EWG's Tap Water Database



Ark Park

Nitrate, a fertilizer chemical, frequently contaminates drinking water due to agricultural and urban runoff, and discharges from municipal wastewater treatment plants and septic tanks. Excessive nitrate in water can cause oxygen deprivation in infants and increase the risk of cancer. 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
20100.800 ppm110.800 ppm
20110.650 ppm110.650 ppm
20120.390 ppm110.390 ppm
20130.390 ppm110.390 ppm
20140.350 ppm110.350 ppm
20150.529 ppm110.529 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 was defined in a peer-reviewed scientific study by EWG and corresponds to 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
2010-03-0210030434-0010.800 ppm
2011-02-2211022845-0010.650 ppm
2012-04-0612041100-0010.390 ppm
2013-06-1013061299-0010.390 ppm
2014-02-2514023147-0010.350 ppm
2015-03-03S5B0685-010.529 ppm