Contaminant Level (MCL)
Diquat is an herbicide used commonly in the United States, Europe and Japan. The World Health Organization reports that it is rarely found in drinking water and that, when used as an aquatic herbicide, “residues … have been found to decrease rapidly to essentially undetectable levels within 7–14 days.” The EPA estimates that the herbicide should disappear from water within 2-4 weeks.
According to the EPA, acute exposure can cause symptoms of dehydration.The agency also reports that long term exposure can lead to cataracts:
Some people who drink water containing diquat in excess of the maximum contaminant level [0.02 milligrams per liter] over many years could get cataracts.
The EPA recommends granular activated carbon (GAC) for the treatment of diquat.
Sources: EPA (1), EPA (2), WHO, Photo: geograph.org.uk, author: Walter Baxter
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