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E. coli Monitoring in Utah's Waters

What is E. coli?

Escherichia coli or E. coli is a type of bacteria commonly found in the intestines and feces of healthy warm-blooded animals and humans.

Why should I care about E. coli?

While E. coli are not generally harmful themselves, their presence indicates that other pathogenic microorganisms might be present. E. coli is a good indicator of the presence of fecal contamination and possible disease-causing bacteria or viruses in water. Health officials use the presence of E. coli to determine if the public needs to be notified of a health risk.

How does E. coli affect individuals?

Most strains of E. coli are not dangerous to people. However, some can cause illness such as diarrhea, urinary tract infections, and other infections. Some infections are very mild, but others are severe or even life-threatening. More information on the health effects of E. coli can be found at the Center for Disease Control and Prevention.

How does E. coli get into lakes and reservoirs?

E. coli comes from human and animal waste from such sources as improper waste dumping, faulty septic tanks or sewer systems, domesticated animals—including dogs and livestock, large concentrations of waterfowl and other wildlife, and stormwater runoff. Pollution of all kinds, including E. coli, are typically higher after rainstorms since water draining into streams and lakes travels over lawns, farm fields, sidewalks, and streets which may contribute sources of fecal contamination.

Are all waters tested for E. coli?

No. While the Utah Division of Water Quality (DWQ) has an E.coli monitoring program, it is not possible to test all waters in the state where people may recreate. DWQ takes a tiered monitoring approach to sampling. Each recreation season from May through October, DWQ monitors many of Utah’s high priority recreation lakes and reservoirs (Tier 1). Rivers and streams are sampled following a targeted rotating basin schedule (Tier 2).

Why is my lake (not) being tested for E. coli?

Ideal monitoring would involve collecting samples weekly at all locations throughout Utah, but monitoring resources are limited. Therefore, testing for potential E. coli contamination is focused on areas where people most frequently recreate.  Each year, DWQ works with local health departments to prioritize highly recreated water bodies across Utah. See the sampling map for the priority water bodies sampled for E. coli.

Less frequented lakes and reservoirs will be sampled in the coming years. Current monitoring plans include sampling at these targeted water bodies once a month from May through October. More frequent sampling may be required at specific lakes or reservoirs when the data suggests that E. coli densities are high. Ultimately, DWQ does intend to sample and assess all lakes and reservoirs in the State as resources become available. 

What is my risk if there is an advisory?

While E. coli is an indicator of fecal contamination and may not be a direct cause of illness, the threshold of 409 most-probable number of density counts per 100mL of water sample (MPN) adopted to issue a swimming advisory relates to a risk factor of 8 illnesses per 1,000 swimmers. As the value of the MPN increases above 409 MPN, the risk of illness if exposed to contaminated waters also increases.

Different waterbodies have different numeric criteria based on their beneficial use as outlined in Utah State Code R 317-2. All waters of the State are protected for contact recreation (Class 2A and 2B), and some waters are classified as drinking water sources (Class 1C). Class 2A waters are protected for frequent primary contact, while Class 2B waters are protected for infrequent primary contact.

To remove the advisories, there must be five consecutive samples under the threshold for the beneficial use class, and the long term average value of all the samples must be below the 30-day numeric criteria. This lower value is more protective of long term exposure. These values have been adopted from the US EPA.

How can I reduce my risk of E. coli exposure?

To reduce potential health risks, you should assume all surface waters contain some E. coli whether or not it has been monitored or an advisory has been issued. This means you should make sure you do not swallow the water, or if you have touched the water, make sure to wash your hands before you touch your mouth or eyes. The single most important way to prevent person to person spread of E. coli is careful hand washing.

Should I be concerned about swimming or boating because of E. coli?

You need to be aware of the potential health issue and avoid ingestion of potentially contaminated water. You may have been swimming and boating for years in waters that have E. coli. However, until DWQ adopted a field sampling method, the water was not routinely tested. We are now trying to educate, not alarm, the public about potential risks in all surface waters. Most samples collected so far indicate the risk of illness is not about a level of concern. When we do see an increased risk of illness from contamination, additional health advisories will be made and signs will be posted at the site.

Is the E. coli in lakes and streams the same as E. coli in food contamination?

Not necessarily. E. coli O157:H7 is a strain of E. coli which may be present in streams and lakes, but is most commonly spread through contaminated meats and vegetables and direct contact with infected people and animals. Waterborne transmission is possible through swimming and ingestion of water contaminated by E. coli. Additional information on E. coli O157:H7 can be found at the Center for Disease Control and Prevention.

Can fish from the lake be contaminated because of E. coli?

Probably not. Because fish are not warm-blooded, E. coli cannot live in the fillets. However, the water covering the fish could contain E. coli, as well as the guts of the fish. Uncooked fish may well have E. coli contamination. Wash and cook the fish, and wash your hands after handling fish and lake water to reduce your risk.

What is being done to reduce the E. coli?

The primary objective of DWQs E. coli monitoring program is to monitor popular swimming and recreation areas to determine if they are high in E. coli. If problems are discovered through testing, additional monitoring will occur to identify areas that might contribute bacterial contamination. This is a difficult task due to the nature of E. coli pollution, since E. coli can come from many different sources and can be spread throughout a watershed.

Once the sources are known, field investigations can assist scientists and managers to identify problem areas and develop strategies to reduce pollution. While broken sewer lines or faulty septic systems can be difficult to find and repair, some sources can be corrected using common sense and care to reduce pollution. Often, this can include simple measures to prevent human or animal waste from being introduced into our waterways.