Heptachlor epoxide
EPA Designation Regulated
EPA Classification Organic Chemicals
EPA Levels 1,2 zero MCLG (mg/L)
0.0002 MCLG (mg/L)
Alternative Names none
Sources Breakdown of heptachlor
Heptachlor epoxide is a beakdown product of heptachlor, a highly toxic and carcinogenic termiticide banned from most applications in the U.S. since 1988.


Heptachlor epoxide is formed when heptachlor breaks down in the environment.


Most uses of heptachlor to kill termites in homes and insects on far crops was canceled in 1978. The only permitted use of heptachlor products is for fire ant control in buried pad-mounted electric power transformers, and in underground cable television and telephone cable boxes.

Health Effects

Some people who drink water containing heptachlor epoxide well in excess of the maximum contaminant level (MCL) for many years could experience liver damage and may have an increased risk of getting cancer.

EPA Data Source: Heptachlor epoxide

EPA Definitions:

1Maximum Contaminant Level Goal (MCLG) - The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety and are non-enforceable public health goals.

Maximum Contaminant Level (MCL) - The highest level of a contaminant that is allowed in drinking water. MCLs are set as close to MCLGs as feasible using the best available treatment technology and taking cost into consideration. MCLs are enforceable standards.

Maximum Residual Disinfectant Level Goal (MRDLG) - The level of a drinking water disinfectant below which there is no known or expected risk to health. MRDLGs do not reflect the benefits of the use of disinfectants to control microbial contaminants.

(TT) Treatment Technique - A required process intended to reduce the level of a contaminant in drinking water.

Maximum Residual Disinfectant Level (MRDL) - The highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial contaminants.

2 Units are in milligrams per liter (mg/L) unless otherwise noted. Milligrams per liter are equivalent to parts per million.