Nitrate and nitrite

San Diego County Water Authority

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
2014	ND	2	0	ND
2015	ND	6	0	ND
2016	ND	5	0	ND
2017	0.382 ppm	6	4	ND - 0.620 ppm
2018	0.260 ppm	4	2	ND - 0.590 ppm
2019	ND	1	0	ND

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
2014-01-06	9590-003-0933	ND
2014-12-29	9590-001-1036	ND
2015-05-07	9590-003-1000	ND
2015-08-05	9590-003-1305	ND
2015-08-25	9590-003-1402	ND
2015-09-03	9590-003-1023	ND
2015-10-05	9590-003-1323	ND
2015-11-03	9590-003-1223	ND
2016-04-05	9590-003-1120	ND
2016-05-03	9590-003-0828	ND
2016-07-08	9590-003-0731	ND
2016-11-08	9590-003-1344	ND
2016-11-29	9590-003-1333	ND
2017-01-24	9590-003-1226	ND
2017-05-03	9590-003-1123	0.540 ppm
2017-07-05	9590-003-1208	0.620 ppm
2017-08-03	9590-003-0807	0.580 ppm
2017-09-07	9590-003-0952	0.550 ppm
2017-10-03	9590-003-1120	ND
2018-01-03	9590-003-1018	0.590 ppm
2018-03-21	9590-003-1013	0.450 ppm
2018-09-04	9590-003-1056	ND
2018-09-17	9590-003-1314	ND
2019-09-17	9590-003-1255	ND