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Contaminants Detected

EXCEED GUIDELINES

Bromodichloromethane

Potential Effect: cancer

This Utility: 8.50 ppb

142x

EWG's Health Guideline: 0.06 ppb

Bromodichloromethane

Bromodichloromethane, one of the total trihalomethanes (TTHMs), is formed when chlorine or other disinfectants are used to treat drinking water. Bromodichloromethane and other disinfection byproducts increase the risk of cancer and may cause problems during pregnancy. Click here to read more about disinfection byproducts.

Bromodichloromethane was found at 142 times above EWG's Health Guideline.

EWG Health Guideline

0.06 ppb or less

This Utility

8.5 ppb

National Average

5.89 ppb

State Average

6.2 ppb

Health Risks

The EWG Health Guideline of 0.06 ppb for bromodichloromethane was based on the California Office of Environmental Health Hazard Assessment's public health goal, the level of a drinking water contaminant that does not pose a significant health risk. This health guideline protects against cancer and harm to fetal growth and development.

Legal Limit

None

Understanding the Data

The state and national averages were calculated using the averages of the contaminant measurements for each utility in 2021-2023.

ppb = parts per billion

Pollution Sources

Treatment Byproducts

Filtering Options

Activated Carbon

Reverse Osmosis

Chloroform

Potential Effect: cancer

This Utility: 19.7 ppb

49x

EWG's Health Guideline: 0.4 ppb

Chloroform

Chloroform, one of the total trihalomethanes (TTHMs), is formed when chlorine or other disinfectants are used to treat drinking water. Chloroform and other disinfection byproducts increase the risk of cancer and may cause problems during pregnancy.

Chloroform was found at 49 times above EWG's Health Guideline.

EWG Health Guideline

0.4 ppb or less

This Utility

19.7 ppb

National Average

16.2 ppb

State Average

27.9 ppb

Health Risks

The EWG Health Guideline of 0.4 ppb for chloroform was based on the California Office of Environmental Health Hazard Assessment's public health goal, the level of a drinking water contaminant that does not pose a significant health risk. This health guideline protects against cancer and harm to fetal growth and development.

Legal Limit

None

Understanding the Data

The state and national averages were calculated using the averages of the contaminant measurements for each utility in 2021-2023.

ppb = parts per billion

Pollution Sources

Treatment Byproducts

Filtering Options

Activated Carbon

Reverse Osmosis

Chromium (hexavalent)

Potential Effect: cancer

This Utility: 0.0404 ppb

2x

EWG's Health Guideline: 0.02 ppb

Chromium (hexavalent)

Chromium (hexavalent) is a carcinogen that commonly contaminates American drinking water. Chromium (hexavalent) in drinking water may be due to industrial pollution or natural occurrences in mineral deposits and groundwater. Read more about chromium (hexavalent).

Chromium (hexavalent) was found at 2 times above EWG's Health Guideline.

EWG Health Guideline

0.02 ppb or less

This Utility

0.0404 ppb

National Average

0.44 ppb

State Average

0.122 ppb

Health Risks

The EWG Health Guideline of 0.02 ppb for chromium (hexavalent) 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.

Legal Limit

None

Understanding the Data

The state and national averages were calculated using the averages of the contaminant measurements for each utility in 2013-2023.

ppb = parts per billion

Pollution Sources

Industry

Naturally Occurring

Filtering Options

Reverse Osmosis

Ion Exchange

Dibromochloromethane

Potential Effect: cancer

This Utility: 2.50 ppb

25x

EWG's Health Guideline: 0.1 ppb

Dibromochloromethane

Dibromochloromethane, one of the total trihalomethanes (TTHMs), is formed when chlorine or other disinfectants are used to treat drinking water. Dibromochloromethane and other disinfection byproducts increase the risk of cancer and may cause problems during pregnancy. Click here to read more about disinfection byproducts.

Dibromochloromethane was found at 25 times above EWG's Health Guideline.

EWG Health Guideline

0.1 ppb or less

This Utility

2.5 ppb

National Average

3.55 ppb

State Average

1.23 ppb

Health Risks

The EWG Health Guideline of 0.1 ppb for dibromochloromethane was based on the California Office of Environmental Health Hazard Assessment's public health goal, the level of a drinking water contaminant that does not pose a significant health risk. This health guideline protects against cancer and harm to fetal growth and development.

Legal Limit

None

Understanding the Data

The state and national averages were calculated using the averages of the contaminant measurements for each utility in 2021-2023.

ppb = parts per billion

Pollution Sources

Treatment Byproducts

Filtering Options

Activated Carbon

Reverse Osmosis

Haloacetic acids (HAA5)

Potential Effect: cancer

This Utility: 28.7 ppb

287x

EWG's Health Guideline: 0.1 ppb

Haloacetic acids (HAA5)

Haloacetic acids are formed when disinfectants such as chlorine are added to tap water. The group of five haloacetic acids regulated by federal standards includes monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid and dibromoacetic acid.

Haloacetic acids (HAA5) was found at 287 times above EWG's Health Guideline.

EWG Health Guideline

0.1 ppb or less

This Utility

28.7 ppb

Legal Limit

60 ppb

National Average

19.8 ppb

State Average

26.4 ppb

Health Risks

The EWG Health Guideline of 0.1 ppb for the group of five haloacetic acids, or HAA5, was defined in a peer-reviewed scientific study by EWG and represents a one-in-a-million lifetime cancer risk level. This health guideline protects against cancer.

Understanding the Data

The state and national averages were calculated using the averages of the contaminant measurements for each utility in 2021-2023.

ppb = parts per billion

Pollution Sources

Treatment Byproducts

Filtering Options

Activated Carbon

Reverse Osmosis

Haloacetic acids (HAA9)

Potential Effect: cancer

This Utility: 34.8 ppb

580x

EWG's Health Guideline: 0.06 ppb

Haloacetic acids (HAA9)

Haloacetic acids are formed when disinfectants such as chlorine are added to tap water. The group of nine haloacetic acids includes monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid and dibromoacetic acid, which are regulated as a group by the federal government (HAA5); and bromochloroacetic acid, bromodichloroacetic acid, chlorodibromoacetic acid, and tribromoacetic acid.

Haloacetic acids (HAA9) was found at 580 times above EWG's Health Guideline.

EWG Health Guideline

0.06 ppb or less

This Utility

34.8 ppb

National Average

23.7 ppb

State Average

33.5 ppb

Health Risks

The EWG Health Guideline of 0.06 ppb for the group of nine haloacetic acids, or HAA9, was defined in a peer-reviewed scientific study by EWG and represents a one-in-a-million lifetime cancer risk level as . This health guideline protects against cancer.

Legal Limit

None

Understanding the Data

The state and national averages were calculated using the averages of the contaminant measurements for each utility in 2018-2021.

ppb = parts per billion

Pollution Sources

Treatment Byproducts

Filtering Options

Activated Carbon

Reverse Osmosis

Total trihalomethanes (TTHMs)

Potential Effect: cancer

This Utility: 54.5 ppb

363x

EWG's Health Guideline: 0.15 ppb

Total trihalomethanes (TTHMs)

Trihalomethanes are cancer-causing contaminants that form during water treatment with chlorine and other disinfectants. The total trihalomethanes group includes four chemicals: chloroform, bromodichloromethane, dibromochloromethane and bromoform.

Total trihalomethanes (TTHMs) was found at 363 times above EWG's Health Guideline.

EWG Health Guideline

0.15 ppb or less

This Utility

54.5 ppb

Legal Limit

80 ppb

National Average

29.1 ppb

State Average

41.9 ppb

Health Risks

The health guideline of 0.15 parts per billion, or ppb, for the group of four trihalomethanes, or THM4/TTHM, was defined in a peer-reviewed scientific study by EWG and represents a one-in-one-million lifetime cancer risk level.

Understanding the Data

The state and national averages were calculated using the averages of the contaminant measurements for each utility in 2021-2023.

ppb = parts per billion

Pollution Sources

Treatment Byproducts

Filtering Options

Activated Carbon

Reverse Osmosis

Includes chemicals detected in 2021-2023 for which annual utility averages exceeded an EWG-selected health guideline established by a federal or state public health authority.


† HAA5 is a contaminant group that includes monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid and dibromoacetic acid. HAA9 is a contaminant group that includes the chemicals in HAA5 and bromochloroacetic acid, bromodichloroacetic acid, chlorodibromoacetic acid and tribromoacetic acid. TTHM is a contaminant group that includes bromodichloromethane, bromoform, chloroform and dibromochloromethane.

OTHER DETECTED

Barium

This Utility: 11.9 ppb

EWG's Health Guideline: 700 ppb

Barium

Barium is a mineral present in rocks, soil and water. High concentrations of barium in drinking water increase the risk of cardiovascular disease and hypertension.

How your levels compare

EWG Health Guideline

700 ppb or less

This Utility

11.9 ppb

Legal Limit

2,000 ppb

National Average

39.5 ppb

State Average

48.2 ppb

Health Risks

The EWG Health Guideline of 700 ppb for barium was defined by EWG as benchmark that protects against harm to the kidneys and the cardiovascular system.

Understanding the Data

The state and national averages were calculated using the averages of the contaminant measurements for each utility in 2021-2023.

ppb = parts per billion

Pollution Sources

Industry

Naturally Occurring

Filtering Options

Reverse Osmosis

Ion Exchange

Chlorate

This Utility: 31.3 ppb

EWG's Health Guideline: 210 ppb

Chlorate

Chlorate forms in drinking water as a byproduct of disinfection. Chlorate impairs thyroid function, making chlorate exposure most harmful during pregnancy and childhood.

How your levels compare

EWG Health Guideline

210 ppb or less

This Utility

31.3 ppb

National Average

116.8 ppb

State Average

136.2 ppb

Health Risks

The EWG Health Guideline of 210 ppb for chlorate was defined by the Environmental Protection Agency as a benchmark for testing under the Unregulated Contaminant Monitoring Rule program. This health guideline protects against hormone disruption.

Legal Limit

None

Understanding the Data

The state and national averages were calculated using the averages of the contaminant measurements for each utility in 2013-2023.

ppb = parts per billion

Pollution Sources

Agriculture

Industry

Treatment Byproducts

Fluoride

This Utility: 0.390 ppm

No EWG Health Guideline

Fluoride

Fluoride occurs naturally in surface and groundwater and is also added to drinking water by many water systems to prevent cavities and support oral health in people.

In 2015, the Department of Health and Human Services updated its recommendation of an optimal level of 0.7 parts per million, or ppm, added to drinking water based on the health benefits of tooth decay prevention. Studies have shown that fluoride added to community water systems at this level reduces dental cavities, especially in children.

And studies have conclusively shown that fluoride in toothpaste and mouthwash can also provide these benefits.

How your levels compare

This Utility

0.39 ppm

Legal Limit

4 ppm

National Average

0.49 ppm

State Average

0.324 ppm

EWG Health Guideline

Not yet determined

Understanding the Data

The state and national averages were calculated using the averages of the contaminant measurements for each utility in 2021-2023.

ppm = parts per million

Pollution Sources

Industry

Treatment Byproducts

Naturally Occurring

Filtering Options

Reverse Osmosis

Manganese

This Utility: 20.3 ppb

EWG's Health Guideline: 100 ppb

Manganese

Manganese is a naturally occurring element that is common in food and drinking water. Excessive manganese exposures may impair children's attention, memory and intellectual capacity. Click here to read more about manganese.

How your levels compare

EWG Health Guideline

100 ppb or less

This Utility

20.3 ppb

National Average

8.66 ppb

State Average

31.4 ppb

Health Risks

The EWG Health Guideline of 100 ppb for manganese was defined by the state of Minnesota as a health risk limit, the concentration of a contaminant that can be consumed with little or no risk to health. This health guideline protects against harm to the brain and nervous system.

Legal Limit

None

Understanding the Data

The state and national averages were calculated using the averages of the contaminant measurements for each utility in 2013-2023.

ppb = parts per billion

Pollution Sources

Industry

Naturally Occurring

Filtering Options

Ion Exchange

Nitrate

This Utility: 0.0240 ppm

EWG's Health Guideline: 0.14 ppm

Nitrate

Nitrate, a fertilizer chemical, frequently contaminates drinking water due to agricultural and urban runoff, and discharges from municipal wastewater treatment plants and septic tanks. Excessive nitrate in water can cause oxygen deprivation in infants and increase the risk of cancer. Click here to read more about nitrate.

How your levels compare

EWG Health Guideline

0.14 ppm or less

This Utility

0.024 ppm

Legal Limit

10 ppm

National Average

0.824 ppm

State Average

0.746 ppm

Health Risks

The EWG health guideline of 0.14 parts per million, or ppm, for nitrate and nitrite is based on the equivalent health guideline for nitrate, as defined in a peer-reviewed scientific study by EWG. This guideline represents a one-in-one-million annual cancer risk level.

Understanding the Data

The state and national averages were calculated using the averages of the contaminant measurements for each utility in 2021-2023.

ppm = parts per million

Pollution Sources

Agriculture

Runoff & Sprawl

Naturally Occurring

Filtering Options

Reverse Osmosis

Ion Exchange

Nitrate and nitrite

This Utility: 0.0414 ppm

EWG's Health Guideline: 0.14 ppm

Nitrate and nitrite

Nitrate and nitrite enter water from fertilizer runoff, septic tanks and urban runoff. These contaminants can cause oxygen deprivation for infants and increase the risk of cancer. Nitrite is significantly more toxic than nitrate. Click here to read more about nitrate.

How your levels compare

EWG Health Guideline

0.14 ppm or less

This Utility

0.0414 ppm

Legal Limit

10 ppm

National Average

0.78 ppm

State Average

0.71 ppm

Health Risks

The EWG health guideline of 0.14 parts per million, or ppm, for nitrate and nitrite is based on the equivalent health guideline for nitrate, as defined in a peer-reviewed scientific study by EWG. This guideline represents a one-in-one-million annual cancer risk level.

Understanding the Data

The state and national averages were calculated using the averages of the contaminant measurements for each utility in 2021-2023.

ppm = parts per million

Pollution Sources

Agriculture

Runoff & Sprawl

Naturally Occurring

Filtering Options

Reverse Osmosis

Ion Exchange

Nitrite

This Utility: 0.0187 ppm

No EWG Health Guideline

Nitrite

Nitrite, closely related to the fertilizer chemical nitrate, comes from urban runoff and from fertilizer applied to agricultural lands to pollute drinking water. Nitrite is significantly more toxic than nitrate. Excessive nitrite in water can cause oxygen deprivation in infants and increase the risk of cancer.

How your levels compare

This Utility

0.0187 ppm

Legal Limit

1 ppm

National Average

0.00334 ppm

State Average

0.000654 ppm

EWG Health Guideline

Not yet determined

Understanding the Data

The state and national averages were calculated using the averages of the contaminant measurements for each utility in 2021-2023.

ppm = parts per million

Pollution Sources

Agriculture

Runoff & Sprawl

Naturally Occurring

Filtering Options

Reverse Osmosis

Ion Exchange

Strontium

This Utility: 0.0595 ppb

EWG's Health Guideline: 1,500 ppb

Strontium

Strontium is a metal that accumulates in the bones. Radioactive strontium-90 can cause bone cancer and leukemia, and any form of strontium at high doses can harm bone health.

How your levels compare

EWG Health Guideline

1,500 ppb or less

This Utility

0.0595 ppb

National Average

0.488 ppb

State Average

0.069 ppb

Health Risks

The EWG Health Guideline of 1,500 ppb for strontium was defined by the Environmental Protection Agency as a benchmark for testing under the Unregulated Contaminant Monitoring Rule program. This health guideline protects against harm to bones.

Legal Limit

None

Understanding the Data

The state and national averages were calculated using the averages of the contaminant measurements for each utility in 2013-2023.

ppb = parts per billion

Pollution Sources

Industry

Naturally Occurring

Filtering Options

Reverse Osmosis

Ion Exchange

Includes chemicals detected in 2021-2023 for which annual utility averages were lower than an EWG-selected health guideline established by a federal or state public health authority.

Other Contaminants Tested

Chemicals tested for but not detected:

1,1,1,2-Tetrachloroethane, 1,1,1-Trichloroethane, 1,1,2,2-Tetrachloroethane, 1,1,2-Trichloroethane, 1,1-Dichloroethane, 1,1-Dichloroethylene, 1,1-Dichloropropene, 1,2,3-Trichloropropane, 1,2,4-Trichlorobenzene, 1,2,4-Trimethylbenzene, 1,2-Dibromo-3-chloropropane (DBCP), 1,2-Dichloroethane, 1,2-Dichloropropane, 1,3,5-Trimethylbenzene, 1,3-Butadiene, 1,3-Dichloropropane, 1,3-Dichloropropene, 1,4-Dioxane, 1-butanol, 11-chloroeicosafluoro-3-oxaundecane-1-sulfonic aci, 2,2-Dichloropropane, 2,4,5-TP (Silvex), 2,4-D, 2-methoxyethanol, 2-propen-1-ol, 3-Hydroxycarbofuran, 4,8-dioxa-3H-perfluorononanoic acid (ADONA), 4:2 Fluorotelomer Sulfonic Acid (4:2 FTSA), 6:2 Fluorotelomer Sulfonic Acid (6:2 FTSA), 8:2 Fluorotelomer Sulfonic Acid (8:2 FTSA), 9-chlorohexadecafluoro-3-oxanone-1-sulfonic acid (, Alachlor (Lasso), Aldicarb, Aldicarb sulfone, Aldicarb sulfoxide, Aldrin, Alpha-hexachlorocyclohexane, Antimony, Arsenic, Asbestos, Atrazine, Benzene, Benzo[a]pyrene, Beryllium, Bromobenzene, Bromochloromethane, Bromoform, Bromomethane, Butachlor, Butanoic acid, 2,2,3,3,4,4-hexafluoro-4-(trifluoro, Butylated hydroxyanisole, Cadmium, Carbaryl, Carbofuran, Carbon tetrachloride, Chlordane, Chlorodifluoromethane, Chloroethane, Chloromethane, Chlorpyriphos, Chromium (total), cis-1,2-Dichloroethylene, Cobalt, Combined uranium, Cyanide, Dalapon, Di(2-ethylhexyl) adipate, Di(2-ethylhexyl) phthalate, Dibromomethane, Dicamba, Dichloromethane (methylene chloride), Dieldrin, Dimethipin, Dinoseb, Diquat, Endrin, Ethoprop, Ethylbenzene, Ethylene dibromide, Germanium, Glyphosate, Heptachlor, Heptachlor epoxide, Hexachlorobenzene (HCB), Hexachlorocyclopentadiene, Hexafluoropropylene oxide dimer acid (HFPO-DA), Lindane, Lithium, m-Dichlorobenzene, Mercury (inorganic), Methomyl, Methoxychlor, Metolachlor, Metribuzin, Molybdenum, Monochlorobenzene (chlorobenzene), MTBE, n-Butylbenzene, N-ethyl perfluorooctane sulfonamido acetic acid (N, N-methyl perfluorooctanesulfonamidoacetic acid, n-Propylbenzene, Naphthalene, Nonafluoro-3,6-dioxaheptanoic acid, o-Chlorotoluene, o-Dichlorobenzene, o-toluidine, Oxamyl (Vydate), Oxyflurofen, p-Chlorotoluene, p-Dichlorobenzene, Pentachlorophenol, Perfluoro(2-ethoxyethane)sulfonic acid, Perfluorobutane sulfonate (PFBS), Perfluorobutanoic acid (PFBA), Perfluorodecanoic acid (PFDA), Perfluorododecanoic acid (PFDoA), Perfluoroheptane sulfonic acid (PFHpS), Perfluoroheptanoic acid (PFHPA), Perfluorohexane sulfonate (PFHXS), Perfluorohexanoic Acid (PFHxA), Perfluorononanoic acid (PFNA), Perfluorooctane sulfonate (PFOS), Perfluorooctanoic acid (PFOA), Perfluoropentane sulfonic acid (PFPeS), Perfluoropentanoic acid (PFPeA), Perfluorotetradecanoic acid (PFTA), Perfluorotridecanoic acid (PFTrDA), Perfluoroundecanoic acid (PFUnA), Permethrin, Picloram, Polychlorinated biphenyls (PCBs), Profenofos, Propachlor, Propanoic acid, 2,2,3,3-tetrafluoro-3-(trifluorome, Quinoline, Radium, combined (-226 & -228), Selenium, Silver, Simazine, Styrene, Tebuconazole, Tetrachloroethylene (perchloroethylene), Thallium, Toluene, Toxaphene, trans-1,2-Dichloroethylene, Tribufos, Trichloroethylene, Vanadium, Vinyl chloride, Xylenes (total)

Find A Filter

Utility: 

Groton Utilities
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Carbon Filters

FILTERS 6 contaminants exceeding guidelines (+0 others)

Can reduce the levels of many common contaminants.

pros

  • Lower upfront cost
  • Reduced maintenance

cons

  • Does not remove all contaminants

Reverse Osmosis

FILTERS 7 contaminants exceeding guidelines (+6 others)

Can reduce the levels of many common contaminants.

pros

  • Most effective

cons

  • Higher upfront cost
  • Requires more maintenance
  • Wastes water

Other Considerations

Ion Exchange

Pros: Softens hard water, Reduces some contaminants

Cons: Doesn’t remove all contaminants

Whole-House Filters

Pros: Useful for reducing radiologicals and TCE

Cons: Expensive to install and maintain, Risk of bacterial contamination

Distillation

Pros: Removes heavy metals and harmful microbes

Cons: Does not reduce most contaminants

Explore filter options for each contaminant. See which technologies are effective at reducing specific contaminants to help you make an informed decision on the best water treatment solution for your needs.

CONTAMINANTS ABOVE HEALTH GUIDELINES activated carbon reverse osmosis ion exchange
Bromodichloromethane
Chloroform
Chromium (hexavalent)
Dibromochloromethane
Haloacetic acids (HAA5)
Haloacetic acids (HAA9)
Total trihalomethanes (TTHMs)
OTHER CONTAMINANTS DETECTED activated carbon reverse osmosis ion exchange
Barium
Chlorate
Fluoride
Manganese
Nitrate
Nitrate & nitrite
Nitrite
Strontium