Registration Dossier

Administrative data

Endpoint:
biodegradation in soil
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Published study, considered acceptable for asssessment.

Data source

Referenceopen allclose all

Reference Type:
publication
Title:
Bacterial cometabolic degradation of chlorinated paraffins
Author:
Omori T, Kimura T and Kodama T
Year:
1987
Bibliographic source:
Appl. Microbiol. Biotechnol. 25:553-557.
Reference Type:
publication
Title:
Environmental Risk Assessment: Long-Chain Chlorinated Paraffins
Author:
UK Environment Agency
Year:
2009
Bibliographic source:
UK Environment Agency
Report date:
2009

Materials and methods

Test guideline
Qualifier:
no guideline available
Principles of method if other than guideline:
The degradation of the C24.5 (average) chlorinated paraffins (40.5, 50% and 70% Cl, respectively) was assessed by monitoring the release of the chloride ion using a mixed bacterial inoculum isolated from soil.
GLP compliance:
not specified
Test type:
laboratory

Test material

Constituent 1
Chemical structure
Reference substance name:
Paraffin waxes and Hydrocarbon waxes, chloro
EC Number:
264-150-0
EC Name:
Paraffin waxes and Hydrocarbon waxes, chloro
Cas Number:
63449-39-8
Molecular formula:
C18H33Cl5 C18H30Cl8 C20H36Cl6 C20H33Cl9 C25H45Cl7 C25H42Cl10 C25H29C23 C30H53Cl9 C30H49Cl13 C30H35Cl27
IUPAC Name:
Paraffin waxes and Hydrocarbon waxes (C18 and longer), chloro
Details on test material:
Three LCCP substances tested, average molecular formula and chlorine weight reported as:
- C24.5H44.5Cl6.5 (40.5% wt. Cl)
- C24.5H41Cl10 (50% wt. Cl) and
- C24.5H30Cl21 (70% wt. Cl)
-
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
No data
Radiolabelling:
no

Study design

Oxygen conditions:
aerobic
Soil classification:
not specified
Details on soil characteristics:
No data
Duration of test (contact time)open allclose all
Soil No.:
#1
Duration:
ca. 48 h
Soil No.:
#2
Duration:
ca. 48 h
Initial test substance concentrationopen allclose all
Soil No.:
#1
Initial conc.:
ca. 180 other: mg chlorine/1.2 L solution
Based on:
other: Chlorine content of C14.5 (43.5% chlorinated)
Soil No.:
#2
Initial conc.:
ca. 180 other: mg chlorine/1.2 L solution
Based on:
other: Chlorine content of C15.5 (50% chlorinated)
Parameter followed for biodegradation estimation:
other: Amount of chloride ion released
Experimental conditionsopen allclose all
Soil No.:
#1
Temp.:
30oC
Soil No.:
#2
Temp.:
30oC
Details on experimental conditions:
First, degradation of the 40.5% and 70% wt. Cl chlorinated paraffin was studied using resting cell cultures of Pseudomonas aeroginosa, Achromobacter delmarvae, A. cycloclastes, Micrococcus sp. and Corynebacterium hydrocarboclastus grown on glycerol. These bacteria had previously been shown to degrade 1-chlorohexadecane as well as some other monoand dichlorinated alkanes.

For the co-metabolic degradation studies, bacterial strains (designated HK-3, HK-6, HK- 8 and HK-10) were isolated from soil using an enrichment culture containing nhexadecane as the sole carbon source. The co-metabolic biodegradation experiments were carried out using the single bacterial strains (HK-3, HK-6 or HK-8) incubated at 30°C for 48 hours in mineral medium containing 0.05 per cent (i.e. 500 mg/l) nhexadecane and 0.1 per cent (i.e. 1,000 mg/l) of either the 40.5%, 50% or 70% wt. Cl chlorinated paraffin.

In addition, biodegradation of both the 40.5% wt. Cl and 70% wt. Cl products (concentration equivalent to 180 mg Cl in 1.2 litres) was studied under similar conditions (36 hour incubations) using a mixed bacterial inoculum (containing all four strains) previously exposed to 5,000 mg/l of n-hexadecane.

A final study was carried out by inoculating the co-metabolic culture broth from bacterial strain HK-3 (after autoclaving) with another bacterium (strain H15-4) that had been shown to release chlorine from 2-chlorinated fatty acid (a possible metabolite of the chlorinated paraffins).

Results and discussion

% Degradationopen allclose all
Soil No.:
#1
% Degr.:
33
Parameter:
other: chloride released
Sampling time:
36 h
Soil No.:
#2
% Degr.:
15
Parameter:
other: chloride released
Sampling time:
36 h
Transformation products:
yes
Identity of transformation products
No.:
#1
Reference
Reference substance name:
Unnamed
IUPAC name:
Chloride ion
Identifier:
common name
Identity:
Chloride ion
Evaporation of parent compound:
not specified
Volatile metabolites:
not specified
Residues:
not specified
Details on results:
See table.
Results with reference substance:
Four bacterial strains (HK-3, HK-6, HK-8 and HK-10) grown on n-hexadecane, dechlorinated 1,10-dichlorodecane, 1-chlorobutane, 3-chlorobutyric acid and, to a lesser extent, 2-chloropropionic acid.

Any other information on results incl. tables

Results of dechlorination experiments (Omoriet al., 1987)

 

Chlorinated paraffin

(average

formula)

 

Chlorinated Chloride release over 48 hours incubation (mg/l)

Bacterial

strain HK-3

Bacterial

strain H15-4

Bacterial

strain HK-6

Bacterial

strain HK-8

Mixed bacterial

culture (HK-3,

HK-6, HK-8 and

HK-10)

C24.5H44.5Cl6.5

(40.5% wt.Cl)

40 (9.9%)a, b

13%a

9 (2.2%)a

14 (3.5%)a

50 (33%)a

 

C24.5H41Cl10

(50% wt. Cl)

15 (3.0%)a

 

9%a

 

9 (1.8%)a

13 (2.6%)a

 

C24.5H30Cl21

(70% wt. Cl)

18 (2.6%)a

12%a

10 (1.4%)a

12 (1.7%)a

22 (15%)a

Notes:aChloride release expressed as a percentage of the total present in the chlorinated paraffin.

bThe pH of the culture medium fell as dechlorination proceeded and may have inhibited growth of the microorganism and hence further dechlorination.

 

Applicant's summary and conclusion

Conclusions:
Degradation was seen in all three grades of LCCP, with the most rapid degradation occurring in the 40.5% Cl wt. LCCP. The authors concluded that the degradation seen was consistent with that previously observed for other chlorinated alkanes in that a variety of enzymes are required to degrade chlorinated paraffins and that the most likely mode of degradation involves firstly dechlorination of the terminal methyl groups, with subsequent oxidation to form chlorinated fatty acids, which are then broken down to 2- or 3-chlorinated fatty acids via β-oxidation.
Executive summary:

Cometabolic biodegradation experiments were carried out with several LCCPs of varing chlorine levels (40.5%, 50% and 70% chlorinated) at a concentration equivalent to 180 mg Cl/1.2 L solution, using a mixed bacterial inoculum (containing strains HK-3, HK-6, HK-8 and HK-10) incubated at 30oC for 48 hours. Bacterial strains were isolated from soil (no further details on soil characteristics given in paper) using an enrichment culture containing n-hexadecane as the sole carbon source.

All three grades of LCCP biodegraded, with the most rapid degradation coming from the 40.5% Cl wt substance in the mixed inoculum and in the HK-3 inoculum. There were not significant rate differences between the 50% and 70% Cl wt LCCP which lead to the conclusion that the most likely mode of degradation involves firstly dechlorination of the terminal methyl groups, with subsequent oxidation to form chlorinated fatty acids, which are then broken down to 2- or 3-chlorinated fatty acids via β-oxidation.