Raw or poorly treated sewage can spread disease. Waterborne diseases can be transmitted to humans through water contact and contaminated shellfish. Shellfish feed by filtering food particles through their bodies. During feeding, bacteria from sewage can enter the shellfish body, thus contaminating the shellfish. When a person eats raw shellfish, the bacteria are then transferred to the person. In 1995 the Journal of the American Medical Association reported that outbreaks of viral gastroenteritis in Florida, Georgia, and Texas were the result of ingestion of raw shellfish. The journal concluded that the outbreak was caused by disposal of marine sewage by commercial and recreational boaters on or near shellfish harvesting sites. Studies also show the possibility of viral transmission in cooked shellfish. Click here for more information on the Watershed Management Bureau Shellfish Program.
Sewage in waterbodies can lower oxygen to levels that are harmful to aquatic life. Organic matter from the sewage is decomposed in the water by bacteria, (Fact Sheet BB-14) which use oxygen during the process. As a result of the reduced oxygen levels, fish, other aquatic animals and plants are stressed. If the oxygen depletion is extreme, it can result in species death.
Sewage contains phosphorus, (Fact Sheet BB-20) which is the plant nutrient that controls algal growth. The overboard discharge of sewage can contribute to algal blooms. When the resulting algae die and decompose they contribute to oxygen depletion. As previously stated, oxygen depletion can result in species death.
Areas that are most likely to be affected by improperly disposed sewage are sheltered waters with low flushing rates, waters with significant recreational value, areas set aside for shellfish harvesting, state and federally designated significant habitats such as those in Coastal Zone programs, as well as waters designated by the Environmental Protection Agency (EPA) as "No Discharge Areas".
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