Registration Dossier

Environmental fate & pathways

Additional information on environmental fate and behaviour

Administrative data

Endpoint:
additional information on environmental fate and behaviour
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
test procedure in accordance with national standard methods
Cross-reference
Reason / purpose:
reference to other study
Reference
Endpoint:
phototransformation in air
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2012
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Qualifier:
no guideline available
Principles of method if other than guideline:
Indirect photolysis with *OH radical
GLP compliance:
no
Specific details on test material used for the study:
- Name of test material (as cited in study report): L-21343
Light source:
other: Mercury-Xenon lamp
Details on light source:
- Lamp: Oriel Instruments UV Lamp, Model 66921 equipped with a 480 W Mercury Xenon bulb
- Emission wavelength spectrum: See Figure 1
- Filters used and their purpose: Manufacturer specifies a transmission range of 200-2500 nm for lamp window. No additional filtration. Some attenuation of IR is expected at quartz window of gas cell.
Details on test conditions:
The atmospheric lifetime of Novec 7700 was determined with respect to reaction with hydroxyl radical (OH). Hydroxyl radicals were produced by photolysis of ozone in the presence of water vapor. The results are based on the relative concentration of Novec 7700 and one of the reference compounds methane (CH4) or 1,1,1-trichloroethane, in the presence of the OH radical at 26-29 °C and at a pressure of approximately one atmosphere. The concentrations were monitored using continuous in-situ Fourier Transform Infrared (FTIR) spectroscopy according to EPA method 320.

The measurements were performed in a 10 meter (5.7L volume) heated FTIR gas cell equipped with a polished semiconductor-grade quartz window (Glass Tech Supplies, Inc.). An I-Series FTIR (Midac Corp.) was used for the analysis. The light source was placed above the gas cell and the UV radiation was introduced to the reagent gases through the quartz window. Novec 7700, methane, humidified nitrogen, dry nitrogen, and ozone were mixed using mass flow controllers. The gas mix was flowed through the FTIR cell. The experiment was conducted at approximately 1 atmosphere pressure. When the concentration of the gases reached the target value, the cell was sealed.

For the first part of the experiment, the quartz cell window was blocked with a shutter and the reagent gas concentrations were monitored for 12 to 36 minutes. After this initial period the lamp was switched on and the gases inside the cell were exposed to UV radiation. The decay of the gas concentrations in presence of UV light radiation was monitored for 37-70 minutes. The linear part of the degradation curve (ca. 40 minutes) was used to determine relative reaction rates. Atmospheric lifetime was then estimated for Novec 7700 by applying the relative reaction rates to the atmospheric lifetime of the appropriate reference substance. Three runs were done in total. Total test duration was 75-90 minutes.

During separate experiments, the sample gas mix was collected for subsequent analysis by GC-MS to ensure that only Novec 7700 was being measured and to screen for possible degradation products. Other degradation products were detected directly be FTIR.

Phototransformation of a specific degradation intermediate identified during the test was done as a second test. The same phototransformation chamber was used with illumination using an Oriel model 6251 UV lamp with a 75-W mercury-xenon bulb and 285-nm cutoff filter. No ozone was used, and acetaldehyde served as reference gas. Concentrations of Novec 7700 were ca. 0.6 ppmv, while concentrations of acetaldehyde were 27-37 ppmv. Duplicate runs were done. Total test durations were ca. 100 min or ca. 130 min.
Reference substance:
yes
Remarks:
methane or 1,1,1-trichloroethane
Key result
DT50:
3.9 yr
Test condition:
Average of three runs with methane or 1,1,1-trichloromethane as reference substance
DT50:
0.9 d
Test condition:
Average of two runs for C10 diketone transformation product
Transformation products:
yes
No.:
#1
No.:
#2

Concentrations of Novec 7700 and a reference substance were monitored in the absence of UV/Visible light to assess the background effect of dark reactions (adsorption to or reaction with the cell walls). Less than 1% losses were observed (Att. 1-3). Based on this result Novec 7700 does not react appreciably with either ozone or water vapor. On irradiation, linear declines in concentration of ozone, Novec 7700 and methane were observed for the first phase of illumination (Att. 1-3). Regression of this portion of the decay curves produced the following equations:

Run 1:

1,1,1-trichloroethane: C/Co = -0.00949 * time + 0.34381, R-sq = 0.997

Novec 7700: C/Co = -0.00953 * time + 0.30284, R-sq = 0.99

k,Novec 7700 / k,1,1,1-trichloroethane = -0.00953/-0.00949 = 1.00

lifetime, Novec 7700 = k,Novec 7700/k,1,1,1-trichloroethane * lifetime, 1,1,1-trichloroethane

Based on the accepted value of 1,1,1-trichloroethane lifetime, 5 years, the atmospheric lifetime of Novec 7700 is 5.0 years.

Run 2:

Methane: C/Co = -0.0135 * time + 0.4130, R-sq = 0.99

Novec 7700: C/Co = -0.00592 * time + 0.20287, R-sq = 0.99

k,Novec 7700/k,methane = -0.00592/-0.0135 = 2.28

lifetime, Novec 7700 = k,Novec 7700/k,methane * lifetime, methane

Based on the accepted value of methane lifetime, 12 years, the atmospheric lifetime is 5.3 years.

Run 3:

Methane: C/Co = -0.0110 * time + 0.1061, R-sq = 0.993

Novec 7700: C/Co = -0.00605* time + 0.06567, R-sq = 0.99

k,Novec 7700/k,methane = -0.00605/-0.0110 = 1.82

The corresponding atmospheric lifetime is 6.6 years.

The overall average atmospheric lifetime of Novec 7700 is 5.6 years, for an average half-life of 3.9 years.

Carbonyl difluoride was identified as a degradation product by FTIR. An unknown degradation product was detected as well. This was determined to be C10 diketone (1,1,1,2,4,4,5,5,7,8,8,8-dodecafluoro-2,7-bis(trifluoromethyl)octane-3,6-dione) by GC-MS compared to a known standard. The C10 diketone degradation intermediate was analyzed in duplicate direct photolysis runs v. acetaldehyde (Att. 4, 5):

Run 4:

Acetaldehyde: C/Co = -0.0019 * time + 0.0476, R-sq = 0.997

Novec 7700: C/Co = -0.0070 * time + 0.2409, R-sq = 0.9999

k,Novec 7700/k,acetaldehyde = -0.0070/-0.0019 = 3.68

Based on the accepted value of acetaldehyde lifetime, 5 days, the atmospheric lifetime is 1.4 days

Run 5:

Acetaldehyde: C/Co = -0.0017 * time + 0.0104, R-sq = 0.996

Novec 7700: C/Co = -0.0069 * time + 0.0397, R-sq = 0.9999

k,Novec 7700/k,acetaldehyde = -0.0069/-0.0017 = 4.06

The corresponding atmospheric lifetime is 1.2 days.

Acetaldehyde: C/Co = -0.0019 * time + 0.0476, R-sq = 0.997

Novec 7700: C/Co = -0.0070 * time + 0.2409, R-sq = 0.9999

k,Novec 7700/k,acetaldehyde = -0.0070/-0.0019 = 2.28

The overall average atmospheric lifetime of the C10 diketone intermediate degradation product is 1.3 days, for an average half-life of 0.9 days. Carbonyl difluoride was detected as transformation product of the C10 diketone as well. Carbonyl difluoride and trifluoroacetyl fluoride have very similar infrared spectra. While not specified in the study report, it is likely that trifluoroacetyl fluoride was also produced during both phototransformation experiments owing to branching in the diketone structure.

Validity criteria fulfilled:
not applicable
Conclusions:
The half-life of Novec 7700 by indirect photolysis in the air is 3.9 years. A ketone intermediate is formed which has a half life of 0.9 days by direct photolysis.
Executive summary:

The atmospheric lifetime of Novec 7700 with respect to *OH was determined using methane or 1,1,1-trichloroethane as reference substance in a 10-m FTIR gas cell. Hydroxyl radical was produced by irradiation of ozone in the presence of water vapor. Temperature was 26-29 °C, and pressure was brought to approximately 1 atmosphere with nitrogen. Progress of the reaction was monitored by FTIR spectroscopy according to EPA method 320. On irradiation, losses of ozone, reference substance, and Novec 7700 were linear for the first phase of the reaction. Regression of the linear portion of the curves was used obtain a rate ratio (k, Novec 7700 / k,reference) for each run. Based on the accepted atmospheric lifetime for the reference substances (1,1,1-trichloroethane, 5 years; methane, 12 years), the atmospheric lifetime of Novec 7700 with respect to *OH is 5.6 years. Carbonyl difluoride was detected as a degradation product. An intermediate degradation product was identified as 1,1,1,2,4,4,5,5,7,8,8,8-dodecafluoro-2,7-bis(trifluoromethyl)octane-3,6-dione (C10 diketone) by GC-MS vs. a known sample. This intermediate was examined via direct phototransformation in the same test chamber but without ozone as a *OH source. The atmospheric lifetime of the C10 diketone was 1.3 days as compared to acetaldehyde (accepted lifetime, 5 days). Carbonyl difluoride was also detected as phototransformation product of this intermediate. While not specified in the study report, it is likely that trifluoroacetyl fluoride was also produced during phototransformation due to branching in the diketone structure.

The study followed sound scientific principles. The study overall was not conducted to GLP criteria. Composition of the reaction mixture is not specified in the report, however the relative reaction rate calculation mitigates the need for this detail. The study assumes phototransformation solely due to hydroxyl radical and does not take direct phototransformation into account. However, the methods described are adequate to obtain the measured result. Therefore, this study is classified as reliable with restrictions. It is suitable for Risk Assessment, Classification & Labeling, and PBT Analysis

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2013
Report Date:
2013

Materials and methods

Test guideline
Qualifier:
no guideline available
Principles of method if other than guideline:
IR spectrum obtained according to EPA method 320, integrated according to Pinnock et al (1995) (J. Geophys. Res., 100, 23227-23238) and used to estimate Global warming potential according to IPCC methods.
GLP compliance:
no
Type of study / information:
Infrared spectrum, global warming potential

Test material

Reference
Name:
Unnamed
Type:
Constituent

Results and discussion

Any other information on results incl. tables

See attachment for IR spectrum of L-21343. Average cross-section in the absorbance range of ozone (1000 - 1100 cm-1) was >0.148, indicating that the radiative forcing does not need to be corrected for confounding by ozone absorbance. Instantaneous radiative forcing was used directly. The instantaneous radiative forcing is 0.611 W∙m-2∙ppbV-1. Assuming an atmospheric lifetime of 5.6 years, the 100-year GWP of L-21343 is 420.

Applicant's summary and conclusion

Conclusions:
The 100-year GWP of L-21343 is 420.
Executive summary:

Potential effects of L-21343 on climate were addressed by calculation of 100-year integrated global warming potential (100-year GWP). A high-resolution infrared spectrum was taken using a protocol following EPA method 320. Integrated IR cross-section and radiative forcing were calculated using the approach of Pinnock et al (J. Geophys. Res., 100, 23227-23238). Atmospheric lifetime was determined in this study to be 5.6 years (reported elsewhere in this dossier). GWP was calculated for this study summary using the WMO 1998 model with updated CO2 response and forcing. The integrated instantaneous radiative forcing was 0.611 W∙m-2∙ppbV-1. The 100-year GWP is 420. No testing guideline has been promulgated to determine global warming potential. However, the infrared cross-section data were collected according EPA method 320, and the radiative forcing and GWP were calculated by methods accepted by IPCC. Therefore, this study is classified as reliable without restrictions.