Drinking Water: Arsenic

Arsenic is a naturally occurring element present in rocks and soil. Arsenic is the 20th most abundant element in the earth's crust and often forms inorganic compounds by combining with oxygen, chlorine and sulfur. As water passes through and over soil and rock formations, it dissolves many compounds and minerals including arsenic. The result is that varying amounts of soluble arsenic are present in some water sources. Arsenic chemistry is complex, because it has many forms.

Arsenic contamination of a drinking water source most often results from natural sources; however, it can result from human activities. Arsenic solutions were used to treat a variety of health disorders in the past. While the medical use of arsenic has declined, an arsenic solution received Food and Drug Administration approval for leukemia treatment in 2000. Arsenic has been used in mining and manufacturing and was a component of some pesticides used in the past. Chromated copper arsenate was used to pressure-treat wood for preservation and to prevent insect damage; this wood commonly was known as CCA-treated lumber.

Indications of Arsenic in Water

Potential Health Effects

Arsenic exposure can cause a variety of adverse health effects. The severity of the effect depends on how much arsenic is in the water, how much water is consumed, how long a person has been drinking the water, and a person's general health. Arsenic poisoning can be acute or chronic. Acute poisoning can occur when a high concentration (over 60 mg/L) of arsenic is ingested over a short time. This is more likely to occur where arsenic has been concentrated by industrial processes or at unregulated waste disposal sites. Chronic poisoning can occur when moderate or small amounts of arsenic are ingested over long periods (usually five years or longer), such as where groundwater containing arsenic is consumed daily for extended periods. Some Nebraska groundwater supplies contain arsenic in high enough concentrations to present a risk of chronic poisoning. Arsenic is a known carcinogen, and long-term ingestion may increase the risk of cancer.

Uncertainty exists in arsenic risk assessment, and more research must be done to determine the connections between level of arsenic, duration of exposure, and health effects. However, studies summarized in a recent report by the National Research Council point to a preponderance of evidence that long-term ingestion of arsenic can increase the risk of skin, bladder, lung, kidney, liver, and prostate cancer. Non-cancer effects of ingesting arsenic may include cardiovascular, pulmonary, immunological, neurological effects, and endocrine problems such as diabetes.

Symptoms of chronic arsenic poisoning are usually delayed, with years of exposure required to initiate the disease process. Factors such as genetics, age, metabolism, diet and overall health may also impact health risks associated with arsenic exposure, because they potentially affect one's ability to clear arsenic from the system. Individuals with chronic Hepatitis B infection, protein deficiency or malnutrition may be more sensitive to the effects of arsenic. Children and older adults may be other groups at special risk.

Note: This publication is not a substitute for professional medical advice. If you have any questions or concerns related to potential health effects from consuming water containing arsenic, consult your physician.

Sampling and Testing

Testing Public Water Supplies

Public water supplies classified as either community or non-transient non-community are required to test for arsenic concentration. If your water comes from a public water supply, contact the water utility for the arsenic level in your water.

Testing Private Water Supplies

Water quality in private wells is not currently regulated; thus, the regular testing of a private water supply is not required under state or federal law. If users want to know the concentration of arsenic in a private water supply, they will need to have the water tested at their own expense. Tests to determine the presence of arsenic in drinking water should be done by a laboratory approved for arsenic testing. The Nebraska Health and Human Services System Division of Regulation and Licensure approves laboratories to conduct tests for drinking water supplies. An approved laboratory might not be approved to test for all potential drinking water contaminants. Rather, approval must be obtained for each specific contaminant. This approval means that recognized, standard tests and quality control procedures are used. Water testing laboratories in Nebraska approved to test private drinking water for arsenic include:

Nebraska Health and Human Services
Department of Regulation and Licensure
Public Health Laboratory
3701 South 14th
Lincoln, NE 68502
402-471-2122

Servi-Tech Laboratories
1602 Park West Drive
Hastings, NE 68901
402-463-3522

Midwest Laboratories, Inc.
13611 B Street
Omaha, NE 68144
402-334-7770

Interpreting Test Results

Public Water Supply Test Results

The quality of water supplied by Public Water Systems is regulated by the U.S. Environmental Protection Agency (EPA) and the Nebraska Health and Human Services System Department of Regulation and Licensure. This includes any well with 15 or more service connections or that regularly serves 25 or more people.

Public drinking water standards established by EPA fall into two categories -- Secondary Standards and Primary Standards. Secondary Standards are based on aesthetic factors such as taste, odor, color, corrosivity, foaming, and staining properties of water that may affect the suitability of a water supply for drinking and other domestic uses. Primary Standards are based on health considerations and are designed to protect human health. The EPA has established an enforceable Primary Standard for arsenic in public drinking water supplies.

The Maximum Contaminant Level (MCL) for arsenic had been 50 parts per billion since 1942. Three expert panel reports on the science, cost of compliance, and benefits analyses on arsenic in drinking water were released in October 2001. They were: The National Academy of Sciences National Research Council's Report, The National Drinking Water Advisory Council Report, and The Science Advisory Board Report. Reports indicated the EPA had underestimated the cancer risks of arsenic in drinking water. With this new information, EPA issued regulations revising the arsenic drinking water standard. EPA established an enforceable MCL for arsenic of 0.010 milligrams per liter (mg/L) which can also be expressed as 0.010 parts per million (ppm). This amount is equivalent to 10 micrograms per liter (ug/L) which can also be expressed as 10 parts per billion (ppb). The new regulation applies to all community water systems (CWS) and non-transient non-community water systems (NTNCWS). A CWS is a public water system that serves at least 15 locations or 25 residents regularly year round (e.g., most cities and towns, apartments, and mobile home parks with their own water supplies). An NTNCWS is a public water system that is not a CWS and serves at least 25 of the same people more than 6 months of the year (e.g., schools, churches, nursing homes, or businesses with their own water supplies).

The new arsenic MCL becomes effective in January, 2006. As many as 82 Nebraska public water systems have historic arsenic levels greater than 10 ppb and could be out of compliance when the new arsenic rule goes into effect. Communities are located throughout the state, with clusters in the Panhandle, southwest, and south central areas. The new arsenic regulations allow public water systems to apply for exemptions, providing them additional time to meet the new standard. All systems may be granted three additional years to comply with the revised standard. Those systems serving 3,300 or fewer people could be eligible for an additional six years beyond that (nine years total). The arsenic concentration in the water, the number of years before achieving compliance, and the financial burden on the water system are some of the factors taken into consideration when determining whether an exemption is granted.

Private Water Supply Test Results

Options

Options For Public Water Supplies

Of the 82 public water systems in Nebraska affected by the arsenic rule, some communities may be able to meet the new MCL by shutting down or replacing one or two wells. Other communities will need to find other alternatives for lowering the arsenic concentration in the drinking water. These alternatives may range from finding new wells that contain water with a lower arsenic concentration, treating the water, or becoming part of a larger rural or community water district (which benefits from economies of scale in treating water or obtaining water from a high quality source). Management and disposal of the waste stream generated (arsenic removed) also must be considered. EPA has provided millions of dollars for research and development of more cost-effective technologies to help public water systems meet the more protective 10 ppb standard. Some of this research is not yet complete. Research results will be available to help communities select the best alternative for their situation.

Water users wishing to reduce arsenic levels prior to a community achieving compliance can treat water as described in the "Options For Private Water Supplies" section below.

Options For Private Water Supplies

Summary

The following individuals reviewed this publication:

Mary K. Warner, Extension Educator, University of Nebraska
Randy Cantrell, Community Development Specialist, University of Nebraska Rural Initiative
Lynne M. Klawer, Project Coordinator, University of Nebraska
David C. Gosselin, Groundwater Geologist, University of Nebraska
Sandra Scofield, Nebraska Rural Initiative Director, University of Nebraska
Wayne Woldt, Extension Water and Environment Specialist, University of Nebraska
Mike Wentink, Training and Certification Officer, Nebraska Health and Human Services System