Nitrate and nitrite

Helena Water System

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.

MORE ABOUT THIS CONTAMINANT

Samples

Samples exceeding legal limit (MCL)

Samples exceeding
health guidelines

Testing results - average by year

Year	Average result	Samples taken	Detections	Range of results
2013	N/A	0	0	N/A
2014	0.403 ppm	3	3	0.0200 ppm - 1.09 ppm
2015	0.333 ppm	3	2	ND - 0.980 ppm
2016	0.447 ppm	3	3	0.0500 ppm - 1.21 ppm
2017	0.402 ppm	6	6	0.0200 ppm - 1.14 ppm
2018	0.527 ppm	3	3	0.0300 ppm - 1.36 ppm
2019	0.523 ppm	3	3	0.0400 ppm - 1.35 ppm

ppm = parts per million

State and national drinking water standards and health guidelines

EWG Health Guideline 0.14 ppm

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

EPA Maximum Contaminant
Level (MCL) 10 ppm

ppm = parts per million

All test results

Date	Lab ID	Result
2014-07-10	H14070201-003A	1.09 ppm
2014-07-10	H14070201-002A	0.1000 ppm
2014-07-10	H14070201-001A	0.0200 ppm
2015-07-08	H15070139-003B	ND
2015-07-08	H15070139-002B	0.980 ppm
2015-07-08	H15070139-001B	0.0200 ppm
2016-07-22	H16070410-003A	1.21 ppm
2016-07-22	H16070410-002A	0.0800 ppm
2016-07-22	H16070410-001A	0.0500 ppm
2017-07-11	H17070141-002B	0.0800 ppm
2017-07-11	H17070141-003A	1.01 ppm
2017-07-11	H17070141-001B	0.0200 ppm
2017-08-16	H17080331-003C	0.120 ppm
2017-08-16	H17080331-002C	1.14 ppm
2017-08-16	H17080331-001C	0.0400 ppm
2018-07-18	H18070399-003A	0.190 ppm
2018-07-18	H18070399-002A	1.36 ppm
2018-07-18	H18070399-001A	0.0300 ppm
2019-07-11	H19070241-001A	0.180 ppm
2019-07-11	H19070241-003A	0.0400 ppm
2019-07-11	H19070241-002A	1.35 ppm