What is Arsenic?
Arsenic is a chemical element that is found naturally in the crust of the earth. In its organic form, arsenic is very toxic. As a widely distributed pollutant, arsenic can be found in the air, the land, and groundwater.
This guide will look at arsenic in drinking water, its health effects, and how to remove it from public and well water supplies.
How Does Arsenic Affect People’s Health?
Exposure to arsenic has been linked to a number of health effects, ranging from milder symptoms of nausea and dizziness to severe and life-threatening side-effects.
Research suggests that arsenic has cancer-causing potential, and can cause lung, bladder and skin cancer. Some studies also linked arsenic to kidney, liver and prostate cancer.
Ingestion of arsenic has been found to cause nausea, vomiting, numbness and tingling of the extremities, diarrhea, skin rashes, and muscle cramping, amongst other problems.
Long-term exposure to arsenic may cause permanent damage to the heart, liver and kidneys, skin changes, and a reduced number of white and red blood cells, which increases the risk of infections.
How Does Arsenic Get Into Drinking Water?
Because arsenic occurs naturally, it is a relatively common drinking water contaminant.
Arsenic mainly gets into drinking water by:
- Naturally entering a groundwater source from arsenic deposits in the earth’s rock formations;
- Industrial and agricultural pollution, usually from factories and farms with poor waste management practices; or
- Rainfall and snow, which transports arsenic in the air into soil and groundwater.
Arsenic in Public Water Systems vs Private Wells
You are far more likely to find arsenic in high quantities in a private well source than you are in a public water system. This is because public water systems are legally obliged to filter out their arsenic, while it is the well owner’s responsibility to check their water for contaminants and filter it accordingly.
What Are the Regulations Around Arsenic in Tap Water?
Because it poses known health risks, arsenic in tap water is regulated by a number of governing bodies.
The most well-known arsenic regulation is the U.S. EPA's Maximum Contaminant Level (or MCL). According to this MCL, public water systems must legally limit their drinking water arsenic levels to less than 10 ppb (parts per billion).
Note that the EPA’s MCL does not apply to bottled water, but the U.S. Food and Drug Administration has also set a limit of 10 ppb for any still or sparkling bottled water sold to the public.
There is no regulation for arsenic in well water. Private well owners should test their water for arsenic periodically and filter their water accordingly.
How is Arsenic Removed From Drinking Water Supplies?
Public Water System Operators
Public drinking water goes through a number of stages of disinfection and filtration before it can be sent to our homes. Using a standard filter is effective in reducing arsenic, and all states must ensure that their water system’s filtration methods are effective enough to reduce arsenic to 10 ppb or below.
The most effective means of arsenic removal is reverse osmosis. This type of filter can remove up to 99.9% of arsenic in water. However, the reverse osmosis process is expensive and produces water waste, meaning it is not economically viable for most large-scale public water treatment applications.
It is possible to remove arsenic from drinking water using an at-home reverse osmosis filter, and this is a popular option amongst city water users who would prefer to drink as little arsenic as possible.
Private Well Owners
It is important to note that simply boiling well water will not remove arsenic. This will only cause some of the water to evaporate, leaving a greater concentration of arsenic per gallon behind.
There are a number of filtration systems that are designed specifically for arsenic removal. These are:
- Anion exchange resins: These use the anion (or ion) exchange process to trap arsenic in a media bed. The media will require periodic flushing when it is saturated with arsenic, and will need to be replaced every six to eight years.
- Reverse osmosis systems: These combine several stages of filtration, including a carbon filter and a semi-permeable membrane. The semi-permeable membrane can remove up to 99.99% total dissolved solids, including arsenic.
- Distillation: This is the process of boiling and condensing water to remove almost all of its impurities. The evaporated water condenses and travels into a clean carafe, while impurities that are unable to evaporate at water’s boiling point, including arsenic, are left behind.
- Activated alumina filters: These filters use an activated alumina media to adsorb a number of contaminants, including arsenic. For arsenic removal, hydrogen peroxide or chlorine bleach will typically be required to convert arsenic into an adsorbable form.
Well water arsenic removal systems can cost anywhere from $1,000 to $3,000 or more, depending on the complexity of the system and the contaminants removed.