Hexyl salicylate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

11/04/1995 - 11/05/1995

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Principles of method if other than guideline:

Not relevant

GLP compliance:

yes

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
Not relevant

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (City of Geneva, Aire) was used. The sludge is collected in the morning, washed three times in the mineral medium (by centrifuging at 1000 g for 10 mins, discarding the supernatant and resuspending in mineral medium) and kept aerobic until being used on the same day.

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
Stock solutions (a)-(d) were prepared by dissolving the following salts in 1 litre of deionised water:

(a) 8.5 g KH2PO4, 21.75 g K2HPO4, 33.40 g Na2HPO4.2H2O, 0.5 g NH4Cl
(b) 27.5 g CaCl2
(c) 22.50 g MgSO4.7H2O
(d) 0.25 g FeCl3.6H2O, one drop of HCl Conc.

The water used during this study is deionised water containing less than 10 mg/L dissolved organic carbon.

The mineral medium was prepared by mixing 50 mL of solution A and 2000 mL deionised water, adding 5 mL of each of the solutions B, C and D and making up to 5 L with deionised water.

TEST SYSTEM
A respirometer was used (Sapromat D 12).
The dry weight of suspended solids is determined by taking two 50 mL samples of the homogenised sludge, evaporating water on a steam bath, drying in an oven at 105 - 110 °C for two hours and weighing the residue.

A volume of suspended sludge corresponding to 7.5 mg dry weight (as determined from 3.6) is placed in a 250 mL volumetric flask and made up with mineral medium. This is poured into each test flask of the Sapromat. The test and reference substances are weighed in small aluminium boats which are added to the test flasks contents. The pH of each flask is measured and, if necessary, adjusted to 7.4 ± 0.2 with phosphoric acid or potassium hydroxide. About 2 g of soda lime is placed in an attachment of the stopper, the flasks are closed and placed in the water bath of the Sapromat. After temperature and pressure equilibration, the oxygen meters of the instrument are set to zero (time zero of the experiment).

CONTROL AND BLANK SYSTEM
A pair of volumetirc flasks of the volumetric respirometer (Sapromat) are filled with:

mineral medium + test chemical (100 mg/L) + aniline (100 mg/L) + inoculum

and their respirations are recorded as for the other flasks. If they are lower than those of the flasks containing:

mineral medium + aniline (100 mg/L) + inoculum
the test chemical can be used assumed to be inhibitory to the inoculum used.

Reference substance:

aniline

Remarks:

100 mg/L; min purity = 99.5 %

Preliminary study:

No details supplied

Test performance:

Degradation of Aniline exceeds 40 % after 7 days and 65 % after 14 days: the activity of the inoculum is thus verified and the test is considered as valid.

Parameter:

% degradation (O2 consumption)

Value:

91

Sampling time:

28 d

Parameter:

% degradation (O2 consumption)

Value:

82

Sampling time:

10 d

Details on results:

Oxygen uptakes, as read on the Sapromat meters are corrected:
-by deducing the basic oxygen uptake of sludge (the average of flasks 1/1 and 2/1)
- proportionally to account for the differences between actual and nominal concentrations of test and reference substances.

Averages of identical flasks have been used to obtain the graph of BOD vs. time, % of biodegradation vs. time and the biodegradation rates.

Hexyl salicylate undergoes 91 % biodegradation after 28 days in the test conditions. Biodegradation reaches 82 % at the end of the 10-day window (days 2 to 12).

Therefore, Hexyl salicylate should be regarded as readily biodegradable according to this test.

Results with reference substance:

Degradation of Aniline exceeds 40 % after 7 days and 65 % after 14 days: the activity of the inoculum is thus verified and the test is considered as valid.

The curve obtained with aniline alone and with Hexyl salicylate + aniline show no toxic effect of Hexyl salicylate on the micro-organisms at the test concentration.

Table 2: BOD for Hexyl salicylate

		Days:	2	7	12	14	21	28
BOD Sludge	1st flask	B1	13.0	19.0	21.0	21.0	21.0	24.0
	2nd flask	B2	13.0	19.0	22.0	23.0	25.0	32.0
	mean	B	13.0	19.0	21.5	22.0	23.0	28.0
BOD test substance	1st flask	C1	57.0	162.0	208.0	215.0	230.0	240.0
	2nd flask	C2	104.6	182.5	213.1	217.0	225.9	233.9
	1^stfl. Corr.	C1-B	44.0	143.0	186.5	193.0	207.0	212.0
	2^ndfl. Corr.	C2-B	91.6	163.5	191.6	195.0	202.9	205.9
% degradation	1 st flask	D1	19	62	81	84	90	92
	2 nd flask	D2	40	71	83	85	88	90
	mean	D	29	67	82	84	89	91

B = (B1 + B2)/2

D1 = 100* (C1-B)/ThOD*[S]

D2 = 100*(C2-B)/ThOD*[S]

D = (D1+D2)/2

[S]: Initial test substance concentration (mg/L)

Validity criteria fulfilled:

yes

Remarks:

Degradation of Aniline exceeds 40 % after 7 days and 65 % after 14 days: the activity of the inoculum is thus verified and the test is considered as valid.

Interpretation of results:

readily biodegradable

Conclusions:

The ready biodegradability of Hexyl salicylate has been determined according to the OECD guideline 301F. In the conditions of the test, Hexyl salicylate undergoes 91 % biodegradation after 28 days. Biodegradation reaches 82 % at the end of the 10-day window (days 2 to 12).

Thus, Hexyl salicylate should be regarded as readily biodegradable according to this test.

At the concentration used in the test (100 mg/L), it is not inhibitory to the micro-organisms

Executive summary:

The ready biodegradability of Hexyl salicylate has been determined according to the OECD guideline 301F. In the conditions of the test, Hexyl salicylate undergoes 91 % biodegradation after 28 days. Biodegradation reaches 82 % at the end of the 10-day window (days 2 to 12).

Thus, Hexyl salicylate should be regarded as readily biodegradable according to this test.

At the concentration used in the test (100 mg/L), it is not inhibitory to the micro-organisms

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable