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Environmental fate & pathways

Biodegradation in soil

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biodegradation in soil: simulation testing
Type of information:
experimental study
Adequacy of study:
key study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference Type:
study report

Materials and methods

Principles of method if other than guideline:
No guideline mentioned, cf. "Any other information on materials and methods" for details,
GLP compliance:
not specified

Test material

Chemical structure
Reference substance name:
Dibutyl phthalate
EC Number:
EC Name:
Dibutyl phthalate
Cas Number:
Molecular formula:
1,2-dibutyl benzene-1,2-dicarboxylate
Specific details on test material used for the study:
Diethyl phthalate, di-n-butyl phthalate, bis(2-ethylhexyl) phthalate, phthalic acid, phthalic anhydride, and benzyl alcohol were purchased from Aldrich Chemical Co. (Milwaukee, WI).

Results and discussion

% Degradationopen allclose all
Key result
Soil No.:
% Degr.:
> 90
Sampling time:
1 wk
Remarks on result:
other: undiluted sludge
Key result
Soil No.:
% Degr.:
> 90
Sampling time:
40 d
Remarks on result:
other: 10% sludge
Transformation products:
Identity of transformation products
Reference substance name:
Molecular formula:

Any other information on results incl. tables

Four of the six PAEs tested were degraded in undiluted sludge (Figure 1). Greater than 90% removal of dimethyl, diethyl, and di-n-butyl phthalate occurred within 1 week while the rate of butyl benzyl phthalate degradation was slightly slower. There was a general decrease in the concentration of di-n-octyl phthalate during the 10-week incubation; however, it was not possible to conclude that

degradation occurred. There was no evidence for the degradation of bis(2-ethylhexyl) phthalate. Recoveries consistently greater than 100% were probably due to an initial addition slightly in excess of 20 ppm.

Degradation of the six PAE's was also measured in 10% sludge. The diluted incubation system was used to evaluate mineralization by measuring methane production over background. This measurement was prohibited in undiluted sludge due to high background methane production. Degradation results for 10% sludge were consistent with the undiluted sludge. Greater than 90% of dimethyl, diethyl, di-n-butyl, and butyl benzyl phthalate were degraded within 40 days (Figure 2). Again, no evidence for any significant degradation of di-n-octyl or bis(2-ethyl-hexyl) phthalate was obtained. Methane production mirrored substrate disappearance (Figure 3). Percent theoretical methane recoveries ranged from 76% to 103% (Table I) for those compounds that were mineralized. Theoretical methane recoveries were 13% and 9% for di-n-octyl and bis(Zethylhexy1) phthalate, respectively, confirming that these compounds were not significantly degraded. There was no significant loss of PAE's in autoclaved controls over the course of the experiment.

These data clearly demonstrated that dimethyl, diethyl, di-n-butyl, and butyl benzyl phthalate were susceptible to anaerobic biodegradation and that di-n-octyl and bis(2 -ethylhexyl) phthalate were persistent under these conditions. Susceptility to degradation was apparently related to size of the alkyl side chain with the larger C-8 groups being more resistant.

Applicant's summary and conclusion

Greater than 90% removal of di-n-butyl phthalate occurred in undiluted sludge within 1 week. Greater than 90% of di-n-butyl phthalate was degraded in 10% sludge.
within 40 days
Executive summary:

Dimethyl, diethyl, di-n-butyl, and butyl benzyl phthalate esters were mineralized in anaerobic digester sludge. In undiluted sludge 20 gg/mL of these phthalate esters was degraded within 1 week

Degradation was also studied in sludge diluted to 10% in an anaerobic mineral salt medium to facilitate detection of intermediates and to measure the quantity of methane produced. Degradation of dimethyl, diethyl, di-n-butyl, and butyl benzyl phthalate was slower in the diluted sludge, but 76-103% of the phthalate ester carbon expected as CHI was found in this form within 30 days. This shows that both the ester groups and the phthalate ring were mineralized.