Atomic number 33 on the periodic table, arsenic is a semi-metal element that is odorless and tasteless. It enters drinking water supplies from natural deposits in the earth, as well as from agricultural and industrial activities. Arsenic occurs naturally in rocks and soil, plants and animals. It can be further released into the environment through volcanic action, forest fires and erosion. Approximately 90 percent of industrial arsenic in the U.S. is currently used as a wood preservative, but arsenic is also used in paints, drugs, soaps and semi-conductors. High arsenic levels can also come from farming operations using certain crop fertilizers and some animal feeding practices. Mining, copper smelting and coal burning also contribute to arsenic in our environment.
Like many contaminants that enter drinking water supplies, arsenic is potentially hazardous at high levels. Higher levels of arsenic tend to be found more in drinking water that comes from ground water sources than from surface water sources such as lakes and rivers. This is because the demand on ground water from municipal systems and private wells may cause water levels to drop, releasing arsenic from rock formations. Compared to the rest of the United States, western states have more systems with arsenic levels greater than the EPA’s standard of 10 parts per billion (ppb). Parts of the Midwest and New England have many systems whose current arsenic levels range from 2-10 ppb, but some are greater than 10 ppb. While many systems may not have detected arsenic in their drinking water above 10 ppb, there may be geographic “hot spots” with systems that have higher levels of arsenic. Because you cannot see, smell or taste arsenic in water, it is essential for the well owner to test for arsenic.
How will arsenic exposure affect my health?
Human exposure to arsenic can cause both short and long term health effects. Short (or acute) effects can occur within hours or days of exposure. Long (or chronic) effects occur over many years. Non-cancer effects can include thickening and discoloration of the skin; stomach pain, nausea, vomiting; diarrhea; numbness in hands and feet; partial paralysis; and blindness. Long-term arsenic exposure has been linked to cancer. According to a 1999 study by the National Academy of Sciences, arsenic in drinking water causes bladder, lung and skin cancer, and may cause kidney and liver cancer. The study also found that arsenic harms the central and peripheral nervous systems, as well as heart and blood vessels. It also may cause birth defects and reproductive problems. If you are looking for more information about health effects, please visit the Center for Disease Control’s arsenic web site.
How can I filter arsenic out of my drinking water?
There are two types of arsenic: Trivalent, or Arsenic III (3) and Pentavalent, or Arsenic V (5). Trivalent arsenic is generally more difficult to filter from drinking water than pentavalent arsenic. Trivalent arsenic can be converted to pentavalent arsenic in the presence of an effective oxidizing agent such as free chlorine. So if the supply water is chlorinated, the Arsenic III is converted to Arsenic V, making it easier to remove. If the water supply is not chlorinated, such as in a private well, the trivalent arsenic will remain as the more difficult trivalent arsenic.
The Environmental Protection Agency has classified arsenic as a known human carcinogen. The EPA has set the arsenic standard for drinking water at 10 parts per billion (ppb) to protect consumers served by public water systems from the effects of long-term, chronic exposure to arsenic.
Reverse osmosis can treat water containing up to 160 ppb of arsenic. Reverse osmosis systems have an approximate 90% reduction rate. For higher arsenic levels and greater reduction, you will need to select an arsenic filter certified by NSF International to reduce arsenic, such as these arsenic filters manufactured by Crystal Quest. While such certification is not necessarily a guarantee of safety, it is an independent verification of the effectiveness of these filters. It is critically important that all filters be maintained and replaced at least as often as recommended by the manufacturer; otherwise they might make your drinking water contaminant problems worse.