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Environmental fate & pathways

Biodegradation in soil

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Endpoint:
biodegradation in soil
Type of information:
experimental study
Adequacy of study:
other information
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
comparable to guideline study
Remarks:
GLP, similar to OECD-guideline, analytical monitoring.
Qualifier:
equivalent or similar to guideline
Guideline:
other: EPA, title 40 Code of Federal Regulations Part 160 (1983, 1989)
GLP compliance:
yes
Test type:
laboratory
Specific details on test material used for the study:
- Radiochemical purity: HPLC (on day of application): 85.4 % (radiolabelled test substance)
- Methacrylic acid was presented as an impurity in the applied methyl methacrylate and was detected in the zerotime soil extracts.
Radiolabelling:
yes
Oxygen conditions:
aerobic
Soil no.:
#1
Soil type:
sandy loam
% Clay:
16
% Silt:
30
% Sand:
54
% Org. C:
3.2
pH:
7.7
CEC:
22.2 meq/100 g soil d.w.
Parameter followed for biodegradation estimation:
radiochem. meas.
Soil No.:
#1
Temp.:
25 °C
Humidity:
17.3 other: % by weight
Details on experimental conditions:
The metabolism of 14C-methyl methacrylate in a Milton sandy loam soil has been studied after application under aerobic conditions after application of 100 and 1000 mg MMA/l dry  weight. Soil samples were incubated in the dark at ca. 25  degree C. 
Soil No.:
#1
% Degr.:
> 99
Parameter:
radiochem. meas.
Sampling time:
2 d
Soil No.:
#1
DT50:
< 1 d
Type:
(pseudo-)first order (= half-life)
Transformation products:
yes
No.:
#1
No.:
#2
Evaporation of parent compound:
yes
Volatile metabolites:
yes
Details on results:
Already after 2 days < 1 % of the radioactivity  was presented as MMA in soil extracts, at either rate of  application. About 60 - 70 % of the radioactivity was lost  due to evaporation of the parent compound at both concentration levels. Of the total volatiles measured,  28.2 (low level) and 15.7 (high MMA level) of applied  compound over the 28-day study period was accounted to CO2  emissions. The indications are that MMA is rapidly lost  from soil either by evaporation or degradation. The estimated half-life for methyl methacrylate in soil was less than one day at both concentration levels.
Executive summary:

The aerobic degradation of 14C-methyl methacrylate after application to a Milton sandy loam soil has been studied at two application rates (100 and 1000 mg/kg dry weight soil). After application at either rate,

methyl methacrylate was rapidly lost from the soil by a combination of evaporative and degradative processes. The estimated half-life for methyl methacrylate in soil was less than one day.

Volatile radioactivity, other than that characterised as 14C02 , was assumed to be associated with the parent compound. Although the study was designed to minimise evaporation of methyl methacrylate, it was still

expected to be significant in view of the highly volatile nature of the compound. After application at 100 and 1000 mg/kg, evaporation of unchanged methyl methacrylate was estimated to account for about 60%

and 70 % of the applied radioactivity respectively. Almost all of this evaporation occurred during the first day after application.

Mineralisation to 14CO2 accounted for 28% of the 100 mg/kg application and 16% of the 1000 mg/kg application after 28 days. Production of 14C02 occurred mostly during the first three days after

application and was more rapid (in terms of % applied radioactivity) after application at 100 mg/kg.

Degradation to non-volatile, non-extractable material accounted for about 5 % of the low level application and 2 % of the high level application after 28 days.

Methacrylic acid was present as an impurity in the applied methyl methacrylate and was detected in the zerotime soil extracts. Tue proportion of methacrylic acid in soil declined rapidly suggesting that it also was degraded or volatilised.

Endpoint:
biodegradation in soil: simulation testing
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
the study does not need to be conducted because the substance is readily biodegradable

Description of key information

Key value for chemical safety assessment

Additional information

In a guideline study in accordance to U.S.-EPA already after 2 days < 1 % of the radioactivity was left as methyl methacrylate in soil extracts, at either rate of application. About 60 - 70 % of the radioactivity was lost due to evaporation of the parent compound at both concentration levels. Of the total volatiles measured, 28.2 (low level) and 15.7 (high methyl methacrylate level) of applied compound over the 28-day study period was accounted to CO2 emissions. The indications are that methyl methacrylate is rapidly lost from soil either by evaporation or degradation. The estimated half-life for methyl methacrylate in soil was less than one day at both concentration levels. In addition, the test substance shows low adsorptive properties (log Koc 1.1) and is readily biodegradable.