WATER CONTAMINANTS
We took over 120,000 samples of water to test for 220 different contaminants. Learn about the different types of contaminants that were detected in our water.
Microbial contaminants, such as viruses and bacteria that may come from sewage treatment plants, septic systems, agricultural livestock operations, and wildlife.
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Inorganic contaminants, such as salts and metals, that can be naturally-occurring or result from urban stormwater runoff, industrial or domestic wastewater discharges, oil and gas production, mining, or farming.
Disinfection and Disinfection Byproducts are compounds that are generated as a part of the water treatment process.
Pesticides, herbicides and fertilizers that may come from a variety of sources such as agriculture, urban stormwater runoff, and residential uses.
Organic chemical contaminants, including synthetic and volatile organic chemicals that are by-products of industrial processes and petroleum production, and can also come from gas stations, urban stormwater runoff, agricultural application, and septic systems.
Radioactive contaminants that can be naturally-occurring or the result of oil and gas production and mining activities.
ARSENIC
What is it?
Arsenic is the 33rd element on the periodic table. Arsenic is in the same chemical family as phosphorus. Phosphorus is important for life because it helps form the backbone of DNA. Arsenic can replace phosphorus in the DNA structure, causing it to become unstable.
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Arsenic can naturally be found in trace amounts in rocks and soils, and is an abundant element in the earth’s crust. Over time, arsenic dissolves in groundwater which may be used as drinking water.
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Arsenic was used throughout the 20th century as an insecticide. While it was banned in the 1980s, it still lingers in soils and groundwater, and can get into food crops like rice and apples. Today, Arsenic has uses in industry and commerce, including wood preservatives, paints, dyes, metals, pharmaceuticals, soaps, rat poison and semiconductors.
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How does it get into our water?
Much of our water comes from snowmelt from the Eastern Sierra Nevada mountains. While otherwise pristine, this water has high levels of naturally-occurring arsenic. It originates from geothermal springs with levels around 200 ppb, and gets diluted when mixed with snowmelt.
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Arsenic is removed at two treatment facilities to reduce the concentration in our water. The first is at a treatment facility along the LA Aqueduct at Cottonwood, and the second is at the LA Aqueduct Filtration Plant in Sylmar. LADWP is currently exploring additional treatment processes to reduce arsenic concentrations.
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Why does it matter?
Long-term Arsenic exposure has become a major health concern throughout the world. Today, more than 140 million people across 50 countries are drinking water that contains arsenic above the maximum contaminant level of 10 parts per billion.
While Arsenic at high concentrations can be lethal, in drinking water it is not present in high enough concentration to cause acute toxicity. Instead, chronic, low-level exposure has been linked to several types of cancer including liver, kidney and bladder cancer. It can also interfere with cell metabolism and cause diabetes.
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Drinking Water Standards
The Chemical Contaminants Rule sets a maximum contaminant level (MCL) for arsenic of 10 parts per billion (ppb). Our treated water has arsenic levels that are consistently below this limit. The Public Health Goal (PHG) for Arsenic is 0.004 parts per billion (ppb).
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Arsenic is removed in our water treatment facilities through the use of coagulation. First, chemicals are added that causes arsenic to form larger particles so they can settle out. Solid arsenic is then removed through filtration. At LACWD we are currently exploring new treatment methods to meet the PHG.