Why Did My Favorite Beach Close Today?

Power to the Peeples is an exclusive Earth911 series written by Bob Peeples, our resident chemical engineer and Program Manager of Earth911’s sister site Beaches911. Bob combines his extensive knowledge of the environment and how things work with an off-the-cuff sense of humor.

It may be because of a risk to your health if you swim there. Risk is probability, and probability is uncertainty. It may seem cold and callous to speak of any risk of human illness in terms of “acceptable numbers” until you realize that zero isn’t an available choice, and we are forced by natural variation to pick a different number.

All rivers, streams, and lakes contain naturally occurring algae, bacteria, viruses, and parasites. These microbiological organisms come from plants, animals, and sometimes human sewage. There are a variety of disease-causing microorganisms (called pathogens) in human and animal feces that survive in marine and freshwater environments. When we contact waters that have been contaminated, we expose ourselves to these pathogens and we risk getting sick. The concentrations of such organisms may be increased by agricultural, industrial, and residential activities. Stormwater, and treated and untreated sewage will eventually find its way to the creeks, the rivers, and the lakes. Agricultural and urban runoff coupled with improperly or partially treated sewage can be major contributors to microbiological pollution. The types and numbers of such organisms are dependent on what flows into the water. The water flow, temperature, level of acidity, chemical composition, amount of organic material, and other factors can also influence how many and what kind of organisms are present.

Most of the pathogenic water-borne organisms are acquired by ingesting contaminated water because they affect the digestive tract. Pathogenic organisms in feces such as Salmonella, Giardia, Campylobacter and Cryptosporidium are known to cause gastrointestinal illnesses. These pathogens cause diarrhea and sometimes vomiting. Although recreational water users may inadvertently swallow water, deliberately drinking from rivers, streams, or lakes is never recommended. Skin, ear, and eye infections can also result from contact with contaminated water. Recent studies indicate that respiratory illnesses, such as those that cause cold and flu-like symptoms, may also result from swimming in sewage-contaminated water.

Although there are a number of diseases that can be caused by exposure to recreational water, reported outbreaks of such diseases have been relatively rare. Most of the organisms in recreational waters are non-pathogenic or are in such low levels they do not cause disease. There is no way to be sure. Because natural bodies of water are so easily changed, scientists can only make general statements about the health risk of certain bodies of water; and can never say exactly what the condition of a specific body of water is at any particular time. We know that pollution increases after rain washes contaminants from land surfaces. This causes concentration problems in small sheltered beaches that have very little exchange with the primary water body and are used as “children’s pools”. The same sheltering features that make it less likely that your child will wash out to sea are the features that put them at higher risk of getting sick from each other’s sub-surface diaper accidents.

You can never eliminate risk. Instead, health professionals manage the risk of getting sick when swimming, surfing or otherwise being exposed to freshwater or seawater by establishing a statistical threshold for acceptable risk. The US Environmental Protection Agency has settled upon a maximum level of risk for ocean and bay waters of a 75% chance of 19 in every 1000 bathers contracting an illness. For the lakes, the accepted level of risk is a 75% chance of 8 in every 1000 bathers contracting an illness.

To tie these acceptable levels with some sort of water quality test, EPA used a 1982 study where water quality at several beaches was tested and then bathers were surveyed to determine if they developed symptoms after being exposed to the water. These studies were used to determine bacterial population counts that correlated with the acceptable level of risk by comparing the testing results to the number of people with symptoms. Because tests for pathogenic viruses, parasites, and bacteria are difficult, costly, and time consuming, EPA selected other bacteria that would serve as “indicators” of sewage contamination. Higher indicator bacteria levels suggest a higher risk of fecal contamination and a greater risk that pathogens are present. If waters exceed the acceptable level of risk, the public is advised that the area is unsuitable for recreational activities.

The system is not foolproof, because scientists are measuring indicators rather than directly measuring the pathogens. Nonpathogenic indicator bacteria can multiply and survive readily in certain types of water, so high levels of indicator bacteria do not necessarily mean the water is unsafe. Samples from bodies of water that exceed the standard only indicate the potential for human sewage to be present. On the other hand, even when water meets the guidelines there will always be a health risk associated with recreational activities.

The following suggestions are common sense, but they can help reduce exposures to recreational water quality hazards:

• Look for posted signs (and follow the advice on them).
• Avoid swimming for two to three days after a heavy rainfall, especially near storm drains.
• Avoid full immersion in water that may be contaminated.
• Do not swim in water that looks dirty, or smells unpleasant.
• Avoid swallowing river, stream, or lake water.
• Limit exposure to shallow water where there may be higher concentrations of pathogens.
• Prevent broken skin from directly contacting recreational water.
• There is a greater risk to those with compromised immune systems, the elderly and the very young.
• Do not add to the problem; use appropriate toilet facilities.