684 systems serving 712,991 people
  This drinking water quality report shows results of tests conducted by water utilities in Montana, provided to the Environmental Working Group (EWG) by the Montana Department 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.

  30 Contaminants Exceeding Health Based Limits

Contaminants detected in Montana 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
Total haloacetic acids (HAAs) 568,674 553,372 214 192
Bromodichloromethane 541,827 541,827 171 171
Lead (total) 504,440 504,440 541 541
Dichloroacetic acid 489,939 489,939 131 131
Arsenic (total) 456,405 456,405 241 241
Dibromochloromethane 518,882 445,023 163 156
Total trihalomethanes (TTHMs) 571,260 426,534 229 130
Chloroform 545,531 406,375 183 99
Trichloroacetic acid 462,046 332,719 136 34
Bromoform 320,003 320,003 84 84

  Sources of Montana Drinking Water Contaminants

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

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

Arsenic (total), Nitrate & nitrite, Nitrate, Nitrite, Selenium (total), Phosphorus, Dalapon, Picloram, Atrazine, Dacthal, 2,4-D, p-Dichlorobenzene, Ethylbenzene

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

Nitrate, Copper, Nitrate & nitrite, Lead (total), Arsenic (total), Tetrachloroethylene, Nitrite, Xylenes (total), Dalapon, Cadmium (total), Antimony (total), Mercury (total inorganic), Dichloromethane (methylene chloride), o-Xylene, Trichlorofluoromethane, Dacthal, p-Dichlorobenzene, Di(2-Ethylhexyl) adipate, Phosphorus, 2,4-D, Naphthalene, n-Propylbenzene

48 Industrial Pollutants

Aluminum, Arsenic (total), Barium (total), Cadmium (total), Chromium (total), Lead (total), Manganese, Mercury (total inorganic), Nitrate & nitrite, Nitrate, Nitrite, Selenium (total), Antimony (total), Beryllium (total), Thallium (total), Phosphorus, Di(2-Ethylhexyl) adipate, Di(2-ethylhexyl) phthalate, Hexachlorocyclopentadiene, Chloromethane, Chloroethane, Trichlorofluoromethane, Naphthalene, Pentachlorophenol, Dibromomethane, 1,2,4-Trimethylbenzene, 1,3,5-Trimethylbenzene, Xylenes (total), Dichloromethane (methylene chloride), p-Dichlorobenzene, 1,1-Dichloroethylene, Carbon tetrachloride, Tetrachloroethylene, Toluene, Ethylbenzene, Isopropylbenzene, Styrene, o-Xylene, n-Propylbenzene, Alpha particle activity (excl radon and uranium), Alpha particle activity (incl. radon & uranium), Combined Uranium (mg/L), Uranium-238, Combined Radium (-226 & -228), Radium-226, Radium-228, Combined Uranium (pCi/L), Gross beta particle activity (pCi/L)

17 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, Bromochloroacetic acid, Monobromoacetic acid, Di(2-ethylhexyl) phthalate, Cadmium (total), Chloromethane, Dibromomethane, Chloroethane

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 (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, Mercury (total inorganic), Chloromethane, Uranium-238, Phosphorus, Silicon

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

Lead (total), Phosphorus, Dacthal, Chloromethane, Chloroethane, Trichlorofluoromethane, Naphthalene, Dibromomethane, 1,2,4-Trimethylbenzene, 1,3,5-Trimethylbenzene, Bromochloroacetic acid, Isopropylbenzene, n-Propylbenzene, Silicon

  Testing Summary for Montana

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

Contaminants reported as tested by water suppliers in Montana 152
  Contaminants tested due to federal law: 86
  Contaminants tested in addition to those required by federal law: 66
  Violation Summary for Montana

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

Violation Type Number of Violations
Failure to monitor regularly 3,609
Failure to monitor, Routine Major (Coliform bacteria) 475
Failure to report information to the public or state agency in the Consumer Confidence Report 374
Monitoring and Reporting Disinfection Byproduct Rule 373
Maximum contaminant level, Monthly (Coliform bacteria) 317
Follow-up and Routine Tap Sampling 257
Initial Tap Sampling for Lead and Copper 132
Failure to monitor or report, Routine/Repeat (Indicators of microbial or virus contamination) 105
Initial Water Quality Parameter Monitoring and Reporting 92
Over maximum contaminant level, Average 89
Over maximum contaminant level, Single Sample 75
Filter Turbidity Reporting 62
Failure to monitor, Routine Minor (Coliform bacteria) 55
Treatment Technique (Surface Water Treatment Rule) 51
Inadequate reporting of information to the public 50
Excess Turbidity at 0.3 NTU 47
Excess Turbidity at 1 NTU 43
Failure to monitor or report, Routine/Repeat (Indicators of microbial or virus contamination) 33
Failure to monitor, Repeat Major (Coliform bacteria) 30
Maximum contaminant level, Acute (Coliform bacteria) 13
Optimal Corrosion Control Treatment Study Recommendation 12
Public Education 11
Initial, Follow-up, or Routine Source Water Treatment Monitoring and Reporting 7
Failure to monitor, Repeat Minor (Coliform bacteria) 4
Failure to Filter (Surface Water Treatment Rule) 1
Public Notification Violation for National Primary Drinking Water Regulations 1
Treatment Technique (Filter Backwash Reporting Rule)? 41 H "Treatment Technique (Surface Water Treatment Rule) 1

Sources : EWG (Environmental Working Group)