Herbicide Registration Review Update

Recently, EPA recently released an Interim Registration Review Decision for the herbicide active ingredient clethodim (Federal Register 82:59606-59607, December 15, 2017). According to the 2011 NCASI herbicide use survey (see NCASI Technical Bulletin 1031, Herbicide Use Patterns on Corporate Forest Lands in the United States, 2011), clethodim (Envoy Plus, Grassout Max) is used in the Pacific Northwest for herbaceous weed control and release.

In the interim decision, EPA proposed label changes to reduce off-target spray drift and establish a baseline level of protection against spray drift that is consistent across all clethodim products. The proposed label changes are consistent with standard practices currently used in forestry aerial applications to reduce spray drift and include requirements to use coarse or coarser spray droplets (ASABE Standard 572.1) for aerial applications, use ½ swath displacement upwind at the downwind edge of the field, and confine spray nozzle distribution along the spray boom to no more than 75% of the rotor diameter. EPA also established a maximum annual application rate of 1.04 lbs. active ingredient per acre.

This decision is identified as an “interim” rather than “final” decision because EPA has not yet completed required national threatened and endangered species assessments, screening for endocrine effects, or assessment of risks to pollinators.

Comments were previously accepted on the Proposed Interim Decision and are addressed in this document. EPA intends to move forward with implementation of the interim decision.

At the same time, EPA released a draft revised human health risk assessment for the herbicide active ingredient 2,4-D (Federal Register 82:59596-59597). The human health risk assessment is one component of the registration review process and will be used to help inform the development of the registration review decision for this herbicide.

According to the 2011 NCASI herbicide use survey, 2,4-D (DMA 4 IVM, Agrisolutions 2,4-D LV6) is used in the Pacific Northwest for site preparation, herbaceous weed control, and release.

EPA evaluated potential risks to human health from use of 2,4-D according to application practices and rates specified on the existing product labels. Based on their assessment, EPA concluded that risks to humans associated with dietary exposures are below the level of concern for the general population and all population subgroups, including children.

Similarly, EPA estimated that risks for residential users (e.g., individual who applies 2,4-D to his/her lawn) and those exposed post-application (e.g., golfers exposed following golf course application) are not of concern for 2,4-D for all scenarios and all routes of exposure. Risk estimates for bystanders exposed to spray drift during applications of 2,4-D also are not of concern.

Occupational handler inhalation risk estimates were of concern for some scenarios, and may be mitigated by appropriate use of personal protective equipment.

This revised risk assessment for 2,4-D updates the previous (2016) human health risk assessment and incorporates the findings of a toxicology systematic literature review, a Tier II epidemiology report focusing on non-cancer effects, and a Tier II epidemiology report focusing on carcinogenic effects. This new information did not alter the overall risk conclusions of the previous risk assessment.  

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