EWG's Tap Water Database — 2021 UPDATE


Heptachlor epoxide

Status: National drinking water standard exists


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




states detected


utilities detected

1.8 million

people served


states over health guideline


utilities over health guideline


people served over health guideline

Health concerns for heptachlor epoxide


Hormone disruption

Harm to the liver

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

States reporting heptachlor epoxide in drinking water

State UtilitiesPeople Served UtilitiesPeople Served
New York134,0003202,000
North Carolina3221,6343853,875

Filtering technologies that reduce heptachlor epoxide

carbon filter icon

Activated Carbon

reverse osmosis icon

Reverse Osmosis

Utilities with the highest amounts of heptachlor epoxide, 2017-2019

UtilityLocationTestsAverage levelPeople served
Aloha Gardens UtilitiesNew Port Richey, FL12 of 120.116 ppb8,136
Ashebrook ParkDenver, NC22 of 240.101 ppb231
Riddle FarmBerlin, MD1 of 20.0850 ppb600
Westwood S/dHoliday, FL8 of 80.0774 ppb344
Royal Acres S/dCary, NC12 of 150.0562 ppb61
Dalewood-monteray Water SystemDenver, NC7 of 90.0530 ppb142
Harbour Light Estates CommunitySalisbury, MD1 of 20.0500 ppb95
Oak Hill EstatesPomfret, MD1 of 20.0500 ppb180
Cedar Village IICarrboro, NC12 of 120.0483 ppb36
Edgewood Mobile Home ParkOcala, FL9 of 110.0477 ppb42
Winningfield S/dDenver, NC5 of 60.0441 ppb28
Henlopen Acres, Town ofRehoboth, DE5 of 60.0437 ppb999
Rolling Acres S/dCary, NC20 of 200.0398 ppb58
Camelot S/dCary, NC11 of 190.0351 ppb604
Orangewood Water SystemHoliday, FL20 of 240.0297 ppb5,937
Quail Ridge S/dDenver, NC5 of 60.0281 ppb142
Colonial Heights-meadowbrookCary, NC9 of 100.0264 ppb77
Hickory Grove Mobile Home ParkDallas, NC1 of 10.0250 ppb69
Helms Water SystemDenver, NC13 of 200.0241 ppb86
Middlesex Water SystemRaleigh, NC6 of 190.0239 ppb975
Amber AcresCharlotte, NC6 of 100.0237 ppb239
Braxton Hills/simmons HeightsHampstead, NC6 of 100.0236 ppb614
Deerwood S/dDenver, NC5 of 60.0233 ppb100
Emerald Village S/dCary, NC5 of 90.0225 ppb125
Snow Creek Heights Water SystemDenver, NC6 of 100.0217 ppb130
Berkshire DownsCary, NC10 of 150.0212 ppb277
Mcconnell S/dDenver, NC5 of 80.0209 ppb124
Sterlingshire S/dDenver, NC1 of 80.0203 ppb147
Country Acres/southgateDenver, NC6 of 80.0201 ppb668
Northwest Grayson County Water Control and Improvement District 1*Gordonville, TX1 of 80.0188 ppb2,706
Eden Mobile Home ParkFruitland, MD1 of 60.0167 ppb250
Port Washington WDPort Washington, NY17 of 410.0164 ppb34,000
Oak Run EstatesOcala, FL9 of 310.0163 ppb11,788
Stone Oaks Mobile Home ParkOcala, FL1 of 10.0160 ppb302
Coronado Shores Water SystemSilverton, TX1 of 70.0143 ppb150
Carmel ParkDenver, NC4 of 70.0136 ppb107
Blue Skies EstatesOcala, FL4 of 50.0132 ppb195
Clearview Acres S/dDenver, NC5 of 110.0130 ppb170
Oakland, City ofOakland, NE1 of 40.0125 ppb1,279
Adams Mobile Home ParkMiddlesex, NC1 of 70.0120 ppb80
Medfield Estates S/dCary, NC6 of 140.0115 ppb779
Spencer Rd ParkDenver, NC4 of 130.0113 ppb142
Cameron Point S/dDenver, NC1 of 60.0108 ppb86
Crestridge Gardens UtilitiesHoliday, FL2 of 40.01000 ppb1,209
River Meadows S/dDenver, NC1 of 60.00967 ppb119
Sherwood Forest S/dDenver, NC3 of 80.00899 ppb160
Cass County Sanitary and Improvement District #7 - Swallow HillsPlattsmouth, NE1 of 70.00857 ppb93
Plattsmouth, City of*Plattsmouth, NE1 of 70.00857 ppb6,503
Brookwood Comm. Water SystemHampstead, NC29 of 1110.00820 ppb15,665
Bone Mesa Domestic Water DistrictPaonia, CO1 of 30.00733 ppb400

* This water utility supplies finished drinking water to at least one other water utility. The purchasing utility is not required to test for or report Heptachlor epoxide, but it likely has the contaminant in its water supply.

UtilityLocationTestsAverage levelPeople served
Port Washington WDPort Washington, NY17 of 410.0164 ppb34,000
Oak Run EstatesOcala, FL9 of 310.0163 ppb11,788
Brookwood Comm. Water SystemHampstead, NC29 of 1110.00820 ppb15,665
University ParkDallas, TX1 of 60.00500 ppb23,040
Southern UtilitiesTyler, TX2 of 790.00266 ppb59,154
Robertsdale, City ofRobertsdale, AL1 of 30.00233 ppb10,905
Water Authority of Western NassauNew Hyde Park, NY1 of 110.00227 ppb120,000
East Lyme Water & Sewer Commission*Niantic, CT1 of 310.00142 ppb15,245
Beverly Hills / Rolling Oaks SubdivisionBeverly Hills, FL2 of 200.00139 ppb11,572
City of Henderson*Henderson, TX1 of 340.00118 ppb13,712
Joint Base Pearl Harbor-Hickam*Jbpph, HI1 of 200.001000 ppb65,230
Newark Water DepartmentNewark, DE1 of 150.000933 ppb36,450
Cliffdale WestHampstead, NC4 of 1300.000909 ppb15,463
Honolulu-Windward-Pearl Harbor*Honolulu, HI23 of 4650.000789 ppb631,389
Marine Corps Base HawaiiKaneohe Bay, HI23 of 4650.000789 ppb16,300
Duxbury Water Department*Duxbury, MA1 of 290.000655 ppb16,445
Mobile County Water and Fire Pro AuthorityTheodore, AL1 of 350.000600 ppb39,573
Naval Air Station Pensacola / Corry StationNas Pensacola, FL3 of 530.000474 ppb22,600
Miramar (East & West) PlantsMiramar, FL1 of 160.000325 ppb127,700
Artesian Water Company*Newark, DE2 of 1690.000296 ppb301,000
Hicksville WDHicksville, NY1 of 750.000293 ppb48,000
WA of Great Neck NorthGreat Neck, NY1 of 760.000276 ppb31,400
Village Water SystemPrinceton, LA2 of 720.000206 ppb10,644
Manchester Water Department*Manchester, CT1 of 310.000203 ppb51,066
North Baldwin Utilities*Bay Minette, AL1 of 280.000143 ppb28,713
Gateway Services DistrictFort Myers, FL1 of 250 ppb12,717
Lee County Utilities*Fort Myers, FL1 of 250 ppb251,502
Bayleaf MasterCary, NC1 of 4270 ppb15,565

* This water utility supplies finished drinking water to at least one other water utility. The purchasing utility is not required to test for or report Heptachlor epoxide, but it likely has the contaminant in its water supply.