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Acetochlor

Please submit any comments, questions or suggestions regarding this page to:

the Comments page.

Additionally, you may refer to the list of EPA Headquarters, Regional and State contacts regarding the Acetochlor pesticide registration.

Information presented here provides public access to details of this unprecedented registration. A brief overview including the Agency's Acetochlor Desk Statement, Questions and Answers and some Talking Points highlight the stringent conditions imposed by this pesticide registration. Additionally, a copy of the Registration Agreement is available on-line.

Subject headings outlining technical areas lead to more detailed presentations on Detection Methods, Usage Targets and Results, Ground Water Monitoring Programs , Surface Water Monitoring Programs and their results.


Acetochlor Desk Statement

In March 1994, EPA approved a registration application proposed by the Acetochlor Registration Partnership (ARP) for the use of the herbicide acetochlor on corn. (The ARP consists of Monsanto Company and Zeneca which later sold its shares to Dow AgroSciences.) In an unprecedented approach to limit potential risks to human health and the environment, the Agency stipulated that the continued registration of this chemical depended on a significant reduction in the total use of U.S. corn herbicides of concern, including alachlor, metolachlor, atrazine, and 2,4-D. In addition, EPA imposed several restrictions and conditions on the use of acetochlor.

First of all, the acetochlor conditional registration included several early-warning measures to ensure that ground and surface water resources remain protected. EPA required the Partnership to complete several prospective ground water studies aimed at limiting the use of acetochlor in areas where migration to ground water was likely. At the end of the first five-year period, the Acetochlor Registration Partnership (ARP) and EPA would reassess the monitoring programs in compliance with the agreement.

In April 1998, the Agency confirmed that two acetochlor degradates of presumed toxicological concern in drinking water (acetochlor oxanilic acid and acetochlor ethanesulfonic acid) needed to be included in the monitoring program. Recently completed studies on the mammalian toxicity of acetochlor oxanilic acid and ethanesulfonic acid are currently in review by the Agency. In its reassessment of the monitoring program in September 1999, EPA recommended that the acetochlor monitoring programs be continued for two more years to develop sufficient data for these potentially toxicologically significant degradates.

As part of the conditional registration, the Agency also restricted the use of acetochlor to certified applicators, prevented aerial application, restricted the types of soils on which acetochlor could be used, and prohibited application to water.

Finally, EPA and the ARP agreed that the registration of acetochlor that was granted in 1994 could be cancelled or suspended if any of the following conditions occurred:

  1. Automatic cancellation if herbicides of concern (alachlor, metolachlor, atrazine, EPTC, butylate and 2,4-D) are not reduced by 4 million pounds within 18 months.
  2. Automatic cancellation if the above herbicides are not reduced by 22.6 million pounds within three years.
  3. Automatic cancellation if the above herbicides are not reduced by 66.3 million pounds within five years (equal to a 33% reduction in herbicide use on corn from 1992 levels).
  4. Automatic suspension of all uses of acetochlor if residues are found in ground water or surface water exceeding certain specified levels.
  5. Under the 10-year sunset provision, cancellation on March 7, 2004 if the Partnership does not submit a complete application for registration with all necessary data by March 7, 2001.

These use restrictions and monitoring programs reflect the Agency's emphasis on pollution prevention and are consistent with the new safety standards in the Food Quality Protection Act (FQPA). Acetochlor has been classified as a probable human carcinogen. The Agency believes that the potential for exposure in drinking water is significant, with degradation products also present at significant levels in many ground and surface water sources of drinking water. Significant exposure is also possible through food and to applicators. The Agency is currently conducting a risk assessment which includes information from multiple years of monitoring for acetochlor and its degradates following registration and also recent studies on the mammalian toxicity of acetochlor degradates.


For additional overview information, please refer to the Questions and Answers or continue reading through the Talking Points. For more options, you may return to the beginning of the OPP Acetochlor Page.


Talking Points

Acetochlor Registration Decision

Acetochlor is a new corn herbicide developed by the Acetochlor Registration Partnership which includes Monsanto Co. and Zeneca, Inc. which later sold its shares to Dow AgroSciences. This chemical can be a direct substitute for many herbicides of known concern, namely alachlor, metolachlor, atrazine, EPTC, butylate, and 2,4-D. EPA's decision to register acetochlor will depend on a substantial reduction in the total use of corn herbicides in the United States. In this unprecedented registration, the Agency is implementing stringent standards for the registration of pesticides and is offering industry an opportunity to demonstrate its willingness to implement measures to meet these environmental safeguards and to ensure a safe food supply.

  • Overview of the Acetochlor Registration Agreement

    • The conditions of this registration ensure that acetochlor will pose a negligible risk to human health and the environment.

    • The agreement provides stringent controls to ensure protection of ground and surface waters.

    • EPA has designed early detection measures to prevent ground water emergencies, including the most protective early-warning system ever included in a pesticide registration.

  • Reduction in the Use of Corn Herbicides. A major benefit of acetochlor is that it will allow growers to substantially reduce the use of other high-risk corn herbicides. The conditions of registration mandate automatic cancellation unless the following occur:

    • At the end of 18 months from the date of registration, a net cumulative reduction from 1992 use levels of 4 million pounds of the herbicides alachlor, metolachlor, atrazine, EPTC, butylate, and 2,4-D on corn; and

    • At the end of 3 years from the date of registration, a net cumulative reduction from 1992 use levels of 22.6 million pounds of these corn herbicides; and

    • At the end of 5 years from the date of registration, a net cumulative reduction from 1992 use levels of 66.3 million pounds of these corn herbicides.

    Achievement of these targets will result in a 33 percent reduction in the aggregate use of these herbicides on corn.

  • Tracking use reduction targets. To ensure compliance with the use reduction goals, the conditions of registration require:

    • Monitoring by an independent market research firm and financed by the registrants;

    • Annual reporting to EPA on progress made in achieving use reduction goals.

    • County-level reporting on use and sales on an annual basis.

  • Sunset registration provisions. These are provisions that require the renewal of the acetochlor registration after 10 years. The registration of acetochlor will be automatically cancelled on March 7, 2004 unless all of the following conditions are met:

    • The Partnership submits a complete application for registration by March 7, 2001; and

    • The Partnership submits by March 7, 2001, all data required by Agency regulations and guidance as of March 7, 1998; and

    • All data submitted are acceptable and sufficient for EPA to make a registration determination.

  • Achieving the "reasonable certainty of no harm" health standard. The conditions of registration ensure that acetochlor will pose a negligible risk to human health and the environment.

    • Although acetochlor has been classified as a probable human carcinogen, exposure to workers and in the diet is expected to be low.

    • The upper bound dietary cancer risk is estimated to be 2.2 x 10-6, however this estimate is considered worst case based on the following assumptions:

      • 100% of the corn crop will be treated with acetochlor;

      • All of the rotational crops will be grown in fields treated with acetochlor; and

      • Residues will be present at tolerance levels.

  • Protecting ground water and surface water (lakes, rivers, and streams). Conditions of acetochlor registration include preventative measures, monitoring programs, and cancellation provisions if preventative measures are not successful.

    • Preventative measures: limits to use only by certified applicators, prohibits aerial application, restricts types of soils on which acetochlor can be used, prohibits application to water, and requires product stewardship efforts to encourage proper use.

    • Monitoring: The Partnership will fund acetochlor surface and ground water monitoring programs in seven major use states (IL, IN, IA, KS, MN, NE, WI).

    • Ground water protection. Automatic cancellation if any of the following occur:

      • Pattern of movement of acetochlor toward ground water in at least four out of eight sites in prospective ground water studies; or

      • Early warning system indicates that detections are being found in ground water wells at low levels (20 State Monitoring Program wells >= 0.10 ppb, or 150 individual wells >= 0.20 ppb, or 20 wells >= 1.0 ppb); or

      • Detections are found in ground water in relatively few wells, but at elevated levels (20 wells >= 1.0 ppb).

    • Surface water protection. The registration also mandates:

      • Cancellation in affected watershed if 1 community water supply system detects acetochlor at an annual concentration >= 2.0 ppb.

      • Nationwide cancellation if 2 large community water supply systems or 10 systems of any size detects acetochlor at an annual concentration >= 2.0 ppb.

      • Biweekly sampling of any community water supply system that detects a single peak concentration of >= 8.0 ppb.

  • Protecting endangered species. Endangered species at greatest risk from the use of acetochlor include aquatic plants, invertebrates, fish, and terrestrial plants in wet areas. Provisions described above to protect ground water and surface water are intended to protect both public health and endangered species. In addition, the Partnership has agreed to refine the locations of endangered species in corn-growing areas and to take mitigation actions in areas where endangered species are identified.

  • Providing analytical methods to detect acetochlor. Critical to the effectiveness of monitoring programs are effective methods for detecting residues. The Partnership has agreed to submit to EPA a validated method for detecting acetochlor and degradates of concern in water samples. The methods will include analyte-specific methods, multi-residue methods, and low-cost enzyme immunoassay methods. The approved methods will be made available to drinking water suppliers.


More specific details about this pesticide registration can be found in the Registration Agreement . For more options, you may return to the beginning of the OPP Acetochlor Page or continue reading the next section on Detection Methods.


Detection Methods

The Partnership has agreed to submit to EPA a validated method for detecting acetochlor and degradates of concern in water samples. The methods will include analyte-specific methods, multi-residue methods, and low-cost enzyme immunoassay methods. The approved methods will be made available to drinking water suppliers.


For more options, you may return to the beginning of the OPP Acetochlor Page or continue reading the next section on Usage.


Usage Targets and Results

The following usage targets were agreed to in the Acetochlor Registration Partnership (ARP) Application for Conditional Registration of Acetochlor:

  1. At the end of 18 months from date of registration, a net cumulative reduction from 1992 levels, adjusted for planted acreage differences, of 4 million pounds of the herbicides alachlor, metolachlor, atrazine, EPTC, butylate and 2,4-D used on corn; or

  2. At the end of three years from the date of registration a net cumulative reduction from 1992 use levels...of 22.6 million pounds; or

  3. At the end of five years from the date of registration a net cumulative reduction from 1992 use levels...of 66.3 million pounds.

OPP/BEAD review of the usage data submitted to the Agency by the ARP indicates that the 18 month and the three years usage targets have been met. The cumulative reduction in adjusted usage of the six herbicides on field corn for the first three years (1994-1996) well exceeded the three year usage target of 22.6 million pounds of active ingredient (lbs AI). The five year target of 66.3 million lbs AI (cumulative reduction, 1994-1998) was exceeded by about 4 million lbs AI in 1998. The cumulative reduction continues to grow and the 1999 usage is about 70 million pounds less AI than in 1992.

The USDA and Doane surveys indicate growth in acetochlor usage between 1994 and 1998. The percent of field corn acres treated with acetochlor has risen steadily from 7 percent in 1994 to 24 percent in 1997. Total usage (in surveyed states) increased from 7.4 million lbs AI in 1994 to 34.4 million lbs AI in 1998. Acetochlor usage seems to have declined somewhat from 1998 to 31.8 million lbs AI in 1999. Percent crop treated, however, increased to about 27 percent.

Acetochlor sales have been reported for the following states:
                                       
Alabama (AL)      Maine (ME)           Oklahoma (OK)    
Arkansas (AR)     Massachusetts (MA)   Oregon (OR)               
California (CA)   Michigan (MI)        Pennsylvania (PA)         
Colorado (CO)     Minnesota (MN)       Rhode Island (RI)
Connecticut (CT)  Missouri (MO)        South Carolina (SC)
Delaware (DE)     Mississippi (MS)     South Dakota (SD)   
Georgia (GA)      Montana (MT)         Tennessee (TN)     
Iowa (IA)         North Carolina (NC)  Texas (TX)               
Idaho (ID)        North Dakota (ND)    Utah (UT)  
Illinois (IL)     Nebraska (NE)        Virginia (VA)        
Indiana (IN)      New Hampshire (NH)   Vermont (VT)  
Kansas (KS)       New Jersey (NJ)      Washington (WA)
Kentucky (KY)     New Mexico (NM)      Wisconsin (WI)
Louisiana (LA)    New York (NY)        West Virginia (WV)
Maryland (MD)     Ohio (OH)            Wyoming (WY)

The remaining states for which there have been no acetochlor sales
include:
	
Alaska (AK)                     
Arizona (AZ)                      
Florida (FL)                   
Hawaii (HI)
Nevada (NV)

A series of maps highlight the areas in the U.S. where acetochlor has been sold. Map scales include the continental U.S. at both the state and county levels. Additionally, there are county level maps for each EPA region. There is also an alphabetical list of states and counties where acetochlor has been sold organized by EPA region.


You may continue reading the next section on Ground Water Programs, or for more options, you may return to the beginning of the OPP Acetochlor Page.


Ground Water Monitoring Programs

Introductory information about the acetochlor Registration Agreement provides details about the ground water monitoring programs and the ground water triggers that would lead to cancellation for failure to protect ground water. A very brief review of those ground water triggers is repeated here followed by access points to graphs of positive acetochlor detections.

Triggers

Three scenarios have been established for automatically canceling the registration for acetochlor based on ground water concerns. The registration for acetochlor will be automatically canceled if any one of the following conditions is met:

  1. If EPA determines that out of 8 prospective ground water (PGW) locations, 4 sites indicate a pattern of movement of acetochlor toward ground water from use in accordance with label directions, or in accordance with widespread and commonly recognized practice.
  2. If detections occur in >= 20 wells included in the State Ground-Water Monitoring(GWM) Program at a concentration of >= 0.10 parts per billion (ppb) followed by 2 subsequent detections at >= 0.10 ppb in monthly sampling of each of these wells, conducted over a 6-month period or if detections of acetochlor occur in >= 150 individual wells at a concentration of >= 0.20 ppb followed by two subsequent detections of >= 0.20 ppb in monthly sampling of those wells, conducted over a period of 6 months.
  3. If detections of acetochlor occur in >= 20 wells at a concentration of >= 1.0 ppb, followed by two subsequent detections at >= 1.0 ppb in monthly sampling of those wells, conducted over a period of 6 months.
Prospective Ground Water Study Information

Site selection and results from Acetochlor prospective ground water studies provide useful information pertaining to this registration.

Also, general background information regarding prospective ground water studies required by EPA briefly explains the importance and utility of these field monitoring studies.

Ground Water Monitoring Program Results

The ARP Monitoring network currently consists of 177 wells across seven states: Iowa, Illinois, Indiana, Kansas, Minnesota, Nebraska and Wisconsin. A U.S. map highlights the states that belong to the ARP Ground Water Monitoring network.

Graphs of positive detections of acetochlor provide a visual reference to the status of ground water protection related to the acetochlor registration.

Raw data from which the graphs of ARP Monitoring Wells were created can be viewed as text.

Detections of Acetochlor in non-ARP Wells

Graphs of positive detections of acetochlor in wells that are not part of the Acetochlor Registration Partnership Monitoring Program indicate some problem areas. These graphs are also available in a version scaled to the value of 1.0 ppb of acetochlor. A limited number of drinking water wells have also been reported as positive for acetochlor.


For more options, you may continue reading about surface water monitoring programs or you may return to the beginning of the OPP Acetochlor Page.


Surface Water Monitoring Programs

Introductory information about the Acetochlor Registration Agreement provides details about the surface water monitoring programs and the surface water triggers that would lead to cancellation for failure to protect surface water. A very brief review of those surface water triggers is repeated here followed by access points to graphs of positive acetochlor detections.

Two scenarios have been established for automatically canceling the registration for acetochlor based on surface water concerns:

1. If a community water supply system that derives its water primarily from surface water detects an annual time-weighted mean concentration of acetochlor of >= 2.0 ppb, EPA may prohibit use of acetochlor in the related watershed. As an alternative to cancellation, the Partnership would be required to upgrade the system.

2. If EPA determines that two large community water supply systems (systems serving over 100,000 people) or 10 community water supply systems of any size have an annual time-weighted mean concentration of acetochlor of >= 2.0 ppb.

In addition, if any community water system detects a single peak concentration of >= 8.0 ppb of acetochlor, the Partnership will perform biweekly sampling of that water system throughout the following 12 months to determine whether the 2.0 ppb annual concentration has been exceeded.

Currently, 175 sites are monitored across twelve states as part of the surface water monitoring programs funded by the Acetochlor Registration Partnership (ARP). Both a U.S. map and a textual list display the states with surface water monitoring programs. Both raw and finished water were monitored as part of these programs. Raw water was monitored at 27 sites in 1995 and at 33 sites in 1996. Finished water from all 175 sites was monitored in both years.

Graphs of positive detections of acetochlor over time in ARP surface water monitoring programs are presented by state as a visual reference to the status of surface water protection related to the acetochlor registration. Three state monitoring programs (Delaware, Maryland, and Wisconsin) indicate no detections of acetochlor in surface water. One monitoring site in Illinois, 214-GI-IL, registered a single peak concentration over 8 ppb on 5/15/96. This detection triggered additional monitoring for 12 months to ascertain the annual concentration does not exceed 2 ppb.

Graphic displays of annual mean concentrations by state at ARP finished surface water sites indicate the status of surface water quality in relation to the triggers established to protect surface water.

Raw data from which the state graphs were created for both positive detections and annual mean concentrations are available for viewing as text.

 

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