# OFFICE OF CHEMICAL SAFETY

AND POLLUTION PREVENTION 

# UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460



# RE : Teleconference between Dow AgroScience s (DAS) and EPA to Discuss the

Challenges DAS Has Encountered with the Flux Study Analytical Method

List of Documents

1. Meeting Summary Page 1

2. Meeting Attendees Page 1

3. DAS Talking Points for the Meeting Page 2

1. Meeting Summary

On Thursday, May 10, 2012 , EPA’s Office of Pesticide Programs met with Dow AgroScience s

(DAS) via teleconference and discuss ed the difficulties DAS ha d encountered with the flux study

analytical method, what DAS ha d done to address the difficulties, and DAS provide d EPA with a

revised study submittal date of July 1, 2012.

2. Meeting Attendees

DAS attendees

Lisa Buchholz, Analytical Chemistry Lab Leader

Joe Gesell, Analytical Chemist

Mike Hastings, Analytical Chemist

Pat Havens, CHP Study Director for Field Fate & Effects Group

Darin Lickfeldt, Regulatory Manager

EPA attendees

Jeff Dawson, HED

Wade Britton, HED

Rochelle Bohaty, EFED

Charles (Chuck) Peck, EFED

Tom Myers, PRD

Joel Wolf, PRDDirect Flux Measurement of Chlorpyrifos andChlorpyrifos-Oxon Emissions Following Applicationsof Lorsban Advanced Insecticide to AlfalfaAnalytical issues and progress review10-May-2012Agenda• Introduction•Study purpose• Field conditions overview• Protocol review comments• Analytical method issues andproposed solutionspp• Next stepsIntroduction• Required by Registration Review DCI, Sept. 2010...providing confirmatory data on the volatility and oxon formationunder actual use conditions, information on the percentage ofapplied chlorpyrifos that volatilized and converts to oxon, and ifproperly designed information on flux This information can beproperly designed information on flux.This information can beused to estimate both near field and longer range transportexposures.• Protocol submitted for review May 6, 2011• EPA comments rec’d Sept 9, 2011Study purpose and design• Field flux study - nota monitoring study•Near LosBanosMerced CA (Central Valley),Merced,CA (Central Valley)• Established alfalfaFoliar application–• Soil volatility unimportant & understood•Aerodynamic flux method• Indirect (off-plot) for first sampling period (2 hrs)–Indirect flux via back-calculation with air dispersion modelField conditions•Application 0.94 lb/acre CHP•2 pints Lorsban Advanced*/acre•~175 x 175 m (7.6 acres)•Samples and met @ 0.15, 0.33,0.55, 0.9, 1.8 m•Indirect ~100 ft offplot•Temps•Mid 60s-70s (night)•High 90s -100 (day)•20% (day) -70% (night) RH•Winds calm to 7-10 mph•No precip* Trademark of Dow AgroSciences LLCProtocol review responses – details will be in final report• Protocol was GLP-compliant and audited• Formulation choice – Lorsban Advanced is commercial standard for DAS• Field size/samplinheights/fetchg g– Majewski ref – “rule of thumb”• Lower sampling heights used preferentially@ 90cm => 90m fetch => 1⁄2 field width 88m => OK• Indirect sampling only in 1st2 hr period – precedent in earlier protocols (fumigants)Bare soil plot not includedprevious work shown not significant•–• Surrounding timings (2 weeks) & distance– Atmospheric half-lives (recent photoreactor results) ~ 6hr for parent and oxon–Plus have pre-application samplesPlus,have pre• Duration of sampling – “extend until harvest”– Not a dissipation or residue study, duration sufficient to define flux patternAnalytical method issues• Initial method based on procedure from U of WAstudy (Fenskeet al 2009),et al.2009)• Significant challenges with implementing method asreported• Minor modifications to fit DAS workflows andi i ith “ i t b ” th d l ipreviousexperienceswith “airtube”methodologiesimplemented with little successChallenges• Ion suppression– Co-eluting species from XAD-2, PUF lead to significant ion suppression of CHP and OxonLC/MS signals• Low Oxon recoveries encountered when air was pulled through tube to simulateactual air sampling–Ion suppression hindered identification of low Oxon recoveries from XAD-2 tubes– Experiments proved low recoveries were not due to analyte breakthrough• Significant efforts made to increase Oxon recovery from XAD-2 tubesDifferent solvent systems and extraction technologies were evaluated (shakesonication–Different solvent systems and extraction technologies were evaluated (shake,and ASE)• Evaluation of Oxon extraction methods/solvents pointed to Oxon degradation on tubeand not lack of extractionChallenges – Cont’d• Degradate identification efforts using non 14C labeled standards suggestedbreakdown product was TCP• 14C Oxon was sourced to confirm TCP as degradate– Definitive ID complicated by low TCP’s lowMS sensitivity (>10 less sensitive than Oxon)N CHP t b lit l t i th i i it f TCP d t d TCP i t–NumerousCHPmetaboliteseluteinthevicinityof TCPandmostproduceTCPsignaturefragments (MS/MS and in source fragmentation)•14C Oxon used to produce TCP in situ to facilitate development of extraction regimesfrom XAD-2 air tubes– Solvents that adequately extract CHP and Oxon are not suitable for TCP1:1 ACN/MeoHsolvent system identified that adequately extracts all three compounds–Challenges – Cont’d• Significant challenges in incorporating TCP into LC/MS method due to:– Lack of TCP LC/MS sensitivity required optimization of HPLC columns and mobilephases to increase sensitivity and allowthe three compounds to be run in oneassay– Change in extraction solvent system led todifferent co-extracted species from airtubes which again caused suppression to all three analytes• Sourced stable isotope internal standards to address ion suppressionissues• 3 analytes individually spiked to XAD-2 air tubes to:– Demonstrate extraction efficiencyCheck for degradation of CHP to the oxon & TCP metabolites and metabolite–stability during air sampling (note: UWA did not look at TCP)CHP Air Tube MD DataSample(250ng spiked)Average%Recovered(expressedasCHPequivalents)Total%recoveredTCP OXON CHPCHPairtubeflow0hrs 0 0 81 81CHPairtubeflow2hrs 1.1 0.5 90.5 92CHPairtubeflow16hrs 4 3 83 89Oxon Air Tube MD DataSample(250ng spiked)Average%Recovered(expressedasOXONequivalents)Total%recoveredTCP OXON CHPOxonairtubeflow0hrs 16 81 0 97Oxonairtubeflow2hrs 63 26 0 88Oxon699078airtubeflow16hrsTCP Air Tube MD DataSample(250ng spiked)Average%Recovered(expressedasTCPequivalents)Total%recoveredequivalents)TCP OXON CHPTCPairtubeflow0hrs 85 0 0 85TCPairtubeflow2hrs 77 0 0 77TCPairtubeflow16hrs 72 0 0 72• DAS Proposal for data reporting in Flux study:CHP residues to be reported without conversion–factors (low formation of Oxon and TCP from CHPspiked air tubes)– Oxon residues to be reported as the sum of Oxonresidues and TCP residues (after conversion to Oxonequivalents)Next steps• NOTE: No study samples analyzed yet – all work inmethod development/validation• Study samples will take a solid 2 weeks for analysisA l ti l itd QA•Analyticalwrite-upan• Flux calculations• Field + flux writeup•Final QAQuestions?