726 systems serving 1,063,278 people
  This drinking water quality report shows results of tests conducted by water utilities in Idaho, provided to the Environmental Working Group (EWG) by the Department of Health and Welfare- Division of Environmental Quality. It is part of EWG's national database that includes 47,667 drinking water utilities and 20 million test results from 45 states and the District of Columbia. Water utilities nationwide detected more than 300 pollutants between 2004 and 2009. More than half of these chemicals are unregulated, legal in any amount. Despite this widespread contamination, the federal government invests few resources in protecting rivers, reservoirs, and groundwater from pollution in the first place. The information below summarizes drinking water quality for this state.

Water Utilities
Population Served
Detected Chemicals
Exceed health guidelines*
Exceed Legal Limits*
Unregulated chemicals detected
* Water utilities are noted as exceeding the legal limit if any test is above the maximum contaminant level (MCL). Most MCLs are based on annual averages so exceeding the MCL for one test does not necessarily indicate that the system is out of compliance.

  40 Contaminants Exceeding Health Based Limits

Contaminants detected in Idaho drinking water above health guidelines, according to an Environmental Working Group analysis of data obtained from state water authorities.

Number of Systems
At Any Level Above Health Limits At Any Level Above Health Limits
Arsenic (total) 756,833 756,833 298 298
Alpha particle activity (excl radon and uranium) 590,518 590,518 84 84
Total haloacetic acids (HAAs) 644,199 571,327 149 142
Radium-228 542,818 542,818 94 94
Combined Radium (-226 & -228) 531,680 531,680 80 80
Bromoform 480,493 480,493 18 18
Radium-226 475,279 475,279 67 67
Total trihalomethanes (TTHMs) 836,618 390,351 233 86
Dibromochloromethane 472,591 383,937 20 16
Bromodichloromethane 382,516 382,516 29 29

  Sources of Idaho Drinking Water Contaminants

The contaminants identified in Idaho drinking water come from a wide variety of sources, including agriculture, industry, water treatment plants, and polluted storm runoff from urban areas.

61 Total Contaminants Detected (2004 - 2009)
13 Agricultural Pollutants
(pesticides, fertilizer, factory farms)

Arsenic (total), Cyanide, Nitrate & nitrite, Nitrate, Nitrite, Selenium (total), Phosphorus, Endothall, Simazine, Atrazine, 2,4-D, Ethylene dibromide (EDB), Ethylbenzene

18 Sprawl and Urban Pollutants
(road runoff, lawn pesticides, human waste)

Nitrate, Copper, Nitrate & nitrite, Lead (total), Arsenic (total), Tetrachloroethylene, Nitrite, Xylenes (total), Cadmium (total), Antimony (total), Mercury (total inorganic), Dichloromethane (methylene chloride), Cyanide, Di(2-Ethylhexyl) adipate, Phosphorus, 2,4-D, bis(2-ethylhexyl) phthalate, 2,3,7,8-TCDD (Dioxin)

44 Industrial Pollutants

Aluminum, Bromide, Arsenic (total), Barium (total), Cadmium (total), Chromium (total), Cyanide, Lead (total), Manganese, Mercury (total inorganic), Nitrate & nitrite, Nitrate, Nitrite, Selenium (total), Antimony (total), Beryllium (total), Thallium (total), Phosphorus, Asbestos, Di(2-Ethylhexyl) adipate, Di(2-ethylhexyl) phthalate, Hexachlorocyclopentadiene, 2,3,7,8-TCDD (Dioxin), bis(2-ethylhexyl) phthalate, Ethylene dibromide (EDB), Xylenes (total), Dichloromethane (methylene chloride), trans-1,2-Dichloroethylene, 1,2-Dichloroethane, Carbon tetrachloride, Trichloroethylene, 1,1,2-Trichloroethane, Tetrachloroethylene, Toluene, Ethylbenzene, Alpha particle activity (excl radon and uranium), Alpha particle activity (incl. radon & uranium), Combined Uranium (mg/L), Combined Radium (-226 & -228), Radium-226, Radium-228, Alpha particle activity, Combined Uranium (pCi/L), Gross beta particle activity (pCi/L)

13 Water Treatment and Distribution Byproducts
(pipes and fixtures, treatment chemicals and byproducts)

Total trihalomethanes (TTHMs), Total haloacetic acids (HAAs), Chloroform, Bromodichloromethane, Dibromochloromethane, Dichloroacetic acid, Trichloroacetic acid, Bromoform, Dibromoacetic acid, Monochloroacetic acid, Di(2-ethylhexyl) phthalate, Cadmium (total), Asbestos

24 Naturally Occurring
(naturally present but increased for lands denuded by sprawl, agriculture, or industrial development)

Nitrate, Copper, Nitrate & nitrite, Barium (total), Lead (total), Arsenic (total), Manganese, Radium-228, Radium-226, Alpha particle activity, Alpha particle activity (excl radon and uranium), Combined Radium (-226 & -228), Gross beta particle activity (pCi/L), Combined Uranium (pCi/L), Chromium (total), Alpha particle activity (incl. radon & uranium), Combined Uranium (mg/L), Aluminum, Selenium (total), Nitrite, Bromide, Mercury (total inorganic), Cyanide, Phosphorus

6 Unregulated Contaminants
EPA has not established a maximum legal limit in tapwater for these contaminants

Bromide, Lead (total), Phosphorus, bis(2-ethylhexyl) phthalate, Uranium-234 (pCi/L), Uranium-238 (pCi/L)

  Testing Summary for Idaho

The federal government has set standards for some of the pollutants found in tap water supplies.

Contaminants reported as tested by water suppliers in Idaho 144
  Contaminants tested due to federal law: 89
  Contaminants tested in addition to those required by federal law: 55
  Violation Summary for Idaho

Data from the U.S. Environmental Protection Agency includes the following violations of federal standards in Idaho since 2004.

Violation Type Number of Violations
Failure to monitor regularly 1,679
Failure to monitor, Routine Major (Coliform bacteria) 500
Maximum contaminant level, Monthly (Coliform bacteria) 421
Monitoring and Reporting Disinfection Byproduct Rule 421
Over maximum contaminant level, Average 407
Failure to monitor, Routine Minor (Coliform bacteria) 134
Failure to monitor or report, Routine/Repeat (Indicators of microbial or virus contamination) 106
Over maximum contaminant level, Single Sample 96
Treatment Technique (Surface Water Treatment Rule) 74
Follow-up and Routine Tap Sampling 51
Filter Turbidity Reporting 23
Failure to monitor, Repeat Major (Coliform bacteria) 22
Initial Tap Sampling for Lead and Copper 21
Failure to monitor, Repeat Minor (Coliform bacteria) 12
Maximum contaminant level, Acute (Coliform bacteria) 10
Failure to notify public of violation 3
Failure to monitor or report, Routine/Repeat (Indicators of microbial or virus contamination) 2
Failure to Filter (Surface Water Treatment Rule) 1
Optimal Corrosion Control Treatment Study Recommendation 1
Non-Acute maximum residual disinfectant level 1

Sources : EWG (Environmental Working Group)