Consumer Factsheet on: DIQUAT
List of Contaminants
As part of the Drinking Water and Health pages, this fact sheet is part of a larger publication: National Primary Drinking Water Regulations
This is a factsheet about a chemical that may be found in some public or private drinking water
supplies. It may cause health problems if found in amounts greater than the health standard set by
the United States Environmental Protection Agency (EPA).
What is Diquat and how is it used?
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 US since the late 1950s to control both
crop and 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.
The list of trade names given below may help you find out whether you are using this chemical at
home or work.
Trade Names and Synonyms:
Reglone
Why is Diquat being Regulated?
In 1974, Congress passed the Safe Drinking Water Act. This law requires EPA to determine safe
levels of chemicals in drinking water which do or may cause health problems. These
non-enforceable levels, based solely on possible health risks and exposure, are called Maximum
Contaminant Level Goals.
The MCLG for diquat has been set at 20 parts per billion (ppb) because EPA believes this level of
protection would not cause any of the potential health problems described below.
Based on this MCLG, EPA has set an enforceable standard called a Maximum Contaminant Level
(MCL). MCLs are set as close to the MCLGs as possible, considering the ability of public water
systems to detect and remove contaminants using suitable treatment technologies.
The MCL has been set at 20 ppb because EPA believes, given present technology and resources,
this is the lowest level to which water systems can reasonably be required to remove this
contaminant should it occur in drinking water.
These drinking water standards and the regulations for ensuring these standards are met, are
called National Primary Drinking Water Regulations. All public water supplies must abide by
these regulations.
What are the Health Effects?
Short-term: EPA has found diquat to potentially cause the following health effects when people
are exposed to it at levels above the MCL for relatively short periods of time: dehydration.
Long-term: Diquat has the potential to cause the following effects from a lifetime exposure at
levels above the MCL: cataracts.
How much Diquat is produced and released to the environment?
Diquat usage in 1980 was estimated to be 200,000 lbs. of active ingredient. 1982 data indicates
that diquat was not produced domestically, but imports were nearly 835,000 lbs. Diquat is
released into the environment during its use as a contact herbicide, aquatic weed control agent,
harvesting aid, or plant growth regulator. It may also be released into wastewater or in spills
during its manufacture, transport and storage.
What happens to Diquat when it is released to the environment?
Diquat rapidly adheres to soil particles. Though it is resistant to breakdown
by microbes or other
means, this binding to soil serves to deactivate it.
Diquat is removed rapidly from water, disappearing in 2-4 weeks. It has little or no tendency to
accumulate in fish.
How will Diquat be Detected in and Removed from My Drinking Water?
The regulation for diquat became effective in 1994. Between 1993 and 1995, EPA required your
water supplier to collect water samples every 3 months for one year and analyze them to find out
if diquat is present above 0.4 ppb. If it is present above this level, the system must continue to
monitor this contaminant.
If contaminant levels are found to be consistently above the MCL, your water supplier must take
steps to reduce the amount of diquat so that it is consistently below that level. The following
treatment methods have been approved by EPA for removing diquat: Granular activated charcoal.
How will I know if Diquat is in my drinking water?
If the levels of diquat exceed the MCL, 20 ppb, the system must notify the public via newspapers,
radio, TV and other means. Additional actions, such as providing alternative drinking water
supplies, may be required to prevent serious risks to public health.
Drinking Water Standards:
Mclg: 20 ppbMcl: 20 ppb
Learn more about your drinking water!
EPA strongly encourages people to learn more about their drinking water, and to support local
efforts to protect and upgrade the supply of safe drinking water. Your water bill or telephone
book's government listings are a good starting point.
Your local water supplier can give you a list of the chemicals they test for in your water, as well
as how your water is treated.
Your state Department of Health/Environment is also a valuable source of information.
For help in locating these agencies or for information on drinking water in general, call: EPA's
Safe Drinking Water Hotline: (800) 426-4791.
For additional information on the uses and releases of chemicals in your state, contact the:
Community Right-to-Know Hotline: (800) 424-9346
List of Contaminants
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