EWG's Tap Water Database — 2021 UPDATE


Heptachlor epoxide

Edgewood Mobile Home Park

Heptachlor epoxide is a breakdown product of heptachlor, a highly toxic and carcinogenic pesticide banned in the U.S. since the 1980s.





Samples exceeding legal limit (MCL)


Samples exceeding
health guidelines

Testing results - average by year

YearAverage resultSamples takenDetectionsRange of results
20140.0675 ppb440.0550 ppb - 0.0850 ppb
20150.0290 ppb21ND - 0.0580 ppb
20160.0595 ppb220.0490 ppb - 0.0700 ppb
20170.0500 ppb110.0500 ppb
20180.0280 ppb110.0280 ppb

ppb = parts per billion

State and national drinking water standards and health guidelines

EWG Health Guideline 0.006 ppb

The EWG Health Guideline of 0.006 ppb for heptachlor epoxide 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) 0.2 ppb

The legal limit for heptachlor epoxide, established in 1991, was based on analytical detection limits at the time that the standard was set. This limit may not fully protect against the risk of cancer.

ppb = parts per billion

All test results

Date Result
2014-03-050.0620 ppb
2014-05-010.0850 ppb
2014-07-010.0680 ppb
2014-10-070.0550 ppb
2015-12-300.0580 ppb
2016-03-220.0700 ppb
2016-06-020.0490 ppb
2017-05-090.0500 ppb
2018-05-080.0280 ppb