When well water is tested for arsenic, the testing lab will often report how much is present as the number of milligrams of arsenic per liter of water (a liter is about a quart). Shorthand for milligrams per liter is "mg/L".
The current drinking water standard for arsenic is 0.01 milligrams per liter of water (or 0.01 mg/L). This standard was adopted in 2002 by the U.S. Environmental Protection Agency to protect the water quality of public water systems. The World Health Organization has also recommended a guideline of 0.01 mg/L.
If your water has arsenic, several factors working together will determine how likely it is for harmful health effects to occur. These factors are:
- DOSE – How much arsenic you have been exposed to;
- DURATION – How long and how often you have been exposed;
- GENERAL HEALTH, NUTRITION, AGE, AND LIFESTYLE – Some people may be affected by lower levels of arsenic in water than others may. Young children, the elderly, people with certain long-term illnesses, people with poor nutrition, and smokers may be at greater risk than others.
For water with arsenic levels less than 0.2 mg/L, the major health concern is an increased chance of getting some types of cancer (such as skin, bladder, lung and possibly liver and kidney). How great is the chance of getting cancer? If 1000 people had long-term use of household water with arsenic levels of 0.01 mg/L, then several people might get cancer. For arsenic water levels higher than 0.01 mg/L the chance of getting cancer increases, while for lower arsenic water levels the chance decreases. How many years of water use also changes your chance of getting cancer.
As arsenic water levels become greater than 0.2 mg/L and length of water use becomes longer than a year, the chance of having other health effects you or your doctor can detect becomes more likely. These health effects include:
- Stomach and intestinal irritation apparent as pain, nausea, vomiting, or diarrhea;
- Blood-related effects, such as decreased numbers of red and white blood cells which may result in fatigue, blood vessel damage resulting in bruising, and abnormal heart rhythm;
- Nervous system effects resulting in either a numbness or a "pins and needles" sensation in your hands and feet;
- Skin changes in coloring appearing as a fine freckled or "raindrop" pattern in the trunk and hands and feet, and unusual skin growth (possibly wart-like) on the palms and soles.
Many of the health effects described above for arsenic are often seen with other common illnesses. This makes it difficult to know if these health effects are due to arsenic exposure. If you are concerned about health problems possibly due to arsenic in your water, you should discuss them with your doctor.
If the arsenic level in your water is greater than 0.01 mg/L, the Bureau of Health recommends that you stop using your well water for drinking and preparing food. Bottled water can be used for these purposes as a quick way to decrease the amount of arsenic getting into your body. Drinking water and eating foods prepared with water are the major ways water-borne arsenic gets into your body. Bathing is unlikely to result in much arsenic getting into your body through skin, but a watchful eye may be needed with kids to prevent play-related drinking of bath water.
Arsenic is rather quickly removed from your body. Most of the arsenic in your body will be gone several days after stopping use of water for drinking and cooking. Some of the health effects described above either partly or completely go away after use of high arsenic water has ended.
Do not attempt to remove arsenic from water by boiling. Boiling water will only increase arsenic levels.
There are in-home treatment systems to remove arsenic from your water. Examples of treatment systems that have been used for individual homes are: Distillation systems, that convert water to steam leaving the arsenic behind and then condense the steam back to water; Reverse Osmosis systems that force water through a filter to remove arsenic; Iron Oxide filter media that use a magnetic like attraction to grab onto and hold arsenic molecules, Anion Exchange systems that replace arsenic in water with a nontoxic chemical; and Activated Alumina systems that adsorb arsenic from water.
Which treatment system or combined systems are best for you will depend on several factors, such as: 1) how high your arsenic water levels are and therefore how much needs to be removed; 2) whether you want to treat all water coming into the house or just water at one or two sinks; and 3) the chemistry of your water – some treatment systems do not remove certain forms of arsenic very well. Costs of systems can range from $500 to more than $3000. Because choosing a system requires thinking about your specific well water chemistry along with your water needs, a water treatment specialist should always be consulted prior to buying a water treatment system. After installing a new water treatment system, ALWAYS retest your water to make sure the arsenic has been removed.
The arsenic in your well water may come from natural sources or human activity. Arsenic is an element commonly found in soil and rocks, and certain rock types tend have higher levels of arsenic. Pesticides and herbicides containing arsenic were commonly used in farming (e.g., blueberry, apple, potato) and other practices during the first half of this century, but their use was greatly restricted after the 1960s. Pressure treated wood contains arsenic that can leach into underlying soils and transfer on to skin from casual contact with wood surfaces that have not been properly treated with a sealant.
A great number of Maine wells could have arsenic levels above the 0.01 mg/L standard. Wells with high arsenic can sometimes occur as a localized group. For this reason, we recommend you inform your neighbors if your water has tested high for arsenic. The Bureau of Health recommends that all residents with a private water supply test their water for arsenic using a laboratory certified by the state to perform this test.
On health effects of arsenic in water:
Maine Center for Disease Control and Prevention – (207) 287-5189
On treatment methods for removing arsenic:
Drinking Water Program - (207) 441-5324