase in the indicator bacteria counts in the recreational water. That means as the number of indicator bacteria in recreational water increased, so did the risk for sickness in humans using it. The indicator organisms that correlated best with the risk of sickness in humans were enterococci/fecal streptococci in marine and freshwater, and E. coli in freshwater. In both marine and freshwater, the increased risk of gastrointestinal illness was associated with water quality values ranging from only a few indicator counts/100 ml to about 30-indicator counts/100 ml. These values are low compared to water qualities frequently encountered in coastal recreational waters. Of note, the majority of these studies were conducted in the US and UK, with few studies evaluated in tropical marine recreational waters.

Haile et al. (1999), among others, evaluated the risk of reported gastrointestinal illness and other symptoms with respect to reported distance from storm drains with untreated run off in Los Angeles County, CA. Over 22,000 persons were interviewed concerning their health nine days after they exposed their faces to recreational beach waters. An increased risk of adverse health outcomes was associated with swimming in ocean water contaminated by untreated urban runoff. There was a significant dose response relationship. That is to say the closer a person swam to a storm drain, the greater their risk of having adverse health outcomes.

How do I know if the marine water is contaminated?
Traditionally, the quality of marine coastal water used for recreational purposes has been regulated by measuring concentrations of indicator microbes. The microbes monitored are those typically found in high concentrations in human feces. An elevated concentration of these microbes in coastal water would indicate that the water has been contaminated by human waste and is unsafe for recreational use.

For more information, visit Microbiological Monitoring of Marine Recreational Waters in Southern California or the US EPA 1999 Progress Report: Detecting and Characterizing Fecal Contamination and Its Sources in Ground and Surface Water (Watersheds and Aquifers.

How can I prevent sickness from sewage-contaminated marine water?
The easiest way to prevent sickness from sewage-contaminated marine water is to avoid exposure. Do not get the contaminated water on your skin, in your eyes or ears, or in your mouth. That means no swimming in contaminated water or eating raw or partially cooked food that came from sewage-contaminated water.

For more information, visit CDC's Division of Parasitic Diseases: Parasitic Pathways - Healthy Swimming Tip.