Know What's in Your Water
Every contaminant profile includes verified sources, health impacts focused on maternal and child health, the difference between legal limits and health-protective goals, and proven removal methods β all backed by peer-reviewed research.
MCL vs. MCLG: Legal Limit vs. Health Goal
The EPA sets two numbers for each contaminant. The MCL (Maximum Contaminant Level) is the legal limit β a compromise between health and treatment cost. The MCLG (Maximum Contaminant Level Goal) is the health-protective target, set at the level with zero known health risk. When the MCLG is zero, it means there is no safe level.
Lead
Lead & Heavy Metals
A neurotoxic heavy metal with no safe exposure level. Lead enters drinking water primarily through corrosion of lead service lines and plumbing fixtures.
π‘ The EPA's own Maximum Contaminant Level Goal (MCLG) for lead is 0 ppb β there is no safe level of lead in drinking water.
Legal Limit (MCL)
15 ppb (EPA action level)
Health Goal (MCLG)
0 ppb
Where It Comes From
- β’Lead service lines connecting homes to water mains (estimated 6β10M lines remain in the US)
- β’Lead solder and brass fixtures in homes built before 1986
- β’Plumbing fixtures legally labeled "lead-free" can contain up to 0.25% lead
- β’Natural deposits in some groundwater sources
Health Impacts
- β’No safe blood lead level in children β even low levels reduce IQ (Lanphear et al., 2005)
- β’Linked to ADHD, learning disabilities, and behavioral problems
- β’Prenatal exposure crosses the placenta and affects fetal brain development
- β’Pregnant women can release stored lead from bones into the bloodstream
- β’Adults: cardiovascular effects, kidney damage, hypertension
How to Remove It
- Reverse osmosis (RO) β removes 95β99% of lead
- Activated carbon filters certified to NSF/ANSI Standard 53 for lead
- Ion exchange systems
- Distillation
Verified Sources
PFAS
PFAS (Per- and Polyfluoroalkyl Substances)
Synthetic "forever chemicals" that persist in the environment and human body. Used in non-stick coatings, firefighting foam, and food packaging. The EPA set the first federal PFAS drinking water limit in 2024.
π‘ The federal PFAS limit of 4 ppt remains in force. In May 2026, the EPA proposed extending compliance deadlines to 2031 β the standard itself was not repealed.
Legal Limit (MCL)
4 ppt (PFOA & PFOS)
Health Goal (MCLG)
0 ppt
Where It Comes From
- β’Aqueous film-forming foam (AFFF) used at airports and military bases
- β’Industrial discharges from chemical manufacturing
- β’Non-stick cookware, stain-resistant fabrics, and food packaging
- β’Landfills and wastewater treatment plant discharges
Health Impacts
- β’Reduced immune response to vaccines in children (Grandjean et al., 2012)
- β’Increased risk of kidney and testicular cancer
- β’Developmental effects: low birth weight, altered metabolism
- β’Hormone disruption and elevated cholesterol
- β’Accumulates in the body β half-life in humans is 2β9 years
How to Remove It
- Reverse osmosis (RO) β most effective for PFAS removal
- Granular activated carbon (GAC) filters β effective for larger PFAS compounds
- Ion exchange resins β effective for short-chain PFAS
- NSF/ANSI 53 and 58 certified systems for PFAS reduction
Verified Sources
TTHMs
TTHMs & Disinfection Byproducts
Total Trihalomethanes are formed when chlorine used to disinfect drinking water reacts with organic matter. They are the most common disinfection byproducts in chlorinated water systems.
π‘ TTHMs are formed by chlorination β the very process that makes tap water microbiologically safe. The challenge is removing the byproducts without compromising disinfection.
Legal Limit (MCL)
80 ppb
Health Goal (MCLG)
0 ppb
Where It Comes From
- β’Chlorination of drinking water containing organic matter
- β’More prevalent in surface water systems (lakes, rivers) than groundwater
- β’Levels can increase in warm months and in areas with old pipes
- β’Also formed in swimming pools and hot showers (inhalation exposure)
Health Impacts
- β’Long-term exposure linked to bladder cancer (Villanueva et al., 2004)
- β’Associated with reproductive issues and low birth weight
- β’Possible increased risk of colorectal cancer
- β’Inhalation during showering can increase exposure beyond drinking
How to Remove It
- Activated carbon filters (NSF/ANSI 53 certified for TTHM reduction)
- Aeration systems (reduces TTHMs in shower water)
- Boiling does NOT remove TTHMs β it can concentrate them
- Letting water sit in an open container for 24 hours can reduce TTHMs
Verified Sources
Nanoplastics
Nanoplastics & Microplastics
As of September 2026, there is no regulatory standard or certified consumer test for nanoplastics in drinking water. Research is ongoing. We present this as an emerging concern, not a regulated contaminant.
π‘ There is no regulatory standard or certified consumer test for nanoplastics as of 2026. We track this as an emerging concern and will update as science evolves.
Legal Limit (MCL)
No standard
Health Goal (MCLG)
No standard
Where It Comes From
- β’Breakdown of plastic bottles, packaging, and synthetic textiles
- β’Wastewater treatment plant discharges
- β’Atmospheric deposition and surface water runoff
- β’Plastic tea bags, coffee cups, and food containers
Health Impacts
- β’No definitive human health studies yet β research is emerging
- β’Animal and in vitro studies suggest cellular inflammation and oxidative stress
- β’Nanoplastics can cross biological barriers including the blood-brain barrier
- β’Potential endocrine disruption from associated chemical additives
- β’Bottled water has been found to contain hundreds of thousands of plastic particles per liter (Columbia University, 2024)
How to Remove It
- Reverse osmosis (RO) β expected to remove most nanoplastics based on size exclusion
- Ultrafiltration and nanofiltration
- No certified consumer standard exists yet for nanoplastic removal claims
- Reducing single-use plastic consumption is the most effective prevention
Arsenic
Arsenic
A naturally occurring element found in rock and soil. It enters drinking water through natural deposits, mining, and agricultural runoff. Chronic exposure is strongly linked to cancer.
π‘ The MCLG for arsenic is 0 ppb β the legal limit of 10 ppb is a compromise between health protection and treatment feasibility, not a safe level.
Legal Limit (MCL)
10 ppb
Health Goal (MCLG)
0 ppb
Where It Comes From
- β’Natural geological deposits (especially in the western US and New England)
- β’Mining and smelting operations
- β’Agricultural pesticides and herbicides (historical use)
- β’Industrial waste discharges
Health Impacts
- β’Strongly linked to skin, bladder, and lung cancer (NRC, 2001)
- β’Cardiovascular disease and hypertension
- β’Developmental effects and reduced cognitive function in children
- β’Skin lesions and pigmentation changes
- β’Diabetes and immune system suppression
How to Remove It
- Reverse osmosis (RO) β effective for arsenic removal
- Ion exchange systems
- Adsorptive media (iron-based or alumina-based)
- Distillation
Nitrates
Nitrates & Agricultural Runoff
Nitrates enter water through agricultural fertilizer runoff, septic systems, and animal feeding operations. They are especially dangerous to infants under 6 months.
π‘ Unlike most contaminants, the MCLG for nitrates equals the MCL (10 ppm) β but this is based on acute infant risk, not chronic health effects. Some researchers argue the limit should be lower.
Legal Limit (MCL)
10 ppm (10,000 ppb)
Health Goal (MCLG)
10 ppm
Where It Comes From
- β’Agricultural fertilizer runoff (the largest source)
- β’Animal feeding operations and manure application
- β’Septic system leaching
- β’Natural soil nitrogen deposits
Health Impacts
- β’Infants under 6 months: methemoglobinemia ("blue baby syndrome") β can be fatal
- β’Pregnant women: increased risk of spontaneous abortion and birth defects
- β’Possible link to thyroid disruption
- β’Some studies suggest increased cancer risk with long-term exposure
How to Remove It
- Ion exchange (anion exchange) β most common for nitrate removal
- Reverse osmosis (RO) β effective for point-of-use treatment
- Distillation
- Boiling does NOT remove nitrates β it concentrates them