EWG's Tap Water Database — 2021 UPDATE


Nitrate and nitrite

Colchester Commons

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.





Samples exceeding legal limit (MCL)


Samples exceeding
health guidelines

Testing results - average by year

YearAverage resultSamples takenDetectionsRange of results
20140.140 ppm32ND - 0.310 ppm
20160.407 ppm32ND - 0.980 ppm
20170.113 ppm330.0200 ppm - 0.250 ppm
20180.557 ppm330.0300 ppm - 1.24 ppm
20190.222 ppm550.0700 ppm - 0.330 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
2014-07-29BG83660NOX0.110 ppm
2014-07-29BG83661NOX0.310 ppm
2016-03-24BK87905NOX0.240 ppm
2016-03-24BK87906NOX0.980 ppm
2017-01-12BX21457NOX0.0700 ppm
2017-04-07BY00694NOX0.0200 ppm
2017-10-10BZ18334NOX0.250 ppm
2018-04-27CA37955NOX0.0300 ppm
2018-04-27CA37956NOX0.400 ppm
2018-04-27CA37957NOX1.24 ppm
2019-10-21CE445540.0700 ppm
2019-10-21CE445550.190 ppm
2019-10-21CE445590.200 ppm
2019-10-21CE445600.320 ppm
2019-10-21CE445560.330 ppm