Chlorate in Oregon Drinking Water
Ranked by max chlorate detected (µg/L) · UCMR 3 data (2013–2015) · Data from EPA SDWIS & UCMR
Chlorate in Oregon: what the data shows
Oregon has 40 cities with chlorate data from the EPA's UCMR 3 program (2013–2015). Chlorate exceeded the 210 µg/L EPA lifetime health advisory in 14 of those cities. The state average max detected level is 305.9 µg/L. Chlorate is a disinfection byproduct that forms when chlorine dioxide or hypochlorite solutions are used to disinfect drinking water. It is most common in systems that use chlorine dioxide for taste-and-odor control or that store hypochlorite for extended periods. There is no federal MCL — the EPA lifetime health advisory is 210 µg/L. Chlorate can interfere with thyroid function by blocking iodide uptake, an effect of particular concern for pregnant women, infants, and people with thyroid conditions. Reverse osmosis and ion exchange (anion-specific) are effective at removing chlorate; standard activated carbon filters provide only modest reduction.
Cities exceeding 210 µg/L EPA lifetime HA (no MCL)
Chlorate data across Oregon
Each dot is a city with UCMR 3 chlorate testing data. Cities where chlorate exceeds the 210 µg/L EPA lifetime health advisory are highlighted. Size reflects population served.
Top 10 cities by chlorate level in Oregon
Highest Chlorate levels (µg/L)
All Oregon cities ranked by chlorate level
| # | City | Level | Level | Over HA? | Violations | Grade |
|---|---|---|---|---|---|---|
| 1 | Portland | 3000.0 µg/L | Over HA | 118 | F | |
| 2 | The Dalles | 1800.0 µg/L | Over HA | 54 | F | |
| 3 | Medford | 610.0 µg/L | Over HA | 44 | F | |
| 4 | Newberg | 537.0 µg/L | Over HA | 270 | F | |
| 5 | Grants Pass | 530.0 µg/L | Over HA | 78 | F | |
| 6 | Clackamas | 430.0 µg/L | Over HA | 21 | D | |
| 7 | Woodburn | 331.0 µg/L | Over HA | 50 | F | |
| 8 | Corvallis | 330.0 µg/L | Over HA | 38 | F | |
| 9 | Albany | 330.0 µg/L | Over HA | 35 | F | |
| 10 | Pendleton | 323.0 µg/L | Over HA | 43 | F | |
| 11 | Ontario | 320.0 µg/L | Over HA | 5 | B- | |
| 12 | Central Point | 318.0 µg/L | Over HA | 68 | D | |
| 13 | Beaverton | 260.0 µg/L | Over HA | 10 | F | |
| 14 | Bend | 250.0 µg/L | Over HA | 116 | F | |
| 15 | Mcminnville | 199.0 µg/L | No | 1 | B+ | |
| 16 | Happy Valley | 198.0 µg/L | No | 17 | F | |
| 17 | Ashland | 190.0 µg/L | No | 15 | D | |
| 18 | Forest Grove | 180.0 µg/L | No | 2 | B+ | |
| 19 | Lake Oswego | 176.0 µg/L | No | 20 | D | |
| 20 | Scappoose | 166.2 µg/L | No | 84 | F | |
| 21 | Sherwood | 160.0 µg/L | No | 7 | B- | |
| 22 | Boardman | 160.0 µg/L | No | 0 | C+ | |
| 23 | Tualatin | 140.0 µg/L | No | 0 | A | |
| 24 | Wilsonville | 130.0 µg/L | No | 10 | C+ | |
| 25 | Canby | 130.0 µg/L | No | 21 | D | |
| 26 | Troutdale | 130.0 µg/L | No | 2 | A- | |
| 27 | Salem | 120.0 µg/L | No | 108 | F | |
| 28 | Lebanon | 100.0 µg/L | No | 16 | F | |
| 29 | La Grande | 85.0 µg/L | No | 7 | B- | |
| 30 | Milwaukie | 84.4 µg/L | No | 1 | F | |
| 31 | Gresham | 73.0 µg/L | No | 0 | B | |
| 32 | Oregon City | 71.0 µg/L | No | 14 | D | |
| 33 | West Linn | 67.0 µg/L | No | 15 | F | |
| 34 | Rhododendron | 64.0 µg/L | No | 4 | B | |
| 35 | Gladstone | 57.0 µg/L | No | 8 | C | |
| 36 | Tigard | 56.0 µg/L | No | 3 | C | |
| 37 | St Helens | 41.8 µg/L | No | 33 | F | |
| 38 | Coos Bay | 40.0 µg/L | No | 14 | D+ | |
| 39 | Roseburg | 24.0 µg/L | No | 35 | F | |
| 40 | Lincoln City | 24.0 µg/L | No | 1 | B+ |
Frequently asked questions about chlorate in Oregon
Is chlorate in Oregon tap water dangerous?
Chlorate has no federal MCL. The EPA lifetime health advisory is 210 µg/L. 14 cities in Oregon exceed this level. Chlorate can interfere with thyroid iodide uptake, which is a particular concern for infants, pregnant women, and people with hypothyroidism.
Where does chlorate in Oregon water come from?
Chlorate is a byproduct of chlorine-based disinfectants — particularly chlorine dioxide and hypochlorite (bleach) solutions. Levels tend to be higher in systems that use chlorine dioxide for taste-and-odor treatment or store sodium hypochlorite at high concentrations or for long periods. Levels vary seasonally with disinfectant use.
How can I reduce chlorate exposure?
Reverse osmosis is the most effective home treatment for chlorate, typically removing 80–95%. Anion exchange systems also work but require regeneration. Standard activated carbon filters provide only limited chlorate reduction. Boiling does NOT remove chlorate.