EWG's Tap Water Database — 2021 UPDATE


Tetrachloroethylene (perchloroethylene)

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Dry cleaning chemical tetrachloroethylene, or perc, can cause cancer. It pollutes soil and groundwater due to emissions from dry cleaning facilities, and automotive, metalworking and other industries. Read More.

The EPA considers tetrachloroethylene a likely human carcinogen. It has been linked with increased incidence of lung, breast and colon cancers. Tetrachloroethylene also damages the liver, kidneys and central nervous system. The California public health goal of 0.06 parts per billion, set to protect against cancer, is 80 times lower than the amount allowed by the federal government, which is a Maximum Contaminant Level of 5 parts per billion.

Click here to read more about carcinogenic VOCs.





Samples exceeding legal limit (MCL)


Samples exceeding
health guidelines

Testing results - average by year

YearAverage resultSamples takenDetectionsRange of results
20146.64 ppb880.900 ppb - 16.3 ppb
20155.65 ppb880.900 ppb - 15.3 ppb
20165.51 ppb880.800 ppb - 12.4 ppb
20175.08 ppb880.800 ppb - 11.5 ppb
20181.18 ppb440.800 ppb - 1.40 ppb
20190.825 ppb440.700 ppb - 0.900 ppb

ppb = parts per billion

State and national drinking water standards and health guidelines

EWG Health Guideline 0.06 ppb

The EWG Health Guideline of 0.06 ppb for tetrachloroethylene 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. This health guideline protects against cancer.

EPA Maximum Contaminant
Level (MCL) 5 ppb

The legal limit for tetrachloroethylene, established in 1991, was based on analytical detection limits at the time that the standard was set. This limit does not fully protect against the risk of cancer due to tetrachloroethylene exposure.

ppb = parts per billion

All test results

Date Lab ID Result
2014-01-082440580116.3 ppb
2014-01-08244057011.000 ppb
2014-04-02253346019.30 ppb
2014-04-02253345010.900 ppb
2014-07-092611030111.1 ppb
2014-07-09261102010.900 ppb
2014-10-01270987011.40 ppb
2014-10-012709880112.2 ppb
2015-01-07122970668.40 ppb
2015-01-07122970451.10 ppb
2015-04-15126429159.20 ppb
2015-04-15126428940.900 ppb
2015-07-15130231538.10 ppb
2015-07-15130231321.10 ppb
2015-10-06133994111.10 ppb
2015-10-061339943215.3 ppb
2016-01-05137632300.800 ppb
2016-01-05137632517.30 ppb
2016-04-05141156231.000 ppb
2016-04-051411564410.4 ppb
2016-07-01145836571.20 ppb
2016-07-01145836789.90 ppb
2016-10-051508855512.4 ppb
2016-10-05150885341.10 ppb
2017-01-05155296200.800 ppb
2017-01-05155296417.50 ppb
2017-04-05159507411.10 ppb
2017-04-05159507628.30 ppb
2017-07-07164263441.000 ppb
2017-07-07164263659.20 ppb
2017-10-05168925451.20 ppb
2017-10-051689256611.5 ppb
2018-01-10381586011.40 ppb
2018-04-04390699011.30 ppb
2018-07-03402015011.20 ppb
2018-10-04413089010.800 ppb
2019-01-09424957010.900 ppb
2019-04-10436562010.900 ppb
2019-07-16450138010.800 ppb
2019-10-10468296010.700 ppb