US finalises fumigant restrictions
Date:07-16-2008
The US EPA has finalised restrictions on the use of the soil fumigants, methyl bromide, metam sodium/potassium, dazomet and chloropicrin. Last year, the Agency suggested a range of risk-reduction measures primarily aimed at acute inhalation risks to workers and bystanders.
The EPA considered the four fumigants, together with 1,3-dichloropropene (1,3-D) and iodomethane, as a cluster to ensure consistency. Iodomethane was granted a temporary approval last year pending the completion of the fumigant review. The EPA will consider whether further risk mitigation measures for iodomethane are required later this year. It has not imposed any specific requirements for 1,3-D, which was re-registered in 1998. However, restrictions may be required as part of the registration review of soil fumigants, which has been brought forward from 2017 to 2013.
All soil fumigants containing 1,3-D, chloropicrin or methyl bromide are classified as restricted-use pesticides. As indicated last year, the EPA plans to extend this requirement to all soil fumigants undergoing re-registration.
The EPA requires a range of site-specific buffer zones to protect bystanders from exposure to the four fumigants assessed. The minimum size of the buffer zone for each fumigant is 25 ft (7.5 m), with the maximum size depending on factors such as application rate, field size, application equipment and methods. The EPA will allow reductions in buffer zones when emission reduction measures, such as high-barrier films, are used and when certain soil conditions reduce emissions.
The use of high-barrier films can reduce buffer zones for methyl bromide by up to 25%, with further reductions of up to 20% depending on soil type. Buffer zones for chloropicrin can be reduced by up to 40% for high-barrier films, with a further 10% reduction for the use of Arysta LifeScience’s Symmetry application technology. Soil factors can also reduce buffer zones for chloropicrin by up to 20%, but the maximum reduction allowed is 50%.
The assessments of metam sodium/potassium and dazomet included an examination of their environmental degradate, methyl isothiocyanate (MITC). Standard barriers, such as polyethylene tarps, are not considered effective at reducing MITC emissions. However, a 10% reduction in buffer distances applies to metam sodium/potassium for certain high-barrier films. Further 10% reductions are available for clay soil, organic matter content and chemigation, with a maximum reduction of 40%. There are no data on the use of barrier films with dazomet so no buffer zone reductions apply. A maximum reduction of 20% is dependent on soil type.
The EPA is restricting certain fumigation application methods, such as “untarped” use of methyl bromide under most circumstances. Maximum application rates on labels are to be reduced to reflect the rates needed for effective use. Other requirements include the posting of notifications about the timing and location of fumigations to ensure that bystanders do not enter buffer zones. The EPA also calls for more stringent worker protection measures and training for those involved in fumigation, and the adoption of site-specific fumigant management plans.
The new rules are subject to a 60-day comment period, with an EPA response expected in late 2008 to early 2009. Registrants are expected to begin implementing training and community outreach programmes in 2009, with revised fumigant labels being issued in 2010.
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