Chlorpyrifos (PC 059101) Air Photolysis (2012)/Page 1 of 26 

MRID 48789701 OPPTS 835.2370 

 

DATA EVALUATION RECORD

Test Material: Chlorpyrifos 

 

MRID 48789701 

 

Title: Munoz, A. 2012. Gas-phase photolysis and photo-oxidation of 

chlorpyrifos and chlorpyrifos-oxon 

 

EPA PC Code: 059101

 

OCSPP Guideline: 835.2370 

For Cambridge Environmental 

 

Primary Reviewer: Lynne Binari Signature: 

Date: 9/11/12 

 

Secondary Reviewer: Kathleen Ferguson Signature: 

Date: 9/11/12 

 

QC/QA Manager: Joan Gaidos Signature: 

Date: 9/11/12 

Chlorpyrifos (PC 059101) MRID 48789701 

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Table 1. Results Synopsis: Phototransformation in Air 

Compound 

Name 

Observed 

DT50 

(hours) 

Observed 

DT90

(hours)

Calculated

Half-life 

(hours)A 

Model Parameters and 

Statistics 

Adjusted 

Half-life 

(days)B 

Phototransformation Products

Common Name 

(maximum approximate ppb 

observed, associated interval)C

Photolysis 

Chlorpyrifos 

[300 ± 5oK 

(22-32oC)] 

ca. 5 >5.5 4.3 J(CHL) = <4.5 x 10-5 s-1

R2 = 0.947 -- 

Chlorpyrifos-oxon (50 ppb, ca. 

5.5 hours) 

Formaldehyde (30 ppb, ca. 1 

hour) 

SO2 (10 ppb, ca. 5.5 hours) 

Acetaldehyde (5 ppb, ca. 1-5 

hours) 

Chlorpyrifosoxon 

[307 ± 5oK 

(29-39oC)] 

ca. 4 >4 4.4 J(CHLO) = <4.4 x 10-5 s-1

R2 = 0.785 -- 

Formaldehyde (10 ppb, ca. 4.4 

hours) 

HCl (10 ppb, ca. 4.4 hours) 

Photo-oxidation (HONO) 

Chlorpyrifos 

[303 ± 5oK 

(25-35oC)] 

ca. 0.5 >2 1.3 kOH(CHL) = (9.1 ± 1.8) x 

10-11 cm3 molecule-1 s-1 -- 

Chlorpyrifos-oxon (40 ppb, ca. 

2 hours) 

Ozone (30 ppb, ca. 1 hour) 

Formic acid (5 ppb, ca. 1.5 

hours) 

Formaldehyde (20 ppb, ca. 1.5-2 

hours) 

SO2 (20 ppb, ca. 1.5-2 hours) 

Pyridinol (5 ppb, ca. 0.5-2 

hours) 

PAN (1 ppb, ca. 1 hour) 

Chlorpyrifosoxon 

[303 ± 5oK 

(25-35oC)] 

ca. 3.5 >3.5 7.8 kOH(CHLO) = (1.6 ± 0.8) 

x 10-11 cm3 molecule-1 s-1 -- 

Ozone (40 ppb, ca. 3.5 hours) 

Formic acid (25 ppb, ca. 3 

hours) 

Formaldehyde (20 ppb, ca. 2 

hours) 

SO2 (15 ppb, ca. 1.5 hours) 

HCl (10 ppb, ca. 3.5 hours) 

Methylglyoxal (10 ppb, ca. 3.5 

hours) 

Pyridinol (5 ppb, ca. 1.5 hours) 

A Model parameters and statistics and half-lives calculated by the study author. Observed DT50 and DT90 values were 

estimated by the reviewer. Calculated half-lives were not determined by the reviewer because only graphical 

representations of test compound concentrations were provided. B

 Dark control-adjusted and adjusted to a 12-hour/day photoperiod at 40°N latitude. 

C

 Concentrations (ppb) estimated by reviewer. 

-- = Not reported.
Chlorpyrifos (PC 059101) MRID 48789701 

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I. Materials And Methods

A. Materials:

1. Test materials Chlorpyrifos (CHL, p. 9) 

 Specific activity: Not applicable. 

 Radiochemical purity: Not applicable. 

Chemical purity: Not reported. 

 Batch No. Not reported. 

 

Chlorpyrifos-oxon (CHLO, p. 10) 

Specific activity: Not applicable. 

Radiochemical purity: Not applicable. 

Chemical purity: Not reported. 

Batch No. Not reported. 

 

Solubility in water: Chlorpyrifos: 1.05 mg/L (p. 9) 

UV absorption: Not reported. 

2. Reference Compounds: The following compounds were used in the analysis. 

Table 2. Reference Compounds 

Applicant’s Code Name Chemical Name Purity (%) Lot No. 

Chlorpyrifos (CHL) O,O-Diethyl-O-(3,5,6-trichloro-2-pyridyl) 

phosphorothioate -- -- 

Chlorpyrifos-oxon (CHLO) Phosphoric acid, diethyl 3,5,6-trichloro-2-pyridyl ester -- -- 

Pyridinol 3,5,6-Trichloro-2-pyridinol -- -- 

CYCL Cyclohexane 99.7 -- 

SF6 Sulphur hexafluoride 99.9 -- 

TMB 1,3,5-Trimethylbenzene (mesytilene) 99 -- 

Data obtained from pp. 9-13 of the study report. 

-- = Not reported. 
Chlorpyrifos (PC 059101) MRID 48789701 

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B. Study Design 

1. Experimental Conditions 

Table 3. Experimental Design 

Parameter Description 

Nature of light source 

Natural sunlight conditions at outdoor European Photoreactor (EUPHORE) 

in Valencia, Spain: longitude = -0.5o, latitude = 39.5oN. Experiments 

conducted between September 6-19, 2011. 

Emission wavelength spectrum Not applicable. 

Nominal light intensity 

Not reported. Graphical representations of the radiation (JNO2) time profiles 

during the experiments are presented in Figure 5B, p. 27; Figures 14A-B, p. 

39; Figure 19B, p. 44; Figure 27B, p. 58; Figure 35A-B, p. 68; and Figure 

41B, p. 73. 

Filters used Fluorine-ethene-propene (FEP) foil chambers 

Relationship to natural sunlight FEP transmission >80% for 280-640 nm.1

Method used to determine relations 

between light source and summer 

sunlight 

Inside chamber: Actinic flux measured using a calibrated filter radiometer 

specific to the photolysis frequency of NO2, and light intensity measured 

using a calibrated spectroradiometer (Bentham DM300, Gigahertz Optik 

Gmbh). 

Outside chamber: Pyranometer (CM3, Kipp & Zonen) measured global solar 

radiation (W/m2

) at 300 to 3,000 nm and photolysis frequency of NO2 → NO 

+ O(3P) reaction. In addition, the Tropospheric Ultraviolet and Visible (TUV) 

Radiation Model (UCAR/NCAR/ACD)2

 used to calculate global radiation 

(RAD, W/m2

) and photolysis frequency (J, s-1) of some species for clear sky 

conditions. 

Pyranometer radiation and TUV model data were compared to obtain a factor 

of the real atmospheric conditions during the experiments using the 

schematic presented in Figure 4, p. 20. 

Comparative photolysis frequency time profiles are presented in Figure 7, p. 

28 and Figure 29, p. 59. 

Duration of the tests (includes 

darkness intervals prior to sunlight 

exposure and at end of test after 

chamber closure) 

8 hours 49 minutes to 10 hours 29 minutes. 

Solution volume Not applicable. Test materials introduced into chamber in gas phase. 

Test 

concentration 

Nominal Not reported. 

Measured (initial 

mixing ratio) 

Experiments 1-4 using chlorpyrifos: 80-140 ppbv. 

Experiments 5-8 using chlorpyrifos-oxon: 150-300 ppbv. 

Control conditions 

Conventional control (dark) samples were not used. Treated air samples were 

removed during darkness interval (ca. 1.5-2.5 hours) prior to sunlight 

exposure. 

Number of 

replicates 

Irradiated Three types of experiments were conducted with each test material: 

1) Photolysis kinetics and products (Experiments 1 and 5; test material, 

SF6, CYCL), 

2) Photo-oxidation kinetics (Experiments 2-3 and 6-7; test material, 

SF6, TMB, CYCL, HONO), and 

3) Photo-oxidation products (Experiments 4 and 8; test material, SF6, 

HONO). 

Darkness 

Test apparatus Irradiated 

Outdoor European Photoreactor (EUPHORE) consisting of two identical 

half-sphere FEP foil chambers with volumes of ca. 200 m3

 (Figure 1, p. 14). 

The surface:volume ratio is close to one to minimize losses by adsorption 

onto the chamber walls. Retractable half-sphere protective housings are 
Chlorpyrifos (PC 059101) MRID 48789701 

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Parameter Description 

Darkness 

closed to exclude light. Two mixing fans within each chamber are used to 

achieve homogenous concentration. The floor is water-cooled. An air 

purification/drying system cleans and dries incoming air. Temperature and 

humidity within the chamber are continuously monitored using PT-100 

thermocouples and a dew-point mirror system (Walz TS-2), respectively. The 

chamber is equipped with various analytical instruments for in situ analysis 

and/or sampling as described below in section 2. Description of Analytical 

Procedures.

Traps 

Organics 

The following were utilized and are described below in section 2. 

Description of Analytical Procedures.

FTIR. 

Ozone, NOx and SO2 monitors. 

TEOM and SMPS aerosol mass concentration monitors. 

SPME. 

C-18 solid-phase cartridges and glass fiber filters (0.45-μm, internal porous). 

CO2 

Test material 

application 

Solvent Not applicable. 

Test solution volume 

used/treatment Not applicable. 

Application method Chlorpyrifos and chlorpyrifos-oxon were "gently heated" to accelerate 

introduction into the chamber. 

Evaporation of 

application solvent Not applicable. 

Indication of test material adsorbing to 

walls of test apparatus? 

Yes. In the photolysis experiments (Experiments 1 and 5), concentrations of 

both chlorpyrifos and chlorpyrifos-oxon "increased slightly" during the initial 

30 minutes of exposure, then decreased. 

Correction of adsorption? Yes 

Correction for leak rate? Yes; kdil based on loss of SF6 Correction for dilution from sampling? 

Experimental 

conditions 

Temperature (°C) 

Experiment 1: 300 ± 5oK (22-32oC). 

Experiment 5: 307 ± 5oK (29-39oC). 

Experiments 2-4 and 6-8: 303 ± 5oK (25-35oC). 

Continuous irradiation Test materials and reference compounds introduced into dark chamber, 

allowed to equilibrate, then sunlight exposure was initiated. Irradiation was 

conducted continuously for ca. 3.5-6 hours. Continuous darkness: 

Sample storage before analysis None reported. 

Data obtained from pp. 4, 8, 14-16, 19-23, 26, 29, 31, 38, 44, 57, 60-62, 66-68, 72; Figures 5A-B, p. 27; Figure 7, p. 28; 

Figure 10, p. 33; Figures 13A-B, p. 39; Figures 14A-B, p. 39; Figures 19A-B, p. 44; Figures 27A-B, p. 58; Figure 29, p. 

59; Figure 32, p. 63; Figures 34A-B, p. 68; Figures 35A-B, p. 68; Figures 41A-B, p. 73; Annex 8.3, pp. 119-122 of the 

study report. 

1 Bohaty, R.F.H. August 4, 2011. Environmental Fate Technical Team. Study Review: gas-phase photolysis and photooxidation of chlorpyrifos and chlorpyrifos-oxon. 

2 University Corporation for Atmospheric Research/National Center for Atmospheric Research/Atmospheric Chemistry 

Division. 
Chlorpyrifos (PC 059101) MRID 48789701 

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2. Description of Analytical Procedures 

In situ and On-line Analyses:

FTIR spectrometer (NICOLET 6700), fitted with a MCT-detector and combined with a long-pass 

absorption system (total optical length 554 m), was used for measurement of compounds in the 

spectral range between 650-4,000 cm-1 (pp. 15-16). Spectra were taken at a resolution of 1 cm-1 and 

sampling time of 5 minutes/spectrum. Compound groups detected by FTIR are listed in Table 2 (p. 

17). Spectra are presented in Annex 8.1, pp. 87-96. SF6 was measured to quantify gas dilution. 

Ozone (Monitor Labs 9810), NOx (Dasibi, ML9841A with TiO2 catalytic converter) and SO2

(Thermo Scientific 43i) concentrations were measured with the specified analyzers (p. 19). 

Aerosol mass concentrations were measured with two instruments (pp. 21-22). Real-time aerosol 

mass concentrations were measured with a tapered element oscillating monitor (TEOM, model 

1400a, Ruppercht and Patashnick Co. Inc.) at a 1-minute scan rate and sampling flow of 3 L/minute. 

Particle size distribution and aerosol mass concentrations were measured with a scanning mobility 

particle sizer (SMPS, model 3080, TSI Inc.) equipped with a differential mobility analyzer (DMA, 

model 3081) and condensation particle counter (CPC, model 3775). The SMPS measured size 

distributions in the 11-982 nm diameter range in real time with a 5-minute scan rate at 27oC; sheath 

and aerosol sampling flows were 4 L/minute and 0.30 L/minute, respectively. Aerosol volume 

concentrations from the SMPS were converted to aerosol mass concentrations by assuming a 

density of 1 g/cm3. 

Off-line Analyses: 

Solid-Phase Microextraction (SPME). Pre-conditioned fibers (65-μm) coated with 

polydimethylsiloxane/divinylbenzene (PDMS/DVB, Supelco) were exposed to the air at floor level 

in the chamber for 10 minutes, then analyzed directly by GC-FID with an HP-5MS column (0.25 

mm x 30 m, 0.25 mm film thickness, crosslinked 5% Ph Me Siloxane; pp. 22-23). 

C-18 and filter samples (for products determination experiments, pp. 23-24). Blank control and 

treated air samples were collected using C-18 solid-phase cartridges (type not specified) at a 

sampling flow rate of 1 L/minute. Aerosol samples were collected using pre-heated 47-mm 

diameter glass fiber filters (0.45-μm, internal porous) and a sampling flow rate of 23 L/minute. 

Particle mass determinations were made using a microbalance (model MC21S, Sartorius). 

Cartridges and filters were extracted with methylene chloride:acetonitrile (1:1, v:v) and sonication. 

The extract was centrifuged, taken to dryness under nitrogen, reconstituted in methylene 

chloride:acetonitrile and again taken to dryness. The sample was derivatized for 24 hours at room 

temperature with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) and 4-

fluorobenzaldehyde as an internal standard of carbonyl derivatization. The sample was then 

derivatized for 1 hour at 90oC with N-methyl-N-trimethyl-silyltrifluoroacetamide (MSTFA) and 

chlorosuccinic acid as an internal standard of hydroxyl derivatization. The double derivatized 

sample was then analyzed by GC/MS with the same column as used for SPME. 

Detection Limits (LOD, LOQ) for the Parent Compound and Transformation Products:

Limits of detection for FTIR analyses are presented in Table 4. Limits of detection and 

quantification for all other methodologies were not reported. 
Chlorpyrifos (PC 059101) MRID 48789701 

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Table 4. Compounds Detected by FTIR During the Experiments

Compound Formula Detection Limit 

(ppb) 

Accuracy 

(%) 

Analysis Region

(cm-1) 

Chlorpyrifos C9H11Cl3NO3PS 1.7 30.0 760-1225 

Chlorpyrifos-oxon C9H11Cl3NO4P 3.0 30.0 760-1225 

3,5,6-Trichloro-2-pyridinol C5H2Cl3NO 4.0 30.0 760-1225 

1,3,5-Trimethylbenzene C9H12 1.3 2.0 800-860 

Cyclohexane C6H12

15.3 9.0 800-1100 

0.7 7.0 2800-2900 

Formaldehyde HCHO 3.0 3.3 2700-2900 

Formic acid HCOOH 0.7 4.5 1050-1150 

Glyoxal C2H2O2 2.5 8.0 2750-2900 

Hydrochloric acid HCl 2.7 30.0 2700-2900 

Nitric acid HNO3 3.4 4.5 825-950 

Nitrous acid HONO 2.5 7.0 760-900 

Methylglyoxal C3H4O2 2.7 15.0 2750-2900 

Ozone O3 3.0 10.0 950-1100 

Peroxyacetyl nitrate C2H3NO5 0.7 3.0 760-1225 

Sulphur hexafluoride SF6 0.1 10.0 920-955 

Data obtained from Table 3, p. 18 of the study report. 
Chlorpyrifos (PC 059101) MRID 48789701 

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II. Results and Discussion 

A. Data 

Study results including distribution of radioactivity are presented in Tables 5a-5b. 

Table 5a. Photodegradation of Chlorpyrifos, Expressed as Approximate ppb, in Air 

Sampling Interval (hours) Prior to irradiation 

(ca. 1.5 hours) 

Chamber opened to 

sunlight 

(initial 30 minutes) 

Chamber closed 

(5 hours 21 minutes 

irradiation) 

End of test 

(ca. 1 hour) 

Replicate 1 1 1 1 

Component Irradiated [300 ± 5°K (22-32oC)] 

Chlorpyrifos (CHL)1 85 90 40 35 

Chlorpyrifos-oxon (CHLO)1 20-25 25 50 50 

SO2

2 <5 <5 10 10 

Ozone1, 3 5 5 115 110 

 Formic acid (HCOOH)1, 3 <5 <5 20 20 

Formaldehyde (HCHO)4 -- 30 10 -- 

Acetaldehyde (CH3CHO)4 -- 5 5 -- 

Glyoxal (C2H2O2)

5 Possible compound, not quantified. 

Methylglyoxal (C3H4O2)

5 Possible compound, not quantified. 

Others5, 6 Not quantified. 

Total Recovery Mass balances were not determined. 

Component Control (Dark) 

Dark control samples only taken during 1.5-hour equilibration interval prior to 

sunlight exposure. 

Results estimated by the reviewer from Figure 10, p. 33 of the study report. Irradiation interval from Annex 8.3, Table 

16, p. 119. Experiment temperature obtained from p. 31 of the study report. 

-- = Not reported. 

1 FTIR. 

2 Monitor, corrected for losses. 

3 May have originated from cyclohexane used to scavenge OH and Cl radicals (p. 34). 

4 LC/MS (not described in analytical methods); sampled at two intervals, after ca. 1 hour and 5 hours of irradiation.

5 C-18 solid-phase cartridge and GC/MS (Table 7, p. 36). 

6 Numerous unknowns (Tables 5-7, pp. 35-36). Analysis of C-18 cartridges with and without derivatization did not 

provide additional information for identifications, except that pyridinol was not detected (p. 34). 

 
Chlorpyrifos (PC 059101) MRID 48789701 

Page 10 of 26

Table 5b. Photodegradation of Chlorpyrifos-oxon, Expressed as Approximate ppb, in Air 

Sampling Interval (hours) Prior to irradiation 

(ca. 2.5 hours) 

Chamber opened to 

sunlight 

(initial 30 minutes) 

Chamber closed 

(4 hours 23 minutes 

irradiation) 

End of test 

(ca. 15 min) 

Replicate 1 1 1 1 

Component Irradiated [307 ± 5°K (29-39oC)] 

Chlorpyrifos-oxon (CHLO)1 125 150 90 75 

Ozone1, 2 <5 <5 75 75 

 Formic acid (HCOOH)1, 2 <5 <5 20 20 

Formaldehyde (HCHO)3 <5 <5 10 <5 

HCl3 <5 <5 10 <5 

Pyridinol4 Possible compound, not quantified. 

Glyoxal (C2H2O2)

4 Possible compound, not quantified. 

Methylglyoxal (C3H4O2)

4 Possible compound, not quantified. 

Others4, 5 Not quantified. 

Total Recovery Mass balances were not determined. 

Component Control (Dark) 

Dark control samples only taken during 2.5-hour equilibration interval prior to 

sunlight exposure. 

Results estimated by the reviewer from Figure 32, p. 63 of the study report. Irradiation interval from Annex 8.3, Table 

20, p. 121. Experiment temperature obtained from p. 62 of the study report. 

-- = Not reported. 

1 FTIR. 

2 May have originated from cyclohexane used to scavenge OH and Cl radicals (p. 34). 

3 Method not reported.

4 C-18 solid-phase cartridge and GC/MS (Tables 13-14, pp. 64-65). 

5 Numerous unknowns (Tables 12-14, pp. 64-65). Analysis of C-18 cartridges with and without derivatization did not 

provide additional information for identifications (p. 63). 
Chlorpyrifos (PC 059101) MRID 48789701 

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B. Mass Balance

Mass balances were not determined. 

C. Volatilization 

Experiments conducted in gas-phase. 

D. Transformation of Chlorpyrifos and Chlorpyrifos-oxon 

Transformation kinetics of the chlorpyrifos and chlorpyrifos-oxon are summarized in Table 6, with 

transformation product information summarized in Tables 7a-7b. Degradation rates were quantified 

taking into account losses from the test chamber due to leakage, dilution from sampling and 

adsorption/desorption on the chamber walls (p. 8). 

Chlorpyrifos - Photolysis. Degradation of chlorpyrifos in an irradiated gas-phase was rapid. The 

study author calculated a lifetime of 6.2 hours (JNO2 = 9.5 ± 1.7 x 10-3) and a half-life of 4.3 hours 

(p. 31). Chlorpyrifos slightly decreased during the ca. 1.5-hour darkness interval prior to irradiation 

(Figure 10, p. 33). 

Despite interferences, particle formation during irradiation was detected with both the SMPS and 

TEOM systems, with secondary organic aerosol (SOA) yields from chlorpyrifos photolysis, 

calculated from aerosol mass formed and corrected for wall losses, of 1.6% for both systems (p. 37). 

Chlorpyrifos - Photo-oxidation (HONO). The study author calculated a lifetime of 1.95 hours and a 

half-life of 1.3 hours for an average 12-hour daytime concentration of OH radicals of 1.56 x 106

radical/cm3

 (p. 43). Dark control samples were not taken in the presence of HONO. 

The cyclohexane rate loss in relation to that of TMB of [kOH(CYCL)/kOH(TMB] = 0.13, compared 

to the calculated value of 0.14 based on their rate constants for reaction with OH, indicated that Cl 

production in the reaction of chlorpyrifos with OH radicals did not significantly affect the rate 

constant [kOH(CHL)] determined for the reaction of OH with chlorpyrifos (p. 41). 

Concentrations measured by FTIR and SPME-GC/FID were similar with no irradiation (start and 

end of test), but differed under sunlight exposure, indicating an intermediate other than 

chlorpyrifos-oxon and pyridinol was formed, but with similar structural features as those 

compounds (pp. 41, 44). 

An absence of HCl in the products formed indicated that degradation of the aromatic ring did not 

occur in the initial stages of oxidation (p. 48). 

Despite interferences, SOA yields from chlorpyrifos photo-oxidation, calculated from the ratio of 

aerosol mass formed to amount of chlorpyrifos reacted at maximum particle concentration, were 

26% and 14% for TEOM and SMPS, respectively (p. 57). 

Chlorpyrifos-oxon - Photolysis. Degradation of chlorpyrifos-oxon in an irradiated gas-phase was 

rapid. The study author calculated a lifetime of 6.2 hours (JNO2 = 9.5 ± 1.7 x 10-3) and a half-life of 

4.4 hours (p. 62). Chlorpyrifos-oxon remained relatively constant during the ca. 2.5-hour darkness 

interval prior to irradiation (Figure 32, p. 63). 
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Despite interferences, particle formation during irradiation, as measured by SMPS, was determined 

to be "unimportant" (p. 66). 

Chlorpyrifos-oxon - Photo-oxidation (HONO). The study author calculated a lifetime of 11.2 hours 

and a half-life of 7.8 hours for an average 12-hour daytime concentration of OH radicals of 1.56 x 

106

 radical/cm3 (p. 72). Dark control samples were not taken in the presence of HONO. 

The cyclohexane rate loss in relation to that of TMB of [kOH(CYCL)/kOH(TMB] = 0.14, compared 

to the calculated value of 0.14 based on their rate constants for reaction with OH, indicated that Cl 

production in the reaction of chlorpyrifos-oxon with OH radicals did not significantly affect the rate 

constant [kOH(CHL)] determined for the reaction of OH with chlorpyrifos-oxon (p. 69). 

Concentrations measured by FTIR and SPME-GC/FID were similar with no irradiation (start and 

end of test), but differed under sunlight exposure, indicating an unidentified intermediate having 

similar structural features as chlorpyrifos-oxon was formed (pp. 70, 73). 

An absence of HCl in the products formed indicated that degradation of the aromatic ring did not 

occur in the initial stages of oxidation (p. 76). 

Despite interferences, SOA yields from chlorpyrifos-oxon photo-oxidation, calculated from the 

ratio of aerosol mass formed to amount of chlorpyrifos-oxon reacted at maximum particle 

concentration, were 35% and 11% for TEOM and SMPS, respectively (p. 79). 
Chlorpyrifos (PC 059101) MRID 48789701 

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Table 6. Phototransformation in Air 

Compound 

Name 

Observed 

DT50 

(hours) 

Observed 

DT90

(hours)

Calculated

Half-life 

(hours)A 

Model Parameters Model 

Statistics 

Dark Control 

Adjusted 

Half-life 

(hours)

Environmental 

Half-life 

(days)

Photolysis 

Chlorpyrifos 

[300 ± 5oK] ca. 5 >5.5 4.3 

kdil = 1.2 x 10-5 s-1

kdil + kwall(T) + kdes(T) = 

-7 x 10-6

J(CHL) = <4.5 x 10-5 s-1

R2 = 0.947 -- -- 

Control: 

Chlorpyrifos 

Dark control samples were not 

used. -- -- 

Chlorpyrifosoxon 

[307 ± 5oK] 

ca. 4 >4 4.4 

kdil = 1.04 x 10-5 s-1

kdil + kwall(T) + kdes(T) = 

-4 x 10-5

J(CHLO) = <4.4 x 10-5 s-1

R2

 = 0.785 -- -- 

Control: 

Chlorpyrifosoxon 

Dark control samples were not 

used. -- -- 

Photo-oxidation (HONO) 

Chlorpyrifos 

[303 ± 5oK] ca. 0.5 >2 1.3 kOH(CHL) = (9.1 ± 1.8) x 

10-11 cm3 molecule-1 s-1 -- -- -- 

Control: 

Chlorpyrifos 

Dark control samples were not 

used. -- -- 

Chlorpyrifosoxon 

[303 ± 5oK] 

ca. 3.5 >3.5 7.8 kOH(CHLO) = (1.6 ± 0.8) x 

10-11 cm3 molecule-1 s-1 -- -- -- 

Control: 

Chlorpyrifosoxon 

Dark control samples were not 

used. -- -- 

A Results obtained from pp. 30-31; Figure 9, p. 31; pp. 42-43, 61-62; Figure 31, p. 62; pp. 71-72 of the study report. Halflives were calculated by the study author. Photolysis rates take into account losses from the chamber through leakage, 

dilution from sampling and adsorption/desorption on the chamber walls (pp. 8, 30-31, 60-62). Photo-oxidation rates take 

into account losses from the chamber through leakage, dilution from sampling, adsorption/desorption on the chamber 

walls and photolysis of the test compound prior to addition of HONO (pp. 38-39, 66-67). Observed DT50 and DT90 values 

were estimated by the reviewer (Figure 10, p. 33; Figure 24, p. 47; Figure 32, p. 63; Figure 46, p. 76; DER Attachment 

2). Calculated half-lives were not determined by the reviewer because only graphical representations of test compound 

concentrations were provided. 

-- = Not reported. 
Chlorpyrifos (PC 059101) MRID 48789701 

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Table 7a. Transformation Products of Chlorpyrifos 

Transformation Products

Maximum 

ppb 

Observed

Associated 

Interval 

Final ppb 

Observed 

Final 

Interval1 

Calculated 

Molar Yield

(%) 

 Photolysis 

Irradiated 

Samples 

Chlorpyrifos-oxon (CHLO) 50 ca. 5.5 hours 50 ca. 5.5 hours 11 

SO2 10 ca. 5.5 hours 10 ca. 5.5 hours 82 

Ozone (FTIR)2 115 ca. 5.5 hours 115 ca. 5.5 hours -- 

Formic acid (HCOOH)2 20 ca. 5.5 hours 20 ca. 5.5 hours -- 

Formaldehyde (HCHO)3 30 ca. 1 hour 10 ca. 5 hours -- 

Acetaldehyde (CH3CHO)3 5 ca. 1 hour 5 ca. 5 hours -- 

Glyoxal Possible compound, not quantified (Table 7, p. 36). 

Methylglyoxal Possible compound, not quantified (Table 7, p. 36). 

Others Numerous unknowns, not quantified (Tables 6-7, pp. 35-36). 

Dark 

Controls 

During the dark interval prior to irradiation, chlorpyrifos-oxon were detected at a maximum of ca. 

25 ppb at 1.5 hours just prior to opening the chamber. SO2 was also reportedly detected, but could 

not be quantified from the graphic representation (p. 32; Figure 10, p. 33). 

 Photo-oxidation (HONO) 

Irradiated 

Samples 

Chlorpyrifos-oxon (CHLO) 40 ca. 2 hours 40 ca. 2 hours 10 and 304

SO2 20 ca. 1.5 hours 20 ca. 2 hours 17 ± 5 

Ozone (Monitor)7 30 ca. 1 hour 10 ca. 2 hours 30 ± 10 

Ozone (FTIR) 50 ca. 0.5 hour 25 ca. 2 hours -- 

Formic acid (HCOOH) 20 ca. 2 hours 20 ca. 2 hours -- 

Formaldehyde (HCHO) 20 ca. 1.5 hours 20 ca. 2 hours <17 

Pyridinol 5 ca. 0.5 hour 5 ca. 2 hours 8 ± 45

Peroxyacetyl nitrate 

(PAN)6 1 ca. 1 hour <1 ca. 2 hours <10 

Aerosols -- -- -- -- 25 ± 8 

Glyoxal Possible compound, not quantified (Table 11, p. 53). 

Others Numerous unknowns, not quantified (Tables 9-11, pp. 50-54). 

Dark 

Controls Dark control samples were not taken in presence of HONO. 

Concentrations in terms of ppb estimated by the reviewer from Figure 10, p. 33; Figure 24, p. 47 of the study report. 

Calculated yields reported by study author (p. 32; Table 8, p. 49). 

1 Chamber closed. 

2 Yields not calculated because may have originated from cyclohexane used to scavenge OH and Cl radicals (p. 34). 

3 From analyses of samples taken after ca. 1 and 5 hours of irradiation. 

4 Not corrected and corrected for secondary losses with OH, where kOH(CHLO) = 1.5 x 10-11 (this study) and 

[OH]average = 1.31 x 10-7 (calculated from losses of CHL based on kOH(CHL) = 9.10 x 10-11; Table 8, p. 49). 

5 Corrected for secondary losses with OH, where kOH(PYRDIINOL) = 1.8 X 10-13 (EPIWEB) and [OH]avearge = 1.31 x 

10-7 (calculated from losses of CHL based on kOH(CHL) = 9.10 x 10-11; Table 8, p. 49). 

6 Secondary product. Yield dependent on NO2/NO concentration ratio. Corrected by thermal losses of PAN at 303oK k 

= 3.3 x 10-4 s-1 (Table 8, p. 49). 

7 Discrepancies between FTIR and Monitor for ozone due to possible positive interferences with FTIR (p. 48). 

-- = Not reported.
Chlorpyrifos (PC 059101) MRID 48789701 

Page 15 of 26

Table 7b. Transformation Products of Chlorpyrifos-oxon 

Transformation Products

Maximum 

ppb 

Observed

Associated 

Interval 

Final ppb 

Observed Final Interval1

 Photolysis 

Irradiated 

Samples2 

Ozone (FTIR)3 75 ca. 4.4 hours 75 ca. 4.4 hours 

Formic acid (HCOOH)3 20 ca. 4.4 hours 20 ca. 4.4 hours 

Formaldehyde (HCHO) 10 ca. 4.4 hours 10 ca. 4.4 hours 

HCl 10 ca. 4.4 hours 10 ca. 4.4 hours 

Pyridinol Possible compound, not quantified (Tables 13-14, pp. 64-65) 

Glyoxal Possible compound, not quantified (Table 14, p. 65). 

Methylglyoxal Possible compound, not quantified (Table 14, p. 65). 

Others Numerous unknowns, not quantified (Tables 13-14, pp. 64-65). 

Dark 

Controls None detected during the ca. 2.5-hour dark interval prior to irradiation. 

 Photo-oxidation (HONO) 

Irradiated 

Samples 

Ozone (Monitor)4 40 ca. 3.5 hours 40 ca. 3.5 hours 

Ozone (FTIR)4 60 ca. 3 hours 40 ca. 3.5 hours 

Formic acid (HCOOH) 25 ca. 3.5 hours 25 ca. 3.5 hours

Formaldehyde (HCHO) 20 ca. 2 hours 15 ca. 3.5 hours 

SO2 15 ca. 1.5 hours 10 ca. 3.5 hours

HCl 10 ca. 3.5 hours 10 ca. 3.5 hours 

Methyglyoxal (m-Gly) 10 ca. 3.5 hours 10 ca. 3.5 hours 

Pyridinol 5 ca. 1.5 hours <5 ca. 3.5 hours 

Peroxyacetyl nitrate (PAN) Observed, not quantified (p. 75) 

Acetone Possible compound, not quantified (Table 15, p. 77) 

Others Numerous unknowns, not quantified (Table 15, pp. 77-78). 

Dark 

Controls Dark control samples were not taken in presence of HONO. 

Concentrations in terms of ppb estimated by the reviewer from Figure 32, p. 63; Figure 46, p. 76 of the study report. 

1 Chamber closed. 

2 No identifiable products detected with FTIR (p. 62). 

3 May have originated from cyclohexane used to scavenge OH and Cl radicals (p. 34). 

4 Yield approached 30% (O3 monitor, p. 76). Discrepancies between FTIR and Monitor for ozone due to possible 

positive interferences with FTIR (p. 76).
Chlorpyrifos (PC 059101) MRID 48789701 

Page 16 of 26

A transformation pathway was provided by the study author and is illustrated below (Figure 25, p. 

56). 

Figure 1. Photo-oxidation (HONO) degradation pathway for chlorpyrifos. Pathway A: Addition of 

OH to the PS bond. Structures include identified and quantified compounds, plus tentatively 

identified compounds through derivatization and GC/MS. 
Chlorpyrifos (PC 059101) MRID 48789701 

Page 17 of 26

III. Study Deficiencies and Reviewer’s Comments

1. Dow AgroSciences previously submitted to EFED a study outline for investigation of gas-phase 

photolysis and photo-oxidation of chlorpyrifos and chlorpyrifos-oxon. The following are the 

deficiencies (a, b, c, etc.) EFED identified in the study outline and whether or not those 

deficiencies were addressed in the study conduct. 

a) The test substances are unlabeled. Radiolabeled test substances are preferred specifically to 

monitor mass balances throughout the study and to ensure that all transformation products at 

≥10% of the applied or that are toxicologically relevant are identified. Additionally, would 

potential losses from the system through dilution or sorption of the test material to the 

incubation vessel walls be monitored? 

i. The test substances used in this study were unlabeled. Additionally, the test substances 

were incompletely characterized; purities and lot/batch numbers were not reported. 

ii. Material balances were not monitored in this study. Molar yields were estimated for 

photolysis and photo-oxidation of chlorpyrifos (p. 32; Table 8, p. 49). 

iii. It could not be determined whether or not any transformation products at ≥10% of the 

applied or that are toxicologically relevant were present, but not identified. FTIR and 

Solid-Phase Microextraction (SPME)/GC-FID were the primary methods for 

identifications. It was unclear whether the provided FTIR spectra were reference spectra or 

experimental spectra from sample analyses (pp. 18-19; Annex 8.1, pp. 87-96). GC/MS of 

derivatized samples obtained from C-18 SPE cartridges only partially characterized 

possible compounds and/or structures. 

iv. Losses from the test chamber due to leakage, dilution from sampling and 

adsorption/desorption on the chamber walls were quantified and taken into account for 

determination of degradation rates (pp. 8, 29-30, 60-61). 

b) At a minimum, reference standards and analysis methods for chlorpyrifos, chlorpyrifos-oxon 

and 3,5,6-trichloro-2-pyridinol should be utilized. Those three references standards were 

utilized (pp. 9-11). The other reference compounds, cyclohexane, sulphur hexafluoride and 

1,3,5-trimethylbenzene, were included as monitoring controls (pp. 12-13). 

c) Temperature maintenance was not specified in the study outline. The incubation temperature 

should be relatively constant at 30oC. The chamber is equipped with a water-cooled floor, 

mixing fans and an air purification/drying system (p. 14). Eight experiments were conducted 

at the following temperatures: 

Experiment 1 (chlorpyrifos photolysis) at 300 ± 5oK (22-32oC; p. 31), 

Experiment 5 (chlorpyrifos-oxon photolysis) at 307 ± 5oK (29-39oC; p. 62), and 

Experiments 2-4 (chlorpyrifos photo-oxidation) and 6-8 (chlorpyrifos-oxon photooxidation) at 303 ± 5oK (25-35oC; p. 38). 
Chlorpyrifos (PC 059101) MRID 48789701 

Page 18 of 26

d) The ability of the SPME to accurately quantify chlorpyrifos, chlorpyrifos-oxon and 3,5,6-

trichloro-2-pyridinol in the chamber should be shown. FTIR was used as the primary 

analytical method. No method validations were included as part of the submission. 

e) Experiments should be conducted in replicate. Only the photo-oxidation kinetics 

experiments (Experiments 2-3 for chlorpyrifos, and 6-7 for chlorpyrifos-oxon) were 

conducted in replicate. Individual experiments were conducted for chlorpyrifos photolysis 

kinetics/products (Experiment 1), chlorpyrifos photo-oxidation products (Experiment 4), 

chlorpyrifos-oxon photolysis kinetics/products (Experiment 5) and chlorpyrifos-oxon photooxidation products (Experiment 8). 

f) Controls were not described in the study outline. Conventional dark controls with air treated 

at the same application rate and incubated at the same temperature for the same duration as 

the irradiated samples were not utilized. Treated air samples were collected during a 1.5- to 

2.5-hour equilibration interval during which the chamber was held in darkness prior to 

sunlight exposure. 

g) Test duration was not specified in the study outline. Air samples should be analyzed at four 

or more sampling time intervals with at least one observation made after one-half life of the 

test substance has degraded or 30 days, whichever comes first. FTIR spectra were 

continuously taken at a sampling time of 5 minutes/spectrum (p. 16). For chlorpyrifos 

photolysis, chlorpyrifos decreased from ca. 90 ppb at start of irradiation to ca. 40 ppb when 

the chamber closed (Figure 10, p. 33). For chlorpyrifos-oxon photolysis, chlorpyrifos-oxon 

decreased from ca. 150 ppb at start of irradiation to ca. 90 ppb when the chamber closed, 

then further decreased to ca. 75 ppb at the final sampling (Figure 32, p. 63). 

h) Light source. The intensity of the experimental light should be compared to natural summer 

sunlight at 40oN. The EUPHORE is located in Valencia, Spain (39.5oN) and the experiments 

were conducted between September 6th and 19th, 2011(p. 14; Annex 8.3, pp. 119-122). 

Photolysis frequencies and/or radiation were measured during the experiments, but not 

compared to natural summer sunlight at 40oN (Figure 5B, p. 27; Figure 7, p. 28; Figure 14, 

p. 39; Figure 19B, p. 44; Figure 27B, p. 58; Figure 29, p. 59; Figure 35, p. 68; Figure 41B, p. 

73). It could not be determined if the reduction in solar transmission (<20%) through the 

chamber wall was considered in the degradation rate equations. 

2. The chlorpyrifos photolysis and photo-oxidation "products" experiments were terminated before 

the pattern of formation and decline of chlorpyrifos-oxon was established (Figure 10, p. 33; 

Figure 24, p. 47). 

3. Limits of detection and quantification for methodologies other than FTIR were not reported. 

IV. REFERENCES 

1. U.S. Environmental Protection Agency. 2008. Fate, Transport and Transformation Test 

Guidelines, OCSPP 835.2370, Photodegradation in Air. Office of Chemical Safety and Pollution 

Prevention, Washington, DC. EPA 712-C-08-014. 
Chlorpyrifos (PC 059101) MRID 48789701 

Page 19 of 26

DER ATTACHMENT 1. Chlorpyrifos and Its Environmental Transformation Products. A 

Code Name/ Synonym Chemical Name Chemical Structure Study Type MRID Maxim

(

PARENT

Chlorpyrifos IUPAC: O,O-Diethyl O-3,5,6-

trichloro-2-pyridyl phosphorothioateCAS: O,O-Diethyl O-(3,5,6-trichloro-2-pyridinyl) phosphorothioate CAS No.: 2921-88-2 Formula: C9H11Cl3NO3PS 

MW: 350.59 g/molSMILES: CCOP(=S)(OCC)Oc1nc(CL)c(CL)cc1CL

835.2370 

Photodegradation 

in air 

48789701 Pho

90 (ca

 TRANSFORMATION PRODUCTS 

Chlorpyrifos oxon IUPAC: Diethyl(3,5,6-trichloro-2-

pyridyl)phosphate CAS: Diethyl 3,5,6-trichloro(2,6)pyridine-2-yl phosphate CAS No.: 5598-15-2 Formula: C9H11Cl3NO4P 

MW: 334.52 g/molSMILES: O=P(Oc1nc(c(cc1CL)CL)CL)(OCC)OCC 

Cl N P

O

H H

H

O

HH

H

O O

Cl Cl

835.2370 

Photodegradation 

in air 

48789701 

Pho

50 (ca

Photo-

40 (c
Chlorpyrifos (PC 059101) MRID 48789701 

Page 20 of 26

Code Name/ Synonym Chemical Name Chemical Structure Study Type MRID Maxim

(

Sulfur dioxide IUPAC: Sulfur dioxide 

CAS No.: 7446-09-5 Formula: SO2

MW: 64 g/molSMILES: O=S=O

835.2370 

Photodegradation 

in air 

48789701 

Pho

10 (ca

Photo-

20 (ca

Ozone IUPAC: Ozone 

CAS No.: 10028-15-6 Formula: O3MW: 48 g/molSMILES: O=O=O

835.2370 

Photodegradation 

in air 

48789701 Photo-

30 (c

Formic acid IUPAC: Formic acid 

CAS No.: 64-18-6 Formula: CH2O2MW: 46 g/molSMILES: O=CO

835.2370 

Photodegradation 

in air 

48789701 Photo-

20 (c

Formaldehyde IUPAC: Formaldehyde 

CAS No.: 50-00-0 Formula: CH2O 

MW: 30 g/molSMILES: O=C

835.2370 

Photodegradation 

in air 

48789701 

Pho

30 (c

Photo-

20 (ca

Acetaldehyde IUPAC: Acetaldehyde 

CAS No.: 75-07-0 Formula: C2H4O MW: 44 g/molSMILES: O=CC

835.2370 

Photodegradation 

in air 

48789701 Pho

5 (ca
Chlorpyrifos (PC 059101) MRID 48789701 

Page 21 of 26

Code Name/ Synonym Chemical Name Chemical Structure Study Type MRID Maxim

(

Pyridinol IUPAC: 3,5,6-Trichloropyridin-2-ol

CAS: 3,5,6-Trichloro-2-pyridinol CAS No.: 6515-38-4 Formula: C5H2Cl3NO 

MW: 198.44 g/molSMILES: Oc1nc(CL)c(CL)cc1CL

835.2370 

Photodegradation 

in air 

48789701 Photo-

5 (ca. 

Peroxyacetyl nitrate 

(PAN) 

IUPAC: Peroxyacetyl nitrateCAS No.: 2278-22-0 Formula: C2H3NO5

MW: 121.05 g/molSMILES: CC(=O)OON(=O)=O

835.2370 

Photodegradation 

in air 

48789701 Photo-

1 (c

Glyoxal IUPAC: Ethanedial 

CAS No.: 107-22-2 Formula: C2H2O2

MW: 58.04 g/molSMILES: O=CC=O

835.2370 

Photodegradation 

in air 

48789701 

Pho

Photo-

Methyl glyoxal CAS: Propanal, 2-oxoCAS No.: 78-98-8 

Formula: C3H4O2

MW: 72.06 g/molSMILES: O=CC(=O)C

835.2370 

Photodegradation 

in air 

48789701 Pho
Chlorpyrifos (PC 059101) MRID 48789701 

Page 22 of 26

Code Name/ Synonym Chemical Name Chemical Structure Study Type MRID Maxim

(

REFERENCE COMPOUNDS NOT IDENTIFIED 

CYCL IUPAC: Cyclohexane 

CAS No.: 110-82-7 Formula: C6H12

MW: 84.16 g/molSMILES: C(CCCC1)C1

835.2370 

Photodegradation 

in air 

48789701 

SF6 IUPAC: Sulfur hexafluoride 

CAS No.: 2251-62-4 Formula: F6S MW: 146.06 g/molSMILES: FS(F)(F)(F)(F)F

835.2370 

Photodegradation 

in air 

48789701 

TMB IUPAC: 1,3,5-Trimethylbenzene 

CAS No.: 108-67-8 Formula: C9H12

MW: 120.19 g/molSMILES: c(cc(cc1C)C)(c1)C

835.2370 

Photodegradation 

in air 

48789701 

A AR means “applied radioactivity”. MW means “molecular weight”. NQ means “not quantified”. NA means “not applicable”. 
Chlorpyrifos (PC 059101) MRID 48789701 

Page 23 of 26

Table 2. Chlorpyrifos oxon and Its Environmental Transformation Products. A 

Code Name/ Synonym Chemical Name Chemical Structure Study Type MRID Maxim

(

PARENT

Chlorpyrifos oxon IUPAC: Diethyl(3,5,6-trichloro-2-

pyridyl)phosphate CAS: Diethyl 3,5,6-trichloro(2,6)pyridine-2-yl phosphate CAS No.: 5598-15-2 Formula: C9H11Cl3NO4P 

MW: 334.52 g/molSMILES: O=P(Oc1nc(c(cc1CL)CL)CL)(OCC)OCC 

Cl N P

O

H H

H

O

HH

H

O O

Cl Cl

835.2370 

Photodegradation 

in air 

48789701 Pho

150 (ca

 TRANSFORMATION PRODUCTS 

Sulfur dioxide IUPAC: Sulfur dioxide 

CAS No.: 7446-09-5 Formula: SO2

MW: 64 g/molSMILES: O=S=O

835.2370 

Photodegradation 

in air 

48789701 Photo-

15 (ca

Ozone IUPAC: Ozone 

CAS No.: 10028-15-6 Formula: O3MW: 48 g/molSMILES: O=O=O

835.2370 

Photodegradation 

in air 

48789701 Photo-

40 (ca
Chlorpyrifos (PC 059101) MRID 48789701 

Page 24 of 26

Code Name/ Synonym Chemical Name Chemical Structure Study Type MRID Maxim

(

Formic acid IUPAC: Formic acid 

CAS No.: 64-18-6 Formula: CH2O2MW: 46 g/molSMILES: O=CO

835.2370 

Photodegradation 

in air 

48789701 Photo-

25 (ca

Formaldehyde IUPAC: Formaldehyde 

CAS No.: 50-00-0 Formula: CH2O 

MW: 30 g/molSMILES: O=C

835.2370 

Photodegradation 

in air 

48789701 

Pho

10 (ca

Photo-

20 (c

Pyridinol IUPAC: 3,5,6-Trichloropyridin-2-ol

CAS: 3,5,6-Trichloro-2-pyridinol CAS No.: 6515-38-4 Formula: C5H2Cl3NO 

MW: 198.44 g/molSMILES: Oc1nc(CL)c(CL)cc1CL

835.2370 

Photodegradation 

in air 

48789701 

Pho

Photo-

5 (ca

Peroxyacetyl nitrate 

(PAN) 

IUPAC: Peroxyacetyl nitrateCAS No.: 2278-22-0 Formula: C2H3NO5

MW: 121.05 g/molSMILES: CC(=O)OON(=O)=O

835.2370 

Photodegradation 

in air 

48789701 Photo-

HCl IUPAC: Hydrochloric acid

CAS No.: 7647-01-0 Formula: ClH MW: 36 g/molSMILES: Cl

835.2370 

Photodegradation 

in air 

48789701 

Pho

10 (ca

Photo-

10 (ca
Chlorpyrifos (PC 059101) MRID 48789701 

Page 25 of 26

Code Name/ Synonym Chemical Name Chemical Structure Study Type MRID Maxim

(

Methyl glyoxal CAS: Propanal, 2-oxoCAS No.: 78-98-8 

Formula: C3H4O2

MW: 72.06 g/molSMILES: O=CC(=O)C

835.2370 

Photodegradation 

in air 

48789701 

Pho

Photo-

10 (ca

Glyoxal IUPAC: Ethanedial 

CAS No.: 107-22-2 Formula: C2H2O2

MW: 58.04 g/molSMILES: O=CC=O

835.2370 

Photodegradation 

in air 

48789701 Pho

Acetone IUPAC: 2-Propanone 

CAS No.: 67-64-1 Formula: C3H6O MW: 58.08 g/molSMILES: O=C(C)C

835.2370 

Photodegradation 

in air 

48789701 Photo-

REFERENCE COMPOUNDS NOT IDENTIFIED 

CYCL IUPAC: Cyclohexane 

CAS No.: 110-82-7 Formula: C6H12

MW: 84.16 g/molSMILES: C(CCCC1)C1

835.2370 

Photodegradation 

in air 

48789701 
Chlorpyrifos (PC 059101) MRID 48789701 

Page 26 of 26

Code Name/ Synonym Chemical Name Chemical Structure Study Type MRID Maxim

(

SF6 IUPAC: Sulfur hexafluoride 

CAS No.: 2251-62-4 Formula: F6S MW: 146.06 g/molSMILES: FS(F)(F)(F)(F)F

835.2370 

Photodegradation 

in air 

48789701 

TMB IUPAC: 1,3,5-Trimethylbenzene 

CAS No.: 108-67-8 Formula: C9H12

MW: 120.19 g/molSMILES: c(cc(cc1C)C)(c1)C

835.2370 

Photodegradation 

in air 

48789701 

A AR means “applied radioactivity”. MW means “molecular weight”. NQ means “not quantified”. NA means “not applicable”.