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Environmental fate & pathways

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Administrative data

Endpoint:
other distribution data
Type of information:
other: From published data
Adequacy of study:
supporting study
Study period:
Not specified
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Taken from publically available data, and is considered accurate based on the registrants experience of the substance.

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1979

Materials and methods

Test guideline
Qualifier:
no guideline followed
GLP compliance:
not specified
Type of study:
other: Oxidation in the troposphere / stratosphere
Media:
other: Not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
not specified
Details on test material:
CAS NO. 75-71—8
TSL NO. PA 82000
Alternate Names: Fluorocarbon-12, Freon-12
Molecular weight: 129.91 (Weast 1977)
Melting point: -158°C (Weast 1977)
Boiling point at 760 torr: -29.8°C (Weast 1977)
Vapour pressure at 20°C: 4306 torr (Pearson and McConnell 1975)
Solubility in water at 25°C: 280 mg/l (Pearson and McConnell 1975)
Log octanol/water partition coefficient: 2.16 (Hansch et al. 1975)

Results and discussion

Any other information on results incl. tables

No information was found pertaining to the oxidation of dichlorodifluoromethane in the aquatic environment under ambient conditions. In addition, dichlorodifluoromethane is known to be relatively stable with respect to attack by hydroxyl radicals present in the troposphere (Environmental Protection agency 1975; Hanst 1978; Lillian et al. 1975; Cox et al. 1976;Howard et al. 1975; Howard and Durkin 1973). For instance, the bimolecular rate of reaction for dichlorodifluoromethane with hydroxyl radicals is less than 1 x 10-16cm3sec-1with a corresponding lifetime (time for reduction to l / e of the original concentration) of greater than 330 years (Cox et al. 1976). According to Howard et al. (1975), fluorocarbon compounds are highly resistant to attack by conventional oxidising agents at temperature below 200°C.

Assuming a troposphere-to-stratosphere turnover time (time for all but 1 / e of tropospheric air to diffuse into the stratosphere) of 30 years, a tropospheric lifetime of 30 years would result in over 90 percent of tropospheric dichlorodifluoromethane eventually reaching the stratosphere. Jesson et al. (1977) and Sze and Wu (1976) have postulated a shorter tropospheric lifetime, on the order of 20 years, based on analysis of the data of other workers in the field, but no known destructive mechanisms in the troposphere (sinks) are identified as being capable of removing dichlorodifluoromethane. A tropospheric lifetime of 20 years would indicate that about 40 per cent of tropospheric dichlorodifluoromethane would reach the stratosphere.

Applicant's summary and conclusion

Conclusions:
Dichlorodifluoromethane introduced into aqueous systems will most likely volatize to the atmosphere. Once in the troposphere, dichlorodifluoromethane remains stable. It eventually diffuses into the stratosphere or is carried back to the earth during the precipitation process. Based on the information found it appears that oxidation is not an important fate process for dichlorodifluoromethane in the aquatic environment.
Executive summary:

Dichlorodifluoromethane introduced into aqueous systems will most likely volatize to the atmosphere. Once in the troposphere, dichlorodifluoromethane remains stable. It eventually diffuses into the stratosphere or is carried back to the earth during the precipitation process. Based on the information found it appears that oxidation is not an important fate process for dichlorodifluoromethane in the aquatic environment.