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Cryptosporidium and drinking water

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Find Cryptosporidium test results and learn how we're changing our water treatment to address Cryptosporidium. If you have a condition that puts you at greater risk from Cryptosporidium in drinking water, find out how you can reduce your risk.
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Information about Cryptosporidium

Unfiltered surface water sources, such as the Bull Run Watershed, are required to be treated for Cryptosporidium. Cryptosporidium is a potentially disease-causing microorganism found in many surface waters in the U.S. From 2012 to 2017, the Water Bureau was granted a variance to these requirements by the Oregon Health Authority (OHA). This variance was revoked in December 2017 due to a series of low-level detections for Cryptosporidium in early 2017. We entered into a Bilateral Compliance Agreement with OHA that is in effect from December 2017 to 2027, when the new filtration facility will be operational.

Photo of woman with long blond hair wearing a white lab coat and purple gloves in a lab using a pipette.

As a result, the Portland Water Bureau does not currently treat for Cryptosporidium, but is required to do so under the drinking water regulations. Portland is working to install filtration by 2027 under a compliance schedule with Oregon Health Authority. In the meantime, the Water Bureau is implementing interim measures such as watershed protection and additional monitoring to protect public health. Consultation with public health officials has concluded that at this time, customers do not need to take any additional precautions.

Exposure to Cryptosporidium can cause cryptosporidiosis, a serious illness. Symptoms can include diarrhea, vomiting, fever, and stomach pain. People with healthy immune systems recover without medical treatment. According to the Centers for Disease Control and Prevention (CDC), people with severely weakened immune systems are at risk for more serious disease. Symptoms may be more severe and could lead to serious life-threatening illness. Examples of people with weakened immune systems include those with AIDS, those with inherited diseases that affect the immune system, and cancer and transplant patients who are taking certain immunosuppressive drugs.

The Environmental Protection Agency has estimated that a small percentage of the population could experience gastrointestinal illness from Cryptosporidium and advises that customers who are immunocompromised and receive their drinking water from the Bull Run Watershed consult with their health care professional about the safety of drinking the tap water.

Several Portland-area drinking water providers receive their water from Bull Run. To learn if your drinking water comes from Bull Run, please contact your local drinking water provider.

Is Portland's drinking water safe to drink?

At this time, we and our public health partners at Multnomah County and the Oregon Health Authority continue to believe Bull Run water is safe to drink and there is no need for the general public to take additional precautions. As always, we recommend that people with severely weakened immune systems seek specific advice from their health care providers about drinking water.

How the Water Bureau is protecting public health

While the filtration treatment facility is being built, we are following interim measures to reduce the risk of Cryptosporidium from the Bull Run Watershed through:

A photo of a man with brown hair, goatee, and glasses wearing a lab coat looking into a large, white microscope in a lab setting.
  • Watershed protection: We are maintaining all existing City of Portland protections on the Bull Run Watershed and conducting field inspections and environmental sampling to monitor for potential sources of Cryptosporidium.
  • Monitoring for Cryptosporidium: We are testing for Cryptosporidium from the Bull Run raw water intake at least twice a week. If Cryptosporidium is detected, testing increases to four times per week as long as detections continue. Test results are posted on the Cryptosporidium monitoring results page.
  • Public notification: We notify the public of all detections through press releases to local media. We also conduct targeted outreach to medical providers who work with people most at risk for Cryptosporidium infection, such as people with AIDS, people with inherited diseases that affect the immune system, and cancer and transplant patients who are taking certain immunosuppressive drugs.
  • Coordination with public health: We continue to consult with state and local public health officials in monitoring for potential effects of Cryptosporidium in drinking water. 

Protecting yourself from Cryptosporidium in drinking water

Exposure to Cryptosporidium in drinking water, especially for those with a condition that severely weakens their immune system, can lead to potentially serious illness. While the general public does not need to take additional precautions for Cryptosporidium, people with compromised immune systems may wish to take the precautions listed below. If you choose to store boiled, filtered, or distilled water in water bottles and ice trays, per the options below, clean them well with soap and water before you fill them.

  • Safe commercially bottled water: Water labeled with any of the following messages has been processed by a method effective against Cryptosporidium: reverse osmosis, distilled, filtered through an absolute 1 micron or smaller filter, or "one micron absolute."
  • Boiling water before consuming: Boiling is the best extra measure to ensure that your water is free of Cryptosporidium and other microbes. Heating water at a rolling boil for one minute kills Cryptosporidium and other microbes. After the boiled water cools, put it in a clean bottle or pitcher with a lid and store it in the refrigerator. Use the water for drinking, cooking, or making ice.
  • Filtering your tap water: Some, but not all, home water filters remove Cryptosporidium. Filters that have the words "reverse osmosis" on the label protect against Cryptosporidium, as do filters with "absolute one micron." Also look for the words "cyst reduction" or "cyst removal" for a tested filter that works against Cryptosporidium. The wording should indicate that the filter is listed and labeled to NSF/ANSI standard 53 or 58 by an ANSI-accredited certification organization. Filters collect microorganisms from your water, so someone who is not immunocompromised should change the filter cartridges for you; if you do it yourself, wear gloves and wash your hands well with soap and water afterwards. Filters may not work as well on Cryptosporidium as boiling does because filters may sometimes have manufacturing flaws that allow a small amount of Cryptosporidium to get past the filter. Poor filter maintenance or failure to replace filter cartridges as recommended by the manufacturer can also cause your filter to fail.
  • Using a home distiller: You can remove Cryptosporidium and other microorganisms from your water with a home distiller. If you use one, you need to carefully store your water. After purification, put the water in a clean bottle or pitcher with a lid and store it in the refrigerator.

Additional Cryptosporidium information can be found on the Centers for Disease Control and Prevention website.

How Cryptosporidium gets in the water

Cryptosporidium enters surface water sources when feces that contain Cryptosporidium enter the water. Fortunately, the Bull Run Watershed is free of the sources of Cryptosporidium most commonly associated with disease outbreaks, such as livestock and human sewage. Wildlife scat is the most likely source of Cryptosporidium in the Bull Run Watershed. Heavy rains in the watershed can increase the chances of Cryptosporidium moving from animal scat into water.

Portland's Cryptosporidium reports

Find our most recent Cryptosporidium test results

Watershed Protection Annual Report

Monitoring for Cryptosporidium: Monthly raw water intake reports

Public notification annual report

Bilateral Compliance Agreement quarterly reports

Previous reports are available upon request.