About Harmful Bacteria
Escherichia coli (E. coli) is a type of fecal coliform bacteria that live in the intestines of animals and humans. The presence of E. coli in the water along Lake Michigan’s shoreline is a strong indication that the water was recently contaminated by sewage or animal fecal waste. These wastes may contain many types of harmful disease-causing organisms. IDEM’s BeachAlert Monitoring and Notification System provides E. coli monitoring data on Lake Michigan's beaches and notifies the public about contamination advisories and beach closures.
Contamination Advisories and Beach Closings
In the event that a water sample collected from a monitored beach exceeds the Indiana single sample maximum water quality standard for E. coli of 235 colony forming units (CFUs) per 100 milliliters (ml), beach managers are required to issue a beach alert such as an Advisory or Closure. In order to warn beachgoers that there is an enhanced risk of illness due to contact with the water due to elevated E. coli levels, the beach managers have the discretion to determine whether to post an Advisory or a Closure, especially in cases where E. coli concentrations are significantly higher than 235 CFUs per 100 ml recreational water quality standard. The Lake Michigan Beach Monitoring and Notification Program page provides examples of the signage that beach managers post.
How Beach Water Gets Contaminated
Beach water can become contaminated by sewage when:
- Wastewater treatment plants malfunction
- Sanitary sewers overflow
- Combined sewer systems overload during rainstorms and discharge raw sewage and polluted run-off from streets into local waterways, including beach areas (see the Combined Sewer Overflows fact sheet on the IDEM Fact Sheets page)
- Boaters improperly manage human waste
- Septic systems malfunction
Beach water can also become contaminated by untreated storm water run-off from cities and rural areas. During rainfalls, snow melts, and other types of precipitation events, the fecal waste from pets, wildlife, and farm animals—which carries bacteria, viruses, and parasites—may be washed into nearby storm drains. Once this pollution has entered the sewer system, it is discharged usually untreated into waterways. Bacteria and pathogen levels in beach water may increase, and high bacteria levels can lead to more beach contamination advisories and closures. During drier weather, broken pipes or connections to poorly-maintained sanitary disposal systems may also contribute pathogens to storm drains.
Health Risks of Swimming in Contaminated Water
Swimmers are at risk for a broad range of adverse health effects if they swim in contaminated water. The most common short-term illness associated with swimming in such water is gastroenteritis. It occurs in a variety of forms with symptoms such as nausea, vomiting, stomachache, diarrhea, headache, and fever. Other, often minor, illnesses associated with swimming include ear, eye, nose, and throat infections.
Not all illnesses from a day at the beach are from swimming. Food poisoning from improperly refrigerated picnic lunches may also result in some of the same symptoms as swimming-related illnesses. Food poisoning symptoms include stomachache, nausea, vomiting, and diarrhea. The U.S. Food and Drug Administration’s guide to outdoor food safety provides additional information.
People Most Vulnerable to Contaminated Water
Children, the elderly, and people with weakened immune systems are most likely to develop illnesses or infections after swimming in polluted water. People who make full body contact with the water or those with exposed cuts are at greater risk than the general population when exposed to contaminated water.
How to Reduce Health Risks at the Beach
- Check the IDEM BeachAlert Monitoring and Notification System for beaches that are regularly monitored for E. coli and pay attention to alerts and posted signage about potential health risks at these locations.
- Choose swimming sites in less developed areas with good water circulation when swimming in areas not monitored regularly.
- Avoid swimming at beaches with visible discharge pipes or at urban beaches after a heavy rainfall.
- Wade or swim without submerging your head to avoid swallowing water and becoming exposed to pathogens.
- Avoid water contact if there are breaks in the skin, such as cuts or open sores.
Citizens can help protect beach water quality by cleaning up after pets and avoiding the feeding of shorebirds. Learn other ways to get involved and protect our environment!
With the IDEM BeachAlert app you can receive notifications of beach advisories and closures via email or text.