Comment submitted by K. Malamud-Roam, American Mosquito Control Association

October 23, 2006 General Docket Environmental Protection Agency Mail Code 4101T, 1200 Pennsylvania Avenue, NW. Washington, DC 20460 Attention Docket ID No. EPA?HQ?OPP?2005?0284: Resmethrin Registration Eligibility Decision. The American Mosquito Control Association (AMCA) is submitting these comments in response to EPA?s Registration Eligibility Decision (RED) for Resmethrin, Docket # EPA?HQ?OPP?2005?0284. The AMCA is a scientific/educational association of individuals and over 600 organized mosquito control programs nationwide that provide mosquito control services to protect public health. As a public health association with a great interest in the safe and effective use of pesticides, the AMCA recognizes the significance of the reregistration process in identifying, evaluating, and mitigating potential hazards to humans and the environment from federally registered pesticides, while allowing reasonable and appropriate use of these products. We submit the following comments in order to assist EPA in fulfilling these crucial tasks. 1. AMCA appreciates EPA?s recognition of the important role of resmethrin in public health vector control, and of the difficulty of replacing this material with other active ingredients. Resmethrin remains a key tool for controlling adult mosquitoes and mosquito-borne diseases in many parts of the country. Unlike the case of the other pyrethroids, the major use of resmethrin in the U.S. is for mosquito control, and it is widely used due to its high efficacy, its relatively low cost, and its long history of use without apparent significant adverse effects to public health or the environment. In addition, in those areas where it is not now used routinely, it is a critical alternative material for use in public health emergencies, to prevent or respond to resistance to other mosquitocides, or in other circumstances where other control methods may not be effective or practical. The AMCA is committed to working with EPA to refine risk assessments and risk management strategies as needed to permit the continued reasonable use of this product without undue regulatory burdens. 2. AMCA recognizes and appreciates the significant improvements made to the Environmental Risk Assessments following the earlier round of comments. To ensure that this valuable public health tool remains available, and that mitigation requirements are warranted by the facts and circumstances, it is critical that the Risk Assessments be based on sound science, realistic usage information, and valid modeling. We note that the RED reflects EPA?s most recent environmental risk assessments which have been significantly improved from earlier versions through incorporation of more realistic information regarding: a. release (boom) heights including canopy level as a baseline where applicable and per-acre application rates for aerial applications of resmethrin-based mosquitocides; b. differentiation between typical and high-end applications in terms of per-acre active ingredient application rates; and c. revision of exposure assumptions used in the original CARC analysis to clarify the absence of cancer risks associated with wide area ULV mosquito control applications. Regarding release height in particular, in a recent (Summer 2006) user survey, AMCA received elevation information for 40 public agencies or their contractors across the country that apply adulticides by aircraft, and the mean application elevation was 184', the median was 200', and the range was 50-300'. Only two applicators reported applications below 100', and none below 50'. No pattern was observed between type of aircraft and application elevation. Very low elevation aerial applications are clearly uncommon. 3. AMCA recognizes EPA?s concerns about the potential consequences of aquatic deposition of resmethrin, and is committed to continued efforts to help ensure that aerial applications of resmethrin for mosquito control do not cause unreasonable adverse ecological impact. In particular, we have, with assistance from researchers at Florida A&M University, conducted dozens of model runs using AgDisp 3.15 and realistic input parameters for these types of applications to supplement the work conducted by EPA?s Environmental Fate & Effects Division (The output files from these runs are large and can be provided to EPA as separate attachments if needed). We have been able to replicate the output values generated for EFED for their standard pond, and we have concluded that EFED is correct that droplet size and boom height are two of the key variables controlling deposition in the standard pond. We have also concluded, however, that modeled deposition in the spray zone and in downwind areas is extremely sensitive to changes in canopy parameters, and that EFED?s exclusive use of the no canopy condition can lead to dramatic over-estimation of deposition both within and downwind of the spray area. We recommend that any future refinements of the environmental risk assessments, for resmethrin and for other mosquito adulticides, compare the results of applications over a range of canopy conditions. Emphasis should be given to situations where the spray zone and/or the downwind area consist largely or exclusively of vegetated wetlands such as swamps or marshes, where mosquitoes may be common but where pesticide deposition would be significantly mitigated by foliar interception. Despite the improvements in input parameters, EFED?s estimated potential exposure of aquatic organisms to resmethrin resulting from mosquito-control use of this pesticide is significantly higher empirical measurements in field studies of resmethrin or other similar mosquitocides or, indeed, than could apparently result from any realistic or reasonable usage scenario. For example, the AGDISP program driving the PRZM/EXAMS aquatic model predicted resmethrin concentrations in surface water after ULV applications many times higher than concentrations reported by the U.S. Geological Survey in field samples collected from water sources during 2002-2004 in Suffolk County, NY. A total of 46 samples taken from both surface interface and six inch depths in marshes were obtained after both aerial and truck applications of Scourge 18:54 (resmethrin + PBO) conducted as part of West Nile Virus control operations. In these operations, resmethrin was applied at a boom height of 150 ft AGL, utilizing a 300 ft. swath and droplet VMD of 27 microns. Samples were collected from 20 minutes to 4 days after spraying. Resmethrin concentrations were less than 5 ng/L in all but three of the subsurface samples, and the highest concentration detected from any surface water body was only 293 ng/L with very low persistence. Concentrations of resmethrin became undetectable after 2 hours in all samples. This field research and its findings are significantly different than modeled data generated by Ag-Drift. USGS website at http://ny.water.usgs.gov/pubs/of/of051384/). Although we hypothesize that this difference can largely be attributed to foliar interception in vegetated wetlands settings, there may be other factors contributing to this discrepancy. We recognize that EPA needs to evaluate the worst case situation of incidental deposition directly onto open water, but we emphasize that mosquito adulticide applications are planned to minimize this deposition, while focusing on drifting adulticides into the vegetated areas which harbor adult mosquitoes (as described in PR Notice 2005-1). Ground application data follow a similar pattern. Researchers at the New Jersey Department of Environmental Protection (NJDEP) Pesticide Control Program found an average peak resmethrin concentration of 0.08 ug/L (range of peaks from 0.000 ? 0.56 ug/L) among 7 sampling sites at two study locations. Like the USGS studies in New York, highest resmethrin concentrations were associated with samples at the top of the water column. Thus, the average peak concentration of resmethrin in surface waters (0.08 ug/L) is more than 12-fold lower than Ag-Drift predicted peak deposition. 4. We recommend that a more careful distinction should be made generally in the RED and in future label requirements between bodies of open water (e.g. lakes, ponds, or rivers) and those ?bodies of water? that are characterized by emergent vegetation (e.g. marshes or swamps). While courts have dramatically expanded the definition of ?waters of the U.S.? for purposes of interpreting the Clean Water Act in recent decades, an overly broad definition of ?bodies on water? creates more confusion than clarity in FIFRA documents. PR Notice 2005-1 was intended to clarify allowable uses of mosquito adulticides, and to explicitly allow applications over water under certain circumstances, but an unfortunate phrasing in the notice is reflected in the proposed resmethrin RED Environmental Hazards language: ?Do not apply over bodies of water (lakes, rivers, permanent streams, natural ponds, commercial fish ponds, swamps, marshes or estuaries), except when necessary to target areas where adult mosquitoes are present, and weather conditions will facilitate movement of applied material away from the water in order to minimize incidental deposition into the water body.? Mosquitoes are rarely found in large numbers over lakes, rivers, ponds, or the open water areas of estuaries, where aquatic deposition of pesticides may be troublesome, but are frequently found over swamps and marshes, where foliage can intercept substantial fractions of aerosol pesticides. As demonstrated in repeated runs of AgDisp with a range of canopy values, aquatic deposition varies by a factor of 100 or more between identical runs with dense canopy over water vs. with no canopy, and aquatic deposition is completely negligible for spray over marshes or swamps that do not have standing water at the time of application. The proposed language is intended (again, see PR Notice 2005-1) to specifically address spraying over open water and to allow it only in those circumstances where drift will move the pesticide from the open water to the areas of mosquito habitat before significant deposition occurs. Therefore, this section should not treat marshes and swamps (often the target area) as equivalent to open water bodies such as lakes or the open-water of estuaries. Nor should the language imply that applications must be planned so that weather conditions move the applied material away from ?the water? if the mosquito habitat itself is defined as a ?water body?. Utilization of wind drift into and over swamps and marshes and other mosquito habitats is a core element of successful ULV applications for adult mosquito control in many settings. Application over open water is periodically needed to ensure downwind drift into the air column in which the targets are to be found at time of application, although in these situations great care is taken to avoid deposition into the open water. Therefore, we suggest the following change in the proposed Environmental Hazards section for Wide Area Mosquito Adulticide Applications: ?Do not apply over OPEN bodies of water (lakes, rivers, permanent streams, natural ponds, commercial fish ponds, swamps, marshes or the open water of estuaries), except when necessary to target areas where adult mosquitoes are present, and weather conditions will facilitate movement of applied material away from the OPEN water in order to minimize incidental deposition into the water body.? In addition, AMCA recommends that EPA consider placing this type of language in the Directions for Use section of the labels, rather than in the Environmental Hazards section, as its purpose is clearly to clarify how best to use the product. 5. AMCA strongly disagrees with the specific proposed droplet spectrum for aerial application of resmethrin as a wide area mosquito adulticide (RED, page 77), and we recommend an alternative droplet size standard for low elevation aerial applications. We understand the rationale for restricting droplet size for aerial and ground-based adulticide use as a mechanism for minimizing the risk of resmethrin deposition into aquatic ecosystems. However, the proposed label amendment (Dv 0.5 < 60 um; Dv 0.9 < 80 um) is not conducive to effective mosquito control in many circumstances, is not justified by the EFED modeling, may cause unintended environmental problems in some circumstances, and is not feasible for many local public health agencies. We do not disagree with Dv 0.5 < 50 or 60 microns, which EFED correctly indicates result in very similar deposition patterns; our argument is against the very low Dv 0.9. While small droplets (20-50 microns) can result in effective mosquito control from the ground, aerial applications must use larger droplets to ensure that the desired size for mosquito control move from the aircraft to the mosquito habitat in sufficient density to result in effective control, and to ensure that the droplets are able to penetrate tree or other vegetative canopies. Extensive operational experience in Florida and elsewhere have demonstrated that droplets with Dv 0.9 < 80 microns are frequently unable to penetrate moderate or dense canopy unless the aircraft flies extremely low (which can be unsafe, as well as likely to increase deposition), or the application rate is higher than would otherwise be needed (which would again lead to greater, rather than lower, potential deposition). More significantly, the EFED environmental risk assessments do not provide any justification for the extremely low Dv 0.9 that is proposed (in fact, it is not clear that EFED ran the AgDisp model with the proposed spray droplet range), and there is some evidence that the very uniform droplets proposed in the RED may lead to unintentionally high aquatic deposition downwind in some circumstances. In the RED text on environmental effects of mosquito spraying, the droplets were characterized solely by their volume median diameter (50 or 60 microns), without an upper range specified, but it appears in the EFED final Risk Assessment that the standard AgDisp runs use a Dv 0.5 = 50.58 microns and Dv 0.9 = 103.42 microns (page B-1). When a range of values are run in AgDisp 3.15, holding all other variables constant at the EPA values, the following initial (i.e. peak) concentrations of active ingredient are obtained in the EPA standard downwind pond (note: these models runs use the permethrin parameters, but the relative concentrations are applicable for any active ingredient with similar physical parameters). Dv 0.5 (microns) Dv 0.9 (microns) Relative Span Initial Concentration (parts per trillion) 50 115 2.0 35 54 110 1.6 34 60 95 1.0 26 60 80 0.6 26 48 98 1.6 24 These data together with the results of other AgDisp runs demonstrate no benefit in terms of deposition to the EPA Standard Pond for droplets with a Dv 0.9 < 100 microns. In addition, repeated AgDisp runs demonstrate that the very narrow relative span (the range of droplet sizes) proposed by EPA will result in some circumstances of increased peak deposition downwind, as the uniform droplets will tend to move in similar paths. If the peak deposition is over open water, the EPA recommendation could actually lead to a greater peak aquatic deposition than droplets with a wider span and more variable flight paths. Finally, while extensive wind-tunnel and laser testing have demonstrated that some combinations of aerial nozzles and adulticide products are capable of achieving the 60/80 micron distribution that has been proposed, this testing has also demonstrated that these results cannot be achieved for many common nozzles and products with any combination of flight speed or nozzle angle (see supplemental materials from Dr. Jonathan Hornby at the end of this letter). For all these reasons, AMCA recommends a standard of Dv 0.5 = 60 microns and Dv 90 = 100 microns for aerial applications made at less than 200' above ground elevation. 6. AMCA additionally recommends an alternative droplet size standard for higher elevation aerial applications. EFED correctly notes in several Risk Assessments that elevation is a very significant predictor of potential deposition in AgDisp models using the EPA Standard Pond, as particles disperse between the aircraft and the ground, and the peak deposition per unit area drops dramatically as flying height increases. Unfortunately, EFED did not look at any elevations greater than 100' agl, and consequently did not evaluate the very strong protection that increased elevation can afford in terms of minimizing peak aquatic deposition. As noted above, however, operational mosquito control pesticide applications frequently are made at higher elevations than 100' for many reasons including safety and local meteorological conditions. Therefore, AMCA conducted numerous AgDisp runs varying altitude while holding other parameters constant, and we have demonstrated that larger droplets are compatible with EPA?s aquatic deposition standards, when applied at reasonable higher elevations (again, these runs were made with the permethin parameters, but the relative deposition rates are applicable). Dv 0.5 (microns) Dv 0.9 (microns) Elevation (ft agl) Peak Deposition, EPA Standard Pond (mg/m2) % of EPA recommendation (60/80 micron, 100' agl) 60 80 100 6.7 x 10-5 100% 60 80 150 1.1 x 10-5 16% 60 80 200 3.7 x 10-6 5% 60 115 150' 1.6 x 10-5 21% 60 115 200' 1.6 x 10-6 2% 70 145 150' 4.7 x 10-5 59% 70 145 200' 1.0 x 10-5 13% This is important because flat fans nozzles, which cannot meet the 100 micron Dv 0.9 standard, are still a common adulticide application tool, reported by eight of 46 aerial applicators in our survey (17%), including two state government mosquito control programs. Recent research by Johathan Hornby (Hornby et al. 2006. J. Am. Mosq. Control Assoc. 22(4) in press) has demonstrated with a solution of permethrin and diluent oil (Permanone 31-66, Orchex 796, 1:1) in wind tunnel tests using laser diffraction analysis that Dv(0.9) values <145 um are attainable for the following flat fan nozzles and conditions: 8000067, 80005, 8001 (Spraying Systems); 45o angle nozzle orientation into wind, 140 mph wind speed, 80 psi, but that smaller droplets were not consistently achievable. Considering that resmethrin specific gravity and droplet aggregation characteristics closely mimic those of permethrin, we would assume that produceable spectra would also be similar. Therefore AMCA recommends that resmethrin labels allow Dv 0.5 = 70 microns & Dv 0.9 = 145 microns for applications over 200' above ground. 7. AMCA requests that EPA clearly state that cancer risk from mosquito control uses of resmethrin in accordance with label conditions is insignificant. Resmethrin was labeled as a ?likely human carcinogen? according to the May 25, 2005 report of EPA?s Cancer Assessment Review Committee (CARC). The CARC had made the decision to classify resmethrin as a likely carcinogen by referencing 2 laboratory studies where rats and mice were fed the daily human equivalent 3.2 fl oz of Scourge 18:54 for 2 years ? a singularly unrealistic exposure scenario with regard to mosquito control applications. Of singular note is the fact that, while tumors were noted in female Sprague-Dawley rats fed the highest doses, they were not found in male rats undergoing the same exposures. In addition, tumors were not noted in female CD-1 mice fed the same amounts as their male counterparts. Nonetheless, the 18 October 2005 RED rolled the positive tumor data into their cancer risk assessments. Unfortunately, the original CARC document has been used in the northeast to emphasize the Q* issue with resmethrin. Because of this, the Massachusetts State Reclamation and Mosquito Control Board has prohibited use of resmethrin for mosquito control around schools. State law prohibits use of likely carcinogens on school property, regardless of exposure risk. Based upon stakeholder and registrant input, EPA promulgated a Resmethrin HED Revised Risk Assessment for RED ? Feb. 26, 2006. This document corrected several unrealistic exposure assumptions and clarified cancer risk. Pg. 7 -- These assessments conclude that for all supported commodities, the acute and chronic aggregate exposure estimates are below HED?s level of concern. Pg. 7 -- The results of the detects only cancer analysis indicate that the cancer risk estimate associated with estimated dietary and drinking water aggregate exposure to supported resmethrin uses is above HED?s level of concern. When detects only are included the estimated excess lifetime cancer combined dietary/drinking water risk for the general US population is 1.4 x 10-5. When both detects and non-detects are included in the cancer analysis, estimated dietary and drinking water risks are not of concern i.e., the estimated excess lifetime cancer risk from dietary and drinking water exposure for the general US population is 1.6 x 10-6. Pg. 8 -- Based on this analysis estimated occupational and residential exposures to resmethrin do not present risks of concern. Pg. 8 -- Based on this analysis, the aggregate risk from estimated residential and dietary/drinking water exposures (including non-detects) is not of concern. Pg. 55 -- Based on this analysis, aggregate food, water and residential exposures to resmethrin do not present risks of concern. Pg. 63 -- For pest control operator and mosquito abatement scenarios, assuming full day, long-term application for each application method may significantly overestimate total exposure. Based on data on usage of likely resmethrin containing pesticides presented in the NPMA survey, this assumption would result in significant overestimate of exposure for PCOs. Similarly, assuming continuous usage of resmethrin containing pesticides for mosquito abatement applications would also significantly overestimate total exposure based on personal communication with mosquito control district officials regarding current usage of these products. Pg. 63 -- However, based on current usage, the assumption for cancer risk assessment that workers are exposed for 240 days per year for 35 years should be considered highly conservative. Pg. 63 -- For the cancer risk estimate for residential exposure, the assumption that adult individuals are exposed annually for a lifetime (i.e., 50 years for applicator, 70 years for postapplication exposure) should also be considered highly conservative. Clearly, resmethrin cannot be considered carcinogenic when used in aerial mosquito control operations. It is in the public?s interest that this be clearly stated by EPA in appropriate contexts. In conclusion, the AMCA fully supports a thorough, scientifically rigorous risk assessment and reregistration process, from which regulators and pesticide users derive valid and reliable cost/benefit formulae that fully account for environmental impact while allowing appropriate vector-borne disease control. Critical to this process is a full realization of the unique application parameters in mosquito adulticiding operations as a basis for labeling decisions. The AMCA believes the public?s interests are best served when models used to characterize environmental impacts associated with resmethrin?s use accurately reflect accepted mosquito control practice. We recognize the efforts made by EPA to appropriately evaluate realistic parameters in their work to date, and we look forward to further collaboration in addressing the comments presented above as EPA deliberates future resmethrin mosquitocide labels. Karl Malamud-Roam, PhD Joseph M. Conlon Legislative & Regulatory Chair Technical Advisor American Mosquito Control Association American Mosquito Control Association 155 Mason Circle 1500 Millbrook Ct. Concord, CA 94520 Orange Park, FL 32003 (925) 685-9301 x107 (904)215-3008 kmr@ccmvcd.net amcata@bellsouth.net