unreasonable adverse effects. As part of regist ration review, the chlorpyrifos preliminary Human Health Risk Assessment (HHRA) was re leased for public comment in July 2011. 2 In the preliminary HHRA, risks to bystanders from spra y drift and exposure from volatilization were identified as concerns. The public comment pe riod closed in October 2011. As the Agency works to finalize its HHRA, it has further refined its analysis regarding sp ray drift from various chlorpyrifos application scenarios in order to have a broader unders tanding of the potential risks. That assessment, Evaluation of the Potential Risk s from Spray Drift and the Impact of Potential Risk Reduction Measures 3 , is being released in conjuncti on with this decision document.
In addition, in 2007, the Natural Resources Defense Council (NRDC) and Pesticide Action Network North America (PANNA) jointly pe titioned the Agency to revoke all tolerances and cancel all registratio ns for chlorpyrifos. 4 One of the issues identified in the Petition deals with inhalation routes of exposure from spray dr ift and volatilization. Th is more refined spray drift assessment and subsequent mitigation measures will inform the Agency’s response to the spray drift portion of petitioners’ inhalation claim. The Agency’s volatilization assessment continues to be refined in th e context of the final HHRA.
This more refined spray drift analysis resulted in a better estimate of potential exposures and risks to bystanders, particular ly children, around treated fields . While the analysis showed there were health risks due to spray drift, the analysis also indicated that the risks could be mitigated by requiring buffer distances and specif ic application methods. Specifically, by linking droplet size with application ra tes and application methods in or der to dictate appropriate buffer distances. Table 1 indicates the various buffer di stances that will be requi red when using certain application rates, nozzle droplettype, and application method.

Table 1: Buffer Distances from Sensitive Sites

Application rate (lb ai/A) Nozzle Droplet Type Required Setback (Buffer Zones) (feet) Aerial Airblast Ground >0.5 - 1 coarse or very coarse 10 10 10 >0.5 - 1 medium 25 10 10

>1 - 2 coarse or very coarse 50 10 10 >1 - 2 medium 80 10 10 >2 - 3 coarse or very coarse 80 1 10 10 >2 - 3 medium 100 1 10 10 >3 - 4 medium or coarse NA 2 25 10

>4 medium or coarse NA 50 10 1 Aerial application of greater than 2 lb ai/A is only perm itted for Asian Citrus Psylla control, up to 2.3 lb ai/A. 2 NA is not allowed.

2 Available at http://www.regulations.gov/#!document Detail;D=EPA-HQ-OP P-2008-0850-0025

. 3 Dawson J, Britton W, Bohaty R, Mallampalli N, Grube A. U.S. EPA (2012). Chlorpyrifos, PC Code 059101, DP Barcode 399483 and 399485; Evaluation of the Potential Risks From Spray Drift and the Impact of Potential Risk Reduction Measures. Available at http://www.regulations.gov/#!doc ketDetail;D=EPA-H Q-OPP-2008-0850

. 4 Petition of Natural Resources Defense Council and Pesticide Action Network North America to Revoke All Tolerances and Cancel All Registrations for the Pesticide Chlorpyrifos (September 12, 2007) at 1. (hereinafter Petition). Available at http://www.regulations.gov/#!documen tDetail;D=EPA-HQ- OPP-2007-1005-0005

.