The following is a list of common water contaminants found in both public and private drinking water supplies across the U.S. and Canada, together with their health effects and the most appropriate treatment methods for their removal. For more information on a particular contaminant or treatment method, please click on the name of the item.
Please note: This list was compiled for research and informational purposes only. It is not intended to suggest that any of the listed contaminants are present in your water supply. Only testing by an accredited lab can identify the presence of contaminants in your water supply.
Contaminant
Name |
Maximum Acceptable Level |
Common
Sources |
Health
Effects |
Most Effective Purification Technology |
| Arsenic |
0.010 mg/L |
Natural deposits, smelters, glass, electronics wastes, orchards |
Skin, nervous system toxicity |
Reverse Osmosis |
| Asbestos |
7 MFL (million fibers / liter) |
Natural deposits, asbestos cement in water systems |
Cancer |
Reverse Osmosis, Activated Carbon |
| Barium |
2 mg/L |
Natural deposits, pigments, epoxy sealants, spent coal |
Circulatory system effects |
Reverse Osmosis |
| Bacteria / Coliform |
- |
animal & human waste, septic fields, sewage, farming |
various illnesses |
Ultraviolet |
| Cadmium |
0.005 mg/L |
Natural deposits, galvanized pipe corrosion, batteries, paints |
Kidney disorders |
Reverse Osmosis |
| Chloradane |
0.002 mg/L |
Leaching from soil treatment for termites |
Cancer |
Activated Carbon |
| Chlorine |
4 mg/L |
Water disinfection |
see chlorination by-products (Trihalomethanes) |
Activated Carbon, KDF |
| Chromium |
0.1 mg/L |
Natural deposits, mining, electroplating, pigments |
Liver, kidney, circulatory disorders |
Reverse Osmosis |
| Copper |
1.3 mg/L |
Natural / industrial deposits, wood preservatives, plumbing |
Gastrointestinal irritation |
Reverse Osmosis, KDF
|
| Cryptosporidium |
Zero |
Animal or human waste, contaminated food products |
Gastrointestinal illness |
Reverse Osmosis, Carbon Block (0.5 micron) |
| E.coli |
Zero |
Naturally occurring, human or animal wastes |
Gastrointestinal disorders (often severe) |
Ultraviolet |
| Fluoride |
4 mg/L |
Natural deposits, fertilizer, aluminum industries, water additive |
Skeletal and dental fluorosis |
Reverse Osmosis |
| Giardia |
Zero |
Naturally occurring, human or animal wastes |
Gastrointestinal disorders (Beaver Fever) |
Reverse Osmosis, Carbon Block (0.5 micron) |
| Hydrogen Sulfide |
n/a |
Natural deposits |
Rotten egg taste and odour |
Manganese Greensand Filter, KDF
|
| Iron |
0.3 mg/L |
Natural deposits |
Staining of laundry, plumbing, appliances |
Iron Reduction Filter |
| Manganese |
0.05 mg/L |
Natural deposits |
Staining of laundry, plumbing, appliances |
Iron Reduction Filter |
| Mercury |
0.002 mg/L |
Crop runoff, natural deposits, batteries, electrical switches |
Kidney, nervous system disorders |
Reverse Osmosis, Activated Carbon |
| Microbiological Contaminants |
- |
animal & human waste, septic fields, sewage, farming |
various illnesses |
Various |
| Nitrate / Nitrite |
10 mg/L |
Animal waste, fertilizer, natural deposits, septic tanks, sewage |
Methemoglobulinemia (blue baby syndrome) |
Reverse Osmosis |
| PCB |
10.0005 mg/L |
Coolant oils from electrical transformers, plasticizers |
Cancer |
Activated Carbon |
| Radium |
5 pCi/L |
Natural deposits |
Bone cancer |
Reverse Osmosis |
| Radon |
|
Natural deposits |
Cancer |
Activated Carbon |
| Selenium |
0.05 mg/L |
Natural deposits, mining, smelting, coal/oil combustion |
Liver damage |
Reverse Osmosis |
| Sulfate |
500 mg/L |
Naturally-occurring |
laxative effect - gastrointestinal irritation (loose stools, diarrhea, etc.) especially in infants or individuals not acclimated to high levels |
Reverse Osmosis |
| Total Dissolved Solids |
500 mg/L |
Erosion of naturally occurring mineral deposits |
Gastrointestinal irritation in some individuals |
Reverse Osmosis |
| Toxaphene |
0.003 mg/L |
Insecticide formerly used on cattle, cotton, soybeans |
Cancer |
Activated Carbon |
| Trihalomethanes (THMs)(chlorination by-products) |
0.08 mg/L |
By-product of chlorination in drinking water |
Cancer |
Activated Carbon, KDF |
| Turbidity |
n/a (5 NTU max. recommended) |
Soil runoff |
Interferes with disinfection, filtration |
Whole-House Sediment Filter, Reverse Osmosis |
| Uranium |
0.03 mg/L |
Natural occurring |
Kidney disorders, cancer |
Reverse Osmosis |
| Viruses |
- |
animal & human waste, septic fields, sewage, farming |
various illnesses |
Ultraviolet |
| Volatile Organic Compounds (VOCs) |
Varied |
Varied |
Varied, incl. cancer |
Activated Carbon |
| Zinc |
5 mg/L |
Natural deposits, industrial waste |
Metallic taste in water |
Reverse Osmosis, KDF |
