Terphenyl, hydrogenated

Endpoint summary

Additional information

Biodegradability in water

K-score + Study role?	30% hydrog. ter-phenyls	40% hydrog. ter-phenyls	40% hydrog. poly-phenyls	Endpoint	Results	Remarks	Conclusion	Reference
K2 preGLP WoE		x		SCAS = primary biodeg.	Feeding level 10 mg:overall mean disappearance rate = 35,1+8,6	With extended exposure to the residue remaining after the normal cycle to the activated sludge, nearly complete disappearance was achieved.	Moderate biodeg.	Saeger and Tucker, 1970
K2 preGLP WoE		x		SCAS = primary biodeg.	Feeding level 50 mg:Disappearance rates = 30% (day 1), 63% (day 2), 85% (day 3) and 90% (day 4)	GC-analysis showed qualitative differences in the degradation rate of the different components. An acclimation period for the activated sludge is necessary.	Moderate biodeg.	Saeger and Tucker, 1970
K2 preGLP WoE		x		RDA = primary biodeg.	At the end of the exposure period (50 days), a five-fold decrease in the initial Terphenyl, hydrogenated level was found.		Moderate biodeg.	Saeger and Tucker, 1970
K2 preGLP WoE		x		CO2 evolution = ultimate biodeg.	Feeding level 15,1 mg/L: 1% after 35 days (non-adapted inoculum)		No mineralization Persistent	Saeger et al., 1977
K2 preGLP WoE		x		CO2 evolution = ultimate biodeg.	Feeding level 10,3 mg/L: 3% after 35 days (non-adapted inoculum)		No mineralization Persistent	Saeger et al., 1977
K2 preGLP WoE		x		CO2 evolution = ultimate biodeg.	Feeding level 16,7 mg/L: 50% after 46 days (SCAS-adapted inoculum)	Adaptation of the inoculum is essential	Moderate biodeg.	Saeger et al., 1977
K4 preGLP WoE		x		SCAS = primary biodeg.	Primary degradation rate = 49+7% (feeding level 7 ppm)	Acclimation period important factor	Moderate biodeg.	Secondary source, reference to AC-71-SS-4
K4 preGLP WoE		x		RDA = primary biodeg.	80% decrease of the substance after 50-day period	Differences of the various components No evidence of highly resistant components	Moderate biodeg.	Secondary source, reference to AC-71-SS-4
K2 preGLP WoE		x		CO2 evolution	Feeding level 45.8 lg/L: 3% after 35 days (non-adapted SCAS supernatant)		There is no significant evolution in degradation of the substance	Saeger et al., 1977
K2 preGLP WoE		x		SCAS = primary biodeg.	Primary degradation rate = 64+5% (feeding level 3 ppm)	There is a need of an extended acclimation period There are differences in degradation rate of the various components, but gave no evidence of highly resistant components	Moderate biodeg. Provided sufficient time for acclimation is provided. Results clearly indicate the benefits of an extended acclimation period	Saeger et al., 1977
K2 preGLP WoE	x			SCAS = primary biodeg.	Primary degradation rate = 68,1+6,5% (feeding level 5 mg) Primary degradation rate = 65,6+13,3% (feedi)	Significant changes in degradability related to the component distribution Terphenyls with only one hydrogenated ring are more biodegradable compared to the ones with two hydrogenated rings	Moderate biodeg.	Saeger et al., 1972b
K2 preGLP WoE	x			RDA = primary biodeg.	Results in agreement with SCAS results on 30 % hydrogenated terphenyls	Significant changes in degradability related to the component distribution	Moderate biodeg.	Saeger et al., 19xx
K2 preGLP WoE			x	CO2 evolution = ultimate biodeg.	CO2 evolution = 14%	Conclusion: low extent of mineralization	Very low level of mineralization. However, previous tests with similar substances have shown that acclimation is essential	Monsanto report ES-80SS-34

 

*40% hydrogenated polyphenyls: the difference between the 30 and 40% terphenyl mixtures is the presence of more quaterphenyls (hydrogenated ones) in the mixture.

 

40% hydrogenated terphenyls: 74-87% hydrogenated terphenyls, < 18% partially hydrogenated quaterphenyls and higher polyphenyls and 3-8% terphenyls

 

 

Several tests have been conducted to assess the biodegradability of hydrogenated terphenyls. Most of the studies were carried out with hydrogenated terphenyls as test substance; however, a limited number of study reports are also available for dilutions of the test substance. Whereas the primary test substance contains 40% of hydrogenated terphenyls, two other test substances consist of 30% hydrogenated terphenyls and a 40% hydrogenated polyphenyl mixture, respectively.

 

With the primary test substance different types of biodegradation tests were carried out. Reports of ready biodegradability tests monitoring CO2 evolution (% of CO2 produced compared to theoretical CO2 production) yielded the following results after 35 days: 1% (initial substance concentration 15,1 mg/L) and 3 % (initial substance concentration 10,3 mg/L) in the first test, while 3% at starting concentration of 45.8 mg/L in the second test. After acclimation of the inoculum in the first test 50% degradation was observed (initial test concentration 16,7 mg/L) after 46 days. 

Several reports of inherent biodegradability tests (semi-continuous activated sludge tests - SCAS) with different feed levels, test durations and exposure durations of the inoculum are available. 68.1% primary degradation was observed in 24 hours in a first test, whereas an overall disappearance rate of 35.1 ± 8.6 % using a 24-hour cycle (overall value calculated over four measurement periods in a testing period of nine months) was calculated in another. With extended exposure of the residue after the normal test period to the activated sludge, nearly complete disappearance was achieved. This observation was confirmed by another SCAS test, which indicated that a primary biodegradation rate of 49 ± 7 % (using a 24-hour cycle) could be obtained with non-acclimated activated sludge during the latter stage of the test, while significantly lower rates were obtained during the first 12 weeks of the test. In yet another SCAS test an overall primary degradation rate of 64 ± 5 % using a 24-hour cycle was observed when using an acclimated inoculum. The results clearly indicated the benefits of an extended acclimation period. Furthermore, it was noted that although differences exist in the degradation rate of the various components of the test substance, no evidence was found of highly resistant components. Finally, a river die away test with the primary test substance showed that 80% of the test substance had disappeared after 50 days when starting at a 1 ppm level.

 

Tests with the two other test substances yielded results that corresponded to expectations based on the composition of the different substances: since the level of hydrogenation is lower 30 % hydrogenated terphenyls, the substance contains a higher proportion of components containing only one hydrogenated ring. The latter are considered to be more biodegradable compared to terphenyl components with two hydrogenated rings. Conversely, the test substance with 40 % hydrogenated polyphenyls has a higher degree of hydrogenation and is therefore expected to be less biodegradable.

A river die away test with 30% hydrogenated terphenyls showed that after 14 days the initial level of test substance was reduced by 95%. After 28 days no components of the substance could be detected anymore. In addition, a SCAS test with this substance yielded mean disappearance rates of 68.1 ± 6.5 (95% confidence interval) and 65.6 ± 13.3 (95% confidence interval) at addition rates of 5 and 20 mg per 24h cycle, respectively. After 4 weeks, no components of the test substance were detected anymore.

Finally, a ready biodegradability test with the test substance with 40 % hydrogenated polyphenyls (with initial concentration of 20.9 mg/L) gave a mean value of 14% CO2 evolution, indicating a low extent of mineralization.

 

To conclude, it can be stated that the primary test substance with 40 % hydrogenated terphenyls is moderately biodegradable provided that sufficient time for acclimation of the inoculum is provided. Moreover, differences in degradation rates of the various components have been observed. However, there is no evidence of highly resistant components. Test results with other substances such containing 30 % hydrogenated terphenyls or 40 % hydrogenated polyphenyls respectively moreover indicated that the extent of biodegradability is related to the level of hydrogenation.

 

 

 Biodegradability in soil

 

The degradation rate (DT50 and DT90) was determined of 14C-labelled 1,4-dicyclohexylbenzene in three different soils (Speyer 2.2 (loam), Speyer 2.3 (sandy loam) and Speyer 6S (clay)) and its degradation route in one of these soils. For this purpose, (phenyl-14C(U))-p-dicyclohexylbenzene was incubated in three soils in the dark. The concentration of the substance was determined after various incubation periods by HPLC of the soil extracts. Major metabolites were characterized and identified if feasible. The duration of the incubation was 120 days.

 

The extractable activity decreased during the first 14 days of incubation from 99% of the applied radioactivity to approximately 25 to 50.3 %. In all investigated soils, the soil extractable activity gradually decreased to 8.1 – 10.5% at the end of the incubation.

Phenyl-14C(U))-p-dicyclohexylbenzene quickly degraded and mineralized in the tested soils. In Speyer 6S soil three major metabolites were formed that were above 10% of the applied activity. In Speyer 2.3 two metabolites were twice above 5% of the applied radioactivity at two consecutive time points. The major metabolites degraded rapidly. Other metabolites were only formed in minor amounts.

 

The DT50 (d) for the parent compound was 4.1, 4.6 and 1.8 in Speyer 2.2, Speyer 2.3 and Speyer 6S, respectively.