Understanding Your Drinking Water
Quality & Testing
Water quality can change between a treatment plant and a tap, including through a building's plumbing. Which contaminants are present depends on the source and local conditions.
What Public Water Reports Can and Cannot Tell You
EPA drinking-water requirements cover regulated contaminants, while other substances may be studied or detected without having a federal drinking-water standard. A utility Consumer Confidence Report describes the public system; it may not reflect conditions inside an individual building's plumbing.
EPA vs. WHO Standards Comparison
A health-based goal and an enforceable limit serve different purposes. Regulatory comparisons do not by themselves establish the risk for a particular person or sample.
| Contaminant | EPA MCL | EPA MCLG | WHO Guideline |
|---|---|---|---|
| Lead | 15 ppb (AL) | 0 ppb | 10 ppb |
| PFOA | 4 ppt | 0 ppt | 100 ppt |
| PFOS | 4 ppt | 0 ppt | 100 ppt |
| Arsenic | 10 ppb | 0 ppb | 10 ppb |
| THMs (total) | 80 ppb | N/A | Various |
| Nitrate | 10 ppm | 10 ppm | 50 ppm |
| Chromium-6 | 100 ppb (total Cr) | Under review | 50 ppb |
MCL = Maximum Contaminant Level (enforceable). MCLG = Maximum Contaminant Level Goal (health-based, non-enforceable). AL = Action Level.
Key Contaminants in Drinking Water
Explore the most critical contaminants found in U.S. drinking water. Each card includes EPA/WHO limits, health effects, and the science behind the risk.
Lead (Pb)
Lead can enter water from plumbing
Health Effects
- Irreversible neurological damage in children
- Kidney damage and hypertension in adults
- Developmental delays and learning disabilities
- No safe level of exposure established by CDC
PFAS (Forever Chemicals)
PFAS has been detected in U.S. tap water
Health Effects
- Linked to kidney and testicular cancer
- Thyroid disease and immune suppression
- Reproductive issues and developmental effects
- Liver damage at chronic low doses
Chlorine & Disinfection Byproducts
Disinfectants are used in many public water systems
Health Effects
- Trihalomethanes (THMs) linked to bladder cancer
- Haloacetic acids associated with reproductive issues
- Chloramine can cause digestive issues
- Taste and odor complaints at >1 ppm
Microplastics
Microplastics have been reported in water samples
Health Effects
- Inflammatory response in gut tissue
- Potential carrier for absorbed chemicals (BPA, phthalates)
- Nano-plastics can cross cellular membranes
- Long-term effects still under active research
Bacteria & Pathogens
Waterborne pathogens can cause illness
Health Effects
- Gastrointestinal illness (E. coli, Giardia)
- Legionnaires' disease from Legionella in plumbing
- Cryptosporidium resistant to chlorine disinfection
- Severe risk for immunocompromised individuals
Nitrates & Nitrites
Nitrate can enter water from runoff and groundwater
Health Effects
- Blue baby syndrome (methemoglobinemia) in infants
- Associated with colorectal cancer risk
- Thyroid disruption at chronic exposure
- Agricultural runoff is primary source
How Contaminated Water Affects Your Food
Cooking does not remove every water contaminant, and some substances may transfer to food. The effects depend on the contaminant and preparation method.
Boiling Concentrates Contaminants
Boiling can reduce some microbial hazards when done according to public-health guidance, but it does not remove many dissolved chemicals and can concentrate them as water evaporates. Follow local advisories for boil-water situations.
Coffee & Tea Absorb More Lead
Hot water may draw more metals from plumbing. For drinking, cooking, or preparing beverages, use cold water and heat it separately; follow your utility's guidance if lead is a concern.
Pasta & Rice Absorb Water Chemicals
Some substances can transfer from cooking water to food, but the amount depends on the substance and preparation method. Cooking does not make contaminated water suitable for use.
Baby Formula & Water
Use water and prepare infant formula according to the product label and public-health guidance. If water quality is uncertain or a contaminant is present, ask the health department or a healthcare professional about appropriate steps.
Who's Most at Risk?
Contaminant exposure doesn't affect everyone equally. These populations face disproportionate risk from drinking water contamination.
Infants & Young Children
Developmental sensitivityChildren are a population of concern for lead exposure. CDC guidance emphasizes that no safe blood lead level in children has been identified; this does not mean a water result directly predicts an individual's health outcome.
Pregnant Women
Critical exposure windowSome contaminants have been studied for possible effects during pregnancy. Associations in research do not establish that a particular water result caused an outcome; discuss individual concerns with a healthcare professional or public-health agency.
Elderly & Immunocompromised
Individual susceptibility variesSome infections can be more serious for people with weakened immune systems. Local health guidance can help address specific exposures and circumstances.
Chronic Exposure (All Ages)
Cumulative lifetime riskHealth assessments may consider duration and amount of exposure. A single sample or general risk statement cannot predict an individual's long-term health outcome.
Laboratory Analysis Methods
Methods vary by test and provider. Review the service documentation and confirm which analytical methods apply before selecting a test.
Analytical Methods
Providers may offer different analytical methods and detection limits. Confirm these details for the selected service.
Know What's in Your Water
Test panels, methods, and provider services vary. Kit purchases are unavailable through Hydrology University while provider details are being confirmed.
Kit purchases are unavailable through Hydrology University while provider details are being confirmed.
Water Testing for Every Use Case
Drinking water is just the beginning. Discover how water quality affects every aspect of your home.