ANALYTICAL SUMMARY REPORT

Transcription

1 Food and Environmental Quality Laboratory Page 1 of 77 ANALYTICAL SUMMARY REPORT 2012 MITC Residential Community Air Assessment; Franklin County, Washington Author Ned Hastings Laboratory Research Director Dr. Vincent R Hebert FEQL Study No.: 0412-MITC Analytical Laboratory Washington State University Food & Environmental Quality Laboratory 2710 Crimson Way Richland, WA Study Timetable Study Initiation Date 9/18/2012 Experimental Start Date 10/1/2012 Experimental Termination Date 11/1/2012 Report Date 7/23/2013

2 Food and Environmental Quality Laboratory Page 2 of 77 LOCATION OF RAW DATA The original raw data, protocol, correspondence logs, and all relevant information for the study titled, 2012 MITC-MIC Residential Community Air Assessment; Franklin County, Washington, along with a certified copy of the signed analytical summary report will be maintained at the testing facility for a period of five years. Laboratory Research Director: Testing Facility: Dr. Vincent Hebert Food and Environmental Quality Laboratory Washington State University 2710 Crimson Way Richland, WA CERTIFICATION The undersigned hereby declares that this study was performed under my supervision according to the procedures described herein, and that this report provides a true and accurate record of the results obtained. Laboratory Research Director: Date: July 23, 2013 Dr. Vincent R. Hebert, Food and Environmental Quality Laboratory Washington State University, Tri-Cities Campus, Richland WA Field and analytical work performed by: Ned Hastings Jane LePage Vincent Hebert Graduate Researcher Research Analyst III Laboratory Research Director

3 Food and Environmental Quality Laboratory Page 3 of 77 TABLE OF CONTENTS Page I. EXECUTIVE SUMMARY 4 Abstract 4 Study Overview Monitoring Program 4 Discussion of Results 5 II. FIELD SUMMARY & SAMPLE INVENTORY 10 A. Personnel 10 B. Test Systems 10 C. Trial Locations 10 Table 1 Monitoring Sites 11 D. Sampling Information 11 Table 2 Sample Inventory 12 E. Field Documentation and Record Keeping 21 F. Weather 21 III. STANDARD PREPARATION 25 IV. ANALYTICAL PROCEDURE 26 A. Working Analytical Method 26 i. Sample control and fortification 26 ii. Procedure 26 B. Quantification 27 i. Instrumentation 27 ii. Calculations 27 C. Method Validation and Analytical Limits 29 D. Interferences 29 E. Confirmatory Techniques 29 F. Time Required for Analysis 30 V. AIR MONITORING RESULTS 30 A. Storage Stability 30 B. Field and Trip Fortification Samples 30 Table 3 Field Fortifications 30 C. MITC Air Concentration Results 32 Table 4 Laboratory Fortifications 33 Table 5 12-hour Air Sampler MITC Results 33 Table 6 4-hour Air Sampler MITC Results 38 APPENDIX A. Project Protocol 42 APPENDIX B. Working Analytical Method 50 APPENDIX C. Weather Data 52 APPENDIX D. Representative Chromatograms 71

4 Food and Environmental Quality Laboratory Page 4 of 77 I. EXECUTIVE SUMMARY Abstract An ambient air monitoring program was conducted in south Franklin County, WA in the fall of The purpose of this study was to specifically assess metam sodium s biologically active ingredient methyl isothiocyanate (MITC) in ambient air near residential and commercial structures during the fall 2012 field fumigation season. Air sampling was performed at five sites, three days per week from October 1 to October 31, For the first three weeks and week five, two 12-hr samples (ca. 7 am 7 pm, and 7 pm to 7 am) were taken over each 24-hr sampling interval. During the fourth week, the week October 22, air sampling was performed at 4-hr intervals over each of the three 24-hr sampling intervals. The 12-hour time weighted averaged (TWA) MITC air concentrations for weeks 1-3 and week 5 ranged from detectable (>0.01 ppb) to 19.9 ppb. The maximum observed TWA air concentration for week 4, 4-hour interval monitoring, was 88 ppb. This observed ambient air concentration exceeds the US-EPA value of 22 ppb for acute human inhalation exposure, for that 4-hour interval. EPA s subchronic human threshold value of 5 ppb for short and intermediate-term inhalation was occasionally exceeded during the study time frame. The five week seasonal TWA residential exposure concentration was 1.9 ppb which exceeded California EPA subchronic reference exposure level (REL) value of 1 ppb but was less than the 5 ppb EPA health effects division level of concern (LOC) for short and intermediate inhalation human exposure. This current air monitoring program supports earlier monitoring work in 2005, 2007, and 2008 indicating MITC air concentrations can periodically exceed federal acute and subchronic regulatory human health inhalation exposure criteria in this important agricultural region now facing expansive urban and commercial development. Study Overview South Franklin County, WA has been undergoing rapid residential and commercial growth into traditional large production agricultural lands. This could contribute to increased risks for human inhalation exposure to agricultural fumigants that have been traditionally used in this region. This 2012 air monitoring program is a continuation from our previous 2005, 2007, and 2008 air monitoring evaluations to further characterize regional inhalation exposure to MITC over the active September through late October metam sodium fumigation season (Merriman and Hebert 2007, WSU-FEQL, 2008) and to continue to establish baseline data before Phase II fumigant label changes took effect in December Monitoring Program MITC was monitored in ambient air near residential and commercial buildings in south Franklin County during the fall fumigation season from October 1 to the morning of November 1. The study was terminated one week after the October 24 th irrigation water cut-off date for the Franklin County Irrigation District. Five sites were selected for monitoring locations, four residential and one commercial (see Figure 1 and Table 1). A sampling mast was constructed for each site location. The mast consisted of Model 224-PCXR8 air sampling units placed at the base of a ringstand with a vertical 1.5-meter crossbar. Tubing was used to connect the air samplers to either two or one gram charcoal-filled glass cartridges (SKC West) located horizontally on the crossbar. The

5 Food and Environmental Quality Laboratory Page 5 of 77 samplers were operated at an air flow rate of ca. 2 L min -1 three days per week over the five week fumigation period (see Appendix A, Protocol). On the 24-hr interval sampling days, 2-g charcoal cartridges were collected and replaced at 12-hr intervals (i.e., day and nighttime sampling). During week four of the study, the daily sampling interval was changed to 4-hr intervals using 1-g cartridges to better assess possible acute MITC human exposure concentrations. At the start and end of all sampling collections, air flow was measured and recorded. The collected charcoal cartridges were immediately placed on blue ice and taken to the WSU-Food and Environmental Quality Laboratory (WSU-FEQL) where they were stored at -80 C until analysis. Field blanks and MITC fortified blanks were routinely shipped with the residential air samples for quality control purposes. Additionally, outside at the WSU-Tri Cities campus, blank control cartridges and fortified cartridges with a known concentration of MITC were run for either12-hr or 4-hr intervals at 2 L min -1 intermittently during the study to evaluate sample breakthrough and field related percent recovery (see Table 3). The extraction and analytical method used for this project was previously validated for use in MITC air sampling studies. During analysis and for each laboratory analytical set, a blank cartridge and MITC laboratory fortified cartridge (at varying concentrations) were included with the residential samples. Laboratory percent recoveries are presented in Table 4. A separate frozen storage stability study was not conducted since all samples were analyzed within 37 days of collection, well before the previously conducted 85-day storage stability evaluation for the 2005 air monitoring program (FEQL-NG-0605, 2006). Discussion of Results The analytical method for the measurement of MITC was found to be rugged with an analytical method limit of quantitation (LOQ) of 0.06 ppb and method limit of detection (LOD) estimated at 0.01 ppb (based on a total volume 2 L min -1 air flow for the 12-hr sampling interval). Two separate 12-hr samples were taken over each 24-hr sampling interval to compare averaged day and nighttime MITC air concentrations. Figure 2 presents the time weighted averaged (TWA) MITC concentrations from each site for each 12-hour sampling interval from October 1 through November 1, Over this five week period, MITC air concentrations were routinely observed above the method s limit of quantitation. The time weighted averaged MITC ambient air concentrations for the 12-hour samples ranged from below detection to 19.9 ppb 1 (see Table 5). The five week seasonal TWA residential exposure concentration was 1.92 ppb which exceeded California EPA subchronic reference exposure level (REL) value of 1 ppb but was less than the 5 ppb EPA health effects division level of concern (LOC) for short and intermediate inhalation human exposure. EPA s subchronic human LOC for short and intermediate-term inhalation (i.e, > 5 ppb extending for periods of 24 hours or more), however, was exceeded at a few sites on three of the study days (Table 5 and 6). The maximum TWA MITC air concentration for the 4-hour samples was observed at one site during the fourth week of October 2013, with an MITC concentration of 266 μg m -3 (88 ppb; Table 1 MITC ppb = (μg m -3 ) x 8.21 x 10-2 L-atm/mole- o K (298 o K) (73.12 gram/mole) (1 atm)

6 Food and Environmental Quality Laboratory Page 6 of 77 6 and Figure 3). This maximum concentration was measured over the time period from 3:24 am to 7:26 am on October 23. This single observed ambient air concentration exceeded the US-EPA value for acute human inhalation exposure of 22 ppb. MITC residues at the other four sites were below 5.5 ppb for that same time period. The 4 and 12-hr TWA MITC air concentration data were not adjusted for percent recovery due to consistent quantitative recoveries from field and laboratory fortified samples (see Tables 2 and 3). References Merriman, J & Hebert, V. Methyl Isothiocyanate Residential Community Air Assessment; South Franklin County, Washington. Bull. of Environ. Contam. and Toxicol. 78(1), (2007). WSU-Food and Environmental Quality Laboratory. MITC residential community air assessment: South Franklin Co, Washington. Analytical Summary Report FEQL-NG-0605, accessed at: (2006).

7 Food and Environmental Quality Laboratory Page 7 of 77 Figure Residential Sampling Site Map South Franklin County, Washington State Site 1 (N 46 o W119 o ) Site 2 (N 46 o W119 o ) Site 3 (N 46 o W119 o ) Site 4 (N 46 o W119 o ) Site 5 (N 46 o W119 o ) 1 mile N

8 Food and Environmental Quality Laboratory Page 8 of 77 Figure 2 South Franklin County, WA - MITC Twelve-hour TWA interval air monitoring: October 1 to November 1, 2012

9 Food and Environmental Quality Laboratory Page 9 of 77 Figure 3 South Franklin County, WA - MITC Four-hour TWA interval air monitoring: October 22-23, 24-25, and 26-27, 2012

10 Food and Environmental Quality Laboratory Page 10 of 77 II. FIELD SUMMARY & SAMPLE INVENTORY INTRODUCTION This monitoring study was initiated October 1 during the typical metam sodium fumigation season and continued one week after Franklin County Irrigation District s October 24 th irrigation cut-off date for this region. The purpose of this study was to estimate residential MITC air concentrations in this region of traditional agriculture and expanding residential communities. A. Field Personnel Jane LePage, Research Analyst Ned Hastings, Graduate Researcher Vincent Hebert, Laboratory Research Director B. Test System Five outdoor sampling masts were deployed to sample ambient air for MITC at residential and commercial locations in south Franklin County from October 1 through November 1, Each mast consisted of a cross-arm at approximately 1.5-m height to support charcoal sampling tube(s). Site 3 had two air samplers for duplicate sampling. Each tube contained 2 g coconut charcoal for the 12-hour or 1 g coconut charcoal for the 4-hour sampling periods employed by this study; both sizes of cartridges were prepared by SKC West, Fullerton, CA. AC-powered air sampling units (SKC samplers Model 224-PCXR8) sampled air at ca. 2 L/min. Actual flows for each sampling cartridge were measured by flow meter at the start and end of each sampling period and recorded. The averaged two-point flow rate reading and sampling duration were used to calculate the total volume of air sampled in cubic meters (Table 2). C. Trial Locations This residential air monitoring study was comprised of five sites in south Franklin County, Washington. Four sites were located at single family homes and one at a commercial building. One of these sites (Sites 3) consisted of duplicate sampling systems. The duplicate samples at sites 3 served as a quality control to demonstrate agreement between the samples. Additionally, an outdoor location at the WSU Tri-Cities campus served for conducting MITC fortified activated charcoal air evaluations. Table 1 and Figure 1 provide approximate locations for the five test sites.

11 Food and Environmental Quality Laboratory Page 11 of 77 Table 1 Monitoring Locations Site 1 S1 Site 2 S2 Township 9 N Township 9 N Range 29 E Range 29 E Section 12 Section 8 Site 3 S3 (duplicate samples) Site 4 S4 Township 9 N Township 9 N Range 29 E Range 29 E Section 9 Section 10 Site 5 S5 Township 9 N Range 29 E Section 2 D. Sampling Information Week 1, 2, 3, and 5; 12-hr interval air sampling. Air monitoring was conducted from October 1, 2012 to the morning of November 1, Air was monitored for 24 hour intervals, three days weekly over this period. Except for the week of October 22, air was sampled during the day for 12 hours from approximately 7 am to 7 pm and in the evening from approximately 7 pm to 7 am on each Monday, Wednesday and Friday. After each 12-hour sampling event the activated charcoal samples were removed from the sampler and transferred on blue ice to the Food & Environmental Quality Laboratory (FEQL), Washington State University, 2710 Crimson Way, Richland, WA where they were placed in frozen storage (-80 C) until analysis. Week of October 22; 4-hour interval air sampling During week four of the study, the sampling frequency was changed to 4-hr intervals to better capture MITC air concentration throughout a 24-hr period. Samples were handled in the same manner as the 12-hour samples. Due to operator error a few samples were mixed up in the field. When possible sample data was reconstructed, if not possible then data was not reported. These sample errors are noted in the data, Tables 2 and 6. Field blanks (FB) routinely accompanied the sample shipments. These cartridges were momentarily attached to a field mast to demonstrate that there was no cross-contamination of samples from the sampling technique. Spiked field blanks (SFB) also accompanied each shipment to demonstrate sample integrity during transport of MITC captured in the charcoal adsorbent. Additionally, at the WSU Tri-City campus, blank charcoal cartridges were routinely fortified and exposed to air sampling for 12-hour intervals to demonstrate stability of MITC on the cartridges under regional air sampling conditions. Control charcoal samples

12 Food and Environmental Quality Laboratory Page 12 of 77 were run concurrently with these fortified field spikes. Sample Coding: Each field sample was given a unique sample code, which included site designation, interval day, and a label for collection timeframe. The dates and times for sample placement for the 12 and 4-hour intervals are provided in Table 2. Interval The coding for 12-hour samples was according to the following: Site Placement Collocation Location Code 1 day Time 1 AC AM/PM 2 AC AM/PM 3 AC AM/PM R/L 4 AC AM/PM 5 AC AM/PM 1 AC designates the adsorbent (activated charcoal). The coding for the 4-hr, week-4 samples was as follows: Site Location Code Day 2 Interval hour 3 Collocation 1 AC1 X, Y, or Z 0, 4, 8, 12, 16, 20 2 AC2 X, Y, or Z 0, 4, 8, 12, 16, 20 3 AC3 X, Y, or Z 0, 4, 8, 12, 16, 20 R/L 4 AC4 X, Y, or Z 0, 4, 8, 12, 16, 20 5 AC5 X, Y, or Z 0, 4, 8, 12, 16, 20 2 X, Y, Z specifies the 3 days of intensive 4-hr sampling before irrigation cut-off 3 The six 4-hr intervals per 24 hr X,Y, or Z monitoring day Table 2 Sample Inventory Sample ID Start Time Start flow rate (L/min) End Time End flow rate (L/min) Total air sampled (m 3 ) Date of extraction Days in frozen storage AC1-1AM 10/1/12 8: /1/12 20: /4/ AC2-1AM 10/1/12 7: /1/12 20: /4/ AC3-1AM-R 10/1/12 7: /1/12 19: /4/ AC3-1AM-L 10/1/12 7: /1/12 19: /4/ AC4-1AM 10/1/12 7: /1/12 19: /4/ AC5-1AM 10/1/12 7: /1/12 18: /4/ AC1-1PM 10/1/12 20: /2/12 7: /9/ AC2-1PM 10/1/12 20: /2/12 7: /9/ AC3-1PM-R 10/1/12 19: /2/12 7: /9/2012 7

13 Food and Environmental Quality Laboratory Page 13 of 77 Sample ID Start Time Start flow rate (L/min) End Time End flow rate (L/min) Total air sampled (m 3 ) Date of extraction Days in frozen storage AC3-1PM-L 10/1/12 19: /2/12 7: /9/ AC4-1PM 10/1/12 19: /2/12 7: /9/ AC5-1PM 10/1/12 18: /2/12 6: /9/ FB-1 10/1/12 6:30 NA 10/2/12 7:33 NA 10/9/ SFB-1 10/1/12 6:30 NA 10/2/12 7:33 NA 10/9/ AC1-2AM 10/3/12 7: /3/12 20: /5/ AC2-2AM 10/3/12 7: /3/12 20: /5/ AC3-2AM-R 10/3/12 7: /3/12 20: /5/ AC3-2AM-L 10/3/12 7: /3/12 20: /5/ AC4-2AM 10/3/12 7: /3/12 20: /5/ AC5-2AM 10/3/12 6: /3/12 19: /5/ AC1-2PM 10/3/12 20: /4/12 7: /9/ AC2-2PM 10/3/12 20: /4/12 7: /9/ AC3-2PM-R 10/3/12 20: /4/12 7: /9/ AC3-2PM-L 10/3/12 20: /4/12 7: /9/ AC4-2PM 10/3/12 20: /4/12 7: /9/ AC5-2PM 10/3/12 19: /4/12 6: /9/ FB-2 10/3/12 6:25 NA 10/4/12 7:29 NA 10/9/ SFB-2 10/3/12 6:25 NA 10/4/12 7:29 NA 10/9/ FFC-2 10/3/12 6: /3/12 18: /9/ FF-2 10/3/12 6: /3/12 18: /9/ AC1-3AM 10/5/12 7: /5/12 19: /11/ AC2-3AM 10/5/12 7: /5/12 19: /11/ AC3-3AM-R 10/5/12 7: /5/12 19: /11/ AC3-3AM-L 10/5/12 7: /5/12 19: /11/ AC4-3AM 10/5/12 7: /5/12 19: /11/ AC5-3AM 10/5/12 6: /5/12 18: /11/ FB-3 10/5/12 6:25 NA 10/5/12 19:39 NA 10/11/ SFB-3 10/5/12 6:25 NA 10/5/12 19:39 NA 10/11/ AC1-3PM 10/5/12 19: /6/12 7: /12/ AC2-3PM 10/5/12 19: /6/12 7: /12/ AC3-3PM-R 10/5/12 19: /6/12 7: /12/ AC3-3PM-L 10/5/12 19: /6/12 7: /12/2012 6

14 Food and Environmental Quality Laboratory Page 14 of 77 Sample ID Start Time Start flow rate (L/min) End Time End flow rate (L/min) Total air sampled (m 3 ) Date of extraction Days in frozen storage AC4-3PM 10/5/12 19: /6/12 7: /12/ AC5-3PM 10/5/12 18: /6/12 6: /12/ AC1-4AM 10/8/12 7: /8/12 19: /15/ AC2-4AM 10/8/12 7: /8/12 19: /15/ AC3-4AM-R 10/8/12 7: /8/12 18: /15/ AC3-4AM-L 10/8/12 7: /8/12 18: /15/ AC4-4AM 10/8/12 7: /8/12 18: /15/ AC5-4AM 10/8/12 6: /8/12 18: /15/ AC1-4PM 10/8/12 19: /9/12 7: /16/ AC2-4PM 10/8/12 19: /9/12 7: /16/ AC3-4PM-R 10/8/12 18: /9/12 7: /16/ AC3-4PM-L 10/8/12 18: /9/12 7: /16/ AC4-4PM 10/8/12 18: /9/12 7: /16/ AC5-4PM 10/8/12 18: /9/12 6: /16/ FB-4 10/8/12 6:25 NA 10/9/12 7:28 NA 10/16/ SFB-4 10/8/12 6:25 NA 10/9/12 7:28 NA 10/16/ AC1-5-AM 10/10/12 7: /10/12 19: /30/ AC2-5-AM 10/10/12 7: /10/12 19: /30/ AC3-5-AM-R 10/10/12 7: /10/12 19: /30/ AC3-5-AM-L 10/10/12 7: /10/12 19: /30/ AC4-5-AM 10/10/12 7: /10/12 19: /30/ AC5-5-AM 10/10/12 6: /10/12 18: /30/ FFC-5 10/10/12 6: /10/12 20: /30/ FF-5 10/10/12 6: /10/12 20: /30/ AC1-5-PM 10/10/12 19: /11/12 7: /5/ AC2-5-PM 10/10/12 19: /11/12 7: /5/ AC3-5-PM-R 10/10/12 19: /11/12 7: /5/ AC3-5-PM-L 10/10/12 19: /11/12 7: /5/ AC4-5-PM 10/10/12 19: /11/12 7: /5/ AC5-5-PM 10/10/12 18: /11/12 6: /5/ FB-5 10/10/12 6:25 NA 10/11/12 7:30 NA 11/5/ SFB-5 10/10/12 6:25 NA 10/11/12 7:30 NA 11/5/

15 Food and Environmental Quality Laboratory Page 15 of 77 Sample ID Start Time Start flow rate (L/min) End Time End flow rate (L/min) Total air sampled (m 3 ) Date of extraction Days in frozen storage AC1-6-AM 10/12/12 7: /12/12 19: /7/ AC2-6-AM 10/12/12 7: /12/12 19: /7/ AC3-6-AM-R 10/12/12 7: /12/12 19: /7/ AC3-6-AM-L 10/12/12 7: /12/12 19: /7/ AC4-6-AM 10/12/12 7: /12/12 19: /7/ AC5-6-AM 10/12/12 6: /12/12 18: /7/ AC1-6-PM 10/12/12 19: /13/12 7: /6/ AC2-6-PM 10/12/12 19: /13/12 7: /6/ AC3-6-PM-R 10/12/12 19: /13/12 7: /6/ AC3-6-PM-L 10/12/12 19: /13/12 7: /6/ AC4-6-PM 10/12/12 19: /13/12 7: /6/ AC5-6-PM 10/12/12 18: /13/12 7: /6/ FB-6 10/12/12 6:25 NA 10/13/12 8:10 NA 11/6/ SFB-6 10/12/12 6:25 NA 10/13/12 8:10 NA 11/6/ AC1-7-AM 10/15/12 7: /15/12 19: /31/ AC2-7-AM 10/15/12 7: /15/12 19: /31/ AC3-7-AM-R 10/15/12 7: /15/12 19: /31/ AC3-7-AM-L 10/15/12 7: /15/12 19: /31/ AC4-7-AM 10/15/12 7: /15/12 19: /31/ AC5-7-AM 10/15/12 6: /15/12 18: /31/ AC1-7-PM 10/15/12 19: /16/12 7: /22/ AC2-7-PM 10/15/12 19: /16/12 7: /22/ AC3-7-PM-R 10/15/12 19: /16/12 7: /22/ AC3-7-PM-L 10/15/12 19: /16/12 7: /22/ AC4-7-PM 10/15/12 19: /16/12 7: /22/ AC5-7-PM 10/15/12 18: /16/12 6: /22/ FB-7 10/15/12 6:25 NA 10/16/12 7:29 NA 10/22/ SFB-7 10/15/12 6:25 NA 10/16/12 7:29 NA 10/22/ AC1-8-AM 10/17/12 7: /17/12 19: /1/ AC2-8-AM 10/17/12 7: /17/12 19: /1/ AC3-8-AM-R 10/17/12 7: /17/12 19: /1/ AC3-8-AM-L 10/17/12 7: /17/12 19: /1/ AC4-8-AM 10/17/12 7: /17/12 19: /1/

16 Food and Environmental Quality Laboratory Page 16 of 77 Sample ID Start Time Start flow rate (L/min) End Time End flow rate (L/min) Total air sampled (m 3 ) Date of extraction Days in frozen storage AC5-8-AM 10/17/12 6: /17/12 18: /1/ FFC-8 10/17/12 6: /17/12 19: /1/ FF-8 10/17/12 6: /17/12 19: /1/ AC1-8-PM 10/17/12 19: /18/12 7: /26/ AC2-8-PM 10/17/12 19: /18/12 7: /26/ AC3-8-PM-R 10/17/12 19: /18/12 7: /26/ AC3-8-PM-L 10/17/12 19: /18/12 7: /26/ AC4-8-PM 10/17/12 19: /18/12 7: /26/ AC5-8-PM 10/17/12 18: /18/12 6: /26/ FB-8 10/17/12 6:25 NA 10/18/12 7:28 NA 10/26/ SFB-8 10/17/12 6:25 NA 10/18/12 7:28 NA 10/26/ AC1-9-AM 10/19/12 7: /19/12 19: /24/ AC2-9-AM 10/19/12 7: /19/12 19: /24/ AC3-9-AM-R 10/19/12 7: /19/12 19: /24/ AC3-9-AM-L 10/19/12 7: /19/12 19: /24/ AC4-9-AM 10/19/12 7: /19/12 19: /24/ AC5-9-AM 10/19/12 6: /19/12 18: /24/ FFC-9 10/19/12 6: /19/12 19: /24/ FF-9 10/19/12 6: /19/12 19: /24/ AC1-9-PM 10/19/12 19: /20/12 7: /29/ AC2-9-PM 10/19/12 19: /20/12 7: /29/ AC3-9-PM-R 10/19/12 19: /20/12 7: /29/ AC3-9-PM-L 10/19/12 19: /20/12 7: /29/ AC4-9-PM 10/19/12 19: /20/12 7: /29/ AC5-9-PM 10/19/12 18: /20/12 6: /29/ FB-9 10/19/12 6:20 NA 10/20/12 7:28 NA 10/29/ SFB-9 10/19/12 6:20 NA 10/20/12 7:28 NA 10/29/ AC1-X-0 10/22/12 7: /22/12 11: /28/ AC2-X-0 10/22/12 7: /22/12 11: /28/ AC3-X-0-R 10/22/12 7: /22/12 11: /28/ AC3-X-0-L 10/22/12 7: /22/12 11: /28/ AC4-X-0 10/22/12 7: /22/12 11: /28/ AC5-X-0 10/22/12 6: /22/12 11: /28/

17 Food and Environmental Quality Laboratory Page 17 of 77 Sample ID Start Time Start flow rate (L/min) End Time End flow rate (L/min) Total air sampled (m 3 ) Date of extraction Days in frozen storage AC1-X-4 10/22/12 11: /22/12 16: /21/ AC2-X-4 10/22/12 11: /22/12 15: /21/ AC3-X-4-R 10/22/12 11: /22/12 15: /21/ AC3-X-4-L 10/22/12 11: /22/12 15: /21/ AC1-X-8(4) 1 10/22/12 16:00 10/22/12 19:47 11/21/ AC2-X-8(4) 1 10/22/12 15:54 10/22/12 19:37 11/21/ AC3-X-8-R 10/22/12 15: /22/12 19: /21/ AC3-X-8-L 10/22/12 15: /22/12 19: /21/ AC4-X-8 10/22/12 15: /22/12 19: /21/ AC5-X-8 10/22/12 15: /22/12 19: /21/ AC4-X-4(8) 1 10/22/12 11:16 10/22/12 15:13 11/21/ AC5-X-4(8) 1 10/22/12 11:01 10/22/12 15:00 11/21/ AC-FFC-X-8 10/22/12 14: /22/12 18: /21/ AC-FF-X-8 10/22/12 14: /22/12 18: /21/ AC1-X-12 10/22/12 19: /22/12 23: /19/ AC2-X-12 10/22/12 19: /22/12 23: /19/ AC3-X-12-R 10/22/12 19: /22/12 23: /19/ AC3-X-12-L 10/22/12 19: /22/12 23: /19/ AC4-X-12 10/22/12 19: /22/12 23: /19/ AC5-X-12 10/22/12 19: /22/12 22: /19/ AC1-X-16 10/22/12 23: /23/12 3: /28/ AC2-X-16 10/22/12 23: /23/12 3: /28/ AC3-X-16-R 10/22/12 23: /23/12 3: /28/ AC3-X-16-L 10/22/12 23: /23/12 3: /28/ AC4-X-16 10/22/12 23: /23/12 3: /28/ AC5-X-16 10/22/12 22: /23/12 2: /28/ AC1-X-20 10/23/12 3: /23/12 7: /19/ AC2-X-20 10/23/12 3: /23/12 7: /19/ AC3-X-20-R 10/23/12 3: /23/12 7: /19/ AC3-X-20-L 10/23/12 3: /23/12 7: /19/ AC4-X-20 10/23/12 3: /23/12 7: /19/ AC5-X-20 10/23/12 2: /23/12 6: /19/

18 Food and Environmental Quality Laboratory Page 18 of 77 Sample ID Start Time Start flow rate (L/min) End Time End flow rate (L/min) Total air sampled (m 3 ) Date of extraction Days in frozen storage FB-X 10/22/12 6:20 NA 10/23/12 7:33 NA 11/19/ SFB-X 10/22/12 6:20 NA 10/23/12 7:33 NA 11/19/ AC1-Y-0 10/24/12 7: /24/12 11: /15/ AC2-Y-0 10/24/12 7: /24/12 11: /15/ AC3-Y-0-R 10/24/12 7: /24/12 11: /15/ AC3-Y-0-L 10/24/12 7: /24/12 11: /15/ AC4-Y-0 10/24/12 7: /24/12 11: /15/ AC5-Y-0 10/24/12 6: /24/12 11: /15/ AC1-Y-4 10/24/12 11: /24/12 15: /15/ AC2-Y-4 10/24/12 11: /24/12 15: /15/ AC3-Y-4-R 10/24/12 11: /24/12 15: /15/ AC3-Y-4-L 10/24/12 11: /24/12 15: /15/ AC4-Y-4 10/24/12 11: /24/12 15: /15/ AC5-Y-4 10/24/12 11: /24/12 15: /15/ AC-FFC-Y-4 10/24/12 10: /24/12 14: /15/ AC-FF-Y-4 10/24/12 10: /24/12 14: /15/ AC1-Y-8 10/24/12 15: /24/12 19: /14/ AC2-Y-8 10/24/12 15: /24/12 19: /14/ AC3-Y-8-R 10/24/12 15: /24/12 19: /14/ AC3-Y-8-L 10/24/12 15: /24/12 19: /14/ AC4-Y-8 10/24/12 15: /24/12 19: /14/ AC5-Y-8 10/24/12 15: /24/12 19: /14/ AC1-Y-12 10/24/12 19: /24/12 23: /14/ AC2-Y-12 10/24/12 19: /24/12 23: /14/ AC3-Y-12-R 10/24/12 19: /24/12 23: /14/ AC3-Y-12-L 10/24/12 19: /24/12 23: /14/ AC4-Y-12 10/24/12 19: /24/12 23: /14/ AC5-Y-12 10/24/12 19: /24/12 22: /14/ AC1-Y-16 10/24/12 23: /25/12 3: /27/ AC2-Y-16 10/24/12 23: /25/12 3: /27/ AC3-Y-16-R 10/24/12 23: /25/12 3: /27/ AC3-Y-16-L 10/24/12 23: /25/12 3: /27/

19 Food and Environmental Quality Laboratory Page 19 of 77 Sample ID Start Time Start flow rate (L/min) End Time End flow rate (L/min) Total air sampled (m 3 ) Date of extraction Days in frozen storage AC4-Y-16 10/24/12 23: /25/12 3: /27/ AC5-Y-16 10/24/12 22: /25/12 2: /27/ AC1-Y-20 10/25/12 3: /25/12 7: /27/ AC2-Y-20 10/25/12 3: /25/12 7: /27/ AC3-Y-20-R 10/25/12 3: /25/12 7: /27/ AC3-Y-20-L 10/25/12 3: /25/12 7: /27/ AC4-Y-20 10/25/12 3: /25/12 7: /27/ AC5-Y-20 10/25/12 2: /25/12 6: /27/ FB-Y 10/24/12 6:30 NA 10/25/12 7:34 NA 11/27/ SFB-Y 10/24/12 6:30 NA 10/25/12 7:34 NA 11/27/ AC1-Z-0 10/26/12 7: /26/12 12: /27/ AC2-Z-0 10/26/12 7: /26/12 11: /27/ AC3-Z-0-R 10/26/12 7: /26/12 11: /27/ AC3-Z-0-L 1 10/26/12 7: /26/12 15: /20/ AC4-Z-0 10/26/12 7: /26/12 11: /27/ AC5-Z-0 10/26/12 6: /26/12 11: /27/ FFC-Z-4 10/26/12 9: /26/12 14: /27/ FF-Z-4 10/26/12 9: /26/12 14: /27/ AC1-Z-4 10/26/12 12: /26/12 15: /20/ AC2-Z-4 10/26/12 11: /26/12 15: /20/ AC3-Z-4-R 1 10/26/12 15:40 11/27/ AC3-Z-4-L 10/26/12 11: /26/12 15: /20/ AC4-Z-4 10/26/12 11: /26/12 15: /20/ AC5-Z-4 10/26/12 11: /26/12 15: /20/ AC1-Z-8 10/26/12 15: /26/12 19: /20/ AC2-Z-8 10/26/12 15: /26/12 19: /20/ AC3-Z-8-R 10/26/12 15: /26/12 19: /20/ AC3-Z-8-L 10/26/12 15: /26/12 23: /26/ AC4-Z-8 10/26/12 15: /26/12 19: /20/ AC5-Z-8 10/26/12 15: /26/12 19: /20/ AC1-Z-12 10/26/12 19: /26/12 23: /26/ AC2-Z-12 10/26/12 19: /26/12 23: /26/

20 Food and Environmental Quality Laboratory Page 20 of 77 Sample ID Start Time Start flow rate (L/min) End Time End flow rate (L/min) Total air sampled (m 3 ) Date of extraction Days in frozen storage AC3-Z-12-R 1 10/26/12 19:24 11/20/ AC3-Z-12-L 10/26/12 19: /26/12 23: /26/ AC4-Z-12 10/26/12 19: /26/12 23: /26/ AC5-Z-12 10/26/12 19: /26/12 23: /26/ AC1-Z-16 10/26/12 23: /27/12 3: /26/ AC2-Z-16 10/26/12 23: /27/12 3: /26/ AC3-Z-16-R 10/26/12 23: /27/12 3: /26/ AC3-Z-16-L 10/26/12 23: /27/12 3: /26/ AC4-Z-16 10/26/12 23: /27/12 3: /26/ AC5-Z-16 10/26/12 23: /27/12 2: /26/ AC1-Z-20 10/27/12 3: /27/12 7: /13/ AC2-Z-20 10/27/12 3: /27/12 7: /13/ AC3-Z-20-R 10/27/12 3: /27/12 7: /13/ AC3-Z-20-L 10/27/12 3: /27/12 7: /13/ AC4-Z-20 10/27/12 3: /27/12 7: /13/ AC5-Z-20 10/27/12 2: /27/12 7: /13/ FB-Z 10/26/12 6:25 NA 10/27/12 7:40 NA 11/13/ SFB-Z 10/26/12 6:25 NA 10/27/12 7:40 NA 11/13/ AC1-10-AM 10/29/12 7: /29/12 19: /8/ AC2-10-AM 10/29/12 7: /29/12 19: /8/ AC3-10-AM-R 10/29/12 7: /29/12 19: /8/ AC3-10-AM-L 10/29/12 7: /29/12 19: /8/ AC4-10-AM 10/29/12 7: /29/12 19: /8/ AC5-10-AM 10/29/12 6: /29/12 18: /8/ AC1-10-PM 10/29/12 19: /30/12 7: /6/ AC2-10-PM 10/29/12 19: /30/12 7: /6/ AC3-10-PM-R 10/29/12 19: /30/12 7: /6/ AC3-10-PM-L 10/29/12 19: /30/12 7: /6/ AC4-10-PM 10/29/12 19: /30/12 7: /6/ AC5-10-PM 10/29/12 18: /30/12 6: /6/ FB-10 10/29/12 6:25 NA 10/30/12 7:30 NA 11/6/ SFB-10 10/29/12 6:25 NA 10/30/12 7:30 NA 11/6/2012 7

21 Food and Environmental Quality Laboratory Page 21 of 77 Start flow rate (L/min) End flow rate (L/min) Total air sampled (m 3 ) Date of extraction Sample ID Start Time End Time AC1-11-AM 10/31/12 7: /31/12 19: /5/ AC2-11-AM 10/31/12 7: /31/12 19: /5/ AC3-11-AM-R 10/31/12 7: /31/12 19: /5/ AC3-11-AM-L 10/31/12 7: /31/12 19: /5/ AC4-11-AM 10/31/12 7: /31/12 19: /5/ AC5-11-AM 10/31/12 6: /31/12 18: /5/ FFC-11 10/31/12 6: /31/12 18: /5/ FF-11 10/31/12 6: /31/12 18: /5/ Days in frozen storage AC1-11-PM 10/31/12 19: /1/12 7: /7/ AC2-11-PM 10/31/12 19: /1/12 7: /7/ AC3-11-PM-R 10/31/12 19: /1/12 7: /7/ AC3-11-PM-L 10/31/12 19: /1/12 7: /7/ AC4-11-PM 10/31/12 19: /1/12 7: /7/ AC5-11-PM 10/31/12 18: /1/12 6: /7/ FB-11 10/31/12 6:27 NA 11/1/12 7:44 NA 11/7/ SFB-11 10/31/12 6:27 NA 11/1/12 7:44 NA 11/7/ Due to operator error these samples were not deployed properly or mixed up with another sample in the field. When possible sample data was reconstructed. If not possible then data was not used. 2 pump failure during sampling interval E. Field Documentation and Record Keeping All operations, data and observations appropriate to this study were recorded directly into the Field Data Book (FEQL-0412). The data book for this study was designed for collecting field information and serves as a record of fieldwork. All field data information will be maintained at the FEQL with the project study file for a period of 5 years. F. Weather Data Data from the NOAA meteorological station located at the Tricities airport, Pasco, WA ( N, W) was obtained for regional air temperature, precipitation, and wind speed from October 1 through November 1st. This weather station was within 5 miles of the sampling site locations. Figures 4, 5, and 6 respectively summarize air temperatures, precipitation, and wind velocity during the 5-week study period. Complete weather station data is archived with the Field Data Book, air temperature, wind direction and speed, precipitation and dew point data is provided in Appendix C.

22 Food and Environmental Quality Laboratory Page 22 of 77 Figure 4 Daily Weather Data Air Temperature ( C) Air Temperature for: Pasco Airport Time Range: 10/1/12 to 11/1/ / 01/ 12 10/ 07/ 12 10/ 14/ 12 10/ 21/ 12 Temperature C 10/ 28/ 12 11/ 01/ 12 Data from NOAA weather station at Tricities Airport (latitude , longitude , elevation 402 ft) Date

23 Food and Environmental Quality Laboratory Page 23 of 77 Figure 5 Daily Weather Data Precipitation (in) 0.25 Precipitation Per Day, Pasco Airport Time Range: 10/1/12-11/1/12 Precipitation, Inches /1/12 10/6/12 10/11/12 10/16/12 10/21/12 10/26/12 10/31/12 Date Data from NOAA weather station at Tricities Airport (latitude , longitude , elevation 402 ft)

24 Food and Environmental Quality Laboratory Page 24 of 77 Figure 6 Daily Weather Data Wind Rose (mph) Data from WSU AgWeathernet Station, Columbia Basin College, Pasco WA (latitude 46.25, longitude , elevation 404 ft.)

25 Food and Environmental Quality Laboratory Page 25 of 77 III. STANDARD PREPARATION Standards were prepared to bracket the range of MITC concentrations expected in the charcoal samples. The following test substances, standards, and standard dilutions were used for this study: Test substance Compound Substance No. Purity Source Methyl isothiocyanate % Chem Service Stock Solution Compound Substance No. Conc. Solvent Methyl isothiocyanate mg/ml methanol Methyl isothiocyanate μg/ml methanol Methyl isothiocyanate μg/ml methanol Dilution of Stock Solution Compound Substance No. Conc. Solvent Methyl isothiocyanate μg/ml 20% CS 2 /ethyl acetate Methyl isothiocyanate μg/ml 20% CS 2 /ethyl acetate Methyl isothiocyanate μg/ml 20% CS 2 /ethyl acetate Methyl isothiocyanate μg/ml 20% CS 2 /ethyl acetate Methyl isothiocyanate μg/ml 20% CS 2 /ethyl acetate Methyl isothiocyanate μg/ml 20% CS 2 /ethyl acetate Methyl isothiocyanate μg/mL 20% CS 2 /ethyl acetate Methyl isothiocyanate μg/ml 20% CS 2 /ethyl acetate Fortification Solutions Compound Substance No. Conc. Solvent Methyl isothiocyanate mg/ml methanol Methyl isothiocyanate μg/ml methanol Methyl isothiocyanate μg/ml methanol All standard solutions were stored in the freezer at ca. -15 C (I.D. Prancer). Dilutions are recorded in the FEQL analytical laboratory standards logbook.

26 Food and Environmental Quality Laboratory Page 26 of 77 IV. ANALYTICAL PROCEDURE A. Working Analytical Method i. Sample control and fortification For each analytical set, at least one control (blank) cartridge and one recovery fortification cartridge were extracted and analyzed in the same manner as the residue samples. The recovery fortification sample was prepared by injecting a known volume of fortification solution of MITC into a prepared charcoal cartridge. ii. Procedure An analytical method was developed and validated for determining methyl isothiocyanate (MITC) from charcoal sampling tubes. This method was adapted from California Department of Pesticide Regulation Air Monitoring for Methylisothiocyanate During a Sprinkler Application of Metam-Sodium Report EH 94-02, The procedure involved extraction of the charcoal media using a 1:4 mixture of carbon disulfide:ethyl acetate (i.e., 20% carbon disulfide in ethyl acetate) followed by sonication, and filtration through a 0.45μm Teflon membrane. The sample extract was then analyzed by gas chromatography using a nitrogen-phosphorus detector (NPD, also known as thermionic specific detection or TSD). The method limit of quantification (LOQ) was estimated to be 0.17 μg m -3 (ca ppb) with a detection limit of 0.03 μg m -3 (ca ppb) based on a 12 hour air sample at 2 L/min. See Appendix B for the working analytical method. For previous method validation and use information, refer to the following projects: FEQL-NG-0605, MITC residential community air assessment; south Franklin County, WA; FEQL-1106 Optimizing fumigant efficacy while minimizing off-target volatile emissions; FEQL-0208 Methyl isothiocyanate air sampling breakthrough evaluations; FEQL-1207A MITC residential community air assessment; Franklin County, WA FEQL-1207B Near field emissions of MITC following shank injection and chemigation metam applications; FEQL-0708 Quantification of MITC in activated charcoal air cartridges from two chemigated circles in Eastern Washington State. FEQL MITC residential community air assessment; Franklin County, WA FEQL-0808 Measuring off site movement of MITC following shank and modified center pivot chemigation application; FEQL-0809 Temperature dependent emission loss of MITC following surface application of sectagon at 75 GPA;

27 Food and Environmental Quality Laboratory Page 27 of 77 B. Quantification i. Instrumentation An Agilent Technologies 6890 N GC System using NPD with 7683B Series Injector was used for MITC detection and quantification. Integration of chromatographic data was performed using Agilent Chemstation software. Column: EC-WAX, 30m x 0.25mm, 0.25 μm film thickness Carrier gas: Ultrapure helium, column flow rate ca 2.7-mL/min. Temperatures: Detector: 260 C Injector port: 225 C Oven program: Initial: 55 C, hold for 0.09min. Ramp 10 C/min to 90 C, hold for 5 min. MITC Retention time: ca min (+/-0.05 min), and based on the observed retention times of external calibration standards in each set. Injection volume: 1 μl The hydrogen, air, and make-up gas flows were set at 3.0 ml/min, 60 ml/min, and approximately 7 ml/min, respectively over the course of the study. The NPD bead current was set at A. ii. Calculations The quantification of MITC was performed by electronic peak area measurement. MITC concentrations were calculated by linear regression from a minimum of four external standards in the concentration range of the matrix-samples. A laboratory matrix control and matrix fortified sample accompanied each analytical set. For quality control during GC analysis, all samples were bracketed with external calibration standards. For each analytical set, at least four linearity standards were used in the calculation of the linear regression curve using a spreadsheet program (Microsoft Excel ). The estimated concentration of MITC in the sample extract was corrected for dilution by multiplying by the final volume of extract. The MITC values (in µg) were calculated according to the following equations. Eq 1: Total MITC (µg) = (x µg/ml detected concentration) (Final volume of extract) For example, sample set 29 included the preparation of air sample AC3-Z-16-R (sample date 10/26/12, extracted on 11/26/12). The sample was extracted for analysis to a final volume of 5 ml. The MITC linear regression line of best fit calculated from calibration standards µg/ml to 1 µg/ml MITC (R 2 = 0.999) of this set was: Y = m X + B Y (area counts) = X(detected concentration in µg/ml)

28 Food and Environmental Quality Laboratory Page 28 of 77 The average MITC-peak area count from duplicate injections of this extract was Therefore, the concentration (in µg/ml) was: X = ( ) = µg/ml The total MITC is then calculated according to Eq. 1: µg/ml x 5 ml = 0.33 µg MITC Once the total micrograms per sample was obtained, the concentration per cubic meter air concentration was calculated by equation 2. Eq 2: μg/m 3 = (x μg total MITC per sample)/ (total m 3 of air sampled) From the example above: μg/m 3 = 0.33 μg MITC / 0.46 m 3 = 0.72 μg/m 3 or ppb MITC Each sample air concentration represents the amount of MITC collected over the specific time interval of the sample. Cartridge sampling times, and beginning and ending flow rates, were recorded in the Field Data Book and used to calculate the total amount of air sampled for each individual cartridge. The 24-hour TWA for each site was then calculated by taking an average of the two 12-hour sample air concentrations (AM and PM). The five-week seasonal TWA was calculated by averaging all of the 24-hour TWA results from all five sites for the days measured. Because air samples were taken only three days per week the actual 5-week TWA may be different than that estimated for this study. To assess overall analysis precision and percent recovery a control sample was fortified with a known amount of MITC prior to extraction. For each analytical set, percent recovery for the fortified sample was calculated using peak areas according to the Equation 3. Eq.3: % Recovery = (Fortified Peak Control Peak)Calculated total MITC x 100 Fortification Amount Example: In sample set 29, a 1g-cartridge, Z-12-FS100, was fortified with 2.5 μg of MITC. The sample extract was prepared to a final volume of 5 ml for residue determination. The linear regression line of best fit for MITC calculated from the µg/ml calibration standards (R 2 =0.999) of this set was: Y = m X + B Y (area counts) = X(detected concentration in µg/ml)

29 Food and Environmental Quality Laboratory Page 29 of 77 The average MITC peak area count for duplicate injections of this fortified sample was The corresponding control sample was none-detected. The fortified sample concentration was: ( ) = X X = = µg/ml MITC The total concentration is then calculated according to Eq. 1: µg/ml x 5 ml = 2.49 µg MITC There was no detected MITC in the control sample in this set, by Eq.3, the percent recovery for this fortified sample was: Percent Recovery = (2.49 µg) x 100 = 99.6% 2.5 µg C. Method Validation and Analytical Limits An analytical method was developed and validated for determining methyl isothiocyanate (MITC) from charcoal sampling tubes. Section IV.A of this report provides reference to previous FEQL projects for which the method was validated and employed. The method has been routinely validated at concentrations ranging from 0.25 µg/ml to 250 µg/ml. In addition to method validation, fortified matrix samples were extracted concurrently with study samples. The sample set was considered acceptable if the fortified recovery was within the range of 70%-120%. Table 4 provides results from the fortified samples extracted during sample analysis. The analytical method for the measurement of MITC was found to be rugged with an analytical method limit of quantification (LOQ) of 0.06 ppb and method limit of detection (LOD) estimated at 0.01 ppb (based on a total volume 2 L min -1 air flow for the 12-hr sampling interval). When MITC was detected but the values per air volume sampled were lower than the calculated LOQ but greater than the method limit of detection, concentrations are reported as parenthetical values, <LOQ. D. Interferences There were no interferences in the chromatographic window of retention time for MITC. E. Confirmatory Techniques Analytical standards were used to detect the presence of MITC in air samples by retention time. In the event that the GC did not confirm the presence of MITC, values were reported as Not Detected (ND). When MITC was detected but the values per air volume sampled

30 Food and Environmental Quality Laboratory Page 30 of 77 were lower than the calculated limit of quantitation but greater than the method limit of detection, concentrations were reported as parenthetical values, <LOQ. F. Time Required For Analysis The time required for an experienced person to work up a set of samples (10 samples plus QC) for analysis was approximately 2.5 hours. The time required for the GC analysis of a single sample was approximately 9 minutes. The duration of the analysis of a sample set depended upon the number of samples in a set and was automated using the auto sampler associated with the instrument. V. AIR MONITORING RESULTS A. Storage Stability A -80 o C storage stability evaluation for MITC on charcoal-filled glass cartridges was completed and reported for the study FEQL-NG-0605, covering a storage interval of 85 days. For this 2012 project, no samples were kept in frozen storage for more than 37 days. B. Field Fortification Samples Field fortifications (field spikes) were performed routinely over the course of the monitoring study. For field fortifications (FF), the intakes of the air sampling cartridges were spiked with a known amount of MITC and placed on the sampling mast located outside at the WSU-Tri-City campus. Air was sampled through the FF cartridges at a rate of 2 L min -1 for ca. 12 hours during the residential air sampling period. Additionally, to verify sample integrity during transport and storage, spiked field banks (SFB) were fortified and routinely accompanied interval samples and unfortified charcoal cartridge field blanks (FB) over the residential sampling period. Table 3a provides a summary of the percent recoveries for the seven field fortifications performed throughout the season. The recoveries from the field fortification samples were 90 ± 27% (n= 2, 0.25 µg MITC; n= 3, 2.5 µg MITC; and n= 2, 25 µg MITC). The high level of volatility in the recovery of the field fortification samples is explained by the fact that all corresponding field fortification control cartridges recorded MITC residues at the field fortification testing site. When field fortification samples are exposed to traces of MITC in the air it becomes more difficult to have consistent recovery values of 100%, due to the complications of accurately off-setting field fortifications with field fortification controls. The 12 and 4-hr TWA MITC residential air concentrations were not corrected for field fortification percent recovery. The average recovery for the spiked field blank samples that routinely accompanied the shipment of samples from the field was 89.5 ± 6% (n=14) (Table 3b).