United States
Environmental Protection
Agency
Office of Water
•Office of Pesticides and
Toxic Substances'
Fall 1990
oEPA National Pesticide Survey
Alachlor
CH2-CH3
What is
Alachlor?
How Does
Alachlor
Behave in
Soil and
Ground
Water?
How Does
Alachlor Get
into Ground
Water?
Alachlor
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. Alachlor was one of the pesticides
detected in the Survey. This fact sheet provides a description of alachlor, its potential
health effects, and guidance on both treating and preventing well contamination.
Alachlor is the common name of an herbicide which is a member of the
chemical family of acetanilides. Alachlor was registered for use in 1969. It has been
sold under the trade names of Lasso, Pillarzo, and the discontinued trade name of
Alatox. Alachlor is also a component of other herbicides such as Bronco, Bullet,
Cannon, Freedom, and Lariat. Alachlor is used to control most annual grasses and
certain broadleaf weeds in corn, cotton, dry beans, peanuts, potatoes, and soybeans.
It may also be used on sunflowers, cabbage, tobacco, sugarcane, and certain
ornamental and established turf species.
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
alachlor 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. Alachlor has a medium potential to be transported, and a
medium potential to be transformed.
Alachlor migration into ground water could result from the presence of alachlor
in the soil due to agricultural applications. Alachlor could also reach ground water
from direct entry into a well through accidental chemical spills or improper storage
near a well.
WPS Alachlor
Printed on Recycled Paper
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Findings of
the National
Pesticide
Survey
What Health
Effects Might
be Caused by
Alachlor 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 alachlor is present, at or
above the analytical detection level of 0.50jug/L used in the Survey, in about 3,140
(0.03%) rural domestic wells nationwide. Considering the precision of the Survey, EPA
estimates that this number could be as high as 101,000. Alachlor is measured in
micrograms per liter (f/g/L) which is equivalent to parts per billion (ppb). Alachlor was
sometimes detected at concentrations above EPA's proposed Maximum Contaminant
Level (MCL) of 2 pg/L EPA notified well owners and operators within 24 hours when
detections were above health-based guidelines or standards. Alachlor was not
detected in any CWS wells.
Non-Cancer Effects: A Lifetime Health Advisory Level for alachlor in drinking water
has not been established by EPA. Ingesting alachlor has been shown to result in
adverse health effects in animal studies, resulting in damage to the liver, kidneys,
spleen, and eyes.
Cancer Risk: Alachlor also causes cancer in laboratory animals that are given high
doses of the pesticide over the course of their lifetimes. Therefore, EPA considers
alachlor to be a probable human carcinogen (cancer-causing agent). EPA estimates
that if an individual consumes water containing alachlor at 0.4 /*g/L over his or her
entire lifetime, that person would theoretically have no more than a one-in-a-million
chance of developing cancer as a direct result of drinking water containing this
pesticide.
Standard: EPA sets enforceable standards for public water systems, called MCLs.
These regulatory standards set achievable levels of drinking water quality to protect
human health. The proposed MCL for alachlor is 2 /jg/L (proposed as of May 22,
1989).
Alachlor ca'n be detected in drinking water by a laboratory using an EPA
method such as #507. If alachlor is detected in well water and confirmed by retesting,
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. Public water suppliers are required to
notify customers if the drinking water that they deliver contains a contaminant that
exceeds its MCL.
You may also be able to treat your well water to remove pesticides and other
contaminants. Treatment by granular activated carbon can remove alachlor from
water. However, this technique is not necessarily appropriate or available in every
situation. State or County health officials should be able to provide advice on the best
approach to follow.
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
NPS Alachlor
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Why was the
National
Pesticide
Survey
Conducted?
Where to Go
for More
Information
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.
Drill a New Well
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 (OFF) Docket
401 M Street, SW Room NEG004
Washington, DC 20460
(202) 382-3587
Information on regulation of
pesticides in drinking
water
Information on health
effects and safe
handling of pesticides
Background documents
for Survey (available
for review)
NPS Alachlor
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National Technical Information Service (NTIS)
5285 Port Royal Road
Springfield, VA 22161
(703) 487-4650
Copies of the
NFS Phase I Report
(available 1991)
and
NFS Phase II Report
(when available)
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.
NPS Alachlor
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