Common Contaminants

The EPA requires testing for common contaminants in drinking water including:

• Microorganisms (1) include bacteria, viruses and parasites. Run-off from rainfall or snow-melt can contaminate wells by washing microorganisms into the well system. Leakage of waste from underground storage tanks (UST) and effluent from septic leach fields can reach a water source and result in microorganisms being present in water wells.

• Nitrates (2) are present in fertilizers used by agriculture. They can contaminate a private well through groundwater movement, surface water seepage and water run-off. Once taken into the body, nitrates are converted into nitrites. Nitrite ingestion via drinking water can cause “blue baby syndrome.” Infants younger than 4 months and pregnant women (3) are at the most risk of harmful health effects from nitrites. Symptoms include, bluish skin from a lack of oxygen, difficulty breathing, nausea, diarrhea, vomiting, and dehydration. 

• Heavy metals (4) like arsenic, antimony, cadmium, chromium, copper, lead, selenium leach into our drinking water via household plumbing, service lines, mining operations, petroleum refineries, electronics manufacturers, municipal waste disposal, cement plants, and natural mineral deposits. These pollutants can contaminate private wells through groundwater movement and surface water seepage and run-off. 

• Organic chemicals (5) are found in many everyday products and are used in agriculture and industry. "Organic" in this case does not mean the same thing as in "organic agriculture," meaning grown without pesticides or chemicals. In this case it is a class of chemicals that contain atoms of carbon that are linked to other atoms, especially hydrogen, oxygen, or nitrogen. Organic chemicals include inks, dyes, pesticides, paints, pharmaceuticals, solvents, petroleum products, sealants, and disinfectants. These contaminants enter groundwater and contaminate private wells through waste disposal, spills, and surface water run-off.

• Disinfection byproducts (DBPs) (6) are most commonly found in chlorinated drinking water. DBPs are formed when disinfectants used to treat drinking water react with naturally occurring materials and organic materials in the water. Long-term chronic exposure to DBPs may increase the risk of cancer. When humans are exposed to especially high amounts of DBPs they can experience liver damage and decreased nervous system activity. Common disinfection byproducts include bromate, chlorate, chlorite, halo acetic acids, and trihalomethanes (THMs).

• Radionuclides (7) are radioactive forms of elements such as uranium. They can be released into the environment from uranium mining, coal mining, and nuclear power operations. These contaminants are naturally occurring in some places especially where there is granite bedrock. These pollutants can contaminate wells through groundwater flow, waste water seepage and flooding. 

The EPA does not require regulation of so-called "nuisance chemicals" (8),  such as iron, sulfide, and zinc, but sets non-mandatory water quality standards for 15 contaminants. EPA does not enforce these "secondary maximum contaminant levels" (SMCLs). They are established as guidelines to assist public water systems in managing their drinking water for aesthetic considerations, such as taste, color, and odor. These contaminants are not considered to present a risk to human health at the SMCL.

Sources:

1. National Primary Drinking Water Regulations from the Environmental Protection Agency (EPA)

2. Estimated Nitrate Concentrations in Groundwater Used for Drinking from the EPA

3. Nitrates/Nitrites Poisoning Patient Education Care Instruction Sheet from the Center for Disease Control (CDC)

4. National Primary Drinking Water Regulations: Inorganic Chemicals

5. National Primary Drinking Water Regulations: Organic Chemicals, except for PFAs from the EPA

6. National Primary Drinking Water Regulations from the EPA includes information on Disinfection Byproducts, including Stage 1 and Stage 2 Disinfectants and Disinfection Byproducts Rules

7. National Primary Drinking Water Regulations - Radionuclides from the EPA

8. Secondary Drinking Water Regulations from the EPA

For further reading and reference:

Drinking Water Standards and Regulations: An Overview from the CDC