EWG's Tap Water Database



Del-Co Water Company Inc.

Atrazine is a herbicide commonly detected in drinking water that comes from cornfield and other agricultural runoff. It is a hormone disrupter that harms the male and female reproductive systems of people and wildlife. Read More.

Federal laws allow up to 3 parts per billion of atrazine in treated tap water. Water suppliers average atrazine measurements collected over a year, which means that the reported values underestimate intense spikes of elevated exposures during the periods in late spring and early summer when atrazine is applied in large amounts on farm fields.

Human epidemiological studies suggest that federal standards for atrazine are insufficient to protect public health. In 1999 the California Office of Environmental Health Hazard Assessment set a public health goal of 0.15 parts per billion for atrazine in drinking water, based on a study finding increased rates of breast cancer in rats exposed to the chemical. California's legal maximum for atrazine in tap water is 1 ppb.

Click here to read more about atrazine.





Samples exceeding legal limit (MCL)


Samples exceeding
health guidelines

Testing results - average by year

YearAverage resultSamples takenDetectionsRange of results
20100.197 ppb74ND - 0.420 ppb
20110.230 ppb87ND - 0.360 ppb
20120.401 ppb770.140 ppb - 1.30 ppb
20130.317 ppb770.220 ppb - 0.500 ppb
20140.311 ppb98ND - 0.570 ppb
20150.496 ppb770.190 ppb - 0.700 ppb

ppb = parts per billion.

State and national drinking water standards and health guidelines

Health Guideline 0.1 ppb

The health guideline of 0.1 ppb for atrazine was defined by EWG based on epidemiological studies of human exposure to atrazine in drinking water.. This health guideline protects against harm to the developing fetus, harm to the reproductive system and hormone disruption.

ppb = parts per billion.

EPA Maximum Contaminant
Level (MCL) 3 ppb

The enforceable federal standard that defines the highest level of a contaminant allowed in drinking water.

ppb = parts per billion.

EPA Maximum Contaminant
Level Goal (MCLG)3 ppb

A non-enforceable federal health guideline. For cancer-causing chemicals, these health goals are typically set to zero.

ppb = parts per billion.

All test results

Date Lab ID Result
2010-04-06103069-030.420 ppb
2010-04-06103070-030.340 ppb
2010-05-04103818-020.310 ppb
2010-06-08104776-010.310 ppb
2011-04-1111-12380-010.220 ppb
2011-04-1111-12380-020.300 ppb
2011-05-0311-12911-020.170 ppb
2011-05-0311-12909-030.300 ppb
2011-06-1411-14162-030.360 ppb
2011-06-1411-14164-030.260 ppb
2011-06-1511-14240-01C0.230 ppb
2012-04-0312-13549-010.270 ppb
2012-04-0312-13552-010.140 ppb
2012-05-0812-15073-010.240 ppb
2012-05-0812-15072-010.180 ppb
2012-06-0512-16248-011.30 ppb
2012-06-0512-16249-010.430 ppb
2012-06-0512-16251-010.250 ppb
2013-04-0813-14226-010.270 ppb
2013-04-0813-14225-010.350 ppb
2013-05-0713-15437-010.280 ppb
2013-05-0713-15438-010.220 ppb
2013-06-0313-16652-010.500 ppb
2013-06-0313-16651-010.300 ppb
2013-06-0313-16650-010.300 ppb
2014-04-0814-14143-010.140 ppb
2014-04-0814-14142-010.530 ppb
2014-05-0614-15305-010.540 ppb
2014-05-0614-15306-010.1000 ppb
2014-05-0714-15406-01C0.180 ppb
2014-06-0314-16744-010.540 ppb
2014-06-0314-16742-010.570 ppb
2014-06-0314-16743-010.200 ppb
2015-04-0615-14123-010.700 ppb
2015-04-0615-14124-010.550 ppb
2015-05-0515-15518-010.350 ppb
2015-05-0515-15517-010.590 ppb
2015-06-0215-17058-010.640 ppb
2015-06-0215-17059-010.450 ppb
2015-06-0815-17517-01C0.190 ppb