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Environmental fate & pathways

Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: screening tests
Adequacy of study:
other information
Principles of method if other than guideline:
BODIS (BOD test for insoluble substances)
GLP compliance:
yes
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Duration of test (contact time):
28 d
Initial conc.:
41.8 mg/L
Details on study design:
20.5-24.0 degrees Celsius
Value:
94
Sampling time:
28 d
Conclusions:
Study concludes DIBP is "easily biodegradable".
Executive summary:

The study (Hüls 1993) showed 94% of DIBP biodegradation within 28 days.

Endpoint:
biodegradation in water: screening tests
Adequacy of study:
other information
Principles of method if other than guideline:
bottle test
Value:
ca. 95
Sampling time:
5 d

No biodegradation of residual concentration (20 -100 ng/L)

Executive summary:

The study showed ca. 95% biodegradation within 6 days, but another study with a low concentration of DIBP showed no biodegradation within 17 days (Furtmann 1993).

Endpoint:
biodegradation in water: screening tests
Adequacy of study:
other information
Qualifier:
according to
Guideline:
other: EU guideline 84/449, C 6
Principles of method if other than guideline:
closed bottle test
GLP compliance:
yes
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Duration of test (contact time):
28 d
Initial conc.:
2 mg/L
Details on study design:
20 degrees Celsius
Value:
79
Sampling time:
28 d
Conclusions:
Study concludes DIBP is "easily biodegradable".
Executive summary:

The study (Hüls 1988) showed 79% of DIBP biodegradation within 28 days.

Endpoint:
biodegradation in water: screening tests
Adequacy of study:
other information
Principles of method if other than guideline:
river die away test
Initial conc.:
25 mg/L
Value:
100
Sampling time:
6 d

same effect (100% biodegradation) shown for polluted (unspecified) seawater; only 15% biodegradation shown for very clean oceanic water within 1 week, 35% after 2 weeks

Executive summary:

The study (Hattori et al. 1975) showed complete biodegradation of DIBP in municipal river water within 6 days.

Endpoint:
biodegradation in water: screening tests
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: well documented and scientifically acceptable, but lacking guidelines
Principles of method if other than guideline:
No guideline mentioned, cf. "Any other information on materials and meethods" for details.
GLP compliance:
not specified
Oxygen conditions:
other: aerobic, anaerobic
Inoculum or test system:
natural water / sediment
Duration of test (contact time):
30 d
Value:
ca. 0
Sampling time:
1 d
Remarks on result:
other: anaerobic
Value:
ca. 31
Sampling time:
5 d
Remarks on result:
other: anaerobic
Value:
ca. 41
Sampling time:
7 d
Remarks on result:
other: anaerobic
Value:
ca. 61
Sampling time:
14 h
Remarks on result:
other: anaerobic
Value:
ca. 98
Sampling time:
30 d
Remarks on result:
other: anaerobic
Details on results:
cf. Table 1 for details and aerobic data

Freshwater hydrosoil degraded both 14C-DBP and 14C-DEHP (Tables l , 2, 3). Since autoclave­killed or NaN3 controls did not significantly degrade either ester, we attributed the degradation of the two phalates to the enzymic action  of microorganisms indigenous to freshwater hydrosoil.

We found marked differences between the conditions and rates of biodegradation of the two esters. Forty-Six percent of the radio-labelled DBP in hydrosoil (Table 2) was degraded aerobically to mono-n-butylphthalate within 24 h and nearly 98 %  (Table l) of all radioactivity disappeared after 5 days. Under the same conditions, nearly 14 days were required for 53 % of the

DEHP­labelled material to disappear (Table 2).

Anaerobiosis slowed biodegradation of both esters. Although nearly 98 % of the radio-labelled DBP disappeared during 30 days of incubation in the hydrosoil, the retarding infiuence of anaerobiosis was evident. Nearly 70% of the DBP radioactivity remained after 5 days of incubation under anaerobic conditions, whereas only 3 % of the extractable labelled  DBP and degradation products remained after 5 days of aerobic incubation. Degradation in anaerobic hydrosoils did not reach the aerobic level until the 30 -day sampling. Ester hydrolysis required twice as much time in anaerobic as in aerobic hydrosoil, and decarboxylation time was about 6 times longer under anaerobic conditions.

Identification of degradation products

In TLC-autoradiography analyses of the 14C­ DBP  and 14C-DEHP hydrosoil extracts we repeatedly found radioactivity in DBP extracts at Rf 0.82, 0.33, 0.25, 0.15, 0.09, and 0.00 (Table 2). The spots at Rf 0.82, 0.33, and 0.09 (Table 4), when  cochromatographed with nonradio-labelled authentic standards, were similar to the spots of di­n-butyl phthalate, n-butyl phthalate,  and phthalic acid, respectively. The spots at R1 0.25, 0.15, and 0.00 did not correspond to known degradation product (Table 4). Quantitation of the radioactivity at each Rf value by liquid scintillation spectrometry indicated that the major degradation product of the 1 -day sample was the monoester (46.3% ). Small amounts of compounds more polar than the monoester (6% of the total recovered radioactivity) were at Rf 0.25, 0.09, and 0.00. Rf 0.09 corresponded to phthalic acid; Rf 0.25 and 0.00 were unidentified compounds.

Significantly, recovery of radioactive material showed that samples incubated for 1 day contained 95 % of the total radioactivity found in the control. This recovery decreased in the 5 -, 7 -. 14 - , and 30 -day samples. In comparison with the control, only 2.9 - 7.9 %  of  the radioactivity introduced into these samples was recovered (Table 2). Qualitative analyses of these extracts by TLC-autoradiography revealed the parent diester, the monoester, phthalic acid and a trace amount of an unknown or unknowns at the origin in an approximate ratio of 76:18:3:1 % (Table 2).

The slower rate of PAE degradation under anaerobic than under aerobic conditions is clearly reflected in the type and quantities  of the radioactive components extracted from hydrosoils after various incubaion intervals (Table 1,2). At least four compounds  were detected in anaerobic DBP samples: the monoester, phthalic acid and two unknowns at Rf 0.25 and 0.00. The compound or compounds at Rf 0.15 was not seen in any of the autoradiograms taken from anaerobic extracts. Although n-butyl phthalate was the major degradation product in either the aerobic or anaerobic samples after 1 day of incubation, the degradation rate was more than 1.5 times faster under aerobic conditions (32 % vs. 50 %). Qualitative comparison of aerobic with anaerobic phthalate degradation after the first 24h incubation periodis at best tenuous because of the rapid loss of radioactivity  from  the samples. We  did, however, observe an increase in the monoester after long incubation and an apparent lack of accumulation of the more polar degradation products in anaerobic samples (Table 2).

Conclusions:
Under aerobiosis, 53% of the radiolabelled DBP was degraded within 24 h, and 98 % within 5 days. Under anaerobiosis degradation was retarded: DBP was degraded only one-sixth as fast in hydrosoil overlayed with nitrogen.
Executive summary:

The phthalic acid esters di-2 -ethylhexyl phthalate (DEHP) and di-n-butyl phthalate (DBP) which are used as plasticizers and recovered in routine chemical analysis of freshwater fish, were incorporated into freshwater hydrosoil in the laboratory.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
other: Well documented report, based on scientific literature.
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: No guideline is reported.
Qualifier:
no guideline available
Principles of method if other than guideline:
No guiddeline is reported.
Oxygen conditions:
aerobic
Inoculum or test system:
other: non-adapted inoculum
Reference substance:
not specified
Parameter:
% degradation (O2 consumption)
Remarks on result:
other: no details are given
Details on results:
no details are given
Key result
Parameter:
BOD5*100/COD
Value:
63 mg O2/g test mat.

BOD5:COD ratio of 0.63 (obtained with a non-adapted inoculum)

Interpretation of results:
readily biodegradable
Conclusions:
DBP may be regarded as readily biodegradable under aerobic conditions like water.

Description of key information

DBP may be regarded as readily biodegradable under aerobic conditions like water.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information