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State Water Resources Control Board <br />Division of Water Quality <br />GAMA Program <br />HEALTH EFFECT INFORMATION <br />Arsenic is a known human carcinogen, and ingestion of arsenic has been reported to <br />increase the risk of cancer in the liver, bladder, kidney, lungs, and skin. Arsenic is <br />known to the State of California to cause cancer for purposes of the Safe Drinking <br />Water and Toxic Enforcement Act of 1986 ("Proposition 65"), and was added to the <br />list of carcinogens in 1987. <br />In November 2008, the California MCL for arsenic was revised from 50 µg/L to <br />10 µg/L. The National Academy of Sciences estimated that the lifetime risk of <br />developing bladder or lung cancer from arsenic in tap water (assuming 2 liters <br />consumption per day) is greater than 3 in 1,000 for an arsenic level of 10 µg/L. The <br />US EPA MCL of 10 µg/l_ has been in effect in California since January 2006. <br />When groundwater is the transport and exposure medium, we are primarily concerned <br />with ingestion of contaminated water as the route for greatest human exposure to <br />arsenic. In humans, arsenic is quickly absorbed after ingestion, while dermal (skin) <br />exposure to arsenic only results in a small amount of arsenic entering the body. Upon <br />absorption from the gastrointestinal tract, the liver changes some of the arsenic to a <br />less harmful organic form. Both inorganic and organic forms are excreted from the <br />body in urine. Most of the arsenic will be excreted within several days, although some <br />will remain in the body for several months or longer. <br />Inorganic arsenic has been recognized as a human poison since ancient times, with <br />large oral doses (above 60,000 gg/L in food or water) producing death. Ingestion of <br />moderate to elevated levels of inorganic arsenic (greater than 300 µg/L) may cause <br />irritation of the stomach and intestines, with symptoms such as pain, nausea, <br />vomiting, and diarrhea. Other effects from the ingestion of arsenic include decreased <br />production of red and white blood cells, abnormal heart rhythm, blood -vessel damage, <br />and impaired nerve function causing a "pins and needles" sensation in the hands and <br />feet. Although there is no strong evidence that arsenic can affect pregnant women or <br />their fetuses, studies in animals show that doses of arsenic that are large enough to <br />cause illness in pregnant females may cause low birth weight, fetal malformations, or <br />even fetal death. <br />Long-term oral exposure to inorganic arsenic may cause patterns of skin changes, <br />including a darkening of the skin and the appearance of small "corns" or "warts" on <br />the palms, soles, and torso. A small number of the corns may ultimately develop into <br />skin cancer. <br />Revised October 2017 <br />