Protecting Public Health and the Environment.

Contaminants in Drinking Water

Drinking water, including bottled water, usually contains at least small amounts of contaminants. However, the presence of contaminants does not necessarily mean that the water poses a health risk. 

EPA Contaminants List

EPA sets standards (maximum contaminant levels [MCLs]) for approximately 90 contaminants that specify the maximum amount of each allowed in drinking water. Information on specific contaminants is available on EPA's website.

Arsenic in Drinking Water

Arsenic is a naturally occurring element found in the earth's crust that is found most everywhere. It occurs naturally in rocks and soil, water, air, and plants and animals. Most arsenic in drinking water comes from natural rock formations. Water that encounters rock formations can dissolve arsenic and carry it into underground aquifers, streams, and rivers that may be used as drinking water supplies. Arsenic has been reported to cause more than 30 different adverse health effects. Learn more.

Lead in Drinking Water

Lead is a toxic metal that, if inhaled or swallowed, can build up in the body over time and cause serious damage to the brain, kidneys, nervous system, and red blood cells. The limited source of lead exposure from your home's water is mostly likely pipe or solder in your home's plumbing. Learn more.

Coliform Bacteria in Drinking Water

Biological organisms are among the oldest health threats to drinking water quality and the agents currently responsible for most waterborne diseases. They are the most common contamination incidents water operators will encounter. Learn more.

Staff Contacts

Drinking Water Program Manager
Jerri Henry
DEQ State Office
Water Quality Division
1410 N. Hilton
Boise, ID 83706
(208) 373-0471

Safe Drinking Water Hotline


More Information

Drinking Water Contaminants

National Primary Drinking Water Regulations

Related Pages

Public Notification Requirements for Public Water Systems