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The biodegradation of a C20–30, 42% wt Cl product has been determined in a prolonged test Biochemical Oxygen Demand (BOD) (Madeley and Birtley, 1980) – determined to have a reliability of 2. The test was carried out using an emulsion of the chlorinated paraffin. Two microbial populations were used in the study: firstly a culture from soil collected close to a CP production plant that was acclimatised over an eight week period to a concentration of 20–50 mg/L of the CP; and secondly, a non-acclimatized culture obtained from the effluent of a laboratory activated sludge unit treating domestic sewage. Results were based on comparing BOD to the theoretical oxygen demand (ThOD) and showed 7.5% biodegradation after 25 days for non-acclimated organisms and 23% biodegradation after 25 days for acclimated organisms.   To investigate the potential for degradation further, Madeley and Birtley (1980) carried out a series of experiments using a 14C-labelled chlorinated pentacosane (radiolabelled on the central carbon) mixed with the same C20–30, 42% wt Cl product in Hach respirometers with non-acclimated microorganisms. After eight weeks incubation, around 11% of the 14C was collected as 14CO2, indicating that where degradation had occurred it was extensive enough to release the central carbon atom of the C25chain. In addition to the above studies, Madeley and Birtley (1980) also reported preliminary studies investigating the degradation of the C20–30, 42% wt Cl product under anaerobic conditions. The anaerobic bacteria were obtained from anaerobic sludge digesters. Gas production (methane and CO2) in the presence of increasing quantities of an emulsion of the CP was determined over 30 days and compared with controls. No significant increase or decrease in bacterial activity was seen at concentrations of the CP of up to 10% by weight of dry sludge solids. It was concluded that the substance was not toxic to the bacterial population present but also was not actively degraded under these conditions.   Additional biodegradation results, reliability 2, by Hildebrecht (1972) were reported by Howardet al.(1975), though the reliability of these data has been questioned as the test systems appear to have contained additional carbon sources that may have been biodegradable under the conditions of the test ( EA 2009). In this study, the biodegradability of a C20-30, 42% wt Cl LCCP and a C20-30, 70% wt Cl LCCP were evaluated using oxygen consumption over 20 hours in a Warburg respirometer or over five days using a BOD method. The sewage seed used was acclimated to up to 100 mg/L of chlorinated paraffins before use in the test. The results obtained are shown in the table below.    

Biodegradation Results Reported by Hildebrecht (1972)

Substance

Formulation Tested

Warburg Respirometry

BOD dilution method

Oxygen Consumption

(mg/L)

Degradation*

BOD

(mg/L)

 

Degradation*

 

C20-30,

40–42% Cl

 

500 mg/L of a mixture containing 75% LCCP, 5% surfactant and 20% water.

83

17.2%

120

 

25%

C20-30,

70% Cl

500 mg/L of a mixture containing 37.5% LCCP, 37.5% perchloroethylene, 5% surfactant and 20% water.

298

17.2%

30

 

2%

Surfactant

500 mg/L surfactant

377

46.5%

530

 

65%

*Degradation was estimated by the authors as the percentage of the theoretical oxygen demand based on the total carbon content of the test solution. Substances other than the chlorinated paraffin contribute to this total carbon content.

 

Omori (1987) observed the potential for LCCP biodegradation through several soil microorganisms.

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.

 

Hoechst AG (1976 and 1977) reported five-day biochemical oxygen demand (BOD5) values for several products: C18–20, 35% Cl, C18–20, 44% Cl, C18–20, 49% Cl and C18–20, 52% Cl. Unfortunately, the reliability of these studies could not be assigned (reliability 4) because few details of how the tests were carried out are given. The results show little or no biodegradation when compared with the measured chemical oxygen demand (COD) values. There is some evidence that LCCPs may be subject to biodegradation in sea water/estuarine sediment (Zitko & Arsenault, 1974 & 1977). It is not possible to derive any biodegradation rates applicable to the marine environment from these data. A study of MCCPs in aerobic sediment system containing oligochaetes (Lumbriculus variegatus), the half-lives of two 14C-labelled C16 chlorinated paraffins were estimated to be about 12 and 58 days for the 35% and 69% chlorinated paraffin, respectively (Fisk 1998).  

Overall, the data indicate that while LCCP have not been demonstrated to readily biodegrade in a standard screening assay, there is evidence that they will biodegrade in the enviroment.