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Oregon EPHT Drinking Water Indicators

Drinking Water Indicator:   Maximum contaminants level (MCL) violations and mean concentrations

Measure : Nitrate MCL violations and mean concentrations in community water systems (CWS) in Oregon

 

 

Nitrate is the most common contaminant in ground water aquifers worldwide.  Nitrates are nitrogen-oxygen chemical units that combine with various organic and inorganic compounds.

Nitrate (NO 3) originates in drinking water from nitrate-containing fertilizers, sewage/septic tanks and decaying natural material, such as animal waste. As a result of human activities and population growth, nitrates are increasing in water resources.   The greatest use of nitrates is as fertilizer.

Nitrates do not evaporate, are very soluble in water and can easily migrate.  Since they are very soluble and do not bind to soils, nitrates have a high potential to migrate to ground water. Because they do not evaporate, nitrates and nitrites are likely to remain in water until consumed by plants or other organisms.

Nitrate was first identified as a public health threat in drinking water in 1945 when high nitrate levels from private wells were shown to cause methemoglobimia or “blue baby syndrome” in infants who received formula mixed with well water.

Long-term exposure to high nitrate levels in drinking water has been found in some studies to be a risk factor for several types of cancer (such as  gastric, colorectal, bladder, urothelial, brain, esophageal and ovarian cancer, and non-Hodgkin’s lymphoma). However, other studies have found no association.

There also is some evidence to suggest that exposure to nitrates in drinking water is associated with adverse reproductive outcomes such as spontaneous abortion (miscarriage), intrauterine growth restriction, and various birth defects. However, other studies have found no association.  

Nitrate regulations became effective in 1992. If nitrate levels consistently exceed the Maximum Contaminant Level (MCL), the community water system must notify the public and possibly provide alternative drinking water supplies. These measures (of community water systems and population served who are potentially exposed to water not meeting MCLs for nitrates) provide simple estimates of the potential for adverse health effects.

 

The proportion of CWS with any nitrate violations and the proportion of people receiving water from CWS with a nitrate violation were both consistently below 0.5 percent in every year between 2002 and 2007.

More than 90 percent of the population received drinking water with average nitrate levels lower than 1 mg/L, i.e., 10 percent of the MCL, and maximum yearly nitrate levels under 3 mg/L or 30 percent of the MCL.

Table 1:  Annual percentage and number of CWS with any nitrate MCL violations, and number of people served by CWS with any nitrate MCL violations.

Table 2:  Number of CWS and number of people receiving water from CWS with different mean and maximum concentrations, by year .  

Table 3:  Annual mean and maximum nitrate concentrations across CWS and the number of people served, by mean and maximum nitrate concentrations. 

Graph 1:  Number of people receiving water from CWS with different mean and maximum nitrate concentrations in 2007. The black bar indicates the maximum contaminant level of 10 mg/L.

Graph 2:  Number of CWS with different mean and maximum nitrate concentrations in 2007.  

_________________________________________________________________________________________________  

Table 1: Annual percentage and number of CWS with any nitrate MCL violations, and number of people served by CWS with any nitrate MCL violations.

 

Annual percentage and count

of CWSs with any nitrate MCL violation

Annual percentage and count of people

 served by CWSs with any nitrate MCL violation

Year

Percent

(count)

Percent

(count)

2002

0.2

(2)

0.2

(6,447)

2003

0.5

(4)

0.1

(3,686)

2004

0.4

(3)

0.3

(10,201)

2005

0.4

(3)

0.1

(2,176)

2006

0.2

(2)

0.1

(1,800)

2007

0.2

(2)

0.1

(1,800)

___________________________________________________________________________________________________

Table 2:   Number of CWS and number of people receiving water from CWS with different mean and maximum nitrate concentrations, by year.

 

 

By Mean Concentration

 

By Maximum Concentration

Year

mcg/L

CWS

People

 

CWS

People

2002

≤ 1

510

2,354,764

 

489

2,156,095

 

<1-3

117

161,525

 

124

264,483

 

>3-5

32

19,559

 

38

56,085

 

>5-10

15

6,489

 

22

61,224

 

>10-20

1

1,997

 

2

6,447

 

>20

0

0

 

0

0

2003

≤ 1

530

2,386,012

 

504

1,536,293

 

<1-3

128

137,321

 

145

912,200

 

>3-5

41

54,433

 

38

68,329

 

>5-10

19

8,334

 

27

65,592

 

>10-20

0

0

 

4

3,686

 

>20

0

0

 

0

0

2004

≤ 1

549

2,372,456

 

517

1,698,314

 

<1-3

141

172,309

 

162

782,091

 

>3-5

35

62,540

 

31

69,359

 

>5-10

22

13,836

 

34

61,176

 

>10-20

0

0

 

3

10,201

 

>20

0

0

 

0

0

2005

≤ 1

543

2,429,350

 

520

2,227,140

 

<1-3

140

161,932

 

153

294,389

 

>3-5

36

49,192

 

36

69,989

 

>5-10

19

3,978

 

27

51,058

 

>10-20

1

300

 

3

2,176

 

>20

0

0

 

0

0

2006

≤ 1

529

2,436,029

 

506

2,250,128

 

<1-3

137

158,212

 

148

280,403

 

>3-5

38

36,386

 

34

34,840

 

>5-10

11

6,661

 

27

71,917

 

>10-20

2

1,800

 

2

1,800

 

>20

0

0

 

0

0

2007

≤ 1

527

2,315,747

 

506

2,169,304

 

<1-3

132

186,529

 

140

225,340

 

>3-5

41

19,018

 

45

83,665

 

>5-10

13

6,401

 

21

47,646

 

>10-20

1

60

 

2

1,800

 

>20

0

0

 

0

0

___________________________________________________________________________________________________

Table 3:  Annual mean and maximum nitrate concentrations across CWS and the number of people served, by mean and maximum nitrate concentrations.

 

 

Mean nitrate concentration

Maximum nitrate concentration

Year

mg/L

CWS

People served

CWS

People served

2002

≤ 1

510

2,354,764

489

2,156,095

 

<1-3

117

161,525

124

264,483

 

>3-5

32

19,559

38

56,085

 

>5-10

15

6,489

22

61,224

 

>10-20

1

1,997

2

6,447

 

>20

0

0

0

0

2003

≤ 1

530

2,386,012

504

1,536,293

 

<1-3

128

137,321

145

912,200

 

>3-5

41

54,433

38

68,329

 

>5-10

19

8,334

27

65,592

 

>10-20

0

0

4

3,686

 

>20

0

0

0

0

2004

≤ 1

549

2,372,456

517

1,698,314

 

<1-3

141

172,309

162

782,091

 

>3-5

35

62,540

31

69,359

 

>5-10

22

13,836

34

61,176

 

>10-20

0

0

3

10,201

 

>20

0

0

0

0

2005

≤ 1

543

2,429,350

520

2,227,140

 

<1-3

140

161,932

153

294,389

 

>3-5

36

49,192

36

69,989

 

>5-10

19

3,978

27

51,058

 

>10-20

1

300

3

2,176

 

>20

0

0

0

0

2006

≤ 1

529

2,436,029

506

2,250,128

 

<1-3

137

158,212

148

280,403

 

>3-5

38

36,386

34

34,840

 

>5-10

11

6,661

27

71,917

 

>10-20

2

1,800

2

1,800

 

>20

0

0

0

0

2007

≤ 1

527

2,315,747

506

2,169,304

 

<1-3

132

186,529

140

225,340

 

>3-5

41

19,018

45

83,665

 

>5-10

13

6,401

21

47,646

 

>10-20

1

60

2

1,800

 

>20

0

0

0

0

 

___________________________________________________________________________________________________

Graph 1:   Number of people receiving water from CWS with different mean and maximum nitrate concentrations in 2007. The black bar indicates the maximum contaminant level of 10 mg/L.

 

___________________________________________________________________________________________________

Graph 2:   Number of CWS with different mean and maximum nitrate concentrations in 2007. The black bar indicates the maximum contaminant level of 10 mg/L.

http://staging.health.oregon.gov/Teamsite/epht/PublishingImages/images/nitrategraph2.PNG   

 

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