Arsenic in Drinking Water

Health effects from drinking water with arsenic depend on two things:

1. How much arsenic is in the water
2. How many years you've been drinking the water

Drinking water with arsenic over a long period of time may cause an increased lifetime risk of bladder, lung or skin cancer. There also may be links to skin and cardiovascular diseases, diabetes or other cancers.

Arsenic is a natural element found in the Earth's crust. As rainwater moves through natural rock formations underground, it can dissolve arsenic and carry it into aquifers that serve as sources of drinking water.

You cannot see, smell or taste arsenic. Testing is the only way to know if arsenic is in your drinking water.

The Health Department recommends testing your well or spring for arsenic every five years. You can order an inorganic chemical test (Kit C) from the Health Department Laboratory, or you can use another certified drinking water lab to test for inorganic chemicals.

The drinking water standard for arsenic is 0.010 mg/L (milligrams per liter). If the arsenic level in your water is more than (>) 0.010 mg/L, the Health Department recommends you stop drinking the water and install a treatment system to remove arsenic, drink bottled water instead, or get water from a known safe location.

Arsenic is known to cause cancer, so even amounts below the drinking water standard could affect your health. If the arsenic level is between 0.001 and 0.010 mg/L, consider treatment.

Need help understanding your drinking water test results? Find out how to read your results

Arsenic levels in drinking water can be lowered by using one of the treatment systems listed below. 

• Adsorptive filters: As the water flows through the filter, arsenic sticks to the filter, which contains a type of granular iron oxide. These filters allow for oxidation and removal in a single-filtration process.
• Distillation units: These units boil water and then recondense the steam. The arsenic is left behind during this process, along with hardness and other minerals. These units can produce several gallons of arsenic-free water per day.
• Reverse osmosis (RO): This system uses a synthetic membrane that allows water to go through but leaves arsenic behind. The membrane is continually rinsed. This system is typically installed under a kitchen sink (point-of-use or POU) but can also be installed as a whole house system (point-of-entry or POE). Install a system with an NSF/ANSI Standard 58 Certification. 

Other treatment systems require two steps to remove arsenic. First, the water must go through an “oxidation” process in order to change arsenic into a form that can be removed. Chlorine injection, specialized media or aeration can be used in this initial step. Treatment system options after oxidation are anion exchange and carbon block.

• Anion exchange treatment: Anion exchange is a treatment like water softening but uses a different media that exchanges the arsenic for chloride. This is installed as a POE system.
• Carbon block: This technology lowers total arsenic as the water passes through a solid carbon block. Install a carbon filtration system with an NSF/ANSI Standard 53 Certification. 

Re-test your drinking water for arsenic after any treatment system is installed to make sure levels are below the drinking water standard.

Funding is available to help you pay for water treatment or to fix your water system. Learn more about financial assistance programs and eligibility.