Problems We Found In Seattle, Washington Drinking Water


Analies Dyjak  |  Policy Nerd
**Updated July 17, 2019 to include current data

For Hydroviv’s water quality assessment of Seattle, Washington we collected water quality test data from the city’s 2019 Consumer Confidence Report and the U.S. Environmental Protection Agency. We cross referenced Seattle’s water quality data with toxicity studies in scientific and medical literature. The water filters that we sell at Hydroviv are optimized to filter out contaminants found in Seattle’s drinking water.

Where Does Seattle Source Its Drinking Water?

Seattle is very fortunate to have watersheds protected by the city and U.S. Forest Service. Seattle’s drinking and tap water comes from the Cascade Mountains down to the Cedar and Tolt Rivers where it’s extracted.

Disinfection Byproducts (DBPs) In Seattle’s Drinking Water

Disinfection Byproducts or DBPs are a category of emerging contaminants. DBPs are formed when chlorine-based disinfectants that are routinely added to the water supply to kill bacteria, react with organic matter. Seattle's water quality had elevated levels of two types of DBPs: Total Trihalomethanes and Haloacetic Acids. In treated water from the Cedar River, concentrations of trihalomethanes ranged from 18 to 53 parts per billion, and 15 to 42 parts per billion in Tolt River water. Concentrations of haloacetic acids ranged from 10 to 63 parts per billion in Cedar River water, and 15 to 42 in the Tolt River water. For a bit of perspective, the federal standard for trihalomethanes is 80 parts per billion and 60 parts per billion for haloacetic acids. Health and regulatory agencies have very little knowledge about the adverse health effects of DBPs, and their toxicity. EPA has stated that they have been linked to an increased risk of bladder cancer, as well as kidney, liver, and central nervous system problems.

Chromium 6 In Seattle’s Drinking Water

Chromium 6 is a highly toxic metal that is currently unregulated by the EPA. Chromium 6 pollution is associated with metal processing, tannery facilities, chromate production, stainless steel welding, and pigment production. According to the most recent report, levels of Chromium 6 reached as high as 0.116 parts per billion. For a bit of perspective, the California Water Boards reported that Chromium 6 concentrations should not exceed 0.02 parts per billion in drinking water. These concentrations are up to 5.8 times higher than the proposed “safe” threshold. EPA has acknowledged that Chromium 6 is a known human carcinogen through inhalation, but is still determining its cancer potential through ingestion of drinking water. Lung, nasal and sinus cancers are associated with Chromium 6 exposure. Ingestion of extremely high doses of chromium 6 compounds can cause acute respiratory disease, cardiovascular, gastrointestinal, hematological, hepatic, renal, and neurological distress which may result in death.

Lead In Seattle’s Drinking Water

Lead enters tap water through old lead service pipes and lead-containing plumbing. 10% of sites tested for lead in Seattle had concentrations over 3 parts per billion. EPA, CDC, and American Academy of Pediatrics all recognize that there is no safe level of lead for children. Additionally, municipalities are only required to test a handful of homes every few years, so the levels reported in Seattle’s annual water quality report might not reflect the lead levels in your tap water. Lead exposure can cause developmental issues, lowered IQ, and damages to the kidneys and brain.

It’s important to note that only a handful of contaminants are required to be included in annual Consumer Confidence Reports, and that there are hundreds of potentially harmful unregulated contaminants that aren’t accounted for. If you’re interested in learning more about water filters that have been optimized for Seattle’s drinking and tap water quality, feel free to visit to talk to a Water Nerd on our live chat feature or send us an email at

Other Articles We Think You Might Enjoy:
What Are Disinfection Byproducts?
Does Your Home Have Lead Plumbing? Here's How To Tell:
Chromium 6 In Drinking Water: What You Need To Know
Previous Post Next Post