Nitrate and nitrite

San Lorenzo Valley Water District

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	0.180 ppm	3	1	ND - 0.540 ppm
2015	0.388 ppm	9	3	ND - 2.20 ppm
2016	N/A	0	0	N/A
2017	N/A	0	0	N/A
2018	0.495 ppm	6	2	ND - 2.30 ppm
2019	0.175 ppm	4	1	ND - 0.700 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
2014-03-26	9590-034-1515	0.540 ppm
2014-09-09	9590-034-1400	ND
2014-11-18	9590-034-1200	ND
2015-02-10	9590-034-1130	ND
2015-05-20	9590-034-1445	0.580 ppm
2015-08-05	9590-023-1430	ND
2015-08-05	9590-024-1500	ND
2015-08-19	9590-022-1415	ND
2015-08-19	9590-025-1445	2.20 ppm
2015-08-19	9590-010-1400	ND
2015-08-19	9590-026-1500	0.710 ppm
2015-08-25	9590-034-1140	ND
2018-07-05	9590-025-1030	2.30 ppm
2018-07-05	9590-034-0915	ND
2018-07-05	9590-026-1000	0.670 ppm
2018-07-18	9590-022-1045	ND
2018-07-18	9590-010-1030	ND
2018-08-14	9590-024-0830	ND
2019-07-30	9590-024-0730	0.700 ppm
2019-07-30	9590-022-1130	ND
2019-07-30	9590-034-0745	ND
2019-07-30	9590-010-1000	ND