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Administrative data

phototransformation in air
Type of information:
experimental study
Adequacy of study:
key study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: non-GLP, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference Type:
study report
Report Date:

Materials and methods

Test guideline
no guideline available
not applicable
Principles of method if other than guideline:
Indirect photolysis with *OH radical produced from ozone.
GLP compliance:

Test material

Test material form:
other: gas
Details on test material:
- Name of test material (as cited in study report): L-21609
- Substance type: Mono-constituent
- Physical state: gas
- Storage condition of test material: as a pressurized liquid

Study design

Light source:
other: Mercury-Xenon
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.
Duration of test at given test condition
47 min
27 °C
Reference substance:
methane or HFC-125

Results and discussion

Dissipation half-life of parent compound
24 yr
Test condition:
based on average of three measurements

Any other information on results incl. tables

Concentrations of L-21609 and methane were monitored for 47 minutes 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 of both L-21609 and methane were observed (Figure 2). Based on this result L-21609 does not react appreciably with either ozone or water vapor (present at 1000 ppmv) over the duration of this experiment.


On irradiation, linear declines in concentration of ozone, L-21609 and methane were observed for the first 40 minutes of illumination. Regression of this portion of the decay curves produced the following equations:


Run 1:

HFC-125: C/Co = -0.00127 * time + 0.05641, R-sq = 0.989

L-21609: C/Co = -0.00111 * time + 0.03429, R-sq = 0.885

k(L-21609)/k(HFC-125) = 0.87

lifetime( L-21609) = k(L-21609)/k(HFC-125) * lifetime(HFC-125 [29y]) = 33y


Run 2:

methane: C/Co = -0.00460 * time + 0.18761, R-sq = 0.98

L-21609: C/Co = -0.00144 * time + 0.04448, R-sq = 0.98

k(L-21609)/k(methane) = 0.31

lifetime (L-21609) = k(L-21609)/k(methane) * lifetime (methane [12y]) = 38y


Run 3:

methane: C/Co = -0.00497 * time + 0.40467, R-sq = 0.992

L-21609: C/Co = -0.00251 * time + 0.16037, R-sq = 0.96

k(L-21609)/k(methane) = 0.37

lifetime (L-21609) = 32y


The average atmospheric lifetime of L-21609 is 35 years.


Applicant's summary and conclusion

The atmospheric lifetime of L-21609 with respect to *OH is 35 years.
Executive summary:

The atmospheric lifetime of L-21609 with respect to *OH was determined using HFC-125 or methane 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 26-28 °C, and pressure was brought to approximately 1 atmosphere with humidified nitrogen. Progress of the reaction was monitored by FTIR spectroscopy according to EPA method 320. Losses of reference substance and L-21609 were <1% due to dark reactions, indicating negligible reaction with ozone or water vapor. On irradiation, losses of ozone, reference substance, and L-21609 in irradiation were linear over the observation period. Linear regression of the kinetic data gave rate ratios of 0.87 v. HFC-125, and 0.31 and 0.37 in two trial v. methane. Based on the accepted atmospheric lifetimes for HFC-125 (29 y) and methane (12 years), the average atmospheric lifetime of L-21609 with respect to *OH is 35 years.


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 result is a relatively long atmospheric lifetime reported to one significant digit, and the methods described are adequate to achieve this level of precision. Therefore, this study is classified as reliable with restrictions. It is suitable for Risk Assessment, Classification & Labeling, and PBT Analysis.