EWG's Tap Water Database — 2021 UPDATE



Hearthstone Manor

Hexachlorocyclopentadiene was historically used for the manufacture of currently banned pesticides, such as endrin, dieldrin and chlordane. It’s still used for production of flame retardants, resins and plastics.





Samples exceeding legal limit (MCL)


Samples exceeding
health guidelines

Testing results - average by year

YearAverage resultSamples takenDetectionsRange of results
20160.0767 ppb32ND - 0.120 ppb
20170.0750 ppb62ND - 0.330 ppb
20180.0920 ppb53ND - 0.160 ppb
20190.0520 ppb51ND - 0.260 ppb

ppb = parts per billion

State and national drinking water standards and health guidelines

EWG Health Guideline 2 ppb

The EWG Health Guideline of 2 ppb for hexachlorocyclopentadiene 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 harm to the stomach and intestines.

EPA Maximum Contaminant
Level (MCL) 50 ppb

The legal limit for hexachlorocyclopentadiene, established in 1992, was based on a toxicity study in laboratory animals conducted in the 1980s.

ppb = parts per billion

All test results

Date Lab ID Result