Air Monitoring (2012)/Page 2 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 2 target rate of 2 pints product/acre (0.878 lb ai/A) in approximately 20 GPA of water. A buffer (BU-pHER) 1 was added to the water to reduce the pH of the sp ray solution from 7.0 to 5.5. The actual application rate was reported as 0.877 lb ai/acre. The appli cation was made on September 9, 2011 between 9:10 – 10:40 am using a ground broadcast method (tractor mounted sprayer). The boom height was 20 inches above the crop canopy. The alfalfa was cut 14 days prior to application. The crop height was 10 inches at the time of application; the alfalfa field had just dried after irrigation.

Air sampling was conducted for three days during and after the application and was performed using SKC 226-52 XAD-2 sampling tubes, Tygon tubing, and SKC air sa mpling pumps set to a flow rate of 1 L/min. Air samples were collected from eight off-field mon itoring stations placed uniformly around each field (30 m from the edge of the treated area) during the first sampling period which included the application event. The sampling height of the off-field monitors w as 1.5 m. After the application, an on-site profile monitoring station was set up in the center of the fiel d which measured concentrations at heights of 0.15, 0.33, 0.55, 0.90, and 1.5 m. The on-field air sampl es were taken at approximately 6 hour intervals from time 0 (after the application) through 24 hours and at 12 hour intervals from time 24 to 72 hours. The 12 hour samples coincided approximately with sunrise an d sunset and were centered at 07:00 and 19:00 hours when possible.

On-site meteorological conditions were monitored continuously at the s ite. Soil samples were collected one day prior to application from four locations acro ss the plot at depths of 0-6”, 6-12”, 12-18”, and 18- 24”. These pre-application soil samples were analyz ed for texture, bulk density, CEC, pH, maximum water holding capacity, organic matter, and soil moistu re by Agvise Laboratories. The soil texture was classified as clay loam (no soil series data reporte d). The organic matter ranged from 0.82-2.1%. The soil pH increased as depth increased ranging from 7.7-8.4.

The samples were analyzed for residues of chlorpyr ifos, chlorpyrifos-oxon, and 3,5-6 tricloropyridinol (TCP) using Dow AgroScience Analytical Method “Det ermination of Residues of Chlorpyrifos in Air Sampling Tubes by High Performance Liquid Chromatography with Mass Spectrometry Detection.” The limit of quantification (LOQ) was 2 ng per tube. Fi eld fortification was conducted during two sampling periods, using three different fortification levels. Air concentrations were calculated in terms of μ 

### g/m 3



### .

Flux rates for chlorpyrifos and total residues in μg/m 2 -s for the first period when the application was in progress (Sampling Period 1) were calculated using th e Indirect Flux Method. Flux rates for the other sampling periods were calculated using both the In tegrated Horizontal Flux (IHF) method and the Aerodynamic (AD) method. Total toxic residues are de fined as the sum of the chlorpyrifos concentration

and the oxon concentration which has been corrected using the toxicity adjustment factor (TAF) of 12. 2

Air samples were initially corrected to account for formation of oxon on the XAD-2 resin (Appendix G). The samples were corrected using the averag e field fortification recoveries. Residues ≤ 0.275 μg were corrected for the average low level field fortification recovery (81.1% for chlorpyrifos and 86.7% for the total toxic residues), residues >1.25 μg were corrected for the average high level field fortification recovery (82.0% for chlorpyrifos and 84.5% for total toxic residues), and residues between 0.275 and 1.25 μg were corrected for the average mid-level field fo rtification recovery (75.3% for chlorpyrifos and 79.6% for total toxic residues). Values reported as below the LOQ were assigned a value of 1⁄2 LOQ.

1 BU-pH-ER is a spray adjuvant designed to improve the e ffectiveness of certain agricu ltural chemicals by reducing the pH of higher alkaline water and contains phosphoric acid, propylene glycol, casuistic soda as well as other

constituents. 2 Email from Wade Britton (OPP/HED) to Roche lle Bohaty (OPP/EFED) September 10, 2012.Air Monitoring (2012)/Page 3 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 3 Reviewer-estimated flux rate values using the Indir ect Method for Period 1 (application period) were 0.22 μg/m 2 -s (for chlorpyrifos and 0.46 μg/m 2 -s for total toxic residues (based on parent toxicity equivalent units). The r 2 values for all of the regressions were above 0.81. The reviewer-estimated flux rate values for chlorpyrifos compare well with the study author’s results even though the study authors did not

correct for field fortification.

The chlorpyrifos flux calculated for the first peri od after application using the AD method was 0.824 μg/m 2 -s. The flux then declined over the next 24 hour s, followed by a second smaller peak of 0.081 μg/m 2 -s. Flux generally continued to decrease over the remainder of the study and was 0.002 μg/m 2 -s by the last sampling interval.

The chlorpyrifos flux calculated for the first period after application using the Indirect Method was 0.591 μg/m 2 -s. The highest flux was observed during the subseque nt period (Period 2) at a considerably higher level of 0.759 μg/m 2 -s. The flux then declined over the next 24 hours, followed by a second smaller peak of 0.167 μg/m 2 -s. Flux generally continued to decrease over the remainder of the study and was 0.004- 0.005 μg/m 2 -s by the last sampling interval.

The reviewer-estimated flux rates for chlorpyrifos using the AD method were comparable to those estimated by the study author. The reviewer-estimat ed flux rate values for chlorpyrifos using the IHF method were much higher than those estimated by the study author. A review of the study author’s calculations indicated that Zp (height of plume) was truncated at 150 cm, which in turn yielded lower flux

rate estimates. The reviewer’s calculations were based on Z p (the height of the plume top in units of meters; see equations in the Flux Calculations section of this document). The flux trends exhibited by both those estimated by the reviewer and tho se by the study authors were very similar.

In this study approximately 29% of the applied chlorpyrifos was observed to volatilize off the field during the first 24 hours following application.

The total toxic residue flux calculated for the firs t period after application using the AD method was 1.102 μg/m 2 -s. The flux then declined over the next 24 hours, followed by a second smaller peak of 0.186 μg/m 2 -s. Two smaller peaks occurred at 0.034 μg/m 2 -s and at 0.052 μg/m 2 -s. Flux was 0.002-0.003 μg/m 2 -s by the last sampling interval.

The total toxic residue flux calculated for the first pe riod after application using the Indirect Method was 0.791 μg/m 2 -s. The highest flux was observed during the subsequent period (Period 2) at a considerably higher level of 1.27 μg/m 2 -s. The flux then declined over the next 24 hours, followed by a second smaller peak of 0.384 μg/m 2 -s. Two smaller peaks occurred at 0.057 μg/m 2 -s and at 0.038 μg/m 2 -s. Flux was 0.007-0.010 μg/m 2 -s by the last sampling interval.

COMPLIANCE :

Signed and dated GLP, Quality Assura nce, and Data Confidentiality statem ents were provided. The study sponsor waived claims of confidentiality within the sc ope of FIFRA Section 10 (d)1(A), (B), or (C). The Study Report indicated that the study was conducte d under EPA Good Laboratory Practice Standards (40 CFR Part 160) and OECD ENV/MC/CHEM (98)17, with the following exceptions: GPS coordinates were collected with a non-GLP compliant instrument; the crop history and chlorpyrifos use were obtained from the grower; sunrise/sunset and cloud cover in formation were obtained from the National Climate Data Center. None of the noted field phase GLP devi ations had any impact on the validity of the study.Air Monitoring (2012)/Page 4 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 4 I. MATERIALS AND METHODS

A. MATERIALS :

1. Test Material :

Formulation: The test substance is Lorsban Advanced Insecticide (Reg. No. 62719-591), a liquid formulation containing 3.66 lb ai/gal (439 g ai/L; 40.2% w/w) chlorpyrifos as the active ingredient. Lot/Batch #: A lot number for the test substance was not provided. Lot numbers

for the reference substances we re: MM 930503-17 (chlorpyrifos reference substance); YC2-106153-76 (chlorpyrifos-oxon reference substance); and 597-F0580-42A (TCP reference substance). Formulation guarantee: The Certificate of Analysis for the test product was not provided. Purity: Reference standard of chlorpyrifos was analyzed and found to have a purity of 99.8% (expiration date not reported). Reference standard of chlorpyrifos-oxon was analyzed and found to have a purity of 98% (expiration date not reported). Reference standard of TCP was analyzed and found to have a purit y of 100% (expiration date not reported). The stable isotope intern al standard of chlorpyrifos was analyzed and found to have a purity of 100% (expiration date 3/17/10). The stable isotope internal standard of chlorpyrifos-oxon was analyzed and found to have a purity of 95% (expiration date not reported). CAS No. (s): 2921-88-2 Storage conditions: Formulation was stored at ambient temperatures, ranging from 19 to

34oC.

2. Relevance of Test Material to Proposed Formulation(s) :

The test product used in this study was Lorsban Ad vanced Insecticide, containing 3.66 lb ai/gal (40.2% w/w) chlorpyrifos. A label was not provided with the study report but the reviewer was able to locate a

label on EPA’s Pesticide Product Labe l System (PPLS) website. The test product formulation appears to

be the same as that listed in the label. Discussion of the uncertainties associated with the formulation used in this study is provided in the Reviewer’s Comments ( RC 1 ) section of this document.

B. STUDY DESIGN :

The study protocol was provided in advance and al so included in the study report. EPA provided comments on the protocol; however, these comments arrived after the study had already started. Many of EPA’s comments were addressed in the study and th e study authors provided a response to each comment in the study report. There were eight amendments and three deviations from the protocol. Protocol amendments involved: 1) removing Appendix B, 2) changing the foliage sample size from 1 kg to 0.5 kg, 3) changing the meteorological monitoring heights fo r relative humidity, solar radiation, and barometric pressure and adding the use of a buffer to lower pH in the spray solution, 4) providing the name and address of the principal analyst, 5) providing the deta ils of the laboratory stability study and changing the name of the principal investigator, 6) supplying s upplemental information to the protocol regarding the analytical method, 7) authorization to reactivate th e study on the master schedule to allow it to be amended to change an incorrect field fortification, and 8) authorization to reactivate the study on the

master schedule to allow it to be amended to cha nge an incorrect chain of custody date. Protocol deviations involved: 1) the front and back sections of the first two air sampling tubes were analyzedAir Monitoring (2012)/Page 5 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 5 separately instead of the first four tubes as called for in the protocol and analyti cal set recoveries were not calculated for each analytical set, 2) the air temperatur e was collected at 1.7 m, and 3) the leaf area index was not collected according to the protocol (see RC 2 ).

The study author stated that none of the deviations had any negative effect on the overall study objectives.

1. Site Description :

Test location: The study was conducted on a 7.59 acre (575 ft x 575 ft) field in Los Banos, California. The plot had establis hed alfalfa that was in its fourth year of production. The plot area was flat and was free of obstacles around the edges. The location of the field is shown in Figure 1 (provided at the end of this report).

Meteorological Data: Meteorological conditions during application and monitoring were typical for the region and season that the application was made. The air temperature and wind were moderate with daily maximum air temperatures that ranged from the high 20’s to the low 30’s (°C). No precipitation occurred during the course of the study.

Meteorological equipment was establis hed within 4 meters of the treated area. The wind monitor orientation was set to true North; the field orientation was approximately 15 degrees east of North. Details of the sensor heights and the meteorological parameters for which data were

collected are illustrated in Table 1 . The location of the meteorological equipment is shown in Figure 2 (provided at the end of this report).

Irrigation during the study was not discu ssed in the study report. Prior to application, the alfalfa field was irrigated and dried.Air Monitoring (2012)/Page 6 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 6 Table 1. Summary of Meteorological Parameters Measured in the Field

Parameter Monitoring height (m) Averaging Period
Wind speed/Wind direction 1 0.15, 0.33, 0.55, & 0.9 1 minute, hourly

Ambient air temperature 1 0.15, 0.33, 0.55, & 0.9 1 minute, hourly
Relative humidity 1.7 hourly

Solar radiation 1.7 hourly
Precipitation 1.8 hourly
Barometric pressure 0.9 hourly

1. While the protocol and study indicated that wind speed and temperature would be co llected at 1.8 m, data were only provided for up to 0.9 m in the final report.

Soil Sampling: Soil samples were collected one day prior to application from four locations across the plot at depths of 0-6”, 6-12”, 12-18”, and 18-24”. Soil samples were analyzed for texture, bulk density, CEC, pH, maximum water holding capacity, organic matter, and soil moisture by Agvise Laboratories. Soil properties are provided in Table 2

.

Table 2. Summary of Soil Analysis Depth (in) 0 to 6 6 to 12 12 to 18 18 to 24 USDA Texture Class Clay Loam Cl ay Loam Clay Lo am Clay Loam USDA Sand (%) 31 29 31 33 USDA Silt (%) 34 36 34 28 USDA Clay (%) 35 35 35 39 Bulk Density, disturbed (gm/cc) 1.18 1.22 1.20 1.23 Cation Exchange Capacity (meq/100 g) 23.2 23.7 23.7 25.5 pH (1:1 soil:water ratio) 7.7 8.1 8.2 8.4 Maximum Water Holding Capacity (g/100 g) 45.4 38.5 36.8 39.1 Moisture (% @ 1/3 bar) 26.0 27.7 27.3 28.9 Moisture (% @ 15 bar) 14.8 16.0 16.2 16.2 Moisture before monitoring (%) 15.6 19.5 21.7 21.8 Organic Matter (%) 2.1 1.7 1.2 0.82

2. Surface Monitored:

Plant Species: Alfalfa: AmeriStand 802 variety. Discussion of the uncertainties associated with the crop used in this study is provided in the Reviewer’s

Comments ( RC 3 ) section of this document

Residential or Public Area: The field site was re presentative of current commercial practice in the California Central Valley. Discussion of the uncertainties associated with the site used in this study is provided in the Reviewer’s Comments ( RC

4 ) section of this document

3. Physical State of Formulation as Applied:

Lorsban Advanced Insecticide (US EPA Reg. No. 62719-591) is a liquid formulation (water emulsion/emulsifiable concentrate) containing 3.66 lb ai/gal (439 g ai/L; 40.2% w/w) of the active ingredient chlorpyrifos.Air Monitoring (2012)/Page 7 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 7 4. Application Details :

Application rate(s): The target application rate was 2 pints product/A (0.878 lb ai/A). The actual application rate was 0.877 lb ai/A (92.5% of the target rate). The

maximum label rate for alfalfa is 2 pints ai/A (0.878 lb ai/A).

Application Regime: One broadcast spray application was made on September 9, 2011 between 9:10 and 10:40 am. The alfalfa was cut 14 days prior to application. The crop height was 10 inches at the time of application; the alfalfa field had just dried after irrigation.

Spray Volume: A spray volume of approximately 20 gallons per acre (GPA) was used for the application. A buffer (BU-pH-ER) 1 was added to the water to reduce the pH of the spray solution from 7.0 to 5.5.

Application Equipment: A Massy Ferguson 2405 tractor-mounted boom sprayer equipped with 15 teejet nozzles spaced 20 inches apart. The boom height was 20 inches above the crop.

Equipment Calibration According to the study pr otocol, equipment calibration results will be Procedures: recorded in the field raw data notebook. No further equipment calibration details were pr ovided in the Study Report.

5. Flux Air Sampling Procedures :

Method and Equipment: For the first flux period (during application), eight off-field monitoring stations were placed uniformly around the field in eight directions at approximately 30 m from the field edges ( Figure 2 ). The sampling height of the off-field monitors was 1.5 m. The on-site profile monitoring station (located approximately at the center of each field) measured concentrations at heights of 15, 33, 55, 90, and 150 cm. Sampling using on-site samplers began less than 2 hours after the center of the plot was treated and was continued for the remainder of the study.

Air sampling was performed using SKC 226-52 XAD-2 resin sampling tubes, Tygon tubing, and SKC air sampling pumps using a flow rate of 1 L/min during the duration of the study. The sorbent tubes were covered with a PVC tube to protect them from sunlight.

Sampling Procedure: The flow rate was measure d at the beginning and end of each monitoring period and recorded. The tubes were removed, capped, and placed in pre-labeled re-sealable bags. Samples were stored frozen (temperature not reported) prior to shipment.

Replicates: Air samples were collected fro m the eight off-field monitoring stations during the application. The air flow was started just prior to application and was concluded after the applicati on was complete. Air samples were collected from the on-field profile monitoring stations approximately 24 hours prior to application. Following application, the on-field air samples were taken at approximately 6 hour intervals from time 0 (after the application) through 24 hours and at 12 hour intervals from time 24Air Monitoring (2012)/Page 8 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 8 to 72 hours. The 12 hour samples coincided approximately with sunrise

and sunset and were centered at 07:00 and 19:00 hours when possible. Single replicates were collected at each sampling station from each sampling period. 6. Sample Handling :

The samples were maintained frozen (temperature not reported) at the field facilities until they were shipped frozen via FedEx to Dow Agro Sciences for analysis. Samples were received at the analytical facility on September 13, 2011 throu gh September 15, 2011 and were stor ed at approximately -20 oC until extraction. The maximum length of frozen storage for the samples from sample collection to analysis was 285 days. Sample extracts were stored 0-8 days prio r to analysis and storage conditions for the extracts were not reported.

7. Analytical Methodology :

Extraction method: The contents of each OSHA Versatile Sampler (OVS) tube were divided into two separate samples. The front section (polytetrafluoroethylene [PTFE] retainer ring, glass fiber filter, 270 mg of XAD-2 sorbent, and the foam separator plug) and the b ack section (140 mg of XAD-2 sorbent and a foam retention plug). Front and back section samples were initially analyzed separately. Since residue levels of the back sections were non-detectable or relatively inc onsequential, the remainder of the samples were analyzed together to represent one sample.

Residues of chlorpyrifos, chlorpyrifos-oxon, and 3,5-6 tricloropyridinol (TCP) were extracted from the air sampling tubes by sonicating and shaking with an acetonitrile/methanol solution (1:1, v:v). Samples were either diluted or concentrated prior to being brought to a final volume of 1.0 mL using an aqueous 0.2% acetic acid solution. 50 μL of a mixed internal standard solution containing 0.1 μg/mL of chlorpyrifos-d10 and 0.1 μg/mL of 3,5,6-trichloropyridin-2-ol-1- 15 N-2,6- 13 C was added to each sample and calibration standard. The solution was mixed and analyzed using LC-MS/MS.

Detection methods: The air sampling tube extracts were analyzed for chlorpyrifos, chlorpyrifos-oxon, and TCP by liquid chromatography with positive-ion electrospray tandem mass spectrometry. A summary of the LC-MS/MS

conditions are shown in Table 3

.Air Monitoring (2012)/Page 9 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 9 Table 3. Typical HPLC/MS/MS Instrument Parameters

Instrument: Agilent Model 1200

Column: Phenomenex Luna C-18, 50 x 2.0 mm, 5 μm

Injection Volume: 20 μl

Mobile Phase A:

Mobile Phase B: Water containing 0.1% acetic acid Acetonitrile containing 0.1% acetic acid

Flow Rate: 0.40 mL/min

Steps Time (min) Flowrate (mL/min) Phase A Phase B

4:00 0.4 75 25

0:00 0.4 75 25

10:00 0.4 0 100 Expected Retention Times Not reported.

Ionization Mode: Positive

Transitions: Chlorpyrifos Chlorpyrifos-oxon

TCP Chlorpyrifos-d10 TCP [M+3] 350.0 → 197.8 and 349.9 → 97.0

334.1 → 277.9 and 334.1 → 197.8

198.0 → 134.0 and 198.0 → 107.0

359.9 → 198.9

202.9 → 109.1

Method validation: A separate method validation study was not conducted prior to the start of the study. The analytical method was validated concurrently by analyzing an appropriate number of air sampling tubes spiked individually at the limit of quantification (LOQ), the limit of detection (LOD), and concentrations high enough to cover the high-end of the expected residues. The LOQ was 2 ng per tube. The LOD was 0.65 ng per tube.

Instrument performance: A series of calibration st andards were injected with each set to quantify residues in the samples. These calibration standards generated a linear plot of chlorpyrifos, chlorpyrifos-oxon, or TCP versus area with 1/x weighting.

Quantification: Quantitation of residues in all samples was achieved by using a

calibration curve for each of the reference substances at multiple

concentrations. 8. Quality Control :

Lab Recovery: Analytical method perform ance was monitored through concurrent analysis of freshly fortified contro l samples. Control air sampling tube samples were fortified with chlorpyrif os at concentrations of 2, 500, 2000, 3000, and 6500 ng/tube and with chlorpyrifos-oxon and TCP at concentrations of 2, 500, and 2 000 ng/tube. Individual concurrent laboratory recoveries ranged from 58% to 99% with an overall mean recovery of 83.7% ± 7.82% (n= 32) for chlorpyrifos, from 61% to 104% with an overall mean recovery of 78.5% ± 11.3% (n= 22) for chlorpyrifos-oxon, and from 61% to 108% with an overall mean recovery of 89.5% ± 12.1% (n= 22) for TCP.Air Monitoring (2012)/Page 10 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 10 Field blanks: During the day before th e application, background sampling was conducted for approximately 12 hours at two off-field sample locations. Background chlorpyrifos and chlorpyr ifos-oxon concentrations were not

detected.

Triplicate field blanks were weathered with the 6-hr and 12-hr field fortification spikes. Residues of chlorpyrifos and chlorpyrifos-oxon

were not detected.

Field Fortifications: Fortified samples were prep ared in the analytical laboratory and shipped to the field prior to the application. Spikes were prepared in triplicate at loading levels that approximate the levels anticipated on the air samples.

The solid sorbent tubes were fortified with chlorpyrifos and chlorpyrifosoxon at 50, 500, and 2,000 ng/tube. Air was drawn through the spiked tubes at similar flow rates and sampling durations (6 and 12 hours) as used for the collection of the on-field air monitoring samples. Field spikes were handled, stored, shipped an d analyzed in the same manner as all other samples. The field for tification experiments were conducted during Periods 5 and 7 for chlorpyrifos and Periods 5 and 9 for chlorpyrifos-oxon.

Table 4 provides a summary of the field fortification recoveries. While some individual field fortification samples indicated low recoveries the overall averages were between 70 and 120 % (generally acceptable range criteria). The overall average recove ries for chlorpyrifos were 81.1%, 75.3%, and 82.0% at the 0.05, 0.5, and 2.00  g fortification levels, respectively. The overall average rec overies for total toxic residues were 86.7%, 79.6%, and 84.5% at the 0.05, 0.5, and 2.00  g fortification levels, respectively.

The field fortification levels bracketed the expected residues in the field.

Table 4. Summary of Fiel d Fortification Recoveries

Analyte Trapping

Interval

(hr) 1 Fortification

Level (μg/sample) n Range of

Recoveries 1
(%) Average Recovery ±

Standard

Deviation (%) Overall Average Percent Recovery ± Standard Deviation (%)

Low Level Mid Level High Level

Chlorpyrifos 6 0.05 3 76.5-98.0 87.0 ± 10.8

81.1 ± 9.84 75.3 ± 13.4 82.0 ± 4.11 0.50 3 49.1-77.4 66.9 ± 15.5

2.00 3 74.8-83.9 79.7 ± 4.59

12 0.05 3 71.2-80.6 75.3 ± 4.83

0.50 3 81.6-85.5 83.6 ± 1.95

2.00 3 82.1-86.8 84.2 ± 2.38

Total Toxic

Residues 2 6 0.05 3 82.8-104 92.6 ± 10.9

86.7 ± 9.98 79.6 ± 12.6 84.5 ± 3.43 0.50 3 54.5-83.3 72.6 ± 15.8

2.00 3 78.7-85.3 82.6 ± 3.46

12 0.05 3 77.5-86.9 80.9 ± 5.24

0.50 3 85.0-88.2 86.6 ± 1.60

2.00 3 84.1-89.2 86.4 ± 2.60Air Monitoring (2012)/Page 11 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 11 1 Presented values represent “with flow” samples.

2 Total toxic residues = chlorpyrifos + total oxon. The chlorpyrifos and oxon values are from the chlorpyrifos field fortification samples.

Travel Recovery: Travel recovery samples were not used in this study.

Application Verification: Tank mix samples were not collected for this study. However, the application rate was confirmed us ing monitoring pads. Prior to application, at least 12 filter pads, measuring 301.4 cm 2 , were placed in shallow foil pans that were put on supports immediately above the plant canopy. Immediately following application, the pads were collected, individually bagged, and stored frozen. The filter pad samples ranged from 1,398 to 4,341  g/sample and averaged 2,751  g/sample. This corresponds to 0.878 lb ai/A, which is 92.5% of the target application

rate.

Storage Stability: Sorbent tu bes were prepared and spiked chlorpyrifos, oxon, or TCP at 50, 500, and 2,000 ng/tube. The samples were aged in a laboratory hood

at ambient conditions for 6 and 12 hours with airflow at 1 L/min. TCP

was stable in the sorben t tubes. Oxon was not stable showing substantial conversion to TCP. Chlorpyrifos w as not stable showing conversion to oxon. The petitioner used a simple linear regression of % conversion vs. time to correct the chlorpyrifos concentrations. See APPENDIX G for a more thorough discussion of the correction factor development.

Table 5 provides a summary of the storage stability recoveries.

Table 5. Summary of Storage Stability Recoveries

Analyte Trapping

Interval

(hr) 1 Fortificatio

n Level (μg/sample) n Range of

Recoveries 1
(%) Average Recovery ±

Standard

Deviation (%) Overall Average Percent Recovery ± Standard Deviation (%)

Low Level Mid Level High Level

Chlorpyrifos 6 0.05 3 81.0-91.9 86.6 ± 5.45

91.6 ± 6.61 97.3 ± 10.1 94.2 ± 3.25 0.50 3 89.6-92.7 91.3 ± 1.58

2.00 3 91.3-93.4 92.5 ± 1.10

12 0.05 3 95.5-98.6 96.7 ± 1.69

0.50 3 89.7-112 103 ± 11.9

2.00 3 91.7-100 95.8 ± 4.15

Total Toxic

Residues 2 6 0.05 3 81.0-91.9 86.6 ± 5.45

91.6 ± 6.61 97.3 ± 10.1 94.2 ± 3.25 0.50 3 89.6-92.7 91.3 ± 1.58

2.00 3 91.3-93.4 92.5 ± 1.10

12 0.05 3 95.5-98.6 96.7 ± 1.69

0.50 3 89.7-112 103 ± 11.9

2.00 3 91.7-100 95.8 ± 4.15

1 Presented values represent “with flow” samples.

2 Total toxic residues = chlorpyrifos + total oxon. The chlorp yrifos and oxon values are from the chlorpyrifos storage stability samples. Note: storage stability recoveries for chlorpyrifos were calculated from total residues because oxon

contributions were minimal.Air Monitoring (2012)/Page 12 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 12 Breakthrough: Front and back sections were in itially analyzed separately. As residue

levels in the back sections were nondetectable, breakthrough analysis

was discontinued.

C. FLUX CALCULATIONS :

Flux rates for Sampling Period 1 were calculated usi ng the Indirect Flux Method. Flux rates for the remaining sampling periods were calculated using the Integrated Horizontal Flux (IHF) Method and the Aerodynamic (AD) Method. A brief descr iption of these methods is given below.

1. Flux determination using the Indirect Method (IM) :

The indirect method, commonly referred to as th e “back calculation” method, was the technique employed for estimating flux rates from fields during application. In the indirect method, air samples are collected at various locations outside the boundaries of a treated field. Meteorological conditions, including air temperature, wind speed, an d wind direction, are also collected for the duration of the sampling event. The dimensions and orientation of the treated field, the location of the samplers, and the meteorological informati on is used in combination with the ISCST3 dispersion model (Version 02035) and a unit flux rate of 0.001 μg/m2•s to estimate concentrations at the sampler locations. Since th ere is a linear relationship between flux and the concentration at a given location, the results from the ISC model runs are compared to those concentrations actually measured and a regressi on is performed, using the modeled values along the x-axis and the measured values along the y-ax is. If the linear regression does not result in a statistically significant relationship, the regression may be rerun forcing the intercept through the origin, or the ratio of averages between the monitored to modeled concentrations may be computed, removing the spatial relationship of th e concentrations. The indirect method flux back calculation procedure is described in detail in Johnson et al. , 1999.

2. Flux determination using the integrated horizontal flux (IHF) method:

The integrated horizontal flux method, also re ferred to as the “mass balance” method, was the technique employed for estimating flux rates from fi elds following application. In the integrated horizontal flux method, a mast is erected in th e middle of the treated field and concentration samples are typically collected at four or five di fferent heights, ranging from approximately 0.5 to 5 feet. Likewise, wind speed data are collected at a variety of heights. A log-linear regression is performed relating the natural logarithm of the sa mple height to the air concentration and wind speed following the log law relationships for the atmospheric boundary layer. These relationships are then incorporated into an equation to estim ate flux. The methods to estimate flux and related equations are presented in Majewski et al. , 1990. The equation for estimating flux using the integrated horizontal flux method is the following expression:



# 

 p Z

Z 

### dz u c

x P

0 

### 1

where P is the volatile flux in units of  g/m 2 ·s, 

### c is the average pesticide residue concentration in

units of  g/m 3 at height Z in units of meters, 

### u is the wind speed in units of m/s at height Z, x is the fetch of the air trajectory blowing across the field in units of meters, Z 0 is the aerodynamic surface roughness length in units of meters, Z p is the height of the plume top in units of meters,Air Monitoring (2012)/Page 13 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 13 and dz is the depth of an incremental layer in units of meters. Following trapezoidal integration, the above equation is simplified as follows (Yates, 1996):



#     P Z

Z 

### dz D z Ln C B z Ln A

x P

0 

### ) ) ( * ( * ) ) ( * ( 1

where A is the slope of the wind speed regression lin e by ln(z), B is the intercept of the wind speed regression line by ln(z), C is the slope of the concentration regression by ln(z), D is the intercept of the concentration regression by ln(z), z is the height above ground level. Z p can be determined from the following equation:



##        



 C D Z P 

### 1

. 0 exp

The minimum fetch requirement of 20 meters for this method to be valid was satisfied at all times. The raw wind speed and wind direction data at varying heights were averaged for the concentration sampling durations. The wind direc tion values were used to calculate a fetch at every minute, which then was av eraged for the concentration sam pling periods. Finally, the period averaged wind speed values were used al ong with the natural logarithm of the height measurements to calculate regression co efficients (slope, intercept, and r 2 ) for each period. Period averaged meteorological parameters fo r each field and the meteorological regression coefficients are shown in Appendix B.

3. Flux determination using the Aerodynamic Method (AD) :

The aerodynamic method, also referred to as the “flux-gradient” method, was the technique employed for estimating flux rates from fields following application. In the aerodynamic method,

a mast is erected in the middle of the treated field and concentration samples are typically collected at four or five different heights, ra nging from 0.5 to 10 feet. Likewise, temperature and wind speed data are collected at a variety of he ights. A log-linear regression is performed relating the natural logarithm of the sample height to the concentration, temperature, and wind speed. These relationships are then incorporated into an equation to estimate flux. These methods to estimate flux and related equations are presented in Majewski et al. , 1990. The equation for estimating flux using the aerodynamic method is Thornthwaite-Holzman Equation which is shown in the following expression:

2

1 2 2



### ] [ln ) )( (

         



z z u c k P

p m



###  

where P is the flux in units of  g/m 2 ·s, k is the von Karman’s constant (dimensionless ~0.4), Δ 

### c is the vertical gradient pesticide residue concentration in air in units of  g/m 3 between heights z top and z bottom in units of meters, Δū is the vertical gradient wind speed in units of m/s between heights z top and z bottom , and 

### 

m and 

### 

p are the momentum and vapor stability correction terms
respectively. Following the conditions expected in the neutrally stable internal boundary layer characterized by an absence of convective (buo yant) mixing but mechanical mixing due to wind shear and frictional drag, a log-linear regression is performed relating the natural logarithm of theAir Monitoring (2012)/Page 14 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 14 sample height to the concentration, temperat ure, and wind speed. The adjusted values of the concentration, temperature, and wind speed from th is regression is incorporated into the equation above to arrive at the following equation, which is ultimate used to compute the flux.

2 2



### ln ) )( ( ) 42

. 0 (

          



bottom top

p m zbottom ztop zbottom ztop



### z z u u c c Flux

 

where 

### 

m and 

### 

p are internal boundary layer (IBL) stability correction terms determined
according to the following conditions based on the calculation of the Richardson number, R i :



### Equation x 3 

#   2 

### 16

. 273 2 ) )( )( 8

. 9 (

zbottom ztop zbottom ztop zbottom ztop bottom top

i



### u u T T T T z z R

     

   

           



where T ztop and T zbottom are the regressed temperatures at the top and bottom of the vertical profile

in units of °C.

if R i >0 (for Stagnant/Stable IBL) 

##   33

. 0 

### 16 1 i m 

### R    and 4

. 0 

### ) 34 1 ( 885

. 0 i p 

### R   

if R i <0 (for Convective/Unstable IBL) 

##   33

. 0 

### 16 1 



###   i m 

### R  and 4

. 0 

### ) 22 1 ( 885

. 0





###   i p 

### R 

The minimum fetch requirement that the fetch is 100 times the highest height of the air sampler

for this method to be valid was not satisfied at all times. The raw wind speed and temperature data at varying heights were averaged for th e concentration sampling durations. The period averaged wind speed and temperature values were used along with the natural logarithm of the height measurements to calculate regression coefficients (slope, intercept, and r 2 ) for each period. Meteorological parameters for each averaging peri od and the regression coefficients are shown in Appendix D. The aerodynamic method used to estimate flux and related equations are presented in Majewski et al. , 1990.

II. RESULTS AND CALCULATIONS

Chlorpyrifos and Total Toxic Residue Concentrations

Air samples were initially corrected to account for formation of oxon on the XAD-2 resin (Appendix G). Air samples were corrected using the average field fortification recoveries. Residues ≤ 0.275 μg were corrected for the average low level field fortification recovery (81.1% for chlorpyrifos and 86.7% for the total toxic residues), residues >1.25 μg were corrected for the average high level field fortification recovery (82.0% for chlorpyrifos and 84.5% for total toxic residues), and residues between 0.275 and 1.25 μg were corrected for the average mid level field fo rtification recovery (75.3% for chlorpyrifos and 79.6% for total toxic residues). Values reported as be low the LOQ were assigned a value of 1⁄2 LOQ. Total toxic residues were estimated by summing the chlorpyrifos concentration and oxon concentration which was corrected using the relative potency factor (TAF of 12X) 2

.Air Monitoring (2012)/Page 15 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 15 Flux Rate Estimates

Reviewer-estimated flux rate values using the Indir ect Method for Period 1 (application period) were 0.22 μg/m 2 -s for chlorpyrifos and 0.46 μg/m 2 -s for total toxic residues. The r 2 values for all of the regressions

were above 0.81. Calcul ations are provided in APPENDIX A

.

Chlorpyrifos

The reviewer-estimated flux rate valu es for chlorpyrifos are presented in Table 6 for AD Flux and Table

7 for IHF along with those estimated by the st udy author. Regression results for the sampler concentrations are provided in APPENDICES C (IHF) and E (AD).

The chlorpyrifos flux calculated for the first peri od after application using the AD method was 0.824 μg/m 2 -s. The flux then declined over the next 24 hour s, followed by a second smaller peak of 0.081 μg/m 2 -s. Flux generally continued to decrease over th e remainder of the study and was 0.002 μg/m 2 -s by the last sampling interval.

The chlorpyrifos flux calculated for the first period after application using the Indirect Method was 0.591 μg/m 2 -s The highest flux was observed during the subsequent period (Period 2) at a considerably higher level of 0.759 μg/m 2 -s The flux then declined over the next 24 hours, followed by a second smaller peak of 0.167 μg/m 2 -s at Sampling Period 6. Flux generally c ontinued to decrease over the remainder of the study and was 0.004-0.005 μg/m 2 -s by the last sampling interval.

Table 6. Estimated Flux Rates for Chlorpyrifos Using AD Method

Period Sample Start

Times Sample End

Times Duration (hh:mm) Estimated

Flux FF (μg/m 2 -s) Study Author

Estimated Flux (μg/m 2 -s)

2 9/9/2011 10:45 9/9/2011 13:00 2.25 0.747 0.657

3 9/9/2011 13:00 9/9/2011 19:00 6.00 0.236 0.204

4 9/9/2011 19:00 9/10/2011 1:00 6.00 0.035 0.035

5 9/10/2011 1:00 9/10/2011 7:00 6.00 0.024 0.022

6 9/10/2011 7:00 9/10/2011 19:00 12.00 0.073 0.068

7 9/10/2011 19:00 9/11/2011 7:00 12.00 0.011 0.008

8 9/11/2011 7:00 9/11/2011 19:00 12.00 0.018 0.015

9 9/11/2011 19:00 9/12/2011 7:00 12.00 0.006 0.005

10 9/12/2011 7:00 9/12/2011 19:00 12.00 0.016 0.012

11 9/12/2011 19:00 9/13/2011 7:00 12.00 0.002 0.002

Table 7. Estimated Flux Rates for Chlorpyrifos Using IHF Method

Period Sample Start

Times Sample End

Times Duration (hh:mm) Estimated

Flux FF (μg/m 2 -s)

2 9/9/2011 10:45 9/9/2011 13:00 2.25 0.591

3 9/9/2011 13:00 9/9/2011 19:00 6.00 0.759

4 9/9/2011 19:00 9/10/2011 1:00 6.00 0.171

5 9/10/2011 1:00 9/10/2011 7:00 6.00 0.054Air Monitoring (2012)/Page 16 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 16 Table 7. Estimated Flux Rates for Chlorpyrifos Using IHF Method

Period Sample Start

Times Sample End

Times Duration (hh:mm) Estimated

Flux FF (μg/m 2 -s)

6 9/10/2011 7:00 9/10/2011 19:00 12.00 0.167

7 9/10/2011 19:00 9/11/2011 7:00 12.00 0.021

8 9/11/2011 7:00 9/11/2011 19:00 12.00 0.033

9 9/11/2011 19:00 9/12/2011 7:00 12.00 0.006

10 9/12/2011 7:00 9/12/2011 19:00 12.00 0.012

11 9/12/2011 19:00 9/13/2011 7:00 12.00 0.005

The reviewer-estimated flux rates for chlorpyrifos using the AD method were comparable to those estimated by the study author. The reviewer-estimat ed flux rate values for chlorpyrifos using the IHF method were much higher than those estimated by the study author. A review of the study author’s calculations indicated that Zp (height of plume) was truncated at 150 cm, which in turn yielded lower flux rate estimates. The flux trends exhibited by both those estimated by the reviewer and those by the study author were very similar.

Chloropyrifos-oxon

The reviewer examined the flux rate values for oxon only; however, attempts at conducting a regression analysis for the residues generated poor fitting results. The study authors also completed this analysis and are consistent with EPA’s analysis. It is unclear if the oxon residues are a result of oxon flux off the field or from transformation of chlorpyrifos in the air or on the tube. As a result, the reviewer decided to examine total toxic residues together (see section below as well as RC 6 ).

Total Toxic Residues

The reviewer estimated flux rate values for total toxic residues are presented in Table 8 for both AD and

IHF methods based on total mass. The flux estimates b ased on based on parent toxicity equivalent units (takes into account the TAF) are provided in Table 9 and Table 10 for the AD and IHF, respectively. Regression results for the sampler concentrations are provided in APPENDICES C (IHF) and E (AD).

Initial attempts at conducting a regression analysis for the total toxic residues generated poor fitting results ( e.g. , r 2 <0.2). In general, the oxon concentrations did not follow a decreasing trend with height like the chlorpyrifos concentrations, resulting in poor results. In an effort to use the available data, a conversion factor was developed for each sampling peri od, which took the total mass of oxon for all four air samplers and divided this total by the total mass of chlorpyrifos for all four air samplers. The mass of chlorpyrifos at each height was then multiplied by th is conversion factor to estimate the mass of oxon at the same height. The mass of the oxon was then multiplied by the TAF (12X) 2 and added to the chlorpyrifos mass and divided by the volume of ai r sampled to estimate the total toxic residues at each height.

An example calculation is provided below for sampling Period 2. The total oxon mass is 0.397 μg and the total chlorpyrifos mass is 12.571 μg, resulting in a co nversion factor of 0.031581. This conversion factor is then applied to each of the chlorpyrifos samp les to estimate a revised oxon amount. The revised oxon amount is then multiplied by the TAF (12) 2 and added to the chlorpyrifos mass to estimate the total toxic

residue. This total toxic residue mass was divided by the sampler flowrate and length of sampling timeAir Monitoring (2012)/Page 17 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 17 for each sampler (131-133 minutes) to arrive at the total toxic residue concentration at each sampler height.

Period Sampler Sampler

Flowrate (L/min) Chlorpyrifos (μg) Oxon (μg) Revised

Oxon (μg) Total

Toxic

Residue

(μg) Total

Toxic

Residue (μg/m 3 )

2 A1 (15 cm) 1.076 3.630 0.082 0.115 5.01 35.54
B1 (33 cm) 1.047 2.901 0.082 0.092 4.005 29.20
C1 (55 cm) 1.029 2.473 0.083 0.078 3.409 25.10
D1 (90 cm) 1.081 2.097 0.086 0.066 2.889 20.25
E1 (150 cm) 1.043 1.470 0.064 0.046 2.022 14.58

These concentrations were then corrected for field for tification or storage stability recoveries and used to estimate the regression for total toxic residues to be used in both the AD and IHF methods. The calculation of the revised total toxic residues is provided in APPENDIX F

.

The total toxic residue flux calculated for the firs t period after application using the AD method was 1.102 μg/m 2 -s. The flux then declined over the next 24 hours, followed by a second smaller peak of 0.186 μg/m 2 -s. Two smaller peaks occurred at 0.034 μg/m 2 -s and at 0.052 μg/m 2 -s . Flux was 0.002- 0.003 μg/m 2 -s by the last sampling interval.

The total toxic residue flux calculated for the first pe riod after application using the Indirect Method was 0.791 μg/m 2 -s. The highest flux was observed during the subsequent period (Period 2) at a considerably higher level of 1.27 μg/m 2 -s. The flux then declined over the next 24 hours, followed by a second smaller peak of 0.384 μg/m 2 -s . Two smaller peaks occurred at 0.057 μg/m 2 -s and at 0.038 μg/m 2 -s. Flux was 0.007-0.010 μg/m 2 -s by the last sampling interval.

Table 8. Estimated Flux Rates for Total T oxic Chlorpyrifos Residues (Chlorpyrifos and Chlorpyrifos-oxon) Using AD and IHF Methods for the Alfalfa Study (based on mass)

Sampling

Period Sample Start

Times Sample End

Times Duration (hh:mm) Hours Post Application at Sample

Collection AD

Method IHF

Method*

Estimate

d Flux

FF (μg/m 2

- s) Estimated

Flux FF (μg/m 2 -s)

2 9/9/2011 10:45 9/9/2011 13:00 2.25 2.25 0.75 0.59

3 9/9/2011 13:00 9/9/2011 19:00 6.00 8.25 0.24 0.78

4 9/9/2011 19:00 9/10/2011 1:00 6.00 14.25 0.034 0.17

5 9/10/2011 1:00 9/10/2011 7:00 6.00 20.25 0.024 0.051

6 9/10/2011 7:00 9/10/2011 19:00 12.00 32.25 0.080 0.18

7 9/10/2011 19:00 9/11/2011 7:00 12.00 42.25 0.010 0.024

8 9/11/2011 7:00 9/11/2011 19:00 12.00 54.25 0.019 0.033

9 9/11/2011 19:00 9/12/2011 7:00 12.00 66.25 0.006 0.006

10 9/12/2011 7:00 9/12/2011 19:00 12.00 78.25 0.018 0.013

11 9/12/2011 19:00 9/13/2011 7:00 12.00 90.25 0.002 0.004 Data provided in this table are based on the appli cation rate used in the study (0.877 lb a.i./A). Flux profile is based on mass only and does not take into account the difference in toxicity between chlorpyrifos and chlorpyrifos-oxon.Air Monitoring (2012)/Page 18 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 18 Table 9. Estimated Flux Rates for Total Toxic Residue Using AD Method*(based on parent toxicity equivalent units )

Period Sample Start

Times Sample End

Times Duration (hh:mm) Estimated Flux FF (μg/m 2 -s)

2 9/9/2011 10:45 9/9/2011 13:00 2.25 1.00

3 9/9/2011 13:00 9/9/2011 19:00 6.00 0.395

4 9/9/2011 19:00 9/10/2011 1:00 6.00 0.040

5 9/10/2011 1:00 9/10/2011 7:00 6.00 0.030

6 9/10/2011 7:00 9/10/2011 19:00 12.00 0.168

7 9/10/2011 19:00 9/11/2011 7:00 12.00 0.018

8 9/11/2011 7:00 9/11/2011 19:00 12.00 0.031

9 9/11/2011 19:00 9/12/2011 7:00 12.00 0.007

10 9/12/2011 7:00 9/12/2011 19:00 12.00 0.047

11 9/12/2011 19:00 9/13/2011 7:00 12.00 0.003 * The study author did not estimate total toxic residue flux rates, instead the study author calculated flux rates for the chlorpyrifos-oxon alone.

Data provided in this table are based on the application rate used in the study (0.877 lb a.i./A). Flux profile takes into account the differen ce in toxicity between chlorpyrifos and chlorpyrifos-oxon.

Table 10. Estimated Flux Rates for Total Toxic Residue Using IHF Method* (based on parent toxicity equivalent units )

Period Sample Start

Times Sample End

Times Duration (hh:mm) Estimated Flux FF (μg/m 2 -s)

2 9/9/2011 10:45 9/9/2011 13:00 2.25 0.791

3 9/9/2011 13:00 9/9/2011 19:00 6.00 1.270

4 9/9/2011 19:00 9/10/2011 1:00 6.00 0.197

5 9/10/2011 1:00 9/10/2011 7:00 6.00 0.064

6 9/10/2011 7:00 9/10/2011 19:00 12.00 0.384

7 9/10/2011 19:00 9/11/2011 7:00 12.00 0.047

8 9/11/2011 7:00 9/11/2011 19:00 12.00 0.057

9 9/11/2011 19:00 9/12/2011 7:00 12.00 0.007

10 9/12/2011 7:00 9/12/2011 19:00 12.00 0.038

11 9/12/2011 19:00 9/13/2011 7:00 12.00 0.007 * The study author did not estimate total toxic residue flux rates, instead the study author calculated flux rates for the chlorpyrifos-oxon alone.

III DISCUSSION:

Flux rates for chlorpyrifos and total toxic residues st arted off low, but reached a peak in the second or third sampling period, depending on the method used to estimate flux rates, and then generally decreased, with other lower subsequent peaks that occurred during daytime hours of Days 2, 3, and 4.

Log-normal regressions developed for wind speed, temper ature, and concentration data versus the lognormal estimates for height usuall y provided good fits, with most r 2 estimates above 0.9.Air Monitoring (2012)/Page 19 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 19 IV REVIEWER’S COMMENTS:

1 While Lorsban Advanced may be an end-use emulsi fiable concentrate (water emulsion) used on a range of crops including alfalfa and is a preferre d chlorpyrifos liquid formulation sold by Dow AgroSciences it may not represent the preferred form ulation by applicators. In addition, Lorsban Advance is reported to be a low VOC (a low vola tility formulation); therefore, the observed flux rates reported in this study may not represent the potential flux for other formulations and the results could under predict the potential exposure fro m other chlorpyrifos formulations. California is currently the only state actively working to redu ce pesticide VOC; therefore, it is not expected

the Lorsban Advance and other low VOC form ulations dominate the market. Additional

information on the use of Lorban Advance and ot her low VOC formulations compared to other “regular/non-low VOC” would be helpful to determ ine the representative nature of the selected

formulation.

2 The study protocol indicated that the leaf ar ea index would be reported. Although reporting the leaf is not a critical component of this study and does not affect the results and conclusions of this study, not having the leaf area index for the studied crop limits the comparative value of this study to other crops.

3 The maximum single application rate for alfalfa (1 lb ai/a; 4 lb ai/a per year) is higher than the 0.878 lb ai/a used in this study. In additi on, these rates are substantially lower than current maximum single applications for grapes (33.3 lb a i/a; 33.3 lb ai/a per year) permitted on currently labeled chlorpyrifos products. In addition to grapes, several other uses also have maximum single application rates substantially higher than alfalfa in cluding citrus (6 lb ai/a; 10.5 lb ai/a per year), mint (2.0 ai/a; 6 lb ai/a per season), and turf (4.0 lb ai/a; no yearly application restriction).

Field volatility studies are typically conducted similar to terrestrial field dissipation studies (OCSPP 835.6100); therefore, the maximum single application rate of all uses is normally recommended. To address this uncertainty, addi tional studies may be necessary to evaluate flux rates under different cropping cond itions and application rates.

4 In addition to temperature, environmental factor s such as humidity and rainfall may influence the amount of chlorpyrifos and chlorpyrifos-oxon observed in air samples. While the temperature throughout the study may have been high, higher humidity may increase the amount of chlorpyrifos and chlorpyrifos-oxon observed in ai r samples. It is uncertain how the results obtained from this study, conducted in the central va lley of California, compare to the results that may be obtained for other sites in the US. To address this uncertainty, additional studies may be necessary to evaluate flux rates under different e nvironmental conditions in different regions of the country.

5 The total oxon chlorpyrifos equivalents for the 12- hour 500 ug sample (pg. 118 of report) were

not consistent with the other data. Either the corr ected concentrations are too high or the raw data is reported incorrectly. The reviewer thinks th e corrected equivalents should be down around 2% based on examination of the molecular weight c onversion. This error was confirmed with the study authors; however, a corrected report has not been provided. If this is the case, the oxon concentration would be slightly less than currently calculated. This is not expected to have a substantial impact on the total toxic residue con centrations and the calculated flux rates because the oxon concentrations are low and the change in th e correction factor is not expected to be great (>5%).Air Monitoring (2012)/Page 20 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 20 6 It is unclear if the oxon residues observed in this study are a result of oxon flux off the field or from transformation of chlorpyrifos in the air or on the tube. As a result, the reviewer decided to examine total toxic residues (chlorpyrifos and chlorpyrifos-oxon) together. The study authors did not complete this analysis. This is thought to be a reasonable approach to account for any toxic residues that may end up in air as a result of chlorpyrifos applications independent of the route of

oxon formation.

V CONCLUSION:

Despite issues with oxon recoveries during the study, th e data and the flux rate estimates derived from the data appear to be scientifically sound. This study is classified as acceptable.

V REFERENCES:

Johnson, B., Barry, T., and Wofford P. 1999. Workbook for Gaussian Modeling Analysis of Air

Concentrations Measurements. State of Californi a Environmental Protection Agency, Department of Pesticide Regulation. Sacramento, CA.

Majewski, M.S., Glotfelty, D.E., Kyaw Tha Paw U ., Seiber, JN. 1990. A field comparison of several methods for measuring pesticide evaporation rates from soil. Environmental Science and Technology, 24:1490-1497.

Wilson, J.D., and Shum. W.K.N. 1992. A re-examina tion of the integrated horizontal flux method for estimating volatilisation from circular plots. Agriculture Forest Meteor. Vol 57:281-295.

Yates, S.R., F.F. Ernst, J. Gan, F. Gao, and Yates, M.V. 1996. Methyl Bromide Emissions from a Covered Field: II. Volatilization,” Journal of Environmental Qu ality, 25: 192-202.Air Monitoring (2012)/Page 21 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 21 Figure 1. Location of Field in CaliforniaAir Monitoring (2012)/Page 22 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 22 Figure 2. Air Quality and Meteorol ogical Monitoring StationsAir Monitoring (2012)/Page 23 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 23 COMPLIANCE CHECKLIST

Applicable Checklist Items Taken from:

FIELD VOLATILITY STUDIES

 Investigators should submit protocols for review purposes prior to the inception of the study. This criterion was met. A protocol was provided in the study report and was submitted prior to the inception of the study. Comments provided by EPA on the protocol were also addressed in the study report.

 Expected deviations from GLPs should be presen ted concurrently with any protocol deviations and their potential study impacts . This criterion was met.

 The test substance must be the typical end use product of the active ingredient . This criterion was

met.

 The production of metabolites, breakdown products , or the presence of contaminants of potential toxicologic concern, should be considered on a case-by-case basis . This criterion was met. Samples were analyzed for chlorpyrifos-oxon and TCP.

 The application rate should be the maximum rate specified on the label. If multiple applications are made, the minimum allowable interval between applications should be used. This criterion

was met.

 The percentage of active ingredient and formula tion type should be reported. Properties of the pesticide (i.e., vapor pressure, water solubility, ad sorption to soil, and texture) should also be

addressed . This criterion was met.

 The study should be conducted domestically (U SA). The site should be typical in geography, topography, soil type, season, and me teorology of those sites with intended use patterns. The use of two or more topographically and meteorologically diverse sites is recommended in order to ascertain the effects of these variables on spray drift . These criteria were partially met. The study was conducted on a representative field in Californi a. However, only one test site was used.

 Field data should be documented, including a rea description, meteorological conditions, application data, and equipment information. Volatility (g/ha/day), air concentrations (μg/m 3 ), and vapor pressure (mm Hg or equivalent) should also be reported . These criteria were partially met. Volatility and vapor pressure data were not provided.

 Appropriate air sampling media should be selected . The medium should entrap a high percentage of the chemical passing through it, and it shoul d allow the elution of a high percentage of the entrapped chemical for analysis. A trapping efficiency test for the monitoring media chosen must

be documented . These criteria were partially met. An appropriate air sampling media was selected. However, a trapping efficiency test was not performed.

 Air monitoring techniques area (i.e., stationary) should contain sufficient samples to characterize the likely range of possible exposure concentr ations, and to ensure that the reentry and/or bystander scenarios can be adequately addressed. St ationary samples should be collected from the center of treated fields and from at least 4 ot her locations, preferably at the cardinal compassAir Monitoring (2012)/Page 24 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 24 points from the center location and at representa tive distances to reflect buffer zones. Air samplers should be placed at a height that is representative of the breathing zone of potentially exposed individual (i.e. 2 to 3 feet for workers removing tarps, 4 to 5 feet for bystanders downwind, etc.) At least three downwind collecti on sites should be used. If homes or structures are present, representative samples should be taken within the structure to establish buffer zones

. These criteria were met.

 The duration of the sampling interval and air flow rates should be maximized within the appropriate flow rate range to increase the potential for capturing enough residues to be quantifiable . This criterion was met. The flow rate w as maintained at 1 L/min (appropriate range for gaseous residue).

 A sufficient number of replicates should be genera ted to address the expos ure issues associated with the population of interest . This criterion was met.

 Air samples should be monitored for residues at intervals wh ich increase with time after application. Sampling should be continued un til the nature of the dissipation curve has been clearly established . This criterion was met.

 A monitoring pump capable of producing airflow of at least 2 L/min. should be used and its batteries should be capable of sustaining maximum airflow for at least 4 hours without recharging. Airflow should be measured at the beginning and end of the exposure period . These criteria were met. The pumps were operated at ai rflow appropriate for the monitoring of gases and were sampled for intervals ranging from 6 to 12 h ours. Airflow was monitored before and after the exposure period to ensure proper operation.

 Field calibration of air monitors should be performed at the beginning and end of the sampling period . This criterion was met.

 An adequate number of field blanks should be a nalyzed for contamination. If an appropriate analytical method had not been established (i.e by NIOSH or OSHA), field fortification samples should be analyzed for correction of residue lo sses occurring during the sampling period. When appropriate, fortified samples and blanks should be fortified at the expected residue level of the actual field samples. Fortified blanks shoul d be exposed to the same weather conditions . These

criteria were met.

 Retention and breakthrough studies should be performed under conditions similar to those anticipated in the field phase of the study to ensure that collected material is not lost from the medium during sampling. It is recommended that at least one test be carried out where the initial trap contains 10x the highest amount of residue expected in the field . These criteria were not met.

 Samples should be stored in a manner that will minimize deterioration and loss of analytes between collection and analyses. Storage stability samples should be extracted and analyzed immediately before and at appropriate periods dur ing storage. The time periods for storage should be chosen so that the longest interval co rresponds to the longest projected storage period for field samples . These criteria were met.

 If exposed media are to be stored prior to extraction, storage me dia/containers should be made of appropriate material that protects against contamination and that does not interfere with analysis

. These criteria were met.Air Monitoring (2012)/Page 25 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 25  Validated analytical methods of sufficient sensitiv ity are needed. The met hod must be specific for the analyte of interest. Information on method efficiency (residue recovery) and limit of quantification (LOQ) should be provided . This criterion was met.

 Analysis methods should be documented and appropri ate. The analytical procedure must be capable of measuring exposure to 1μg/hr (or less, if the toxicity of the material under study warrants greater sensitivity). Not applicable.

 Method accuracy should range betw een 70 and 120 percent. Precision values should be less than or equal to 20 percent (coefficient of variation). The extraction efficiency of laboratory fortified controls is considered acceptable if the lower lim it of the 95% confidence interval is greater than 75%, unless otherwise specified by the Agency . These criteria were met

 Information on recovery samples must be included in the study report. A complete set of field recoveries should consist of at least one blank control sample and three or more each of a lowlevel and high-level fortification. These fortifications should be in the range of anticipated residue levels in the field study. Total recovery from fie ld-fortified samples must be greater than 50% for the study . These criteria were met.

 Raw residue data must be corrected if appropr iate recovery values are less than 90 percent . This criterion was not met. The study authors did not correct for field recoveries. However, the petitioner used a simple linear regression of % c onversion vs. time to correct the chlorpyrifos

concentrations.

 Residues should be reported as μg pesticide ac tive ingredient per sample and as an airborne concentration (μg/m3). Distributional data should be reported, to the extent possible . This

criterion was met.

 A sample history sheet must be prepared by the laboratory upon receipt of the samples . This

criterion was met.Air Monitoring (2012)/Page 26 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 26 APPENDIX A

Indirect Method Regression AnalysisAir Monitoring (2012)/Page 27 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 27 Indirect Regression Analysis for Chlorpyrifos (Adjusted for Field Fortification)

Location Measured concentration (μg/m3) Modeled concentration (μg/m3)

OP - 0 0 0.000

OP - 45 0 0.000

OP - 90 1.67721 1.381

OP - 135 7.75345 2.208

OP - 180 11.41688 2.315

OP - 225 0.01814 0.019

OP - 270 0.00008 0.000

OP - 315 0 0.000

Linear Regression

0.219083 0.168975

0.036237 0.178115

0.858993 0.427006

36.55118 6
Least Squares Regression

0.237325 0

0.030495 #N/A

0.896401 0.423945

60.56806 7

Is LR Slope Sig.? Yes

Is LR Intercept Sig.? No

Is Intercept < 25 Per. No

Is LSR Slope Sig.? Yes

Flux 0.22

Flux source Linear RegressionAir Monitoring (2012)/Page 28 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 28 Indirect Regression Analysis for Total Residues (Adjusted for Field Fortification)

Location Measured concentration (μg/m3) Modeled concentration (μg/m3)

OP - 0 0 0

OP - 45 0 0

OP - 90 1.67721 3.244886

OP - 135 7.75345 4.758321

OP - 180 11.41688 4.799108

OP - 225 0.01814 0.018528

OP - 270 0.00008 0

OP - 315 0 0

Linear Regression

0.458671 0.406291

0.087951 0.432297

0.819261 1.036372

27.19712 6
Least Squares Regression

0.502534 0

0.073923 #N/A

0.868456 1.027697

46.21409 7

Is LR Slope Sig.? Yes

Is LR Intercept Sig.? No

Is Intercept < 25 Per. No

Is LSR Slope Sig.? Yes

Flux 0.459

Flux source Linear RegressionAir Monitoring (2012)/Page 29 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 29 APPENDIX B

Integrated Horizontal Flux Method Meteorological CalculationsAir Monitoring(2012)/Page 30 of 44Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a30IHF Method Meteorological Parametersfor Chlorpyrifos and Total ResiduesPeriodStartEndDuration(hours)Period Averaged Wind Speed m/sRegression CoefficientsFetchDateTimeDateTime15 cm33 cm55 cm90 cmSlopeInterceptR2(m)2 9/9/2011 10:45 9/9/2011 13:00 2.25 0.440.56 0.63 0.74 0.16 0.74 0.99104.53 9/9/2011 13:00 9/9/2011 19:00 6.00 0.791.11 1.23 1.59 0.42 1.57 0.9687.74 9/9/2011 19:00 9/10/2011 1:00 6.00 0.310.44 0.57 0.74 0.23 0.73 0.9691.25 9/10/2011 1:00 9/10/2011 7:00 6.00 0.230.36 0.48 0.62 0.22 0.62 0.9893.96 9/10/2011 7:00 9/10/2011 19:00 12.00 0.550.76 0.94 1.14 0.33 1.15 0.9999.37 9/10/2011 19:00 9/11/2011 7:00 12.00 0.921.18 1.40 1.69 0.43 1.69 0.9888.08 9/11/2011 7:00 9/11/2011 19:00 12.00 0.600.83 0.97 1.17 0.31 1.18 0.9999.39 9/11/2011 19:00 9/12/2011 7:00 12.00 0.550.77 0.94 1.14 0.33 1.15 0.99105.710 9/12/2011 7:00 9/12/2011 19:00 12.00 0.650.98 1.15 1.40 0.41 1.43 1.0093.311 9/12/2011 19:00 9/13/2011 7:00 12.00 0.310.44 0.57 0.75 0.24 0.74 0.9788.1Air Monitoring (2012)/Page 31 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 31 APPENDIX C

Integrated Horizontal Flux Method Concentration CalculationsAir Monitoring(2012)/Page 32 of 44Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a32IHF Method Concentration Parameters for Chlorpyrifos (Field Fortifications)PeriodStartEndDuration(hours)Period Averaged Concentrations (μg m-3)1Regression CoefficientsDateTimeDateTime15 cm33 cm55 cm90 cm150 cmSlopeInterceptR22 9/9/2011 10:45 9/9/2011 13:00 2.25 31.419 25.804 22.213 17.929 12.935 -7.45 17.43 1.003 9/9/2011 13:00 9/9/2011 19:00 6.00 17.652 15.768 12.746 9.644 7.153 -4.47 9.81 0.954 9/9/2011 19:00 9/10/2011 1:00 6.00 10.750 10.308 7.459 5.673 2.699 -2.95 5.82 0.885 9/10/2011 1:00 9/10/2011 7:00 6.00 8.064 6.772 5.340 3.392 1.679 -2.56 3.52 0.966 9/10/2011 7:00 9/10/2011 19:00 12.00 5.255 4.828 3.714 3.011 2.073 -1.29 3.00 0.937 9/10/2011 19:00 9/11/2011 7:00 12.00 0.683 0.614 0.446 0.371 0.269 -0.18 0.36 0.948 9/11/2011 7:00 9/11/2011 19:00 12.00 1.173 1.010 0.793 0.679 0.425 -0.29 0.65 0.989 9/11/2011 19:00 9/12/2011 7:00 12.00 0.594 0.507 0.385 0.269 0.167 -0.18 0.27 0.9710 9/12/2011 7:00 9/12/2011 19:00 12.00 0.608 0.498 0.371 0.323 0.196 -0.17 0.30 0.9811 9/12/2011 19:00 9/13/2011 7:00 12.00 0.460 0.408 0.332 0.227 0.109 -0.13 0.24 0.931. As wind data were only provided up to 90cm, only the concentration data up to 90 cm were used in generating the regressioncoefficients.Air Monitoring(2012)/Page 33 of 44Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a33IHF Method Concentration Parameters forTotal Residue (Field Fortifications)PeriodStartEndDuration(hours)Period Averaged Concentrations (μg m-3)1, 2Regression CoefficientsDateTimeDateTime15 cm33 cm55 cm90 cm150 cmSlopeInterceptR22 9/9/2011 10:45 9/9/2011 13:00 2.25 42.035 34.523 29.718 23.987 17.305 -9.97 23.32 1.003 9/9/2011 13:00 9/9/2011 19:00 6.00 29.545 26.392 21.334 16.143 11.973 -7.48 16.42 0.954 9/9/2011 19:00 9/10/2011 1:00 6.00 12.349 11.841 8.568 6.517 3.020 -3.38 6.68 0.885 9/10/2011 1:00 9/10/2011 7:00 6.00 10.019 8.414 6.635 4.104 2.032 -3.23 4.29 0.956 9/10/2011 7:00 9/10/2011 19:00 12.00 12.041 11.064 8.510 6.900 4.361 -2.97 6.88 0.937 9/10/2011 19:00 9/11/2011 7:00 12.00 1.213 1.089 0.854 0.652 0.472 -0.32 0.66 0.958 9/11/2011 7:00 9/11/2011 19:00 12.00 1.958 1.686 1.323 1.133 0.703 -0.48 1.08 0.989 9/11/2011 19:00 9/12/2011 7:00 12.00 0.636 0.542 0.408 0.285 0.177 -0.20 0.28 0.9610 9/12/2011 7:00 9/12/2011 19:00 12.00 1.754 1.437 1.060 0.923 0.560 -0.49 0.84 0.9811 9/12/2011 19:00 9/13/2011 7:00 12.00 0.752 0.612 0.499 0.341 0.164 -0.22 0.34 0.981.As wind data were only provided up to 90 cm,only the concentration data up to 90 cm were used in generating the regression coefficients.2.This takes into account the toxicity adjustment factor of 12x.Air Monitoring (2012)/Page 34 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 34 APPENDIX D

Aerodynamic Flux Method Temperat ure and Wind Speed CalculationsAir Monitoring(2012)/Page 35 of 44Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a35AD Method Temperature Parameters for Chlorpyrifos and Total ResiduesPeriodStartEndDuration(hours)Period Averaged Temperature oCRegression CoefficientsTemperature oCDateTimeDateTime15 cm33 cm55 cm90 cmSlopeInterceptR290 cm33 cm2 9/9/2011 10:45 9/9/2011 13:00 2.25 29.7 29.4 29.4 29.0 -0.33 30.60 0.88 29.1 29.53 9/9/2011 13:00 9/9/2011 19:00 6.00 31.3 31.5 31.6 31.7 0.25 30.59 0.97 31.7 31.54 9/9/2011 19:00 9/10/2011 1:00 6.00 22.4 22.7 23.0 23.4 0.57 20.79 0.97 23.4 22.85 9/10/2011 1:00 9/10/2011 7:00 6.00 17.0 17.3 17.6 18.1 0.64 15.13 0.96 18.0 17.46 9/10/2011 7:00 9/10/2011 19:00 12.0029.8 29.8 29.8 29.8 0.01 29.750.14 29.8 29.87 9/10/2011 19:00 9/11/2011 7:00 12.00 20.6 20.7 20.8 21.0 0.18 20.11 0.97 20.9 20.88 9/11/2011 7:00 9/11/2011 19:00 12.00 22.8 22.7 22.7 22.7 -0.06 22.94 0.81 22.7 22.79 9/11/2011 19:00 9/12/2011 7:00 12.00 17.7 17.8 17.9 18.1 0.26 16.93 0.98 18.1 17.810 9/12/2011 7:00 9/12/2011 19:00 12.00 25.8 25.6 25.6 25.4 -0.20 26.34 0.92 25.4 25.611 9/12/2011 19:00 9/13/2011 7:00 12.00 17.4 17.7 17.9 18.2 0.45 16.18 0.99 18.2 17.7AD Method Wind Speed Parameters for Chlorpyrifos and Total ResiduesPeriodStartEndDuration(hours)Period Averaged Wind Speed m/sRegression CoefficientsWind Speed m/sDateTimeDateTime15 cm33 cm55 cm90 cmSlopeInterceptR290 cm33 cm2 9/9/2011 10:45 9/9/2011 13:00 2.25 0.44 0.560.63 0.74 0.16 -0.01 0.99 0.73 0.563 9/9/2011 13:00 9/9/2011 19:00 6.00 0.79 1.111.23 1.59 0.42 -0.37 0.96 1.52 1.104 9/9/2011 19:00 9/10/2011 1:00 6.00 0.31 0.440.57 0.74 0.23 -0.35 0.96 0.71 0.4745 9/10/2011 1:00 9/10/2011 7:00 6.00 0.23 0.360.48 0.62 0.22 -0.38 0.98 0.60 0.386 9/10/2011 7:00 9/10/2011 19:00 12.00 0.55 0.760.94 1.14 0.33 -0.36 0.99 1.12 0.797 9/10/2011 19:00 9/11/2011 7:00 12.00 0.92 1.181.40 1.69 0.43 -0.27 0.98 1.649 1.2228 9/11/2011 7:00 9/11/2011 19:00 12.00 0.60 0.830.97 1.17 0.31 -0.24 0.99 1.15 0.849 9/11/2011 19:00 9/12/2011 7:00 12.00 0.55 0.770.94 1.14 0.33 -0.35 0.99 1.12 0.7910 9/12/2011 7:00 9/12/2011 19:00 12.00 0.65 0.981.15 1.40 0.41 -0.47 1.00 1.384 0.97211 9/12/2011 19:00 9/13/2011 7:00 12.00 0.31 0.440.57 0.75 0.24 -0.35 0.97 0.71 0.47Air Monitoring (2012)/Page 36 of 44 Chlorpyrifos / 059101/ MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 36 APPENDIX E

Aerodynamic Flux Method Co ncentration CalculationsAir Monitoring(2012)/Page 37 of 44Chlorpyrifos / 059101 / MRID 48883201 OPPTS 835.8100 / DACO 5.9a37AD Method Concentration Parameters forChlorpyrifos (Field Fortifications)PeriodStartEndDuration(hours)Period Averaged Concentrations (μg m-3)1Regression CoefficientsChlor. μg/m3DateTimeDateTime15 cm33 cm55 cm90 cm150 cmSlopeInterceptR290 cm33 cm2 9/9/2011 10:45 9/9/2011 13:00 2.25 31.419 25.804 22.213 17.929 12.935 -7.45 51.76 1.00 18.21 25.693 9/9/2011 13:00 9/9/2011 19:00 6.00 17.652 15.768 12.746 9.644 7.153 -4.47 30.39 0.95 10.28 14.764 9/9/2011 19:00 9/10/2011 1:00 6.00 10.750 10.308 7.459 5.673 2.699 -2.95 19.38 0.88 6.13 9.085 9/10/2011 1:00 9/10/2011 7:00 6.00 8.064 6.772 5.340 3.392 1.679 -2.56 15.31 0.96 3.79 6.366 9/10/2011 7:00 9/10/2011 19:00 12.00 5.255 4.828 3.714 3.011 2.073 -1.29 8.96 0.93 3.14 4.447 9/10/2011 19:00 9/11/2011 7:00 12.00 0.683 0.614 0.446 0.371 0.269 -0.18 1.20 0.94 0.38 0.568 9/11/2011 7:00 9/11/2011 19:00 12.00 1.173 1.010 0.793 0.679 0.425 -0.29 1.97 0.98 0.68 0.979 9/11/2011 19:00 9/12/2011 7:00 12.00 0.594 0.507 0.385 0.269 0.167 -0.18 1.11 0.97 0.29 0.4710 9/12/2011 7:00 9/12/2011 19:00 12.00 0.608 0.498 0.371 0.323 0.196 -0.17 1.06 0.98 0.31 0.4811 9/12/2011 19:00 9/13/2011 7:00 12.00 0.460 0.408 0.332 0.227 0.109 -0.13 0.82 0.93 0.25 0.381. As wind and temperature datawere only provided up to 90 cm, only the concentration data up to 90 cm were used in generatingthe regression coefficients.AD Method Concentration Parameters forTotal Residues (Field Fortifications)PeriodStartEndDuration(hours)Period Averaged Concentrations (μg m-3)1,2Regression CoefficientsTotal Resμg/m3DateTimeDateTime15 cm33 cm55 cm90 cm150 cmSlopeInterceptR290 cm33 cm2 9/9/2011 10:45 9/9/2011 13:00 2.25 42.035 34.523 29.718 23.987 17.305 -9.97 69.24 1.00 24.37 34.373 9/9/2011 13:00 9/9/2011 19:00 6.00 29.545 26.392 21.334 16.143 11.973 -7.48 50.87 0.95 17.21 24.714 9/9/2011 19:00 9/10/2011 1:00 6.00 12.349 11.841 8.568 6.517 3.020 -3.38 22.26 0.88 7.04 10.435 9/10/2011 1:00 9/10/2011 7:00 6.00 10.019 8.414 6.635 4.104 2.032 -3.23 19.19 0.95 4.63 7.886 9/10/2011 7:00 9/10/2011 19:00 12.00 12.041 11.064 8.510 6.900 4.361 -2.97 20.53 0.93 7.19 10.177 9/10/2011 19:00 9/11/2011 7:00 12.00 1.213 1.089 0.854 0.652 0.472 -0.32 2.12 0.95 0.69 1.018 9/11/2011 7:00 9/11/2011 19:00 12.00 1.958 1.686 1.323 1.133 0.703 -0.48 3.28 0.98 1.13 1.619 9/11/2011 19:00 9/12/2011 7:00 12.00 0.636 0.542 0.408 0.285 0.177 -0.20 1.19 0.96 0.31 0.5010 9/12/2011 7:00 9/12/2011 19:00 12.00 1.754 1.437 1.060 0.923 0.560 -0.49 3.08 0.98 0.89 1.3811 9/12/2011 19:00 9/13/2011 7:00 12.00 0.752 0.612 0.499 0.341 0.164 -0.22 1.38 0.98 0.37 0.591.As wind and temperature data were only provided up to 90 cm, only the concentration dataup to 90 cm were used in generating the regression coefficients.2.This takes into account the toxicity adjustment factor of 12x.Air Monitoring (2012)/Page 38 of 44 Chlorpyrifos / 059101 / MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 38 APPENDIX F

Total Residue EstimationAir Monitoring(2012)/Page 39 of 44Chlorpyrifos / 059101 / MRID 48883201 OPPTS 835.8100 / DACO 5.9a39PeriodSamplerSamplerFlowrate(L/min)Chlorpyrifos(μg)Oxon(μg)Ratio of TotalOxon to TotalChlorpyrifosRevisedOxon(μg)TotalResidueAdjustedfor FF(μg)1TotalResidueAdjustedfor FF(μg/m3)12A1 (15 cm)1.076 3.630 0.0820.0315810.115 5.925 42.03B1 (33 cm)1.047 2.901 0.082 0.092 4.735 34.52C1 (55 cm)1.029 2.473 0.083 0.078 4.037 29.72D1 (90 cm)1.081 2.097 0.086 0.066 3.423 23.99E1 (150 cm)1.043 1.470 0.064 0.046 2.399 17.313A2 (15 cm)1.011 5.266 0.210.0604310.318 10.753 29.55B2 (33 cm)1.022 4.766 0.169 0.288 9.732 26.39C2 (55 cm)1.018 3.827 0.256 0.231 7.815 21.33D2 (90 cm)1.026 2.928 0.274 0.177 5.979 16.14E2 (150 cm)1.047 2.210 0.239 0.134 4.513 11.974A3 (15 cm)1.014 3.206 0.0150.0153320.049 4.493 12.35B3 (33 cm)0.993 3.012 0.032 0.046 4.221 11.84C3 (55 cm)0.980 2.157 0.035 0.033 3.023 8.57D3 (90 cm)0.980 1.636 0.048 0.025 2.293 6.52E3 (150 cm)1.027 0.751 0.035 0.012 1.117 3.025A4 (15 cm)0.992 2.367 0.0510.0233820.055 3.588 10.02B4 (33 cm)1.008 2.020 0.047 0.047 3.062 8.41C4 (55 cm)1.004 1.582 0.042 0.037 2.398 6.63D4 (90 cm)1.005 0.926 0.022 0.022 1.489 4.10E4 (150 cm)1.011 0.461 0.01 0.011 0.741 2.036A5 (15 cm)1.015 3.146 0.2580.1134960.357 8.795 12.04B5 (33 cm)1.007 2.864 0.273 0.325 8.007 11.06C5 (55 cm)1.018 2.230 0.252 0.253 6.235 8.51D5 (90 cm)1.016 1.802 0.247 0.205 5.038 6.90E5 (150 cm)1.016 1.139 0.239 0.129 3.184 4.367A6 (15 cm)1.018 0.378 0.0240.0731530.028 0.891 1.21B6 (33 cm)1.023 0.341 0.023 0.025 0.804 1.09C6 (55 cm)1.022 0.267 0.021 0.020 0.630 0.85D6 (90 cm)1.015 0.221 0.018 0.016 0.478 0.65E6 (150 cm)1.017 0.160 0.014 0.012 0.346 0.47Air Monitoring(2012)/Page 40 of 44Chlorpyrifos / 059101 / MRID 48883201 OPPTS 835.8100 / DACO 5.9a40PeriodSamplerSamplerFlowrate(L/min)Chlorpyrifos(μg)Oxon(μg)Ratio of TotalOxon to TotalChlorpyrifosRevisedOxon(μg)TotalResidueAdjustedfor FF(μg)1TotalResidueAdjustedfor FF(μg/m3)18A7 (15 cm)1.026 0.652 0.0210.0638480.042 1.446 1.96B7 (33 cm)1.055 0.577 0.026 0.037 1.280 1.69C7 (55 cm)1.039 0.446 0.037 0.028 0.989 1.32D7 (90 cm)1.047 0.385 0.027 0.025 0.854 1.13E7 (150 cm)1.039 0.258 0.037 0.016 0.525 0.709A8 (15 cm)1.025 0.330 0.0010.0110290.004 0.469 0.64B8 (33 cm)1.017 0.279 0.000 0.003 0.397 0.54C8 (55 cm)1.019 0.229 0.003 0.003 0.299 0.41D8 (90 cm)0.975 0.153 0.004 0.002 0.200 0.28E8 (150 cm)0.997 0.097 0.004 0.001 0.127 0.1810A9 (15 cm)1.072 0.353 0.0400.1709970.060 1.353 1.75B9 (33 cm)1.048 0.283 0.040 0.048 1.085 1.44C9 (55 cm)1.070 0.232 0.048 0.040 0.816 1.06D9 (90 cm)1.086 0.205 0.037 0.035 0.721 0.92E9 (150 cm)1.048 0.120 0.039 0.021 0.422 0.5611A10 (15 cm)1.005 0.270 0.0110.0503360.014 0.544 0.75B10 (33 cm)1.001 0.238 0.011 0.012 0.440 0.61C10 (55 cm)0.987 0.191 0.010 0.010 0.353 0.50D10 (90 cm)0.990 0.131 0.007 0.007 0.242 0.34E10 (150 cm)1.005 0.064 0.006 0.003 0.118 0.161.This takes into account the toxicity adjustment factor of 12x.Air Monitoring (2012)/Page 41 of 44 Chlorpyrifos / 059101 / MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 41 APPENDIX G

Stability of Chlorpyrifos and Chlorpyrifos-oxon on Sorbent TubesAir Monitoring (2012)/Page 42 of 44 Chlorpyrifos / 059101 / MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 42 The study authors reported that in a recent air mon itoring study (Fenske et al., 2009) where chlorpyrifosoxon was analyzed in air samples, it was found that ox on could form on the air sampler sorbent resin.

Fenske et al. examined the rate of conversion as a f unction of the starting chlorpyrifos concentration and sampler flow rate. However, by correcting for this conversion artifact, Fenske et al. could still not

account for all of the oxon found and thus conclude d that it had formed in the environment.

To further examine these issues, the study authors sp iked separate sets of sorbent tubes at 50, 500, and 2000 ng chlorpyrifos, oxon and 3,5-6 tricloropyridinol (TCP) per tube. Sets were aged in a laboratory hood (ambient conditions, approximate ly 70°F)) for 6 and 12 hours, with half aged with airflow at 1 L/min and the other half with no flow (each sample w as run in triplicate). Duplicate spiked controls (nonaged) were also included. Tubes spiked with parent chlorpyrifos were analyzed for chlorpyrifos, chlorpyrifos-oxon and TCP. Tubes spiked with oxon were analyzed for oxon and TCP, and tubes spiked with TCP were analyzed for TCP only. As a result, TCP analyses were determined to be necessary during the course of analytical method validation, as chlorpyrifos-oxon was found to significantly convert to

TCP on the sorbent material.

Based on the sorbent tube analyses, study authors estimat ed correction factors of 1.1, 3.4 and 6.8% for 2, 6 and 12 hour sampling periods, respectively. These corr ection factors were then applied to the analytical results for parent and oxon. For example, a measured chlorpyrifos concentration from a 12-hour sample period would be increased by a factor of 1.068 (6 .8%) and the corresponding oxon reduced by same molar amount. Final oxon values were expressed as the sum of oxon and TCP values (with TCP in oxon molar equivalents).

The raw data are presented below ( Table G-1 ). This raw data was used to develop a regression equation to estimate the correction factors (see Figure G-1 ).Air Monitoring (2012)/Page 43 of 44 Chlorpyrifos / 059101 / MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 43 Table G-1. Storage Stability Data Us ed to Develop Correction Factors

Sample Name Measure chlorpyrifos

(μg/tube) Measure oxon (μg/tube) Total oxon, chlorpyrifos equivalents 1 

### % oxon in CPF equivalents

No flow L-c-sp1-50-nf-1 L-c-sp1-50-nf-2 L-c-sp1-50-nf-3 0.040

0.046

0.044 0

0

0 0

0

0 0

0

0 L-c-sp1-500-nf-1 L-c-sp1-500-nf-2 L-c-sp1-500-nf-3 0.432

0.467

0.449 0

0

0 0

0

0 0

0

0 L-c-sp1-2000-nf-1 L-c-sp1-2000-nf-2 L-c-sp1-2000-nf-3 1.833

1.910

1.757 0

0

0 0

0

0 0

0

0 L-c-sp2-50-nf-1 L-c-sp2-50-nf-2 L-c-sp2-50-nf-3 0.046

0.047

0.043 0

0

0 0

0

0 0

0

0 L-c-sp2-500-nf-1 L-c-sp2-500-nf-2 L-c-sp2-500-nf-3 0.436

0.539

0.482 0

0

0 0

0

0 0

0

0 L-c-sp2-2000-nf-1 L-c-sp2-2000-nf-2 L-c-sp2-2000-nf-3 1.890

1.940

1.894 0

0

0 0

0

0 0

0

0 6-hour flow period L-c-sp1-50-1 L-c-sp1-50-2 L-c-sp1-50-3 0.040

0.043

0.046 0

0

0 0

0

0 0

0

0 L-c-sp1-500-1 L-c-sp1-500-2 L-c-sp1-500-3 0.463

0.458

0.449 0

0

0 0

0

0 0

0

0 L-c-sp1-2000-1 L-c-sp1-2000-2 L-c-sp1-2000-3 1.818

1.824

1.781 0.039

0.043

0.044 0.041

0.045

0.046 2.25

2.46

2.58 12-hour flow period L-c-sp2-50-1 L-c-sp2-50-2 L-c-sp2-50-3 0.048

0.048

0.049 0

0

0 0

0

0 0

0

0 L-c-sp2-500-1 L-c-sp2-500-2 L-c-sp2-500-3 0.408

0.513

0.485 0.017

0.020

0.024 0.041

0.048

0.056 9.97

9.33

11.58 L-c-sp2-2000-1 L-c-sp2-2000-2 L-c-sp2-2000-3 1.760

1.936

1.845 0.071

0.061

0.065 0.074

0.064

0.068 4.21

3.28

3.71
1. Total oxon (chlorpyrifos equivalents) = total oxon * (350.59/334.52). Using the percent oxon (in CPF equivalents) values above as a function of aging time, the plot and regression shown below was produced. Although there is some difference in stability at the 12-hr aging period between spiking levels, there was not sufficient data to form a complete relationship with measured concentration (oxon was onlyAir Monitoring (2012)/Page 44 of 44 Chlorpyrifos / 059101 / MRID 48883201 OPPTS 835.8100 / DACO 5.9a



### 44 detected at the highest spiking level at 6 hours), the data were combined to form the re gression shown. Using the regression, the % correction factors were 1.1, 3.4 and 6.8% for 2, 6 and 12 hour sampling periods, respectively.

Figure G-1. Regression Analysis for Correction Factors