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Human Health & Well Water

Contaminants in Well Water

While many wells in Oregon provide clean water, some wells do become contaminated due to natural and un-natural causes. This contamination can cause both short and long-term health effects. This page includes information on: 


The best way to know if your well water is safe is to get it tested!

How to get your water tested

What contaminants can be present in well water?

Naturally occurring contaminants and contaminants introduced by people can be present in well water.

Natural chemical or mineral contaminants may include arsenic and radon.

Contaminants introduced by people result from land use, stormwater overflow, and other events happening near your well. These may include: 

  • Pesticides,
  • chemicals and 
  • harmful bacteria
Contaminants vary by location and all wells, despite a neighbor's lack of contaminants or varying well depth, should be routinely monitored to ensure your and your family's good health.

In Oregon, routine testing for: 

  • Nitrate (English), nitrato (Spanish), 
  • Coliform bacteria (English), bacterias coliformes (Spanish) and 
  • Arsenic (English) arsénico (Spanish) are recommended. If selling property in Oregon, these tests are required by law.

Visit the Well User Resource Toolkit for more information about common well water contaminants in Oregon. 

Can these contaminants make me and others sick?

The short answer to this question is yes. While it may depend on the toxicity of a chemical, its concentration, and the duration of exposure, well water contaminants can lead to short and or long term health effects. The Centers for Disease Control and Prevention (CDC) have identified the following to be the most common outbreaks in domestic well systems:  

  • Hepatitis A (liver disease usually spread by ingesting fecal matter)
  • Giardia intestinalis (diarrheal disease caused by feces contamination)
  • Campylobacter (infectious disease caused by bacteria)
  • E. coli (bacteria caused disease)
  • Shigella (infectious disease caused by a group of bacteria)
  • Salmonella (infectious disease caused by a group of bacteria)
  • Cryptosporidium (diarrheal disease caused by parasite)
  • Arsenic and Nitrate poisoning (cancer and other symptoms)
  • NEW! Harmful Algae Blooms English / Spanish (produce toxins, and when ingested can cause negative health effects)

While everyone in your household may not be affected, vulnerable populations (i.e.: children, the elderly, pregnant women, and autoimmune compromised individuals) are particularly susceptible. For other contaminants and their health effects, visit Drinking Water Services' list of chemicals.  

More information

Visit the Domestic Well Safety Program webpages for more information including details on: