United Siatea
Environmental Protection
Agency
&EPA National
Bentazon
Office of Water
Office of Pesticides and
Toxic Substances
Fall 1990
Survey
/CH-CHg
Bentazon
What is
Bentazon?
How Does
Bentazon
Behave in
Soil and
Ground
Water?
How Does
Bentazon Get
into Ground
Water?
The U.S. Environmental Protection Agency (EPA) has completed its five-year
National Survey of Pesticides in Drinking Water Wells (NPS), a study of the presence
of 127 pesticides, pesticide degradates, and nitrate in community water system (CWS)'
wells and rural domestic drinking water wells. Bentazon was detected in the Survey.
This fact sheet provides a description of bentazon, its potential health effects, and
guidance on both treating and preventing well contamination.
Bentazon (Bentazone) is the common name of an herbicide which has been
sold under the trade name of Basagran. Bentazon is also a component of other
herbicides such as Tackle Plus, Acumen, Caresine 2, Herbatox, Triagran, Vega,
Laddok, and Galaxy. Bentazon is used to control a number of broadleaf and sedge
weeds in most grasses, and many large-seeded crops such as winter and spring
cereals, groundnuts, maize, dry peas, rice, lima beans, and mint.
The behavior of a pesticide after it is released to the environment is dependent
upon its movement in air, water, and soil as well as the rate at which it is transformed,
or broken down. Pesticides applied to crops or the soil surface may volatilize
(vaporize) to the atmosphere, be carried off by surface runoff, be carried to ground
water through leaching, or remain in the soil through adsorption (adherence) to soil
particles and undergo little movement in air or water. Pesticides may be transformed
by reaction with water, microorganisms, and exposure to sunlight. The likelihood that
bentazon will migrate into ground water is influenced by its tendency to be transported
(move) from soil to air and water and to be transformed by these various processes,
as well as by the characteristics of the site, such as soil type, moisture, temperature,
and depth to ground water. Bentazon has a high potential to be transported, and a
medium potential to be transformed.
Bentazon migration into ground water could result from its presence in the soil
due to applications of bentazon on agricultural and non-agricultural land. Bentazon
could also reach ground water from direct entry into a well through accidental
chemical spills or improper storage near a well.
WPS Bentazon
Printed on Recycled Paper
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Findings of
the National
Pesticide
Survey
What Health
Effects Might
be Caused by
Bentazon in
Drinking
Water?
How is Water
Treated to
Remove
Contami-
nants?
How Can
Water
Contamina-
tion be
Prevented?
Based on the results of the NFS, EPA estimates that bentazon is present, at or
above the analytical detection level of 0.25 ^g/L used in the Survey, in about 7,160
(0.1%) rural domestic wells nationwide. Considering the precision of the Survey, EPA
estimates that this number could be as high as 109,000. Bentazon is measured in
micrograms per liter (jjg/L) which is equivalent to parts per billion (ppb). Bentazon
was not detected at concentrations above EPA's drinking water Lifetime Health
Advisory Level (HAL) of 20 jug/L Bentazon was not detected in any CWS wells.
Non-Cancer Effects: EPA has set a Lifetime Health Advisory Level for bentazon in
drinking water at 20 /jg/L EPA believes that water containing bentazon at or below
this level is acceptable for drinking every day over the course of one's lifetime, and
does not pose health concerns. Lifetime HALs are based on health effects that were
found in animals given high doses of the pesticides in laboratory studies. This level
includes a margin of safety. Consuming bentazon, however, at high levels well above
the Lifetime Health Advisory Level over a long period of time has been shown to result
in adverse health effects in animal studies, including excessive weight loss and
inflammation of the prostate gland.
Cancer Risk: Data from laboratory studies are inadequate for EPA to determine if
bentazon can increase the risk of cancer in humans.
Standard: EPA sets enforceable standards for public water systems, called maximum
contaminant levels (MCLs). These regulatory standards set achievable levels of
drinking water quality to protect human health. EPA has not established a MCL for
bentazon, but plans to list bentazon on the Drinking Water Priority List for future MCL
consideration.
Bentazon can be detected in drinking water by a laboratory using an EPA
method such as #515.1. If bentazon is detected in well water and confirmed by
retesting to be above 20 ;ug/L, State or County health officials should be consulted.
They may advise periodic retesting to get an accurate overall picture of the water
quality because changes in seasonal precipitation and changes in pesticide use can
cause variations in the amount of chemicals found in water wells. They also may
advise using an alternative drinking water supply (bottled water is an example of a
temporary alternative), treating the water, or drilling a new or deeper well.
At present, EPA has no information on treatment technologies that can
effectively remove bentazon from water.
Several steps may be taken to prevent pesticides or nitrate from entering wells,
such as eliminating direct entry through the well wall, drilling a new well, or modifying
or reducing pesticide and fertilizer use.
Eliminate Direct Entry of Pesticides Through the Well Wall
If pesticides or nitrate are present in well water, they may be entering the
ground water through the well itself rather than through the soil. If the well is old or
poorly constructed, or if there are visible cracks in the well casing, obtain expert
advice on whether or not improvements can be made to the well. In addition,
investigate simple methods of capping the well or sealing it at the surface to prevent
entry. Do not conduct any mixing activities near the well if you use well water to mix
pesticides because a spill could lead to direct contamination of the well.
WPS Bentazon
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Drill a New Well
Why was the
National
Pesticide
Survey
Conducted?
Where to Go
for More
Information
If the soil surrounding the well is the source of contamination, drilling a new or
deeper well may make sense if water can be drawn from a deeper, uncontaminated
aquifer. Unfortunately, it often is difficult to know the quality of the ground water
without drilling or extensive testing. Seek expert advice before you drill.
Learn More about Pesticide Use
If you use pesticides, whether for agricultural or home lawn and garden
purposes, you should consider attending training courses given by your State or
County agriculture department on how to reduce activities that can contaminate
ground water. You may find that you can eliminate or lessen the frequency or quantity
of your pesticide usage by choosing alternative methods of pest control.
EPA conducted this Survey to determine the frequency and concentration of
pesticides, pesticide degradates, and nitrate in drinking water wells nationwide and to
examine the relationship between the presence of pesticides in drinking water wells
and patterns of pesticide use and ground-water vulnerability. The Survey sampled
566 community water system wells and 783 rural domestic wells for 127 pesticides,
pesticide degradates, and nitrate. The wells were selected as a representative
statistical sample to provide nationwide estimates of the presence of pesticides and
nitrate in drinking water wells, and are not meant to provide an assessment of
pesticide contamination at the local, County, or State level.
This fact sheet is part of a series of NFS outreach materials, fact sheets and
reports. The following additional fact sheets are available through EPA's Public
Information Center (401 M Street SW, Washington, DC 20460, (202) 382-2080):
Survey Design
Survey Analytes
Quality Assurance/
Quality Control
Analytical Methods
Summary Results
Fact Sheet for each
detected analyte
Project Summary
Glossary
How EPA Will Use
The NPS Results
Additional information on the Survey and on pesticides in general can be obtained
from the following sources:
U.S. EPA Safe Drinking Water Hotline
1-800-426-4791 (In Washington, DC (202) 382-5533)
Monday-Friday, 8:30 am to 4:30 pm Eastern Time
National Pesticide Telecommunications Network
1-800-858-7378
24 hours a day
U.S. EPA Office of Pesticide Programs (OPP) Docket
401 M Street, SW Room NEG004
Washington, DC 20460
(202) 382-3587
National Technical Information Service (NTIS)
5285 Port Royal Road
Springfield, VA 22161
(703) 487-4650
Information on regulation of
pesticides in drinking
water
Information on health
effects and safe
handling of pesticides
Background documents
for Survey (available
for review)
Copies of the
NPS Phase I Report
(available 1991)
and
NPS Phase II Report
(when available)
WPS Bentazon
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If you are concerned about the presence of pesticides and nitrate in your
private water well, contact your local or State health department. Other experts in
your State environmental agency or agriculture and health departments may also be
helpful to you. If you receive your drinking water from a community water system and
have questions about your water quality, contact your local community water system
owner/operator or the State water supply agency.
Bibliography Meister Publications. Farm Chemicals Handbook. Ohio: Meister Publications, 1990.
U.S. Environmental Protection Agency. Drinking Water Health Advisory: Pesticides.
Michigan: Lewis Publishers, 1989.
U.S. Environmental Protection Agency. Drinking Water Regulations and Health
Advisories. April, 1990.
U.S. Environmental Protection Agency. Health Advisory Summaries, January 1989.
U.S. Environmental Protection Agency. Pesticides in Drinking Water Wells, September
1989.
Weed Science Society of America. Herbicide Handbook of the Weed Science Society
of America. 5th ed. Illinois: Weed Science Society of America, 1983.
Worthing, Charles R., ed. The Pesticide Manual. 8th ed. Thornton Heath: The British
Crop Protection Council, 1987.
WPS Bentazon
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