Arsenic is a naturally occurring element found in the Earth’s crust. It is widely distributed throughout the environment in the air, water, and land. As water moves through certain rock formations, it can dissolve arsenic and carry it into underground aquifers, becoming a contaminant in drinking water.
Health Impacts of Arsenic Exposure
Long-term exposure to inorganic arsenic, primarily through contaminated drinking water, can lead to various health problems. Initial symptoms often appear on the skin, including pigmentation changes or hard patches (hyperkeratosis) on palms and soles. These skin manifestations can take at least five years to develop and may indicate an increased risk of skin cancer.
Beyond skin conditions, prolonged consumption of arsenic-contaminated water is linked to a heightened risk of several internal cancers, including bladder, lung, kidney, liver, prostate, and nasal passages. Exposure can also contribute to cardiovascular disease, diabetes, and neurological issues. Developmental effects like low birth weight and premature delivery have also been associated with arsenic exposure.
Understanding Acceptable Arsenic Levels
“Acceptable levels” of arsenic in drinking water refer to regulatory limits established by health organizations to mitigate these potential health risks. The U.S. Environmental Protection Agency (EPA) has set a Maximum Contaminant Level (MCL) for arsenic in public drinking water at 0.010 milligrams per liter (mg/L), which is equivalent to 10 parts per billion (ppb). This standard is enforceable for public water systems, meaning they must ensure their water meets this limit.
The World Health Organization (WHO) also recommends a guideline value of 10 micrograms per liter (μg/L), or 0.01 mg/L, for arsenic in drinking water. While this guideline is considered provisional due to practical difficulties in arsenic removal, it reflects an international consensus on a desirable level. It is important to note that the EPA’s Maximum Contaminant Level Goal (MCLG) for arsenic is zero, reflecting no completely risk-free level for a known carcinogen. However, this health-based goal is not an enforceable limit for public water systems.
These federal regulations apply to public water supplies. Private wells, which provide water to individual homes, are not subject to federal oversight, placing the responsibility for water quality directly on the well owner.
Sources of Arsenic and Water Testing
Arsenic primarily enters drinking water from natural geological sources, as water dissolves the element from rocks and soil. Certain regions have naturally elevated arsenic levels due to their geology. Less common sources include industrial processes, mining, and the historical use of pesticides or wood preservatives.
Since arsenic is odorless, tasteless, and colorless, it is impossible to detect its presence without testing. Testing is especially important for private well owners, who are responsible for ensuring their water is safe. Water can be tested by collecting a sample and sending it to a state-certified laboratory. These laboratories accurately measure arsenic concentrations, providing information to determine if treatment is needed.
Reducing Arsenic in Drinking Water
If water testing reveals arsenic levels above acceptable limits, several treatment options are available. These include point-of-use systems, which treat water at a single tap (like an under-sink filter), or point-of-entry systems, which treat all water entering a home. Effective technologies for arsenic removal include reverse osmosis, activated alumina, and ion exchange. Oxidation/filtration and coagulation/filtration are also used.
Boiling water does not remove arsenic; boiling can concentrate arsenic as water evaporates, potentially increasing levels. Consulting with water treatment professionals is advisable to select the most appropriate system, as effectiveness depends on water chemistry and the form of arsenic present.