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Home>Water University>Water Contaminants>Endothall


This is a fact sheet 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 Endothall and how is it used?

Endothall is an organic solid of white odorless crystals. Endothall is used as a defoliant for a wide range of crops and as a herbicide for both terrestrial and aquatic weeds. It is used as a desiccant on lucerne and on potato, for the defoliation of cotton, to control aquatic weeds and as an aquatic algicide growth regulator. It has been used for: sugar beets, turf, hops sucker suppression; alfalfa, clover desiccants; potato vine killers.

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:

Endothall Turf Herbicide
Endothall Weed Killer
Herbicide 273
Herbon Pennout

Why is Endothall 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 endothall has been set at 0.1 parts per million (ppm) 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 0.1 ppm 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 endothall to potentially cause the following health effects when people are exposed to it at levels above the MCL for relatively short periods of time: depressed breathing and heart rate.

Long-term: Endothall has the potential to cause the following effects from a lifetime exposure at levels above the MCL: increase in size of some internal organs, particularly the stomach and intestine.

How much Endothall is produced and released to the environment?

EPA estimated total domestic usage in 1982 to have been approximately 1.5 million lbs. Release of endothall to the environment is expected to occur primarily during its use as a pre-emergence, post-emergence, turf and aquatic herbicide and harvest aid. Other sources of release include loss during manufacturing, formulation, packaging or disposal of this herbicide.

What happens to Endothall when it is released to the environment?

Endothall is expected to be quickly broken down by microbes in soil or water. It is also able to leach through soil into ground water; however, rapid degradation would limit the extent of leaching.

Endothall is not likely to accumulate in aquatic life.

How will Endothall be detected in and removed from my drinking water?

The regulation for endothall 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 endothall is present above 9 parts per billion. 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 endothall so that it is consistently below that level. The following treatment methods have been approved by EPA for removing endothall: Granular activated charcoal.

How will I know if Endothall is in my drinking water?

If the levels of endothall exceed the MCL, 0.1 ppm, 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.

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).

Drinking Water Standards:

Mclg: 0.1 ppm (parts per million)

Mcl: 0.1 ppm

Note: This fact sheet is part of a larger publication adapted from U.S. EPA publication: EPA National Primary Drinking Water Regulations.