EPA Designation Regulated
EPA Classification Organic Chemicals
EPA Levels 1,2 0.02 MCLG (mg/L)
0.02 MCLG (mg/L)
Alternative Names none
Sources Runoff from herbicide use
Diquat is a non-selective herbicide and dessicant used extensively for control of crop and aquatic weeds; it may cause cataracts.


Diquat is an organic solid of colorless or yellow crystals. A water solution is dark red-brown.


Diquat is a herbicide that has been used extensively in the United States since the late 1950s to control both cropand aquatic weeds. It is used on potatoes; as an aid in harvesting cotton, rapeseed and other oil seed crops; to wilt and dry out silage, standing hay, etc., for storage; a plant growth regulator and sugar cane-flowering suppressant.

Health Effects

Some people who drink water containing diquat well in excess of the maximum contaminant level (MCL) for many years could get cataracts.

EPA Data Source: Diquat

EPA Definitions:

1Maximum Contaminant Level Goal (MCLG) - The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety and are non-enforceable public health goals.

Maximum Contaminant Level (MCL) - The highest level of a contaminant that is allowed in drinking water. MCLs are set as close to MCLGs as feasible using the best available treatment technology and taking cost into consideration. MCLs are enforceable standards.

Maximum Residual Disinfectant Level Goal (MRDLG) - The level of a drinking water disinfectant below which there is no known or expected risk to health. MRDLGs do not reflect the benefits of the use of disinfectants to control microbial contaminants.

(TT) Treatment Technique - A required process intended to reduce the level of a contaminant in drinking water.

Maximum Residual Disinfectant Level (MRDL) - The highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial contaminants.

2 Units are in milligrams per liter (mg/L) unless otherwise noted. Milligrams per liter are equivalent to parts per million.