Arsenic is a naturally occurring semi-metal. Arsenic is fairly common in Montana’s groundwater. High concentrations are often found in mountainous areas, near hot springs and glacial deposits. The mountainous nature of Missoula and Ravalli counties makes specific site location of the naturally occurring arsenic difficult. Countywide well and water source arsenic sampling has not been completed, which only adds to the difficulty.
Another source of dangerously high concentrations of arsenic are mining waste and industrial deposits, such as those commonly found at mines and paper mills. Consequently, locations in the surrounding Missoula area that are particularly susceptible to arsenic contamination are those in and near the Milltown Reservoir and Frenchtown. Arsenic has also been confirmed in areas east of Corvallis.
Surface arsenic-related pollutants enter the ground water system by gradually moving with the flow of ground water from rains, melting of snow, etc. Either way, ongoing testing for arsenic is an important strategy for private well owners to safeguard the health and well being of their family. If your water comes from a municipal or privately owned water company that has more than 15 service connections or serves 25 people more than 6 months of a year, they are already required by law to test for arsenic in your water.
Like many contaminants that enter drinking water supplies, arsenic is potentially hazardous at high levels. Because you cannot see or taste arsenic in water, you cannot rely on taste, odor, or appearance of the water to determine arsenic levels. Your best course of action is to get your water professionally tested and also compile as much information as possible about your water supply source, well construction, surrounding land-use, and local geology. Note: we do not recommend just testing your water for arsenic because there may be other contaminants in your water. At a bare minimum, the EPA recommends that private well owners test their water annually for coliform bacteria, nitrate, pH, and specific conductance.
Arsenic has long been recognized as a poison. According to the EPA, chronic exposure to low doses in food or water can cause cancer of the bladder, lungs, skin, kidney, nasal passages, liver and prostate. In addition, arsenic has been reported to affect the vascular system in humans and has been associated with the development of diabetes, nervous system problems, and low birth weights. Observable, non-cancer symptoms of arsenic poisoning can include thickening and discoloration of the skin, stomach pain, nausea, vomiting, diarrhea, numbness in hands and feet, partial paralysis, and blindness. Whether someone will develop any of these symptoms depends on the amount of arsenic consumed, the length of exposure, the form of the arsenic, and the general health and sensitivity of the person.
EPA has set the arsenic standard for drinking water at .010 parts per million (10 parts per billion) to protect consumers served by public water systems from the effects of long-term, chronic exposure to arsenic.
If you do have an arsenic problem, there are whole house and point-of-use arsenic removal technologies available that can either reduce or fully remove arsenic from your drinking water. The most common are reverse osmosis or arsenic specific removal media. Be sure to use only an NSF certified product and always sample your water annually to check that your removal system is working correctly. Which type of system is the best solution for your situation should be decided only after consultation with you water treatment professional.
In short, if you own your own, individual well, you are responsible for testing it! Contact your local health department or a testing professional who is certified to test drinking water. Your can also call the Safe Drinking Water Hotline at 800-426-4791 and ask for the state certification officer who can give you names of labs in your area that can do the testing.
If you have any questions, or you would like to have your water professionally tested, don’t hesitate to give us call.
Kinetico of Missoula and Ravalli
Missoula: (406) 728-6400 or
Hamilton: (406) 363-1782