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General information about arsenic and its health effects

What is arsenic and where does it come from?
Arsenic is a naturally occurring element found in the earth’s crust. As water flows through certain rock formations, the arsenic can be dissolved and carried into underground aquifers, streams or rivers that might be used as drinking water sources.

How can arsenic affect my health?
Arsenic is a health hazard. Drinking water that has high levels of arsenic can cause health effects such as:

  • Thickening and discoloration of the skin;
  • Stomach pain, nausea, vomiting and diarrhea;
  • Heart, lung, liver, immune, nervous or reproductive system disorders and diabetes; and
  • Cancer of the bladder, lungs, skin, kidney, liver and prostate.
When does arsenic in drinking water become a health concern?
Arsenic is measured in parts per billion (ppb), parts per million (ppm) or milligrams per liter (mg/l). Parts per million and milligrams per liter are the same. Parts per billion is the same as ppm divided by 1000. The federal government has established the safe drinking water standard, also called maximum contaminant level or MCL, for arsenic as 10 ppb (0.010 ppm). If your water has arsenic levels above 10 ppb (0.010 ppm), it is recommended to switch to bottled water.
Safely using arsenic-contaminated water (See Table below.)

Does boiling the water remove arsenic?
Don't boil the water! Boiling contaminated water does not remove arsenic and can, in fact, increase arsenic levels.

Can I wash, prepare and cook my food with arsenic-contaminated water?
If arsenic levels in your water are above 10 ppb (0.010 ppm), you should use bottled water to wash, prepare and cook your food. Water that is to be used for drinking, beverage-making or food preparation can be obtained from a known safe source and used on a temporary basis. Non-ingested uses of water pose much less hazard, but are not entirely safe if arsenic levels are significantly above the drinking water limit.

Can I irrigate or water my garden with arsenic-contaminated water?
If your water has more than 100 ppb (0.100 ppm) of arsenic, you should not use it for irrigation. Over a period of years, the amount of arsenic in the soil can build up to levels that are poisonous for some plants. An increase in soil arsenic can also pose a direct hazard to humans by accumulating in food crops.

What about bathing and showering?
Arsenic does not easily enter the body through the skin. Bathing, swimming and showering with water that has levels as high as 500 ppb (0.500 ppm) is safe as long as you avoid swallowing the water. Supervise small children when they are bathing and brushing teeth to ensure they do not swallow the water.

What about washing dishes, utensils and food preparation areas?
Only a very small amount of water clings to smooth surfaces, like dishes. Water contaminated with arsenic to 500 ppb (0.500 ppm) can safely be used to wash and sanitize dishes, tables and eating utensils.

What about general cleaning and laundry?
Very little water remains on washed surfaces and in laundered fabrics. Water contaminated with arsenic up to 500 ppb (0.500 ppm) can safely be used for general cleaning and washing of clothing, bedding and linens.

What about my pets?
Animals should not drink water that is above 10 ppb (0.010 ppm).

Learning about arsenic levels in your drinking water

For people on municipal or public water systems:
Public drinking water providers are required to monitor for arsenic and ensure levels are below the drinking water standard of 10 ppb (0.010 ppm). If your water comes from a public water system (i.e., you pay a water bill), you can find results on the Oregon Drinking Water Services Data Online website. Your drinking water provider may also be required to provide a Consumer Confidence Report to its customers every year. This report contains the most recent arsenic test results. Contact your drinking water provider for a copy of the most recent consumer confidence report.

For private well owners:
If your drinking water comes from your own well, you will have to find an accredited laboratory that does water testing for private property owners. These labs can provide information and instructions for getting your well water tested. For a list of accredited laboratories in Oregon, call Oregon Environmental Laboratory Accreditation Program (ORELAP) at 503-693-4122.

Removing arsenic from drinking water

For public drinking water system operators:
Arsenic can be reduced or removed entirely from drinking water, but treatment processes are expensive and require careful maintenance and monitoring.Treatment options include activated alumina, electrodialysis, reverse osmosis and ion exchange resins. Alternatives to treatment include developing a different water source or connecting to another safe water source in the area.

Not all kinds of treatment are effective, and no single treatment method can remove all contaminants from water. Before deciding on treatment equipment, contact Oregon Drinking Water Services for regulatory requirements for public water systems.

For private well owners:
Several treatment methods can remove arsenic from drinking water. The one most commonly used is called reverse osmosis.

Treatment equipment must be carefully maintained in order to work properly, and might not be effective if arsenic levels are very high. It is recommended that treated water be tested at least once a year. Untreated water should be tested at least every 3 years.

Check to be sure that any treatment system is certified by a recognized, third-party testing organization that meets strict testing procedures established by the American National Standards Institute (ANSI) and the National Sanitation Foundation (NSF) International.

For more information


Updated: February 2015


Safely using arsenic-contaminated water
Arsenic Level Water Use Recommendations
10 ppb or less
(0.010 ppm or less)
  • SAFE for drinking, cooking and all other domestic uses
  • Test water once every 3 years
Between 10 and 99 ppb
(between 0.010 and 0.099 ppm)
  • NOT SAFE for drinking, mixing into beverages, cooking or washing fruits and vegetables
  • NOT SAFE for pets to drink
  • SAFE for all other domestic uses, including bathing, washing dishes, doing laundry or irrigating gardens
  • Use bottled water (or approved water filtration system) for drinking, cooking and washing fruits and vegetables.
  • Use bottled water for pets.
  • Supervise children to help them avoid swallowing water while bathing, brushing teeth, etc.
  • If you have a treatment system, test treated water at least once a year. Test untreated water (pre-treatment unit) at least every 3 years
Between 100 and 499 ppb
(between 0.100 and 0.499 ppm)
  • Same restrictions as above
  • NOT SAFE for irrigating gardens – arsenic can build up in soil over time and be taken up into vegetables
  • SAFE for all other domestic uses
500 ppb and greater
(0.500 ppm and higher)
  • NOT SAFE for any domestic uses
  • Contact your local or state health department or Oregon Drinking Water Services at 971-673-0405

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