Pouring It On

Nitrate Contamination of Drinking Water

February 1, 1996

Pouring It On: Nitrogen Contamination of Drinking Water

Nitrate contamination of drinking water is a serious and growing problem that places thousands of infants at acute risk of contacting potentially deadly methemoglobinemia. Since 1986, over two million people drank water from municipal water systems that EPA found to be "significant non-compliers" with the federal drinking water standard for nitrate. Many of these water suppliers continued to supply unsafe water for years after problems were first discovered. An additional 3.8 million individuals who rely upon private wells contaminated with unsafe levels of nitrate for their tap water. Finally, tens of millions receive their water from water suppliers or wells that have nitrate contamination problems that are dangerously close to the current EPA standard, and already exceed guidelines established by international health authorities.

These contamination problems pose significant long and short-term risks, and are made even more critical by the fact that:

  • The federal drinking water standard for nitrate contains no margin of safety to protect infants from acute, life-threatening methemoglobinemia, and does not adequately protect the population from potential risks of chronic health effects such as cancer and birth defects. The EPA nitrate standard is more than twice as weak as the same standard established by German and South African health authorities, and is much weaker than the same European Community guideline.
  • The federal regulatory system does virtually nothing to prevent contamination of drinking water sources until it is too late -- when standards have already been violated and water consumers are placed at risk. This system virtually guarantees that once problems appear, they will continue to get worse. Current levels of nitrate contamination, even if they are not yet above EPA standards, are often precursors to full blown public health problems (Hallberg and Keeney 1993; Mueller, et al. 1995).

Our in depth study of nitrate contamination identifies four populations affected by varying degrees of nitrate contamination problems:

  • Water systems that have been cited as significant non-compliers for violating the federal nitrate standard.
  • Water systems that have some sources of drinking water contaminated at levels that exceed the federal standard, but have yet to be cited for violating the standard.
  • Water systems suffering from systemic nitrate contamination that is extremely close to EPA standards and that typically exceeds international health guidelines for nitrate.
  • Millions of families who rely on privately owned wells that are contaminated above federal standards.

First, we identified 2,016 water systems serving nearly 2.2 million people that were reported to EPA for violating the nitrate standard at least once between 1986 and 1995. All of these water systems were termed "significant non-compliers" by EPA (Table 14). In any given year, approximately 560 of these water systems will be cited for violating the nitrate standard.

Table 14: Over two million people drank water from systems that were significant non-compliers with the EPA nitrate standard.

State Number of Systems in Violation Population Affected
Ohio 36 413,441
Arizona 42 400,765
California 112 380,670
Illinois 156 274,332
Pennsylvania 456 154,877
Kansas 103 86,130
Washington 39 67,325
Oklahoma 132 66,938
Iowa 137 52,970
Nebraska 116 44,513
Texas 60 41,685
Colorado 22 39,707
Connecticut 8 21,142
Delaware 85 19,142
Michigan 74 18,435
Maryland 59 15,983
New Jersey 59 10,511
New York 16 10,323
Wisconsin 63 6,015
Florida 36 4,964
Minnesota 44 4,440
Indiana 35 3,798
Kentucky 5 3,428
North Carolina 19 2,720
South Dakota 13 2,619
West Virginia 6 2,303
New Mexico 12 1,938
Virginia 10 1,889
Oregon 8 1,820
Vermont 2 1,680
Idaho 4 1,530
Rhode Island 8 1,240
Montana 8 963
Alaska 7 850
Missouri 4 634
South Carolina 10 395
Maine 5 365
Georgia 1 200
North Dakota 3 155
Massachusetts 1 25
Total 2,016 2,162,860

Source: EPA. Safe Drinking Water Information System. 1996.

Table 15: Columbus, OH was the largest city affected by a violation of the nitrate standard between 1986 and 1995

          Time Spent in Violation of the Nitrate Standard
Rank System City State Population Served Years Most Recent Yr  
1 Columbus-Dublin Road Wtp Columbus OH 269,400 5 1989*  
2 Scottsdale, Municipal Water Scottsdale AZ 174,170 1 1988  
3 Chandler Municipal Water Dept. Chandler AZ 104,000 1 1993  
4 Decatur Decatur IL 83,885 8 1992  
5 Upland, City Of Upland CA 64,973 1 1987  
6 Bloomington Bloomington IL 54,566 8 1992  
7 Peoria, City Of Peoria AZ 50,618 1 1989  
8 Manteca, City Of Manteca CA 43,000 1 1987  
9 West Bernardino CWD Rialto CA 41,454 1 1987  
10 Gilbert, Town Of Gilbert AZ 40,000 1 1989  
11 Interstate Water Company Danville IL 38,000 7 1991  
12 Jurupa CSD Riverside CA 34,000 1 1986  
13 Richland, City Of Richland WA 32,600 1 1993  
14 Bowling Green, City Of Bowling Green OH 30,000 1 1986  
15 Del Este WC - #4 Empire Modesto CA 25,770 1 1988

* The Columbus water system has exceeded the nitrate standard since 1989. However, under an agreement with the state they are allowed to exceed the standard as long as they notify water drinkers (Evans 1995).

Source: EPA. Safe Drinking Water Information System. 1996.

These "significant non-compliers" represent only a small facet of much more widespread nitrate contamination problems. Our original analysis of community-level drinking water monitoring data, using a database of over 150,000 testing results for nitrate obtained from state drinking water agencies, uncovered 1,077 water systems where at least one source of drinking water (usually a well, in some cases a river or reservoir) has exceeded the 10 ppm federal standard since 1993 (Table 16). These water suppliers served a population of over 12.4 million individuals.

Table 16: Over 1,000 water systems serving 12.4 million people have at least one water source polluted with nitrate at concentra

State Number of water systems with sources exceeding the federal nitrate standard Population Affected
Arizona 75 1,951,730
California 139 8,701,240
Colorado 32 83,849
Delaware 60 12,759
Illinois 27 18,797
Iowa 56 90,160
Kansas 67 93,049
Maryland 45 28,962
Michigan 6 3,442
Minnesota 15 27,098
Montana 5 270
Nebraska 118 107,027
Ohio 13 100,650
Oregon 24 6,642
Pennsylvania 112 220,796
South Dakota 8 1,914
Tennessee 2 760
Texas 114 734,478
Washington 126 104,329
Wisconsin 9 88,722
Total 1,053 12,376,674

Source: State drinking water agency nitrate monitoring database. Compiled by Environmental Working Group.

Table 17: Los Angeles, Santa Ana, and San Jacinto were the largest water systems in California to have one source of drinking wa

Rank System City Population Served Date of most recent sample over federal nitrate standard Percent of samples over federal nitrate standard Number of samples taken Maximum test result
1 Los Angeles Los Angeles 3,600,000 6/15/95 1.1% 190 12.5
2 City Of Santa Ana Santa Ana 293,700 11/22/95 24.0% 146 12.9
3 Eastern MWD San Jacinto 253,705 5/9/95 3.7% 54 12.2
4 City Of Riverside Riverside 245,000 11/30/95 6.6% 457 35.6
5 Glendale-City, Water Dept. Glendale 184,000 11/7/95 5.4% 331 11.9
6 California Water Service Bakersfield 182,670 7/13/95 3.6% 357 13.1
7 City Of Modesto Modesto 180,320 10/7/94 7.7% 260 13.9
8 City Of Pasadena Pasadena 153,217 6/23/93 8.3% 24 12.8
9 San Gabriel Valley Water Co. El Monte 150,105 3/13/95 3.2% 317 12.3
10 City Of Garden Grove Garden Grove 148,000 1/12/93 1.3% 77 14.5
11 City Of Ontario Ontario 143,285 1/25/94 1.1% 179 10.2
12 Pomona- City, Water Dept. Pomona 136,525 12/4/95 38.0% 739 22.5
13 Cucamonga CWD Rancho Cucamonga 128,000 11/22/95 11.3% 160 15.5
14 Desert Water Agency Palm Springs 125,000 1/27/93 1.6% 61 11.8
15 City Of Corona Corona 104,000 8/9/95 50.0% 44 26.7
16 San Gabriel Valley WC Fontana 102,599 11/7/95 9.2% 295 18.3
17 California Water Service Salinas 100,300 9/8/94 5.3% 114 13.3
18 Suburban Water Systems San Jose 93,758 11/15/95 17.9% 563 30.9
19 Daly City MWU Daly City 92,311 10/19/95 50.0% 18 15.1
20 City Of Alhambra Alhambra 86,300 6/8/94 5.7% 35 12.7
21 California Water Service Visalia 82,300 4/8/93 0.5% 182 10.0
22 Cal-Water Service Co. Chico 73,220 12/15/94 2.3% 177 13.6
23 Palmdale WD Palmdale 70,000 2/2/95 4.9% 41 12.3
24 Redlands City MUD Redlands 69,300 5/16/95 4.0% 430 36.0
25 City Of Upland Upland 66,383 5/31/94 1.7% 59 17.5
26 Casitas Municipal WD Oakview 60,000 2/21/95 50.0% 2 12.0
27 California Water Service South San Francisco 56,200 12/29/94 40.0% 25 18.4
28 East Valley WD San Bernardino 55,000 10/12/95 6.3% 573 16.7
29 Calif Water Service Los Altos 53,740 3/21/94 1.3% 80 10.0
30 City Of Chino Chino 52,130 10/26/95 35.3% 85 19.2
31 City Of Tustin Tustin 52,100 1/26/95 31.6% 38 15.9
32 California Water Service Livermore 50,670 10/6/94 22.2% 27 15.8
33 Cal. American Water Co. San Marino 49,353 5/22/95 10.5% 105 15.2
34 Azusa Valley WC Azusa 49,000 6/2/94 1.1% 179 10.6
35 City Of Arcadia Arcadia 48,290 10/10/95 3.6% 448 28.0
36 Valencia WC Valencia 48,000 10/19/94 1.8% 55 10.4
37 City Of Turlock Turlock 48,000 3/16/94 1.8% 56 10.9
38 Glendora-City, Water Dept. Glendora 48,000 11/21/95 28.1% 488 15.5
39 San Gabriel CWD San Gabriel 45,000 11/28/95 28.4% 148 14.2
40 Lake Hemet MWD Hemet 43,939 11/15/95 12.5% 24 14.2
41 City Of Covina Covina 43,800 8/15/95 100.0% 12 24.9
42 South California WC San Dimas 43,056 11/22/95 70.2% 161 17.5
43 City Of San Luis Obispo San Luis Obispo 42,500 1/27/93 1.5% 67 12.0
44 Tulare, City Of Tulare 39,800 7/21/95 3.4% 59 10.7
45 Monte Vista CWD Montclair 38,000 11/1/95 32.6% 141 30.9
46 City Of Monrovia Monrovia 37,545 1/5/95 4.8% 227 15.9
47 Calif Cities Water Orcutt 33,218 7/3/95 3.9% 76 11.1
48 City Of Azusa Azusa 33,066 2/25/93 4.2% 24 23.4
49 Indian Wells Valley CWD Ridgecrest 32,630 2/2/94 2.8% 36 11.0
50 South California WC Claremont 32,543 5/10/95 20.9% 86 24.6

Source: State drinking water agency nitrate monitoring database. Compiled by Environmental Working Group.

Table 18: Phoenix, El Paso, and Mesa, AZ were the largest water systems with one source of drinking water with concentrations ab

Rank System City State Population Served Date of most recent sample of federal nitrate standard Percent of samples over federal nitrate standard Number of Samples Taken Maximum Test Result
1 Phoenix Munic. Water System Phoenix AZ 1,000,000 10/26/94 7.3% 82 17.4
2 El Paso Water Utilities El Paso TX 620,000 5/26/93 2.0% 49 13.5
3 Mesa, Munic. Water Dept. Mesa AZ 302,000 8/10/94 2.4% 41 11.0
4 Scottsdale Scottsdale AZ 174,170 10/20/94 1.0% 105 10.0
5 Glendale Munic. Water CC Glendale AZ 150,000 3/1/95 10.5% 57 16.0
6 Chandler, Munic. Wtr Dept. Chandler AZ 120,000 10/12/94 5.0% 60 13.9
7 Janesville Water Utility Janesville WI 52,133 12/5/94 100.0% 1 11.0
8 Peoria, City Of Peoria AZ 50,618 10/6/94 13.3% 15 12.6
9 State College Boro. Water Auth. State College PA 47,000 2/18/93 3.2% 31 10.4
10 Newark, City Of Newark OH 46,000 11/10/94 2.8% 36 41.0
11 Gilbert, Town Of Gilbert AZ 45,000 6/24/94 7.1% 14 19.4
12 Utility Parkway Cedar Falls IA 34,298 4/10/95 1.4% 71 10.6
13 Richland, City Of Richland WA 32,600 6/27/95 19.3% 942 19.0
14 Friendswood, City Of Friendswood TX 27,108 6/12/95 5.0% 20 30.1
15 AZ Water Co., Casa Grande Casa Grande AZ 26,121 1/11/94 8.3% 24 12.1
16 Pasco Water Department Pasco WA 25,465 8/30/94 33.3% 36 17.4
17 Citizens Util., Mohave Bullhead City AZ 25,000 6/13/95 31.3% 16 15.0
18 SACWSD - Shallow Well #18 Commerce City CO 22,400 6/7/95 8.5% 59 12.3
19 Avondale, City Public Works Avondale AZ 22,000 6/16/93 22.2% 9 14.0
20 Kearney, City Of Kearney NE 21,751 7/14/93 25.0% 8 16.4
21 Dodge City, City Of Dodge City KS 21,294 2/8/95 17.8% 45 16.2
22 Bonney Lake Water Department Bonney Lake WA 18,586 5/10/94 14.3% 14 27.0
23 Great Bend PWS/Central KS Utils Great Bend KS 15,427 3/1/95 7.1% 28 10.4
24 Spanaway Water Company Spanaway WA 14,613 9/22/94 7.7% 26 27.0
25 Brighton, City Of Brighton CO 14,500 5/25/93 15.4% 26 18.5
26 Ephrata Joint Authority Ephrata PA 14,300 7/14/93 2.9% 35 11.0
27 Shippensburg Boro. Water Shippensburg PA 13,500 5/20/94 5.3% 19 10.2
28 Horsham Water Authority Horsham PA 13,304 1/26/93 2.3% 44 101.7
29 Beatrice, City Of Beatrice NE 12,891 7/14/94 36.4% 22 252.9
30 Sterling, City Of Sterling CO 12,500 7/11/94 23.5% 34 13.1
31 Dover Township Water Dover PA 12,050 7/6/95 11.8% 51 17.0
32 Vernon, City Of Vernon TX 12,001 6/13/95 91.7% 24 16.0
33 Fitchburg Utility District 1 Fitchburg WI 11,890 5/24/94 100.0% 1 11.1
34 Lamesa, City Of Lamesa TX 11,838 6/12/95 33.3% 3 10.5
35 Valley View Mobile Home Park Manchester OH 11,500 5/20/94 18.5% 27 11.8
36 Urbana,City Of Manchester OH 11,500 5/24/95 28.1% 57 12.9
37 Trenton, City Of Manchester OH 11,500 6/15/94 5.3% 19 10.2
38 New Waterford, Village of Manchester OH 11,500 10/11/94 9.1% 11 18.0
39 Oconomowoc Waterworks Oconomowoc WI 10,993 1/24/94 100.0% 1 11.7
40 Burkburnett, City Of Burkburnett TX 10,668 3/7/95 75.0% 12 18.4
41 Shakopee Shakopee MN 10,300 2/21/95 25.9% 27 12.0
42 Tri County Joint Mun. Auth. Fredericktown PA 10,000 2/3/93 14.3% 7 12.9
43 Kutztown Borough Kutztown PA 9,100 4/25/94 8.3% 24 10.1
44 Ft. Morgan, City Of Fort Morgan CO 9,000 8/1/95 6.3% 32 11.0
45 USAF-Davis Monthan AFB Tucson AZ 8,900 5/17/94 2.3% 44 96.0
46 Mccook, City Of Mccook NE 8,404 11/10/93 23.8% 21 16.4
47 Gering, City Of Gering NE 7,760 12/20/93 20.0% 25 12.5
48 Coatesville, City of Authority Coatesville PA 7,500 1/13/95 15.4% 13 10.0
49 Plover Waterworks Plover WI 6,850 3/24/94 100.0% 1 13.4
50 Catasauqua Mun. Water Works Catasauqua PA 6,700 10/12/94 7.7% 13 11.6

Source: State drinking water agency nitrate monitoring database. Compiled by Environmental Working Group.

Three quarters of these water suppliers with demonstrated contamination above federal standards have not been cited as significant non-compliers for violating the federal nitrate standard. There are a number of reasons for this.

  • Many water suppliers simply fail to adequately monitor their water for nitrate contamination. According to data obtained from the EPA's Safe Drinking Water Information System, in 1993-1994 over 11.6 million people drank water from nearly 10,000 water systems that violated a federal nitrate monitoring requirement.
  • Many state regulatory agencies have been lax in reporting violations to the federal EPA. Audits by the EPA, the General Accounting Office, and private organizations have indicated that states frequently fail to report any violation of drinking water standards to EPA (GAO 1990; NRDC 1994).
  • Many surface water supplied systems, particularly in Ohio and Illinois, are essentially sanctioned by the state to provide water that does not meet current standards. Some of these communities have been frequent violators of the nitrate standard in past years. Rather than solving the problem, these water systems are allowed to serve unsafe water to their communities with the stipulation that the public is warned when their water is unsafe for infants to drink. As long as these systems inform the community that the water is unsafe for pregnant women and infants, they are not reported in violation of the nitrate standard, though the levels of nitrate in the water may exceed 10 ppm. In spite of these warnings, infants in these communities remain at significant risk because of prolonged exposures (during heavy runoff periods) to nitrate at concentrations that are extremely close to or above the 10 ppm federal standard.
  • Where water suppliers are dependent upon groundwater, systems are often able to avoid serving water with illegal levels of nitrate in spite of contamination of individual wells that exceeds federal standards. This is accomplished by mixing contaminated water with clean water, or closing contaminated wells. Unfortunately, the costs of these band-aid solutions is high: thousands of water suppliers have had to close contaminated wells, dig new wells, or make other expensive adjustments in water service to lower nitrate levels in tap water. These expenses cost the polluters nothing. They often, however, impose significant costs on water customers. And of course, if contamination continues, eventually some of these systems will no longer have adequate supplies of uncontaminated water.

Some international health authorities have recognized the health risks for infants of exposure to nitrate below the current EPA standard of 10 ppm. The European Community has established a health guideline for nitrate of 5.6 ppm; in Germany and South Africa, the enforceable standard is set at 4.4 ppm. In the United States, the state of Illinois requires community-wide warnings when nitrate levels exceed 8.5 ppm. These indications of concern from health authorities underscore the risks to the millions of individuals in the third group of communities we identify, over 5,600 water systems serving 35 million people where the drinking water is contaminated with nitrate above natural background levels, that is often extremely close to EPA standards and that typically exceed international health guidelines (Table 19).

Table 19: Millions drink water that exceeds international health guidelines for nitrate

  Systems with a sample over 3 ppm Systems with a sample over the international health guideline
State Systems Population Systems Population
Arizona 306 2,920,707 172 2,741,447
California 550 17,017,216 322 14,022,314
Colorado 121 500,303 75 456,388
Delaware 221 367,782 150 252,521    
Illinois 174 1,294,347 97 744,778
Iowa 206 906,576 137 724,617
Kansas 315 430,221 185 291,552
Maryland 312 591,451 176 193,339
Michigan 31 51,194 16 14,135
Minnesota 79 185,502 39 113,754
Montana 43 20,177 22 17,374
Nebraska 465 376,389 317 291,992
Ohio 112 564,826 43 229,782
Oregon 245 218,315 111 133,209
Pennsylvania 739 5,432,162 392 2,077,889
South Dakota 65 30,491 22 11,508
Tennessee 85 99,043 16 27,223
Texas 494 1,267,739 261 875,133
Washington 879 1,264,087 372 524,825
Wisconsin 121 1,281,902 52 303,611
Total 5,563 34,820,430 2,977 24,047,391

Source: State drinking water agency nitrate monitoring database. Compiled by Environmental Working Group.

In many cases, nitrate contamination of these water systems is still at relatively low levels. Unfortunately, in many others it is already exceeding international guidelines, or approaching the EPA's 10 ppm standard. We identified twenty-four million individuals in nearly 3,000 communities where tap water or wells contain nitrate at concentrations that exceed the European health guideline. And we identified 313 additional water systems serving 2.8 million people with "water to watch" -- where at least one sample was above 9 parts per million (Table 20).

Table 20: Water to Watch: Hundreds of water systems have water supplies contaminated with nitrate at concentrations approaching

Rank System City State Population Served Highest Sample Date of Highest Sample Number of Samples Taken % over Int'l Standard
1 Waterloo Water Works Waterloo IA 66,467 9.9 8/10/94 113 25.7%
2 East Hempfield Water Authority Landisville PA 13,493 9.9 9/15/93 73 58.9%
3 Harford County Dpw Bel Air MD 63,000 9.9 7/26/93 20 10.0%
4 Westminster Westminster MD 22,766 9.9 2/18/93 18 77.8%
5 City Of Wasco Wasco CA 13,774 9.8 2/14/95 7 42.9%
6 Northern Il Wtr Corp-Pontiac Pontiac IL 11,200 9.8 3/26/95 63 50.8%
7 City Of Lancaster Authority Lancaster PA 108,000 9.8 2/8/94 18 38.9%
8 Cal. Water Service Co.-East L.A. San Jose CA 152,970 9.8 7/13/93 21 23.8%
9 Morro Bay City Water Dept Morro Bay CA 15,000 9.8 7/5/95 25 28.0%
10 City Of Manteca Manteca CA 44,500 9.8 3/5/93 24 41.7%
11 City Of Chino Hills Chino Hills CA 49,000 9.8 11/10/93 17 35.3%
12 Chippewa Falls Waterworks Chippewa Falls WI 12,989 9.7 8/30/93 1 100.0%
13 Hillcrest Wc - 1,2,3 & 4 Yuba City CA 10,062 9.6 7/25/95 6 33.3%
14 City Of Fresno Fresno CA 390,350 9.6 8/31/94 312 17.6%
15 Garden City, City Of Garden City KS 24,097 9.5 5/9/94 27 22.2%
16 Ottumwa Water Works Ottumwa IA 24,488 9.5 5/1/95 14 50.0%
17 Lca-Wlsa Central Division Wescosville PA 17,285 9.4 6/21/94 244 95.9%
18 Bucks Co Water And Sewer Auth Warrington PA 16,200 9.4 12/26/93 3 33.3%
19 La Crosse Waterworks La Crosse WI 51,000 9.4 12/15/93 1 100.0%
20 Decatur Decatur IL 83,885 9.4 6/6/95 134 43.3%
21 Cuc - Suburban Sacramento CA 32,000 9.3 2/16/95 69 14.5%
22 City Of Davis Davis CA 48,250 9.3 7/26/95 116 13.8%
23 City Of Bakersfield Bakersfield CA 57,740 9.3 10/3/94 62 8.1%
24 West San Bernardino Cwd Rialto CA 41,454 9.3 3/6/95 34 50.0%
25 Bloomington Bloomington IL 52,000 9.3 5/30/95 63 41.3%
26 City Of Downey Downey CA 91,000 9.2 2/17/93 53 3.8%
27 Northampton Bucks Co. Mun Auth Richboro PA 30,000 9.2 9/8/94 40 2.5%
28 Metropolitan Water Co Tucson AZ 36,250 9.2 12/23/93 109 6.4%
29 City Of Rialto Rialto CA 48,418 9.1 12/7/93 131 27.5%
30 Oxnard Wd Oxnard CA 146,571 9.1 6/22/95 23 17.4%
31 Del Este Modesto CA 11,851 9.1 5/12/93 8 37.5%
32 Chester Water Authority Chester PA 110,000 9.1 1/21/94 11 45.5%
33 City Of Anaheim Anaheim CA 286,680 9.0 8/9/95 136 22.8%
34 University of Pennsylvania University Park PA 37,000 8.9 7/13/94 45 37.8%
35 Il American Wtr Cmpny-Pekin Pekin IL 39,000 8.9 7/19/94 34 11.8%
36 San Jose Water Company San Jose CA 921,000 8.9 5/17/93 264 11.4%
37 City Of Ceres Ceres CA 28,988 8.9 2/2/95 8 50.0%
38 City Of Delano Delano CA 29,944 8.9 8/10/93 47 53.2%
39 Us Army Fort Irwin Fort Irwin CA 16,000 8.8 2/14/95 42 26.2%
40 Security W&SD Colorado Springs CO 10,007 8.8 4/3/95 80 93.8%

Source: State drinking water agency nitrate monitoring database. Compiled by Environmental Working Group.

Because the current regulatory system allows nitrate contamination to continue until it has exceeded the 10 ppm standard many of these systems will likely face substantial health risks and costs to fix future problems. In the interim, pollution of these aquifers or other sources of drinking water is allowed to continue, and sensitive populations are put at increased risk of immediate and long-term health problems due to nitrate contamination.

Finally, we also identify 3.8 million people drinking water from private wells that are contaminated with nitrate above the 10 ppm health standard (Table 21). Contamination of these wells is important and unique because they are not regulated. As a consequence, health authorities in most states cannot ensure that families with contaminated wells and small children avoid drinking the water.

Table 21: 3.8 million individuals drink water from domestic wells that exceed federal nitrate standards

State Population Above EPA Stds. % Contaminated Above EPA Stds.
Delaware 48,311 35.0%
Kansas 69,944 28.0%
Iowa 124,771 18.3%
California 428,301 15.0%
New York 239,685 15.0%
Nebraska 52,870 14.0%
Arizona 37,612 14.0%
Illinois 164,510 12.0%
Colorado 29,800 12.0%
Wisconsin 148,582 10.0%
Texas 80,404 9.4%
Minnesota 134,365 9.3%
Pennsylvania 245,241 9.0%
Connecticut 55,412 9.0%
Maryland 67,437 8.0%
Maine 43,100 8.0%
New Jersey 61,936 6.8%
South Dakota 9,428 6.7%
Virginia 96,205 6.4%
Wyoming 6,899 6.4%
Missouri 51,330 5.0%
Oregon 27,477 5.0%
North Dakota 7,170 4.6%
Indiana 69,900 4.5%
Kentucky 42,289 4.2%
Idaho 9,536 4.0%
Nevada 3,215 4.0%
Arkansas 22,341 3.9%
Ohio 66,474 3.8%
Montana 7,342 3.8%
North Carolina 59,926 3.2%
Alaska 4,763 3.2%
New Mexico 6,165 2.0%
Utah 1,140 2.0%
Washington 13,533 1.5%
New Hampshire 5,809 1.4%
Vermont 3,213 1.4%
Michigan 20,234 1.2%
Oklahoma 5,762 1.2%
Florida 17,099 1.0%
Georgia 13,141 1.0%
Massachusetts 5,118 1.0%
Tennessee 8,175 0.9%
West Virginia 5,396 0.9%
Louisiana 4,855 0.8%
South Carolina 9,579 0.7%
Mississippi 1,316 0.2%

Source: Compiled by Environmental Working Group from state and federal monitoring data.

Public Water Systems

Millions Drink Water that Exceeds EPA Nitrate Standards

According to data reported to the EPA's Safe Drinking Water Information System (SDWIS), 2,016 water systems serving over two million people have been cited for violating EPA's nitrate standard in the ten year period between 1986 and 1995 (Table 14). In EPA parlance, these water systems immediately become "significant non-compliers" by virtue of exceeding the nitrate standard. Because the EPA nitrate standard contains no safety factor, each violation presents a significant, immediate risk of acute methemoglobinemia to infants in those communities.

Between 1986 and 1995, violations of the nitrate standard were reported in 40 of the 50 states. Much of the affected population, however, is concentrated in Ohio, where 413,441 people drank from these most contaminated systems, Arizona, with 400,765 people affected, and California, with 380,670 people served water from systems that violated the nitrate standard. In two other states, Illinois and Pennsylvania, more than 100,000 people drank water from water suppliers cited as significant violators of the nitrate standard (Table 14).

Nitrate Contamination Affects Communities Large and Small

The ten largest communities reporting violations of EPA's nitrate standard since 1985 were Columbus, OH; Scottsdale, AZ; Decatur, IL; Upland, CA; Bloomington, IL; Peoria, IL; Manteca, CA; Gilbert, AZ; West Bernadino, CA; and Danville, IL (Table 15). The vast majority of water systems with EPA certified nitrate violations, however, were small or medium sized, serving populations of less than 10,000 people. Of the 2,016 water systems reporting a violation in the eleven year period, 36 served populations of greater than 10,000 (accounting for a total of 1.46 million people), 37 served populations between 3,330 and 10,000 (accounting for a total of 205,000 people), and 1,943 water systems, 96 percent of those affected, served populations of less than 3,300 people (accounting for a total of 495,000 people).

The severity of the nitrate problem is a particular concern in small communities because they are the least well equipped to solve drinking water problems. Due to the small populations they serve, it is difficult and expensive for these communities to remedy a nitrate contamination problem, either by digging new wells or by installing new treatment techniques. To make matters worse, amendments to the Safe Drinking Water Act (S. 1316) that passed the Senate in November 1995, would allow small systems variances from some contamination standards as long as the ensuing solution is "adequate to protect the public health". This loophole -- which makes a weak section of current law even weaker -- is tailor-made to avoid real solutions to nitrate contamination problems. Under this amendment it is certain that more small systems will deal with nitrate in drinking water at levels over 10 ppm through warnings, attempting to provide expensive bottled water, or other band-aid type strategies that place the onus on the drinkers, place more infants at risk, and do not in any way reduce nitrate contamination problems.

Many Water Systems Suffer From Repeated or Unsolved Problems

EPA data also indicate that when nitrate problems are found, they often remain unsolved. In an average year between 1985 and 1994, 568 water systems, serving a population of 650,000 people officially violated the nitrate standard. Of the 2,016 public water systems that reported a violation, nearly 60 percent -- 1,190 -- were repeat violators of the nitrate standard during the years between 1986 and 1995. And more than 625 water systems serving a total population of almost 773,000 people, experienced violations of the nitrate standard in at least four calendar years between 1986 and 1995. Ten water systems reported a violation of the nitrate standard in every year between 1986 and 1995. And seven large systems -- Pontiac, Streator, Decatur, Bloomington, and Danville, IL, as well as Burkburnett, Texas and Morgan Hill, California -- all reported violations of the nitrate standard in at least six of the ten calendar years.

These repeat incidents indicate that many water systems are simply unable to guarantee safe water for their community. Because the nitrate problem is caused by upstream pollution that local authorities have been powerless to stop, problems continue to go unsolved. Faced with the choice of either installing new, expensive treatment systems, or serving unsafe tap water with warnings, the response of many water systems has been simply to warn the community and hope that the problem will go away on its own, despite clear evidence that it will not. And many state governments, including some of the hardest-hit states like Ohio and Illinois, simply go along with these band-aid solutions, doing little to require farmers and other polluters to modify their activities, or to force water suppliers to build new treatment systems.

The Problem Is Getting Worse and Is Linked To High Fertilizer Use

EPA's Safe Drinking Water Information Systems (SDWIS) data indicate that the problem is getting worse. In 1993-94, the most recent two-year period for which complete data are available, 890 water suppliers, serving 734,000 people, violated the nitrate standard. This was a 25% increase in the number of violators in the previous two-year period (1991-92), and the highest two year total in the ten years for which data are available.

There is also a clear relationship between states and regions with high fertilizer use and nitrate contamination violations. Of the ten states with the most number of people affected by nitrate problems, six -- California, Ohio, Illinois, Kansas, Iowa, and Nebraska -- were also among the ten states with the highest annual fertilizer usage. The other four, Arizona, Pennsylvania, Washington, and Oklahoma, all have heavy regional use of fertilizer or manure within the state.

Over 10 Million People Drink Water from Systems with Wells Contaminated by Nitrate at Levels Over Federal Health Standards

Nitrate monitoring data obtained from 21 state drinking water agencies shows that in addition to the hundreds of public water supplies that are reported to EPA for violating a nitrate standard each year, thousands of these systems must contend with supply wells that are contaminated, often above the current standard. The majority of these systems have not been reported to EPA by their state governments for violating the nitrate standard. This does not mean, however, that there are no problems with the community water supply.

Many public water suppliers rely on more than one raw water source. They may draw water from a number of different wells, or from a local river in addition to wells. Our review of over 150,000 monitoring records provided by 21 state drinking water agencies, shows that more than 12.4 million people were served by over 1,000 water suppliers who reported at least one well or tap water sample containing nitrate above the current EPA standards of 10 ppm (Table 16).

California has the nation's most extensive nitrate contamination problems. Since 1993, 139 of the states public water suppliers had at least one sample from a major well or tap water source that contained nitrate at a concentration that exceeded the current EPA standard ((Table 16) and (Table 17)). Together, these water systems served 8.7 million of the state's 30 million citizens. In five other states, Kansas, Nebraska Delaware, Iowa, and Colorado, more than five percent of the state's water suppliers for which we had data had at least one sample of nitrate above EPA standards. Arizona reported 75 systems serving almost two million people with one major source of drinking water over the 10 ppm standard at some point in the past three years. Texas is third with 734,000 people drinking from 114 water systems with at least one tap water sample or major source of drinking water over the 10 ppm standard at some point in the past three years, followed by Pennsylvania with 220,000, Nebraska with 107,000, Washington with 104,000, and Ohio with 100,000. And the Ohio total does not include the cities of Columbus, Alliance, Tiffin and several others that are essentially allowed to provide drinking water contaminated with nitrate at over 10 ppm based on agreements with the state that require public notification. In all of these states, nitrogen fertilizer use is high, and accounts for the majority of nitrogen contamination.

Some of the largest cities with at least one well that is contaminated above EPA standards include Los Angeles, Phoenix, and Mesa, Arizona, as well as Santa Ana, San Jacinto, and Riverside, California ((Table 17) and (Table 18)). In some cases, large communities have reported contamination in wells that exceeds the federal standard by wide margins. The highest nitrate sample reported in a large water system (defined as a water system serving more than 10,000 people) was 253 ppm, in Beatrice, Nebraska.

To their credit, water suppliers with nitrate contamination problems frequently solve problems before they are officially considered to be in violation of EPA standards. In many cases, however, individuals in these communities were served water that contained unsafe concentrations of nitrate even as water suppliers took aggressive measures to ensure that citizens in these communities could drink water that met EPA standards. Unfortunately, these solutions often require difficult and expensive efforts by water providers to deliver safe water to their communities. Generally, water suppliers must either dig new, deeper wells, install new water treatment techniques, or, more frequently, mix water from contaminated wells with water from uncontaminated wells to ensure that nitrate concentrations remain below a level of concern. Polluters of course, pay none of these costs -- they are all passed on to those who are forced to drink the polluted water. And in many cases, vulnerable infants may drink water in violation of health standards as the problem is being fixed.

Future Problems With Contaminated Water Systems

Our analysis of communities with contaminated wells points to even greater long-term problems1 -- communities where drinking water is polluted with nitrate at concentrations that are approaching EPA standards, and that frequently have already exceeded international health guidelines. Because the current regulatory system allows nitrate contamination to continue until it is too late -- when it has exceeded the 10 ppm standard and water drinkers are saddled with unsafe water and the bill to fix the problem -- many of these systems will likely face problems in the future. In the interim, pollution of these aquifers or other sources of drinking water is allowed to continue, and sensitive populations are put at increased risk of short and long-term health problems due to nitrate contamination. In just the twenty-one states for which data was available, we identified more than 24 million people, served by nearly 3,000 water systems that reported at least one well or tap water sample containing nitrate above international health guidelines (5.6 ppm, the guideline established by the European Community) (Table 19), and nearly 35 million people, served by 5,563 water systems that reported at least one well or tap water sample that is contaminated with nitrate from man-made sources2.

In California, 20 percent of the water suppliers for which data are available have at least one well or water source with nitrate contamination that exceeds the European health guideline of 5.6 ppm (Table 19). The Corn Belt, the region of highest fertilizer use, is also hard hit. In Kansas and Nebraska, 30 percent or more of the states' water systems have nitrate contamination that exceeds 5 ppm. In Pennsylvania, 19% of the states water systems have one source of water contaminate by nitrate above 5 ppm; and in Maryland and Delaware, 18% and 26% of the states' water systems exceed the international health guideline.

This nitrate contamination, particularly when it approaches EPA standards, poses important health risks, particularly to sensitive members of the population. The scientific literature reports that numerous cases of methemoglobinemia have been reported at concentrations below EPA's current 10 ppm standard (Sattelmacher 1964; Simon 1962). Nitrate exposure below EPA standards has also been linked to increased risk of cancer and other chronic effects (see previous chapter for detail discussion). And because nitrogen-based fertilizers continue to be used in record amounts, many of these contamination problems will continue to get worse until they have exceeded EPA standards.

Many of the larger water systems that have nitrate contamination problems rely upon polluted rivers for their drinking water. Some of these water suppliers (such as Decatur, IL and Columbus, OH) have been frequent violators of the nitrate standard in past years, or have come quite close (in communities such as Lancaster, PA and Ottumwa, IA). Rather than solve the problem, most of these water systems are simply relying upon the hope that nitrate contamination in the river will not exceed standards again. Unfortunately, infants in these communities remain at significant risk because of prolonged exposures (during heavy runoff periods) to nitrate at concentrations that are extremely close to the 10 ppm standard.

Hundreds of communities have "water to watch" -- meaning that, although they have not yet exceeded the nitrate standard in any well or water source, they have come extraordinarily close. A total of 313 water systems serving 2.8 million people in the 21 states have had at least one nitrate sample between nine and ten parts per million. Four large water systems reported samples of 9.9 ppm nitrate - extremely close to violating the nitrate standard. (Table 20). Other large water systems that have come close to exceeding the standard include Lancaster, Pennsylvania (with one sample at 9.8 ppm), Fresno (9.6 ppm), and LaCrosse, Wisconsin (9.4 ppm).

All of the water systems that have water to watch, whether they rely upon surface or ground water, are clearly high-risk communities. Infants in these communities may be at greater risk than infants in communities that violate the standard because in nearly all of these cases, no warnings will be made, nor any efforts required to reduce these nitrate levels, which some health authorities consider to be unsafe for infants (see discussion of German and South African health standards and European health guidelines, chapter 1)

The Costs of Nitrate Contamination

The costs of nitrate contamination of drinking water can be seen in many ways. Unfortunately, it is consumers, not polluters, who pay the bill when water suppliers are forced to dig new wells or install new treatment technologies to reduce nitrate contamination. For example, after years of persistent nitrate problems and water alerts caused by upstream farmers use of fertilizer, the Des Moines, Iowa Water Works was forced to install a new $4 million water treatment system. Unfortunately, Des Moines citizens had to pay for this new system, although fertilizer use by upstream farmers caused the problem (Huber 1992).

Similarly, residents of Bowling Green, Ohio were faced with increased costs and more pesticides in their water due to efforts that the utility was forced to undertake because of upstream farmers overruse of fertilizer. Bowling Green gets its water from the Maumee River, which is heavily polluted by nitrate and agricultural weed killers. The utility was forced to build a vast holding tank so that they could selectively draw water from the river on days when nitrate concentrations were low to avoid exceeding the nitrate standard. Unfortunately, later studies found that this holding tank had the effect of increasing the concentrations of weed killers that were in city tap water supplies (Cohen, et al. 1995). Because of upstream nitrate pollution, Bowling Green residents were forced to pay for "improvements" to their water system -- which ultimately increased their exposure to other chemical contaminants.

In other cases, communities were forced to close wells, develop capacity to blend contaminated water with less contaminated water, or dig new wells. Personal communication with water suppliers indicates that in many cases, the cost of digging new wells arranging blending plans, or closing contaminated wells runs in the range of $200,000-$500,000 per well. Nationwide, thousands of wells have been shut down because of nitrate contamination problems.

In 1988, in what was clearly an underestimate of the total cost of nitrate contamination in the state (because many water systems fixed problems without having to apply for state aid), a report to the California State Legislature concluded that water systems in California had requested over $48 million in state aid in that year alone (equivalent to over $65 million in 1995 dollars) for remedial measures to solve nitrate contamination problems (Anton, et al. 1988).

Using extremely conservative estimates, assuming that California accounts for one third of the nation's nitrate problems, the 1988 estimates would mean that nationwide, water suppliers are spending approximately $200 million per year to solve nitrate problems. And on top of this, there are an estimated 3.8 million individuals with domestic wells that exceed the nitrate standard. These individuals must either dig new wells or buy bottled water -- which can cost hundreds of dollars per year -- in order to ensure the safety of their infants. Finally, farmers themselves pay for their high use of nitrate. If the nations' farmers could match their Iowa brethren and reduce fertilizer use by approximately 20%, they would save an estimated $750 million per year on fertilizer use. These conservative estimates make it abundantly clear: overuse of fertilizer, and the attendant drinking water problems have cost water drinkers and fertilizer users billions of dollars in the last decade.

Domestic Drinking Water Wells

Approximately 45 million people nationwide receive their tap water from private wells rather than municipal water systems. A number of factors make these domestic wells particularly susceptible to contamination. As a general rule, private wells are shallower than most municipal supply wells. While municipal wells are routinely drilled to a depth of one hundred feet or more, it is not uncommon to find individual wells that are less than 20, or even less than 10 feet deep. In addition, many of these wells are located on farms, or in rural areas where nitrogen fertilizer use is high. This is especially troubling because private wells are typically beyond the purview of federal, state, and even local health standards, leaving public health authorities unable to ensure adequate protection from nitrate contamination for the children and families using these wells.

3.8 Million Drink From Private Wells Contaminated Over the 10 PPM Nitrate Standard

A series of state and national studies have shown that a large population is placed at risk due to contamination on individual water supply wells. The most recent and comprehensive national-scale study of nitrate in domestic water supply wells was conducted by the United States Geological Survey (USGS) as part of their National Water Quality Assessment Program (NAWQA) (Mueller, et al. 1995). This study consisted of over 12,000 ground water samples from a variety of different land use settings (agricultural, urban, forest, and rangeland) and well types and depths, including domestic and public supply wells. Nine percent of all domestic water supply wells tested -- wells which provide drinking water for approximately 3.8 million people -- were contaminated with nitrate above the EPA's Maximum Contaminant Level.

The results further showed that a significant number of wells were contaminated, although not yet above EPA standards. Thirty-one percent of all domestic wells -- providing water for a population of over 13 million people, contained some evidence of nitrate contamination from human sources (above 3 ppm), and one in five domestic wells contained nitrate concentrations that exceeded five parts per million.

Agricultural Regions Are Hardest Hit

Agricultural regions of the country -- where nitrogen fertilizer use is highest -- have the worst nitrate contamination problems (Mueller, et al. 1995). The USGS study analyzed wells in four separate land-use regions -- agricultural, range, forest, and urban -- and found the highest levels of contamination in agricultural regions. In agricultural regions, 21.2 percent of all wells tested exceeded the drinking water nitrate MCL -- a contamination rate that was significantly higher than the rate for wells found in forest (3.0%), range (8.5%), or urban (7.0%) areas. The median nitrate concentration in agricultural wells was 3.4 parts per million -- again, far higher than the median concentration for wells found in forest (0.1 ppm), range (1.5 ppm) or urban (1.8 ppm) wells. The authors of the study concluded that,

"Elevated nitrate concentrations in areas of more homogeneous cropland probably were a result of intensive nitrogen fertilizer application on large tracts of land" (Mueller, et al. 1995 p. 1).

Nitrate Contamination of Ground Water Is Increasing

Contamination problems are increasing with time. Many researchers have concluded that the full effect of overapplication of nitrate fertilizer will not be felt for 30 to 40 years (Hallberg and Keeney 1993), meaning that for most wells that are already contaminated, problems will only become worse.

In one of the nation's most thoroughly studied areas, the Big Spring Basin in Iowa, nitrogen fertilizer use increased approximately three-fold between 1960 and 1990, and the increase in nitrate in ground water "directly paralleled these increases" (Hallberg and Keeney 1993).

The recent USGS report documented a number of other cases where nitrate contamination had increased over time. Six wells in an agricultural region in the Southeast and four from agricultural regions in the Snake River Basin were analyzed over a period of ten to twenty years, and in every case these wells showed statistically significant increases in nitrate concentration (Mueller, et al. 1995).

And, over a ten year study of the Platte River valley in Nebraska, as heavy fertilizer use continued, nitrate concentrations increased throughout the underlying aquifer (Spalding and Exner 1990).

As long as widespread overapplication of nitrogen fertilizer continues, contamination of groundwater will continue to get worse. If a community or an individual has a contaminated well due to overapplication of fertilizer, action must begin immediately to solve the problem. Farmers must begin using less fertilizer, and using it more efficiently today in order to prevent additional problems tomorrow.

State Level Analyses - Data Sources

To complement the recent USGS NAWQA studies, as well as other national and regional scale studies, and to better quantify the number of people drinking from contaminated private wells on a state by state basis, we analyzed a number of additional data sources.

For fourteen states -- Arkansas, Illinois, Iowa, Indiana, Kansas, Louisiana, New Jersey, North Carolina, Ohio, Oregon, Texas, Virginia West Virginia, and Wisconsin -- we used data from state level sources (generally, in-state university researchers) to estimate the number of individuals exposed to nitrate at concentrations greater than 10 ppm.

For other states, we relied upon the most recent USGS NAWQA studies. If adequate data were available -- more than 100 samples -- we based our estimates only on samples collected from domestic supply wells. This was the case in nine states, California, Florida, Georgia, Maryland, Missouri, Nebraska, Nevada, Pennsylvania, and Washington. In other cases, there was insufficient data from water supply wells, and we based estimates on USGS samples of all wells. This was the case in nine additional states, Colorado, Connecticut, Delaware, Georgia, Idaho, Maine, Massachusetts, New Mexico, New York, and Oregon. In all states, the number of individuals drinking ground water from privately owned wells was obtained from U.S. Geological Survey water-use data (Perlman 1994).

In the majority of states, the percentage of domestic wells that were contaminated above the federal standard was higher than the percentage of all wells (including domestic drinking water wells, industrial wells, irrigation wells, observation wells, etc.) that were contaminated above the standard. Nationally the USGS found that seven percent of all wells, but nine percent of domestic wells were contaminated at greater than 10 ppm nitrate. This means that, in cases where we looked at data from all wells instead of just domestic supply wells, our results most likely underestimated the affected population.

These 32 states account for the majority of the nations well water drinkers, as well as accounting for most the regions of intense agriculture. For the remaining states where recent state or USGS data was not available, we relied upon older compilations of USGS data, collected from 1960-1985. Again, these compilations most likely underestimate the current extent of contamination. On a national basis, the older USGS studies estimated that 6.4 percent of all sampled wells contained nitrate above the EPA MCL. More recent USGS studies indicate that nine percent of domestic wells are contaminated above the EPA standard.

State Level Results

The states with the highest percentages of domestic wells contaminated above federal standards are Delaware, Kansas, Iowa, California, and New York (Table 21). A total of ten states, Nebraska, Arizona, Illinois, Colorado, and Wisconsin, in addition to the previous five -- have over 10 percent of the wells in their state contaminated above the federal standards. In twelve more states more than five percent of domestic wells are contaminated by nitrate at concentrations that exceed federal safety standards.

In seventeen states, more than 50,000 people were exposed to unsafe concentrations of nitrate in domestic wells, and in seven states -- California, Pennsylvania, New York, Illinois, Wisconsin, Minnesota, and Iowa -- more than 100,000 people were exposed to unsafe levels (Table 21). In these states, thousands, of infants are at acute risk of contacting potentially fatal methemoglobinemia from their tap water.

Not surprisingly, virtually all of the states with high percentages of contaminated wells or large exposed populations also have high statewide or regional use of fertilizer or nitrate. Six of the ten states with the highest percentages of wells above the standard -- Kansas, Iowa, California, Nebraska, Texas, and Minnesota -- also were among the ten states with the highest application of fertilizers in 1994. And the percentage of wells that are contaminated in the ten highest fertilizer use states is also significantly higher than the percentage in the remaining states. In the 1995 study of over 12,000 wells conducted by the United States Geological Survey (Mueller, et al. 1995), nine percent of all wells sampled in the top ten fertilizer using states were found to be contaminated above the current EPA standard. In contrast, thirty-three percent less -- six percent of all tested wells -- were contaminated in the forty states with lower fertilizer use. And as previously noted, this same study found that 21 percent of domestic water wells in agricultural regions were contaminated at levels above the nitrate standard, a rate far higher than in urban, forest, or rangeland areas.


1. Throughout the remainder of this section, when referring to contaminated water supplies, we are referring to those with nitrate concentrations detected above 3 parts per million (ppm). As discussed previously, nitrate is a naturally occurring compound, and it can frequently be detected in groundwater at low concentrations. However, it is generally accepted that concentrations detected above 3 ppm are an indication of contamination from anthropogenic sources -- either fertilizer, manure, or some other point source of contamination.
2. Nitrate was detected at a concentration of greater than 3 ppm in these wells. This represents the generally accepted cutoff point between naturally occurring nitrate and nitrate contamination due to human sources.