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EWG's Tap Water Database — 2019 UPDATE

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Uranium

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Uranium is a known human carcinogen. The federal legal limit for uranium is set at 30 micrograms per liter (corresponding to parts per billion), but utilities can also report uranium in picocuries per liter (pCi/L), which is a measure of radioactivity in water. EWG translated all uranium results to pCi/L using a conversion factor developed by the EPA. With this conversion approach, the limit of 30 ppb corresponds to 20 pCi/L. Drinking water with this much uranium would cause more than 4.6 cancer cases in a population of 100,000. California set a public health goal for uranium of 0.43 pCi/L. Read More.

Multiple forms of uranium can be detected in water, including uranium-234, uranium-235 and uranium-238. Uranium-234 is the most toxic form of uranium for human health.

 

162

Samples

4

Samples exceeding legal limit (MCL)

106

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
20123.87 pCi/L1810ND - 16.08 pCi/L
20133.25 pCi/L3320ND - 23.45 pCi/L
20146.31 pCi/L1915ND - 18.76 pCi/L
20155.36 pCi/L2516ND - 22.11 pCi/L
20164.22 pCi/L3319ND - 21.44 pCi/L
20175.12 pCi/L3426ND - 19.43 pCi/L

pCi/L = picocuries per liter

State and national drinking water standards and health guidelines

EWG Health Guideline 0.43 pCi/L

The EWG Health Guideline of 0.43 pCi/L for uranium was defined by the California Office of Environmental Health Hazard Assessment as a public health goal, the level of a drinking water contaminant that does not pose a significant health risk. Three most common uranium isotopes are U-234, U-235 and U-238. All isotopes of uranium are radioactive, and the total radioactivity depends on the ratio of isotopes. This health guideline protects against cancer.

EPA Maximum Contaminant
Level (MCL) 20 pCi/L

pCi/L = picocuries per liter

All test results

Date Lab ID Result
2012-02-28R12056878.04 pCi/L
2012-03-05R1206227ND
2012-04-10R1210107ND
2012-05-30R1215648ND
2012-06-20R1218349ND
2012-06-21R12185267.37 pCi/L
2012-06-25R12188610.67 pCi/L
2012-07-16R12213734.69 pCi/L
2012-07-17R12216546.70 pCi/L
2012-07-25R12227996.70 pCi/L
2012-07-31R12234854.02 pCi/L
2012-07-31R12234821.34 pCi/L
2012-08-02R122379214.07 pCi/L
2012-08-02R1223793ND
2012-08-14R122518016.08 pCi/L
2012-09-06R1228030ND
2012-10-30R1234016ND
2012-11-08R1235149ND
2013-03-11R1310330ND
2013-03-11R13103213.35 pCi/L
2013-03-11R1310327ND
2013-03-27R13130271.34 pCi/L
2013-05-13R13203345.36 pCi/L
2013-05-16R132115915.41 pCi/L
2013-05-16R13211512.68 pCi/L
2013-05-17R13213162.68 pCi/L
2013-05-17R1321312ND
2013-05-20R13215644.69 pCi/L
2013-05-20R13215624.02 pCi/L
2013-05-20R1321568ND
2013-06-05R13239093.35 pCi/L
2013-06-05R132391414.07 pCi/L
2013-06-05R13239212.01 pCi/L
2013-06-18R1326015ND
2013-06-18R13260191.34 pCi/L
2013-07-09R13293404.69 pCi/L
2013-07-09R1329337ND
2013-07-09R1329336ND
2013-07-09R13293352.01 pCi/L
2013-07-09R13293314.02 pCi/L
2013-07-09R1329338ND
2013-07-09R1329342ND
2013-07-09R1329344ND
2013-07-09R1329583ND
2013-07-10R13295932.68 pCi/L
2013-07-11R13298120.67 pCi/L
2013-08-07R1333783ND
2013-08-07R133377923.45 pCi/L
2013-08-07R13337812.01 pCi/L
2013-08-09R13342397.37 pCi/L
2013-12-20R1353342ND
2014-03-04R14077160.67 pCi/L
2014-03-04R14077188.04 pCi/L
2014-03-04R14077237.37 pCi/L
2014-03-04R1407728ND
2014-03-04R1407733ND
2014-06-12R14214926.03 pCi/L
2014-06-12R14214988.71 pCi/L
2014-06-17R1422333ND
2014-06-27R14240045.36 pCi/L
2014-07-01R14245626.70 pCi/L
2014-07-08R142542811.39 pCi/L
2014-07-16R14270585.36 pCi/L
2014-07-17R14272291.34 pCi/L
2014-07-30R142910814.74 pCi/L
2014-08-05R14298674.69 pCi/L
2014-08-11R14308976.70 pCi/L
2014-08-19R143228114.07 pCi/L
2014-08-19R143227918.76 pCi/L
2014-10-28R1442939ND
2015-03-06R15086595.36 pCi/L
2015-03-09R1508865ND
2015-03-12R1509544ND
2015-05-28R152065113.40 pCi/L
2015-06-04R1521792ND
2015-06-04R1521777ND
2015-06-04R15217793.35 pCi/L
2015-06-09R1522527ND
2015-06-15R15231900.67 pCi/L
2015-06-24R15252961.34 pCi/L
2015-06-24R15252985.36 pCi/L
2015-06-24R15253012.68 pCi/L
2015-07-15R15286746.70 pCi/L
2015-07-15R15286696.03 pCi/L
2015-07-22R152974510.72 pCi/L
2015-07-22R15297434.02 pCi/L
2015-07-23R1530002ND
2015-07-24R1530228ND
2015-08-05R153242715.41 pCi/L
2015-08-05R1532426ND
2015-08-11R153356816.75 pCi/L
2015-08-12R153368913.40 pCi/L
2015-09-01R153705022.11 pCi/L
2015-12-04R1552193ND
2015-12-17R15543266.70 pCi/L
2016-03-31R1612951ND
2016-06-23R1627644ND
2016-06-23R1627647ND
2016-06-23R16276494.69 pCi/L
2016-06-24R1627836ND
2016-06-24R16278316.70 pCi/L
2016-06-27R16281204.02 pCi/L
2016-06-27R1628115ND
2016-06-27R1628113ND
2016-06-27R1628111ND
2016-06-28R1628433ND
2016-06-28R1628435ND
2016-06-28R1628437ND
2016-06-29R1628651ND
2016-06-29R16286538.71 pCi/L
2016-06-30R16287533.35 pCi/L
2016-07-06R16295830.67 pCi/L
2016-07-06R16295824.69 pCi/L
2016-08-02R1634614ND
2016-08-02R16346126.03 pCi/L
2016-08-02R163461111.39 pCi/L
2016-08-03R16349300.67 pCi/L
2016-08-03R1634925ND
2016-08-18R16375191.34 pCi/L
2016-08-18R163756419.43 pCi/L
2016-08-22R163791719.43 pCi/L
2016-08-22R16379071.34 pCi/L
2016-08-29R163908420.77 pCi/L
2016-08-29R163915721.44 pCi/L
2016-08-30R16394181.34 pCi/L
2016-09-06R16405092.01 pCi/L
2016-09-19R16428951.34 pCi/L
2016-10-11R1646713ND
2017-03-14R1710138ND
2017-03-14R17101356.03 pCi/L
2017-05-30R172257910.05 pCi/L
2017-05-30R1722577ND
2017-05-30R17225745.36 pCi/L
2017-05-31R172275117.42 pCi/L
2017-05-31R17227536.70 pCi/L
2017-06-19R17261115.36 pCi/L
2017-06-21R17267724.69 pCi/L
2017-06-21R1726778ND
2017-06-21R172677910.72 pCi/L
2017-06-22R17269602.68 pCi/L
2017-07-11R17301354.69 pCi/L
2017-07-11R1730137ND
2017-07-17R17313046.70 pCi/L
2017-07-20R17322151.34 pCi/L
2017-07-20R17322191.34 pCi/L
2017-07-25R17327224.69 pCi/L
2017-07-25R17328113.35 pCi/L
2017-08-03R17345676.70 pCi/L
2017-08-03R17345653.35 pCi/L
2017-08-07R17350982.01 pCi/L
2017-08-07R17350999.38 pCi/L
2017-08-22R173803316.08 pCi/L
2017-08-28R17389306.03 pCi/L
2017-08-29R1739246ND
2017-08-30R173932519.43 pCi/L
2017-09-26R17445479.38 pCi/L
2017-10-20R17492234.69 pCi/L
2017-11-15R1753299ND
2017-11-15R17532954.02 pCi/L
2017-11-15R17532972.01 pCi/L
2017-12-07R1756877ND
2017-12-07R1756879ND