NAAA eNewsletter - 11/05/2020

NAAA submitted comments to the EPA on the registration review documents for 18 pesticides this week. The EPA is required by the Federal Insecticide Fungicide and Rodenticide Act (FIFRA) to review the registrations for all crop protection products every 15 years. Nine of the comments dealt with risk assessments and the other nine were on proposed interim decisions. Risk assessments are conducted by the EPA for each active ingredient being reviewed to assess any risks to the environment and human health of the products being evaluated. Interim decisions are being used by the EPA instead of a full reregistration of a product because the biological evaluations and pollinator protection assessments still need to be completed for most products.

The risk assessments were for amicarbazone, aminopyralid, dimethenamid/dimethenamid-p, endothall, fluoxastrobin, folpet, iprodione, metconazole and prothioconazole. All of the risk assessments once again had been conducted using the Tier 1 model in AgDRIFT. This model uses many inaccurate assumptions overestimating the risks of drift associated with modern aerial applications. These include variables such as use of a smaller than commonly used droplet size, a swath displacement shorter than industry standards, a slight inversion during the application, wind speed measured at a height appropriate for ground applications instead of aerial applications, an application to bare ground instead of a standing crop, and the assumption that a second application would occur with a wind speed and direction identical to the first application.

NAAA suggested the EPA use the more detailed Tier 3 model in AgDRIFT because it allows for many of the variables from the Tier 1 model to be changed to improve the model’s accuracy at estimating drift from aerial applications. NAAA recommended specific assumptions and settings to be used in the Tier 3 model. To start, NAAA suggested a turbine-powered aircraft be used instead of one with a radial engine. NAAA suggested the wind speed be increased from 10 to 15 mph to reflect real-world spraying conditions and the fact that many labels currently allow spraying in wind speeds up to 15 mph.

NAAA suggested boom length be set at 75% of the wingspan and boom drop set at 1.3 feet lower than the current Tier 1 level to reflect the boom positioning commonly seen on agricultural aircraft today. Instead of a fine droplet size, NAAA suggested using a medium droplet size, which is easily created by many of the commonly used nozzles on agricultural aircraft today. A swath displacement of half a swath displacement was suggested instead of only one-third of a swath displacement on the downwind field edge. Settings for the atmospheric stability component of the model were recommended to accurately model applications not occurring during an inversion, as all labels already prohibit applications when an inversion is present.

NAAA recommended a more appropriate height for measuring wind speed and direction such as at the location of where a smoker or Aircraft Integrated Meteorological Measurement System (AIMMS) would measure the conditions and to run the Tier 3 model assuming the presence of a crop instead of bare ground. Bare ground aerial applications are not nearly as common as aerial applications to a standing crop and the bare ground setting in AgDRIFT results in a much higher drift estimate. Finally, NAAA urged EPA to use a component of the AgDRIFT model to reflect the unlikelihood that if more than one application of a single pesticide is made, both applications will take place under identical weather conditions with wind blowing in the exact same direction at the same speed.

In a few of the risk assessments, the EPA did model drift from aerial applications using larger droplet sizes. However, the agency still used the Tier 1 AgDRIFT model and the other faulty assumptions within it. NAAA pointed out that simply using a larger droplet size does not fully correct the issues with Tier 1, and that the EPA needs to fully utilize the Tier 3 model when conducing risk assessments. The risk assessment for folpet found potential inhalation risk estimates of concern for mixers/loaders for aerial applications using wettable powder formulations of folpet, even when using a PF10 respirator. NAAA pointed out if these risks of concern are partly driven by the larger number of acres treated daily by aerial application, it is erroneous to assume that simply applying to a larger number of acres somehow results in a higher level of concern compared to treating fewer acres. NAAA also pointed out the exposure data used in the risk assessments is not as reliable as more recently accumulated data.

The proposed interim decisions for fenamidone, flumioxazin, MCPB, metolachlor/S-metolachlor, terbacil and triclopyr had drift mitigation label language for aerial applications that was largely acceptable. Like many recently proposed interim decisions, the labels for these active ingredients would set the wind speed limit to 15 mph. There would be a requirement that when applying in wind speeds of 11 to 15 mph, the boom length be reduced to a maximum of 65% of wingspan for fixed-wing aircraft and a maximum of 75% of rotor diameter for helicopters. For applications at wind speeds of 10 mph or less, maximum boom length would be 75% of wingspan for fixed-wing aircraft or 90% of rotor diameter for helicopters. Swath displacement would be half swath on the downwind edge of the field when winds are 10 mph or less, and three-fourths swath on the downwind edge of the field when wind speeds are 11 to 15 mph.

The proposed interim decision for propanil suggested a 10 mph wind speed limit for aerial applications instead of 15 mph, so NAAA recommended that the EPA use the same drift mitigation language in the other proposed interim decisions for propanil. The proposed interim decisions for acequinocyl and fenbutatin oxide proposed prohibiting aerial applications. NAAA objected, citing the advantages aerial application has over other application methods, including speed, timelines and better efficacy.

NAAA will continue to monitor the pesticide registration review process throughout the remainder of 2020 and into 2021 for both risk assessments and interim decisions and comment accordingly to the EPA.