EWG's Tap Water Database — 2019 UPDATE



City of Duncanville

Simazine is a hormone-disrupting herbicide related to atrazine. It affects the male and female reproductive systems. In studies of laboratory animals, simazine increases blood levels of estrogen, decreases prolactin and progesterone, and causes mammary and ovarian tumors.





Samples exceeding legal limit (MCL)


Samples exceeding
health guidelines

Testing results - average by year

YearAverage resultSamples takenDetectionsRange of results
20120.320 ppb330.290 ppb - 0.370 ppb
20130.150 ppb330.0700 ppb - 0.270 ppb
20140.157 ppb330.0800 ppb - 0.240 ppb
20150.0417 ppb61ND - 0.250 ppb

ppb = parts per billion

State and national drinking water standards and health guidelines

EWG Health Guideline 0.1 ppb

The EWG Health Guideline of 0.1 ppb for simazine 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.

EPA Maximum Contaminant
Level (MCL) 4 ppb

The legal limit for simazine, established in 1992, was based on toxicity studies in laboratory animals conducted in the 1980s. This limit does not fully protect against harm to the reproductive system, harm to the developing fetus, and hormone disruption.

ppb = parts per billion

All test results

Date Lab ID Result