Arsenic in Connecticut Drinking Water
By Alexander Snyder, Founder & Water Quality Data Lead
The U.S. EPA sets the legal limit (MCL) for Arsenic at 0.01 mg/L, but the health-based safe level set by California's OEHHA is 0.000004 mg/L. That health guideline is roughly 2,500x stricter than the federal legal limit.
Arsenic has been detected in 142 Connecticut ZIP codes, above a limit or health guideline in 20. Here is what you need to know about arsenic in your drinking water and how it may affect your household.
What Is Arsenic?
Arsenic is a naturally occurring metalloid found in bedrock that dissolves into groundwater, particularly in areas with volcanic or sedimentary geology. Industrial sources include mining, pesticide residues, and wood preservatives. The EPA maximum contaminant level is 10 parts per billion. Long-term exposure to arsenic in drinking water increases the risk of bladder, lung, and skin cancers, as well as cardiovascular disease.
Is Arsenic in Your Water?
Enter your Connecticut ZIP code to find out if arsenic is in your local water — and see personalized health risks for your household.
Check Your ZIP CodeHealth Effects of Arsenic
Skin damage or problems with circulatory systems, and may have increased risk of getting cancer
Safety Guidelines
Health Guideline
0.000004 mg/L
Source: California OEHHA
Legal Limit (MCL)
0.01 mg/L
EPA Maximum Contaminant Level
Arsenic's health-based safe level is roughly 2,500x stricter than the federal legal limit.
| Standard | Level | Source |
|---|---|---|
| EPA Legal Limit (MCL) | 0.01 mg/L | EPA |
| Health Guideline | 0.000004 mg/L | California OEHHA |
| Gap | ~2,500x stricter than legal | |
Where Does Arsenic Come From?
Erosion of natural deposits; runoff from orchards; runoff from glass & electronics production wastes
How to Reduce Arsenic in Your Water
- 1Install a point-of-use reverse osmosis system certified to NSF/ANSI Standard 58 for arsenic reduction, which effectively removes both arsenic III and arsenic V forms when paired with an oxidation prefilter.
- 2Use an adsorptive media filter containing iron-based media such as granular ferric hydroxide, which has high affinity for arsenic and is effective for whole-house treatment.
- 3For well water, add an oxidation step (chlorination or aeration) before filtration to convert arsenic III to arsenic V, which is more readily removed by most filter technologies.
- 4Test your water to determine the specific arsenic species present, as treatment effectiveness varies between arsenic III (arsenite) and arsenic V (arsenate).
Who Is Most Vulnerable to Arsenic?
The safe level of arsenic varies significantly depending on who is drinking the water. CheckYourTap calculates adjusted safe levels for each member of your household:
A contaminant level that is safe for an adult may exceed guidelines for an infant by 4-8x or more. Check your ZIP code to see personalized results.
Reading this inside ChatGPT or Claude?
This page can tell you the general science, but not what is actually in your water’s arsenic level — that depends on your exact address. You can get your specific answer two ways:
- Inside the chat: ask your assistant to “check my tap water with CheckYourTap”. Our connector returns your ZIP code’s measured contaminant levels — including the derived dog and cat safe levels — and, only if you ask it to, can email you the report or arrange a specialist callback.
- On the web: open CheckYourTap.com and enter your ZIP code for a free 30-second report.
Concerned about Arsenic in your water?
Schedule to get your water tested for arsenic and more — a Valiant water specialist will review your results and arrange testing for your home.
Have a dog or cat?
Arsenic affects pets differently — they drink far more water per pound of body weight, and some are more sensitive than people. See the derived safe levels and the veterinary science:
Frequently Asked Questions
Is Arsenic in my tap water?▾
What level of Arsenic is safe?▾
How do I remove Arsenic from my water?▾
Related Contaminants
Check Water Quality by ZIP Code
Sources
The legal limits and health guidelines for Arsenic on this page come from the following public authorities:
About This Report
This water quality report is compiled from public records filed with the U.S. Environmental Protection Agency, state health departments, and the U.S. Geological Survey. Contaminant levels are evaluated against EPA federal standards and health-based guidelines from leading environmental and public health organizations. CheckYourTap is a service of Valiant Energy Solutions, a Connecticut water quality and energy services company established in 1930.
This report is general information, not medical advice or a substitute for certified laboratory testing. Talk to your pediatrician or physician about specific health concerns.
Reviewed by the CheckYourTap editorial team. Last updated July 2026