Today, the Portland Water Bureau received results that Cryptosporidium, a potentially pathogenic microorganism, was detected in a water sample collected Wednesday, February 1, from the Bull Run watershed, which provides drinking water to Portland and neighboring communities. The lab results show that one individual Cryptosporidium oocyst was present in a 50-liter (~13 gallons) sample of water.
At this time, we do not believe there is any increased public health risk as a result of this most recent detection. The general public is not being asked to take any special precautions. We continue to recommend that people with severely weakened immune systems seek specific advice about drinking water from their health care provider.
The Portland Water Bureau currently does not treat for the parasite Cryptosporidium because of a variance issued by the State of Oregon Health Authority (OHA) in 2012. Instead, the Portland Water Bureau is required to conduct routine monitoring for Cryptosporidium and notify the public of any detections.
This detection at the intake is the fourth detection this year. January 2nd was the first detection since the Portland Water Bureau began operation under the variance in April 2012. Prior to that, the last time Cryptosporidium was detected was December 2011, when a single oocyst was also detected.
As required by the conditions of the variance, the Portland Water Bureau had been testing for Cryptosporidium at the source water intake twice a week. Since January 8th, the Portland Water Bureau began monitoring at the source water intake at least four times per week for one year to demonstrate whether the Cryptosporidium concentration in the source water is less than 0.075 oocysts per 1,000 liters.
“The Portland Water Bureau is carefully tracking these results and working closely with our partners at the Multnomah County Health Department and Oregon Health Authority,” said Water Bureau Administrator Mike Stuhr. “While the health risk of these results is low, we take seriously our commitment to protecting public health.”
The City continues to consult with the Multnomah County Health Department and OHA. Public health officials have determined that no special precautions for Portland’s drinking water are currently necessary for the general public.
“Historically, we cannot find any evidence of a cryptosporidiosis outbreak tied to drinking Bull Run water.” said Multnomah County Health Officer Paul Lewis. “The county’s ongoing disease surveillance has shown no unexplained increase in Cryptosporidium cases.”
The Water Bureau is continuing its’ investigation into the recent detections. Wildlife found in the Bull Run are the most likely source of the Cryptosporidium detections, however no specific source has been identified. The Water Bureau will notify the public if any additional precautions are necessary.
Additional information regarding Water Bureau’s treatment variance is available at www.portlandoregon.gov/water/lt2treatmentvariance. Customers with questions regarding water quality can call the Water Line at (503) 823-7525.