Registration Conditions

Acetochlor Registration Partnership


To secure registration approval in March 1994, the Acetochlor Registration Partnership (ARP) agreed to several stringent conditions of the U.S. Environmental Protection Agency (EPA). Failure by the ARP to meet these conditions could result in automatic cancellation. The conditions related to acetochlor are in three key areas:

Reduction of Use

The ARP will document that the use of acetochlor will result in a net usage reduction of the six mentioned corn herbicide products equal to 66.3 million pounds – a one-third decrease from baseline levels – five years after registration of acetochlor. Interim use reduction targets are 4 million pounds after 18 months and 22.6 million pounds after three years.

Use reduction is monitored by an independent market research firm selected by the ARP and accepted by EPA. According to EPA and USDA figures, the 18 month and 3 year target reduction figures have been achieved.

Protection of Ground Water

Three conditional scenarios were established to ensure protection of ground water.

  1. The ARP agreed to fund monitoring of 25 wells per state, in conjunction with Departments of Agriculture, in the seven states that represent 80% of expected usage.

    If detections occur in any of the 175 wells at 0.1 part per billion (ppb) followed by two subsequent detections at 0.1 ppb in monthly monitoring over a six-month period, the ARP will suggest mitigation procedures such as a reduced labeled rate, or soil type or geographical restrictions. If 20 such detections occur, followed by two subsequent detections, the ARP will voluntarily withdraw the acetochlor registration.

    Monitoring by non-ARP programs, such as by states or universities, could also result in cancellation if 150 wells have a concentration of 0.2 ppb followed by two subsequent detections of 0.2 ppb over a six-month period. (See also State Ground Water Monitoring Program Update)

  2. The ARP agreed to conduct prospective ground water studies at eight locations representative of acetochlor use. If a pattern of movement to ground water is observed in four of those sites and determined to be a result of labeled use or widespread use, the registration could be lost. (See also Prospective Ground Water Monitoring Study Update)
  3. If monitoring shows 20 wells across a wide variety of geographic and soil types with concentrations of 1.0 ppb followed by two subsequent detections of 1.0 ppb over six months, the registration could be lost.

In all three situations, the ARP will have an opportunity to verify detections and provide mitigation in those instances where concentrations exceed the standard.

Protection of Surface Water (See also State Surface Water Monitoring Program Update)

Registration also could be canceled in the event of detections in finished drinking water derived from surface water sources.

  1. Loss of use in a particular watershed could result if a community water supply has an annual average concentration of 2 ppb or greater. As an alternative to cancellation, the ARP would be required to restore the community water system to compliance.
  2. Registration would be lost if two or more large community water systems (100,000 people) or 10 systems of any size have annual average concentrations in excess of 2 ppb.

If any water system is found with a single peak concentration of 8 ppb, the ARP will conduct bi-weekly sampling of that system over the following 12 months to determine whether the 2 ppb annual time-weighted mean concentration has been exceeded.

The unprecedented conditions attached to the registration of acetochlor should not be interpreted as a reflection of EPA's assessment of the product. Rather, they are an indication of EPA's new direction. EPA has stated:

"This agreement establishes a model for registering corn herbicides that have health and environmental characteristics similar to acetochlor ... EPA will consider the restrictions placed on acetochlor in determining the eligibility for reregistration of toxicologically similar active ingredients."

The ARP is confident that acetochlor registration is fully sustainable under terms of the agreement, based on years of intensive research and knowledge concerning how the product is used. This confidence is supported by the development of a comprehensive stewardship, education and training program to ensure that dealers and farmers use acetochlor properly. This confidence was further bolstered in early 2002, when the State Ground Water and State Surface Water monitoring programs were successfully completed without tripping the stringent cancellation triggers established in the Registration Agreement.

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This page was last updated on 13-Jan-03.
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Dave Gustafson
Monsanto Company
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St. Louis, MO 63167