EWG's Tap Water Database — 2021 UPDATE



Town of Longboat Key

Diquat is a herbicide used on potato crops and aquatic weeds.





Samples exceeding legal limit (MCL)


Samples exceeding
health guidelines

Testing results - average by year

YearAverage resultSamples takenDetectionsRange of results

ppb = parts per billion

State and national drinking water standards and health guidelines

EWG Health Guideline 6 ppb

The EWG Health Guideline of 6 ppb for diquat was defined by the California Office of Environmental Health Hazard Assessment as a public health goal, the level of a drinking water contaminant that does not pose a significant health risk. This health guideline protects against cataracts.

EPA Maximum Contaminant
Level (MCL) 20 ppb

The legal limit for diquat, established in 1992, was based on a toxicity study in laboratory animals conducted in the 1980s.

ppb = parts per billion

All test results

Date Result