EWG's Tap Water Database — 2021 UPDATE



City of Flagstaff

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
20140.377 ppm98ND - 1.000 ppm
20150.511 ppm11110.140 ppm - 1.40 ppm
20160.460 ppm109ND - 1.40 ppm
20170.519 ppm1210ND - 1.90 ppm
20180.508 ppm109ND - 1.50 ppm
20190.526 ppm96ND - 1.60 ppm

ppm = parts per million

State and national drinking water standards and health guidelines

EWG Health Guideline 0.14 ppm

The EWG Health Guideline of 0.14 ppm for nitrate was defined by EWG . This health guideline protects against cancer and harm to fetal growth and development.

EPA Maximum Contaminant
Level (MCL) 10 ppm

The legal limit for nitrate, established in 1962, was developed to protect infants from acute methemoglobinemia, a life-threatening disorder of oxygen transport in the body. This limit does not fully protect against the risk of cancer and harm to the developing fetus.

ppm = parts per million

All test results

Date Lab ID Result
2014-04-07201404120026I0.280 ppm
2014-04-07201404120025I0.270 ppm
2014-04-07201404120024I1.000 ppm
2014-04-07201404120023I0.180 ppm
2014-04-07201404120022I0.180 ppm
2014-04-07201404120021I0.150 ppm
2014-05-02201405060750I0.600 ppm
2014-05-29201405300314I0.730 ppm
2015-03-09201503120031I0.180 ppm
2015-03-09201503120030I0.150 ppm
2015-03-09201503120029I1.000 ppm
2015-03-10201503120032I0.140 ppm
2015-03-10201503050252I0.180 ppm
2015-04-14201503050251I0.150 ppm
2015-07-09201507100072I0.570 ppm
2015-07-28201507210370I0.580 ppm
2015-07-30201507310184I0.980 ppm
2015-08-27201508280194I1.40 ppm
2015-09-10201509120269I0.290 ppm
2016-02-17201602180314I0.750 ppm
2016-02-17201602180313I0.150 ppm
2016-07-11201607120775I0.160 ppm
2016-07-11201607120774I0.130 ppm
2016-07-11201607120773I0.990 ppm
2016-07-11201607120772I1.40 ppm
2016-07-11201607120771I0.290 ppm
2016-07-25201607260445I0.580 ppm
2016-08-17201608180220I0.150 ppm
2017-03-07201703090160I1.10 ppm
2017-03-07201703090159I0.290 ppm
2017-03-07201703090158I0.150 ppm
2017-03-07201703090157I0.160 ppm
2017-03-07201703090156I0.150 ppm
2017-05-1520170516059410.580 ppm
2017-08-15201708170127I1.90 ppm
2017-08-28201708290222I0.980 ppm
2017-08-28201708290221I0.140 ppm
2017-09-11201709120606I0.780 ppm
2018-05-15201805160793 I0.360 ppm
2018-05-15201805160792 I1.50 ppm
2018-05-15201805160791 I0.630 ppm
2018-06-11201806120451 IND
2018-06-13201806140903I0.150 ppm
2018-06-13201806140902I0.980 ppm
2018-08-27201808281003I1.000 ppm
2018-08-27201808281002I0.170 ppm
2018-08-27201808281001I0.130 ppm
2018-08-27201808280602I0.160 ppm
2019-04-29201904300311I0.150 ppm
2019-04-29201904300310I0.380 ppm
2019-07-22201907230199I0.960 ppm
2019-09-25201909260285I1.60 ppm
2019-09-25201909260284I0.640 ppm
2019-10-23201910240268I1.000 ppm