Well Water Contaminants

Learn more about the well water contaminants that can pose a risk to your health, home, and longterm well-being.

Contaminants marked with a star indicate particular concern for southwest Montana.
Contaminant What It Is Why It Matters Who Is Most Vulnerable
Arsenic Naturally occurring metalloid. Long-term exposure linked to developmental effects, diabetes, and cancer risk. Pregnant women and individuals with long-term exposure.
Boron Naturally occurring metalloid. High levels may affect digestive system and kidney/liver function. Pregnant women, infants, young children.
Iron Naturally occurring metal. High levels give water a metallic taste and cause reddish-brown staining. Does not pose health risks, but can affect plumbing.
Lead Metal that often enters water through corrosion of pipes. Damages brain and nervous system; serious developmental impacts. Pregnant women, infants, young children.
Lithium Naturally occurring metal. High levels linked to nausea, tremors, thyroid and kidney effects; developmental research ongoing. Infants, pregnant women, individuals with thyroid/kidney conditions.
Manganese Naturally occurring metal. High levels linked to neurological and developmental effects. Infants, young children, pregnant women.
Selenium Naturally occurring metalloid; may also result from industrial sources. Elevated exposure associated with neurological and other health effects. Individuals with long-term exposure.
Strontium Naturally occurring metal. High levels may interfere with bone development. Infants and young children.
Uranium Naturally occurring radioactive metal. Long-term exposure primarily affects kidney function. Individuals with long-term exposure or kidney conditions.

Metals and Metalloids

Contaminant What It Is Why It Matters Who Is Most Vulnerable
Hardness Elevated calcium and magnesium dissolved in water. Causes scale buildup in pipes and appliances; reduces efficiency. Not a health risk. Homes with older plumbing or high-efficiency appliances.
Sodium Absorption Ratio (SAR) Measures sodium relative to calcium and magnesium. High SAR can damage soil structure and harm plant growth. Not a drinking water health risk. Property owners using water for irrigation or agriculture.
Conductivity Measures how well electricity moves through water, used to estiamte Total Dissolved Solids. Provides a general measure of water quality and levels of dissolved ions, which can indicate potential contamination. High conductivity is an indicator of potential contamination and indicates that more robust testing is needed.
Total Dissolved Solids (TDS) Total concentration of dissolved minerals and salts. Affects taste; very high levels may cause temporary digestive discomfort. Infants and young children.
pH Measures how acidic or basic your water is. Low pH can corrode plumbing, potentially allowing metals like lead or copper to leach into drinking water; high pH can contribute to scale buildup in plumbing. Homes with metal plumbing are more susceptible to corrosion from low pH water.

Physical Properties

Contaminant What It Is Why It Matters Who Is Most Vulnerable
Fluoride Naturally occurring mineral; often added to public water for dental health. Low levels protect teeth; high levels can cause dental or skeletal fluorosis. Young children during tooth development.
Chloride Naturally occurring mineral; road salt runoff or water softeners can be additional sources. High levels can affect taste, increase sodium intake, and corrode plumbing. Individuals on sodium-restricted diets.
Sodium Naturally occurring mineral; may increase from water softeners. Affects taste and increases dietary sodium intake. Individuals on sodium-restricted diets.
Sulfate Naturally occurring mineral. Can affect taste and smell; may cause temporary digestive upset. Infants and individuals new to the water supply.

Inorganics

Contaminant What It Is Why It Matters Who Is Most Vulnerable
Coliform bacteria Bacteria found in the environment and feces of warm-blooded animals. Indicates possible contamination and potential presence of harmful pathogens. Infants, older adults, immunocompromised individuals.
E. coli Type of coliform bacteria indicating fecal contamination. Some strains cause vomiting, diarrhea, and stomach cramps. Infants, young children, older adults, immunocompromised individuals.

Bacterial Contamination

Contaminant What It Is Why It Matters Who Is Most Vulnerable
Nitrogen (Nitrate + Nitrite) Nitrate and nitrite are forms of nitrogen that commonly enter groundwater from septic systems and fertilizer use. Can interfere with the blood’s ability to carry oxygen. Infants and pregnant women.

Nutrients