Swimming in lakes or any other natural body of water involves risks. By far, the greatest risk is drowning caused in part by cloudy water, fast currents, submerged objects, or the lack of lifeguards. Water at Iowa’s state-owned swimming beaches is monitored to assess the public health risk from waterborne diseases that may result from immersion in the water.

Water samples from the beaches are analyzed for microorganisms, known as bacteria. These indicator bacteria are one-celled organisms visible only under a microscope. High levels of these bacteria indicate that the water has come into contact with fecal material. Indicator bacteria (Bacteria that normally are not pathogenic [disease causing] but serve as indicators of certain types of pollution such as sewage or manure runoff) are commonly used by state environmental agencies and by the U.S. EPA to determine the suitability of beaches for swimming-type uses.

The indicator bacteria for which we monitor do not themselves make you sick. These bacteria are easy to collect and analyze and are relatively safe to handle. They are very common in the environment, including lakes and rivers. High levels of these bacteria indicate that the water has come into contact with fecal material and that pathogens or disease-causing microorganisms may be present.  Levels of indicator bacteria above the water quality standard indicate a greater risk of becoming sick for people recreating in the water.

Disease-causing organisms, known as pathogens, exist as bacteria, viruses or parasites. Monitoring for these pathogens is expensive and difficult. Large volumes of water are needed to monitor for pathogens because they are present in such small numbers. Many different types of pathogens exist and testing for a single pathogen may not accurately assess the health risk present due to other pathogens. Because indicator bacteria occur in greater numbers than pathogens and are easier to isolate in a laboratory, monitoring for them is more cost-effective.

Fecal bacteria, and sometimes pathogens, are present in the intestines of warm-blooded animals, including humans. They are carried into the water with fecal material. Fecal contamination occurs due to improperly constructed and operated septic systems and sewage treatment plants, manure spills, storm water runoff from lands with wildlife and pet droppings, or direct contamination from waterfowl, livestock, or small children in the water.
 

Samples are collected weekly at 39 state owned beaches from the week prior to Memorial Day through Labor Day.   Water samples are taken at three locations along the beach and at three water depths (ankle-, knee- and chest-deep).The water from these locations is mixed to form one sample, which is placed in a sterilized bottle and taken to a laboratory for analysis.

The United States Environmental Protection Agency (EPA) has guidelines for the amount of bacteria acceptable in water bodies designated for primary body contact recreation, including swimming and water skiing. In Iowa, these waters are called "Class A waters". The bacteria level in the water is acceptable if the “geometric mean” is not greater than 126 colonies per 100 milliliters of water for E. coli bacteria. According to U.S. EPA guidelines, the “geometric mean” is calculated using at least five consecutive samples collected during a 30-day period. Additionally, Iowa also has a "one-time" standard for E. coli bacteria of 235 colony forming units per 100 milliliters of water.

Fecal contamination of beach water occurs due to improperly constructed and operated septic systems and sewage treatment plants, manure spills, storm water runoff from lands with wildlife and pet droppings, or direct contamination from waterfowl, livestock, or small children in the water. In Iowa, rain appears to be one of the most important factors in generating high levels of bacteria. Surface runoff after a heavy rainfall may transport high levels of fecal bacteria to the water at the beach. The rain also increases the sediment in the water causing it to be murky. Since bacteria are destroyed by sunlight, murky water aids in their survival.

Thousands of people swim at Iowa's beaches every year and most of them do not get sick. However, children, the elderly and people with weakened immune systems have an increased risk of becoming ill when in contact with contaminated water. A variety of diarrheal diseases, and other infections such as skin, ear and respiratory infections, are associated with swimming in contaminated water. Diarrhea is one of the most common illnesses associated with swimming. Diarrhea is spread when disease- causing microorganisms from human or animal feces get into the water. You can get diarrhea by accidentally swallowing small amounts of water that contains these microorganisms.

Avoid swimming after a heavy rainfall when indicator bacteria levels are generally higher and the water is murky. Avoid swallowing the water. Young children swimming at the beach can leak fecal bacteria and associated pathogens from their diapers, so change your child’s diapers often and visit bathrooms frequently. If you or your child has diarrhea, please stay out of the water because you may contaminate the water with fecal material. Although swimmers with diarrhea do not mean to contaminate the water, this is often how disease is spread.

High levels of indicator bacteria or pathogens have no influence on the quality of fish for human consumption. While alive, the fish is protected from water-borne contaminants by the skin, scales and mucus covering its body. Proper fish cleaning, rinsing, refrigeration and cooking should always be used.