EWG's Tap Water Database


Nitrate and nitrite

Missouri American St. Louis County & St. Charles County

Nitrate and nitrite enter water from fertilizer runoff, septic tanks and urban runoff. These contaminants can cause oxygen deprivation for infants and increase the risk of cancer. Nitrite is significantly more toxic than nitrate. Click here to read more about nitrate.





Samples exceeding legal limit (MCL)


Samples exceeding
health guidelines

Testing results - average by year

YearAverage resultSamples takenDetectionsRange of results
20100.995 ppm1716ND - 1.99 ppm
20111.02 ppm20200.250 ppm - 2.00 ppm
20120.673 ppm25250.210 ppm - 1.41 ppm
20130.576 ppm550.110 ppm - 1.36 ppm
20141.16 ppm15150.300 ppm - 2.19 ppm
20150.968 ppm550.430 ppm - 1.44 ppm

ppm = parts per million.

State and national drinking water standards and health guidelines

Health Guideline 0.14 ppm

The health guideline of 0.14 ppm for nitrate and nitrite was defined by based on the equivalent health guideline for nitrate, as defined in a peer-reviewed scientific study by EWG. . This health guideline protects against one-in-one-million annual cancer risk level.

ppm = parts per million.

EPA Maximum Contaminant
Level (MCL) 10 ppm

The enforceable federal standard that defines the highest level of a contaminant allowed in drinking water.

ppm = parts per million.

EPA Maximum Contaminant
Level Goal (MCLG)10 ppm

A non-enforceable federal health guideline. For cancer-causing chemicals, these health goals are typically set to zero.

ppm = parts per million.

All test results

Date Lab ID Result
2010-02-02CO037360.01000 ppm
2010-04-22CP178830.1000 ppm
2010-04-22CP180081.99 ppm
2010-04-22CP180971.97 ppm
2010-04-22CP180981.98 ppm
2010-06-28CP179480.560 ppm
2010-07-20CP507621.73 ppm
2010-07-20CP507611.68 ppm
2010-07-20CP506531.69 ppm
2010-07-20CP505920.410 ppm
2010-07-21CP505090.270 ppm
2010-10-04CP802800.260 ppm
2010-10-05CP804321.45 ppm
2010-10-05CP804311.28 ppm
2010-10-05CP803411.23 ppm
2010-10-05CP802140.300 ppm
2011-01-12CR179461.99 ppm
2011-01-12CR179452.00 ppm
2011-01-12CR178551.98 ppm
2011-01-12CR177940.470 ppm
2011-01-12CR177260.560 ppm
2011-04-05CS270660.390 ppm
2011-04-05CS271270.340 ppm
2011-04-05CS271821.97 ppm
2011-04-05CS272621.83 ppm
2011-04-05CS272631.88 ppm
2011-07-06CS620301.39 ppm
2011-07-06CS620291.37 ppm
2011-07-06CS619301.38 ppm
2011-07-06CS618740.320 ppm
2011-07-06CS617940.250 ppm
2011-10-03CS997150.450 ppm
2011-10-03CS997140.450 ppm
2011-10-03CS996320.460 ppm
2011-10-03CS995750.400 ppm
2011-10-03CS995120.530 ppm
2012-01-05155873011.17 ppm
2012-01-05155954010.460 ppm
2012-01-05158254010.490 ppm
2012-01-05158278011.22 ppm
2012-01-05158289011.29 ppm
2012-04-10174084010.990 ppm
2012-04-10174066011.03 ppm
2012-04-10164206011.01 ppm
2012-04-16161138010.330 ppm
2012-04-16161157010.320 ppm
2012-07-05191808011.41 ppm
2012-07-05174085011.35 ppm
2012-07-05174067011.40 ppm
2012-07-11169926010.560 ppm
2012-07-11171318010.250 ppm
2012-10-09198955010.210 ppm
2012-10-09198949010.210 ppm
2012-10-09198937010.560 ppm
2012-10-09198928010.510 ppm
2012-10-09191809010.230 ppm
2012-10-23202750010.370 ppm
2012-10-23202749010.380 ppm
2012-10-23202748010.390 ppm
2012-10-23202747010.290 ppm
2012-10-23202746010.400 ppm
2013-04-02214908010.750 ppm
2013-04-02214926011.36 ppm
2013-04-03214917010.540 ppm
2013-10-08236418010.120 ppm
2013-10-08236415010.110 ppm
2014-04-15251433010.800 ppm
2014-04-16251415010.540 ppm
2014-04-16251424010.470 ppm
2014-07-29AC297611.98 ppm
2014-07-29AC297602.19 ppm
2014-07-29AC297590.390 ppm
2014-07-29AC297580.350 ppm
2014-07-29AC297571.96 ppm
2014-07-29269567010.350 ppm
2014-07-29269566010.300 ppm
2014-07-29269565011.87 ppm
2014-07-29269564011.97 ppm
2014-07-29269563011.90 ppm
2014-10-08271619011.09 ppm
2014-10-09271622011.30 ppm
2015-04-22286266011.03 ppm
2015-04-22286248010.510 ppm
2015-04-22286257010.430 ppm
2015-10-26303178011.43 ppm
2015-10-26303175011.44 ppm