Heptachlor epoxide
Helms Water System
Heptachlor epoxide is a breakdown product of heptachlor, a highly toxic and carcinogenic pesticide banned in the U.S. since the 1980s.
Samples
Samples exceeding legal limit (MCL)
Samples exceeding
health guidelines
Testing results - average by year
| Year | Average result | Samples taken | Detections | Range of results |
|---|---|---|---|---|
| 2014 | 0.0355 ppb | 4 | 3 | ND - 0.0490 ppb |
| 2015 | 0.0285 ppb | 2 | 2 | 0.0260 ppb - 0.0310 ppb |
| 2016 | 0.0265 ppb | 6 | 4 | ND - 0.0510 ppb |
| 2017 | 0.0178 ppb | 4 | 2 | ND - 0.0430 ppb |
| 2018 | 0.0120 ppb | 2 | 1 | ND - 0.0240 ppb |
| 2019 | 0.0145 ppb | 2 | 1 | ND - 0.0290 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 | Lab ID | Result |
|---|---|---|
| 2014-01-20 | C316588-02 | 0.0487 ppb |
| 2014-01-20 | C316588-01 | ND |
| 2014-04-24 | C402892-01 | 0.0490 ppb |
| 2014-04-24 | C402892-02 | 0.0442 ppb |
| 2015-04-15 | 0.0260 ppb | |
| 2015-04-15 | 0.0310 ppb | |
| 2016-04-19 | CZ02799-02 | ND |
| 2016-04-28 | CZ05893-01 | 0.0490 ppb |
| 2016-07-20 | CZ08152-01 | 0.0310 ppb |
| 2016-07-20 | CZ08152-02 | ND |
| 2016-10-25 | CZ12962-01 | 0.0510 ppb |
| 2016-10-25 | CZ12962-02 | 0.0280 ppb |
| 2017-01-24 | CZ18152-01 | 0.0430 ppb |
| 2017-01-24 | CZ18152-02 | ND |
| 2017-05-11 | CA02652-01 | 0.0280 ppb |
| 2017-05-11 | CA02652-02 | ND |
| 2018-04-30 | CB02844-01 | 0.0240 ppb |
| 2018-04-30 | CB02844-02 | ND |
| 2019-06-06 | CC03216-01 | 0.0290 ppb |
| 2019-06-06 | CC03216-02 | ND |