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At very high dosages arsenic causes immediate effects including nausea, vomiting, and diarrhea. Ingestion of 2 grams or more may be lethal in a very short time. More commonly, arsenic exposure involves much less than this, and may not cause any immediate or observable effects.
Arsenic at low doses over a long period of time is known to cause skin changes that may lead to skin cancer. More recently arsenic has been found to cause other kinds of cancer including lung, colon and bladder cancers. It is classified as a Class A (known) human carcinogen by the US Environmental Protection Agency, and has also been associated with harmful effects on the heart and the circulatory system.
Chronic exposure of animals to arsenic in water may also be harmful to them. Prolonged use of arsenic-rich water for irrigation can results in elevated soil arsenic levels that may become harmful to plants, animals and human beings in the area.
There is no health-based drinking water standard for copper because its offensive characteristics become apparent at concentrations much lower than any known toxic effects.
Copper in water can cause staining of fixtures, hair and fabrics at levels between 0.5 and 4.0 ppm (mg/L). It also imparts a bitter taste to water at 1 – 5 ppm. The US EPA has adopted an action level of 1.3 ppm for public water systems to avoid these economic and aesthetic effects. Systems that have copper at greater levels than this can try corrosion control treatments.
Habitual consumption of drinking water having more that 0.015 mg/L lead is believed to contribute to impaired brain and nerve development and decreased learning ability in young children. Non pregnant, healthy adults are thought to be much more tolerant to low level lead exposures than very small children and developing fetuses.
Nitrate levels above 10 mg/L may present a serious health concern for infants and pregnant or nursing women. Adults receive more nitrate exposure from food than from water. Infants, however, receive the greatest exposure from drinking water because most of their food is in liquid form. Nitrate can interfere with the ability of the blood to carry oxygen to vital tissues of the body in infants of six months old or younger. The resulting illness is called methemoglobinemia, or “blue baby syndrome”.
Pregnant women may be less able to tolerate nitrate, and nitrate in the milk of nursing mothers may affect infants directly. These persons should not consume water containing more that 10 mg/L nitrate directly, added to food products, or beverages (especially in baby formula).
Other domestic uses of affected water such as irrigation, washing and bathing do not result in nitrate absorption. The 10 mg/L standard for Nitrate in water has been devised to protect a select group of sensitive persons.
It has been suggested in human studies that nitrate ingestion may be linked to gastric or bladder cancer. This link, however, has not been firmly established and current exposure levels do not appear to put the population at risk. There is also some evidence that areas having elevated nitrate in drinking water may have increased incidence of spontaneous miscarriage.
Gastrointestinal distress.
EPA List of Drinking Water Contaminants & MCL's
