National Drinking Water Database
Arsenic (total) in Delaware
Arsenic contaminates drinking water due to mining runoff, erosion of natural deposits, emissions from glass and electronics processing and the use of arsenical compounds as wood preservatives and pesticides. [read more]
Arsenic is an element that is widely distributed in the earth's crust. Elemental arsenic is ordinarily a steel grey metal-like material that sometimes occurs naturally. However, arsenic is usually found in the environment combined with other elements such as oxygen, chlorine, and sulfur. Arsenic combined with these elements is called inorganic arsenic. Arsenic combined with carbon and hydrogen is referred to as organic arsenic. Organic forms of arsenic are usually less harmful than inorganic forms.
Presently about 90 percent of all arsenic produced is used as a preservative for wood to make it resistant to rotting and decay. The preservative is chromated copper arsenate (CCA) and the treated wood is referred to as "pressure-treated." In the past, arsenic was primarily used as a pesticide, most often on cotton fields and in orchards. Inorganic arsenic compounds can no longer be used in agriculture. However, organic arsenicals, namely cacodylic acid, disodium methylarsenate (DSMA) and monosodium methylarsenate (MSMA), are still used as pesticides, principally on cotton. Small quantities of arsenic metal are added to other metals to form metal mixtures or alloys with improved properties. The greatest use of arsenic in alloys is in lead-acid batteries used in automobiles. Other common uses of arsenic compounds include manufacturing of glass, semiconductors and light-emitting diodes.
Arsenic is a known human carcinogen with toxic effects on nearly all organ systems (ATSDR 2000d). Studies of people who drink tap water with high levels of arsenic show increased risk for cancers of the skin, bladder, lung, kidney, liver and colon (National Toxicology Program (NTP) 2002a). In laboratory animals, arsenic causes cancer when exposure occurs early in life, producing malignant, benign and precancerous lesions in adulthood at multiple sites including the lung, liver, adrenal gland and ovary (Waalkes 2003). In addition, arsenic causes proliferative lesions in the uterus and oviduct in exposed animals.
In 2001, a report by the National Academy of Sciences concluded that people who consume drinking water with three parts per billion (ppb) arsenic daily would have about a 1 in 1000 increased risk of developing bladder or lung cancer. At 10 ppb, the risk is even greater (National Research Council (NRC) 2001). Since 2006, EPA has decreased the highest allowable level, called a maximum contaminant level (MCL), of arsenic in drinking water from 50 ppb to 10 ppb (USEPA 2003c; USEPA 2006a). In 2004, the California Environmental Protection Agency established a long-term objective (called a public health goal) for a maximum drinking water concentration for arsenic of four parts per trillion, 2500 times lower than the EPA's MCL of 10 ppb. Four parts per trillion is a level of arsenic in drinking water that would not be expected to pose a significant human health risk (California Environmental Protection Agency 2004).
Long-term ingestion of arsenic in drinking water results in pronounced vascular changes, peripheral vascular insufficiency and adverse effects on bone marrow (ATSDR 2000d). Studies of communities with high drinking water levels, such as in Bangladesh, India and Taiwan, show that arsenic is associated with increased risk of diabetes (Longnecker and Daniels 2001; Tseng 2002), high blood pressure and heart disease (Tseng 2003; Wang 2002), skin disorders, neurological problems, chromosome damage (Mahata 2003), respiratory problems and birth defects. Arsenic has also been linked with harmful developmental effects in children (California Environmental Protection Agency 2004).
In 2004, the U.S. EPA's Toxics Release Inventory (TRI) reported that in 2002, U.S. industrial facilities released 1,842,882 pounds of arsenic and 403,580,936 pounds of arsenic compounds into the environment, mostly to the land (such as landfills, surface soil, spills and holding ponds) (USEPA 2009i).
The Most Polluted Communities in Delaware
65 water utilities reported detecting Arsenic (total) in tap water since 2004, according to EWG's analysis of water quality data supplied by state water agencies
Ranked by highest average Arsenic (total) level
|Rank||System||Population Served||Positive test results of total reported tests||Average Level|
|1||Felton Water Department|
|1,591||8 of 8||10.34 ppb|
(5 to 28.7 ppb)
|2||Clayton Water Department|
|2,250||14 of 14||8.29 ppb|
(6.3 to 10.77 ppb)
|450||45 of 46||6.69 ppb|
(0 to 13 ppb)
|450||106 of 112||5.23 ppb|
(0 to 13 ppb)
|204||3 of 3||4.27 ppb|
(3.9 to 5 ppb)
|6||Holly Hill Estates|
|831||1 of 1||3.3 ppb|
|7||Long Farm Estates|
|123||4 of 4||3.05 ppb|
(2.5 to 3.4 ppb)
|8||Bridgeville Water Department|
|1,350||1 of 1||3 ppb|
|213||1 of 3||2.93 ppb|
(0 to 8.8 ppb)
|10||Camden Wyoming Sewer and Water Authority|
|3,500||1 of 1||2.8 ppb|
Health Based Limits for Arsenic (total)
|Maximum Contaminant Limit Goal (MCLG)||A non-enforceable health goal that is set at a level at which no known or anticipated adverse effect on the health of persons occurs and which allows an adequate margin of safety. Source: U.S. Environmental Protection Agency.||0 ppb|
|California Public Health Goals||Defined by the State of California Office of Environmental Health Hazard Assessment (OEHHA) as the level of contaminant that is allowed in drinking water. For acutely toxic substances, levels are set at which scientific evidence indicates that no known or anticipated adverse effects on health will occur, plus an adequate margin-of safety. PHGs for carcinogens or other substances which can cause chronic disease shall be based solely on health effects without regard to cost impacts and shall be set at levels which OEHHA has determined do not pose any significant risk to health.||<0.01 ppb|
|EPA Human Health Water Quality Criteria||Water quality criteria set by the US EPA provide guidance for states and tribes authorized to establish water quality standards under the Clean Water Act (CWA) to protect human health. These are non-enforceable standards based upon exposure by both drinking water and the contribution of water contamination to other consumed foods. Source: U.S. Environmental Protection Agency.||0.02 ppb|
|One in one million (10-6) Cancer Risk||The concentration of a chemical in drinking water corresponding to an excess estimated lifetime cancer risk of 1 in 1,000,000. Source: U.S. Environmental Protection Agency.||0.02 ppb|
|One in ten thousand (10-4) Cancer Risk||The concentration of a chemical in drinking water corresponding to an excess estimated lifetime cancer risk of 1 in 10,000. Source: U.S. Environmental Protection Agency.||2 ppb|
|Maximum Contaminant Limit (MCL)||The enforceable standard which defines the highest level of a contaminant that is allowed in drinking water. MCLs are set as close to health-based limits (Maximum Contaminant Level Goals, or MCLGs) as feasible using the best available analytical and treatment technologies and taking cost into consideration. Source: U.S. Environmental Protection Agency.||10 ppb|
|Drinking Water Equivalent Level||A lifetime exposure concentration protective of adverse, noncarcinogenic health effects, that assumes all of the exposure to a contaminant is from drinking water. Source: U.S. Environmental Protection Agency.||10 ppb|
Violation Summary for Arsenic (total) in Delaware
Data from the U.S. Environmental Protection Agency includes the following violations of federal standards in Delaware since 2004
|Violation Type||Number of Violations|
|Over maximum contaminant level, Average||3|