Metam-sodium

Biodegradation in soil

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in soil, other

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Data is from peer reviewed journal

Justification for type of information:

Data is from peer reviewed journal

Qualifier:

according to guideline

Guideline:

other: as mentioned below

Principles of method if other than guideline:

Biodegradation study in soil was conducted for determining the half-life of the chemical Metam-sodium.

GLP compliance:

not specified

Test type:

field trial

Specific details on test material used for the study:

- Name of test material (IUPAC name): Metam-sodium
- Common name: Sodium methyldithiocarbamate
- Molecular formula: C2H5NNaS2
- Molecular weight: 129.1826 g/mol
- Smiles notation: C(=S)(NC)[S-].[Na+]
- InChl: 1S/C2H5NS2.Na/c1-3-2(4)5;/h1H3,(H2,3,4,5);/q;+1/p-1
- Substance type: Organic
- Physical state: Solid

Radiolabelling:

not specified

Oxygen conditions:

not specified

Soil no.:

#1

Soil type:

other: For soil samples taken from field trials.

% Clay:

> 2.4 - < 25

% Silt:

> 4 - < 32

% Org. C:

> 1.3 - < 19

pH:

> 4 - < 8.1

Soil no.:

#2

Soil type:

other: For soil samples taken from problem fields.

% Clay:

> 2.1 - < 6.2

% Silt:

> 1.2 - < 14

% Org. C:

> 1.2 - < 18

pH:

> 4.7 - < 7.3

CEC:

> 0 - < 1.4 other: %

Soil no.:

#3

Soil type:

other: For soil samples taken from greenhouses.

% Clay:

> 1.8 - < 6.9

% Silt:

> 7 - < 25

% Org. C:

> 3.1 - < 8.6

pH:

> 6 - < 7

CEC:

> 0.1 - < 1.9 other: %

Soil no.:

#4

Soil type:

other: For soil samples taken from loamy soil fields.

% Clay:

> 30 - < 36

% Silt:

> 45 - < 59

% Org. C:

> 2.5 - < 4.2

pH:

> 7.3 - < 7.4

CEC:

> 8 - < 10 other: %

Details on soil characteristics:

SOIL COLLECTION AND STORAGE
- Geographic location: Soils for the transformation studies were collected from: a) field trials, b) "problem" fields, c) greenhouses and d) fields with loamy soils.

- Collection procedures: If possible, untreated soil was collected from a spot outside (50-100 m) the trial, in the same field or from an adjacent field. This was done for the Lelystad, Oosternijkerk, Vredepeel and Creil fields. For the Smilde trial field, no untreated soil was available.
The six greenhouse soils were chosen for sampling because frequent application of high rates of metham-sodium (up to 600 kg/ha) could have induced microbial adaptation, resulting in enhanced transformation.
Three heavier loam soils were collected in the young polder East Flevoland.

- Sampling depth (cm): At each location, soil sample was collected from 15 sites (0-20 cm layer).

- Storage conditions: The total mass of soil sample was mired thoroughly and then stored in a moist condition in partly open plastic bags at a temperature range of 10-15⁰C in the dark.

Soil No.:

#1

Duration:

15 d

Soil No.:

#1

Initial conc.:

3.75 mg/kg soil d.w.

Based on:

test mat.

Parameter followed for biodegradation estimation:

test mat. analysis

Soil No.:

#1

Temp.:

15 ± 0.2⁰C

Details on experimental conditions:

EXPERIMENTAL DESIGN
- Soil preincubation conditions (duration, temperature if applicable): Incubation of the soil started 2-8 weeks after the collection of soil sample.
- Soil (g/replicate): 50 g/soil
- Test apparatus (Type/material/volume): Glass flask (300 ml) was used as a test vessel for the study.

Experimental conditions (in addition to defined fields)
- Continuous darkness: Yes

SAMPLING DETAILS
- Sampling intervals: From 0.1 d on, up to 15 d the headspace of the flasks was sampled after increasing intervals by withdrawing a 0.1-0.5 ml sample with a 1 ml gas syringe.

- Sampling method for soil samples: At the sampling times the remaining masses of methyl isothiocyanate were calculated. The masses were expressed as a fraction {%) of the dose of methyl isothiocyanate, or of the theoretical dose for the flasks to which metham-sodium had been added.

Key result

Soil No.:

#1

% Degr.:

> 90

Parameter:

test mat. analysis

Remarks:

(%degradation)

Sampling time:

0.1 d

Remarks on result:

other: Other details not known

Key result

Soil No.:

#1

Remarks on result:

other: > 90% in 0.1 days (2.4 hrs)

Transformation products:

yes

No.:

#1

Details on transformation products:

- Formation and decline of each transformation product during test: methyl isothiocyanate

Evaporation of parent compound:

not specified

Volatile metabolites:

not specified

Residues:

not specified

Details on results:

MAJOR TRANSFORMATION PRODUCTS
The transformation of metham-sodium to methyl isothiocyanate at 15°C was very fast in most soils. The highest rates were found for the three loamy soils (Topper, Geerlig, Westerdijk) the Meijer "problem" soil and the Vellekoop greenhouse soil. In these soils, the highest concentrations of methyl isothiocyanate were already measured at the first sampling, 0.1 d after addition of metham-sodium. In the other humic and sandy soils, with lower pH, the highest concentrations of methyl isothiocyanate were measured at the second and third sampling, 0.3 and 1 d respectively after application of the metham-sodium. In the Odoorn soil maximum, concentration was measured after 4 d, which Indicated a slow transformation for part of the metham-sodium. The maximum amount of methyl isothiocyanate measured in the incubation flasks depends on the ratio between the rates of formation and transformation of methyl isothiocyanate in the soils. Therefore, the extent to which metham-sodium was transformed to methyl isothiocyanate was estimated wherein the amounts of methyl isothio'cyanate on each sampling time were plotted on a logarithmic scale against time. The amounts of methyl isothiocyanate produced were estimated by linear back extrapolation and found to be more than 90 % (90-98) of the amount that could theoretically be produced.

Table: Formation of methylisothiocyanate from metham-sodium in different soils.

 

Field	Maximum amount of methyl isothiocyanate measured in incubation flask (% of theoretical dose) (% of theoretical dose)	Time after application (d)
Vredepeel Odoorn Kooyenburg Bergentheim De Jonge A De Jonge B Bodenstaff Dijksterhuis Geerts Beuker Meijer Vellekoop Topper Geerlig Westerdijk	83 73 72 59 71 67 68 75 84 75 89 72 95 96 89	0.3 4 0.3 1 0.3 0.3 1.0 0.3 0.3 1.0 0.1 0.1 0.1 0.1 0.1

Conclusions:

The percentage degradation of test chemical Metam-sodium in soil was determined to be >90% in 0.1 days (2.4 hrs). The major transformation of the test chemical was determined to be methyl isothiocyanate.

Executive summary:

Biodegradation study in soil was conducted for determining the half-life of the chemical Metam-sodium (CAS no. 137-42-8).Soils for the transformation studies were collected from: a) field trials, b) "problem" fields, c) greenhouses and d) fields with loamy soils. If possible, untreated soil was collected from a spot outside (50-100 m) the trial, in the same field or from an adjacent field. This was done for the Lelystad, Oosternijkerk, Vredepeel and Creil fields. For the Smilde trial field, no untreated soil was available. The six greenhouse soils were chosen for sampling because frequent application of high rates of metham-sodium (up to 600 kg/ha) could have induced microbial adaptation, resulting in enhanced transformation. Three heavier loam soils were collected in the young polder East Flevoland.At each location, soil sample was collected from 15 sites (0-20 cm layer).The total mass of soil sample was mired thoroughly and then stored in a moist condition in partly open plastic bags at a temperature range of 10-15⁰C in the dark. Incubation of the soil started 2-8 weeks after the collection of soil sample. Glass flask (300 ml) was used as a test vessel for the study. The test vessel glass flask was stoppered with Mininert gas sampling valves. Metham-sodium(3.75 mg) was added to two flasks in 1 cm3 of a diluted aqueous solution of the trade product AAmonam GC (a.i., 510 g/litre).This dose is equivalent to 2.12 mg methyl isothiocyanate at complete conversion.The flasks were placed in the dark in a water bath at 15 (± 0.2) "C and were occasionally shaken to ensure quick equilibration of methyl isothiocyanate between the gas, water and solid phases. From 0.1 d on, up to 15 d the headspace of the flasks was sampled after increasing intervals by withdrawing a 0.1-0.5 ml sample with a 1 ml gas syringe.At the sampling times the remaining masses of methyl isothiocyanate were calculated. The masses were expressed as a fraction{%)of the dose of methyl isothiocyanate, or of the theoretical dose for the flasks to which metham-sodium had been added. The soils were extracted with ethyl acetate (100 ml) and water (50 ml) by shaking for 2 h on a reciprocating shaker. Part of the supernatant organic layer was pipetted off and dried with anhydrous sodium sulphate. Recovery for each soil type was calculated from the amounts extracted from two flasks after incubation for 0.1-0.2 d. Recovery for all soils ranged from93-102%of the dose. No corrections were made for this recovery. Headspace samples (0.1-0.5 ml) were injected directly into the gas chromatograph. At each sampling time, two samples were taken, which always gave similar results (mean difference 3 % of the mean concentration).Methyl isothiocyanate was determined to be the transformation product of the test chemicalMetam-sodium. Thus, concentrations of methyl isothiocyanate in the ethyl acetate extracts and in the headspace samples were measured with a Pye Unicam GCV gas chromatograph equipped with a flame photometer detector, operated in the sulphur mode (394 nm filter). The glass column (length 1.4 m; inner diameter 4 mm) was packed with 3% Carbowax 20 M on Chromosorb W AW-DMCS, particle size 0.15-0.18 mm. At a carrier gas (nitrogen) flow rate of 60 ml min~* and a column temperature of 110 °C, the retention time of methyl isothiocyanate was 1 min. The temperatures of injector and detector were 150 and 210°C .respectively. Concentrations in the extracts and headspace samples were calculated with the external standard method, based on peak heights or integrated peak areas obtained with 3 pi injections of standard solutions of methyl isothiocyanate (99.8%)in ethyl acetate(0.1-10mg/litre).The transformation of metham-sodium to methyl isothiocyanate at 15°C was very fast in most soils. The highest rates were found for the three loamy soils (Topper, Geerlig, Westerdijk) the Meijer "problem" soil and the Vellekoop greenhouse soil. In these soils, the highest concentrations of methyl isothiocyanate were already measured at the first sampling, 0.1 d after addition ofmetham-sodium. In the other humic and sandy soils, with lower pH, the highest concentrations of methyl isothiocyanate were measured at the second and third sampling, 0.3 and 1 d respectively after application of the metham-sodium. In the Odoorn soil maximum, concentration was measured after 4 d, which Indicated a slow transformation for part of the metham-sodium.The maximum amount of methyl isothiocyanate measured in the incubation flasks depends on the ratio between the rates of formation and transformation of methyl isothiocyanate in the soils.Therefore, the extent to which metham-sodium was transformed to methyl isothiocyanate was estimated wherein the amounts of methyl isothio'cyanate on each sampling time were plotted on a logarithmic scale against time. The amounts of methyl isothiocyanate produced were estimated by linear back extrapolation and found to be more than 90%(90-98) of the amount that could theoretically be produced.The percentage degradation of test chemicalMetam-sodiumin soil was determined to be >90% in 0.1 days (2.4 hrs). The major transformation of the test chemical was determined to bemethyl isothiocyanate and the amounts of methyl isothiocyanate produced were estimated by linear back extrapolation and found to be more than 90%(90-98) of the amount that could theoretically be produced.Thus, based on percentage degradation, it is concluded that the chemicalMetam-sodiumis not persistent in the soil environment and the exposure risk to soil dwelling animals is moderate to low.

Description of key information

Biodegradation study in soil was conducted for determining the half-life of the chemical Metam-sodium (CAS no. 137-42-8) (J.H. Smelt, et. al; 1989). Soils for the transformation studies were collected from: a) field trials, b) "problem" fields, c) greenhouses and d) fields with loamy soils. If possible, untreated soil was collected from a spot outside (50-100 m) the trial, in the same field or from an adjacent field. This was done for the Lelystad, Oosternijkerk, Vredepeel and Creil fields. For the Smilde trial field, no untreated soil was available. The six greenhouse soils were chosen for sampling because frequent application of high rates of metham-sodium (up to 600 kg/ha) could have induced microbial adaptation, resulting in enhanced transformation. Three heavier loam soils were collected in the young polder East Flevoland.At each location, soil sample was collected from 15 sites (0-20 cm layer).The total mass of soil sample was mired thoroughly and then stored in a moist condition in partly open plastic bags at a temperature range of 10-15⁰C in the dark. Incubation of the soil started 2-8 weeks after the collection of soil sample. Glass flask (300 ml) was used as a test vessel for the study. The test vessel glass flask was stoppered with Mininert gas sampling valves. Metham-sodium(3.75 mg) was added to two flasks in 1 cm3 of a diluted aqueous solution of the trade product AAmonam GC (a.i., 510 g/litre).This dose is equivalent to 2.12 mg methyl isothiocyanate at complete conversion.The flasks were placed in the dark in a water bath at 15 (± 0.2) "C and were occasionally shaken to ensure quick equilibration of methyl isothiocyanate between the gas, water and solid phases. From 0.1 d on, up to 15 d the headspace of the flasks was sampled after increasing intervals by withdrawing a 0.1-0.5 ml sample with a 1 ml gas syringe.At the sampling times the remaining masses of methyl isothiocyanate were calculated. The masses were expressed as a fraction{%)of the dose of methyl isothiocyanate, or of the theoretical dose for the flasks to which metham-sodium had been added. The soils were extracted with ethyl acetate (100 ml) and water (50 ml) by shaking for 2 h on a reciprocating shaker. Part of the supernatant organic layer was pipetted off and dried with anhydrous sodium sulphate. Recovery for each soil type was calculated from the amounts extracted from two flasks after incubation for 0.1-0.2 d. Recovery for all soils ranged from93-102%of the dose. No corrections were made for this recovery. Headspace samples (0.1-0.5 ml) were injected directly into the gas chromatograph. At each sampling time, two samples were taken, which always gave similar results (mean difference 3 % of the mean concentration).Methyl isothiocyanate was determined to be the transformation product of the test chemicalMetam-sodium. Thus, concentrations of methyl isothiocyanate in the ethyl acetate extracts and in the headspace samples were measured with a Pye Unicam GCV gas chromatograph equipped with a flame photometer detector, operated in the sulphur mode (394 nm filter). The glass column (length 1.4 m; inner diameter 4 mm) was packed with 3% Carbowax 20 M on Chromosorb W AW-DMCS, particle size 0.15-0.18 mm. At a carrier gas (nitrogen) flow rate of 60 ml min~* and a column temperature of 110 °C, the retention time of methyl isothiocyanate was 1 min. The temperatures of injector and detector were 150 and 210°C .respectively. Concentrations in the extracts and headspace samples were calculated with the external standard method, based on peak heights or integrated peak areas obtained with 3 pi injections of standard solutions of methyl isothiocyanate (99.8%)in ethyl acetate(0.1-10mg/litre).The transformation of metham-sodium to methyl isothiocyanate at 15°C was very fast in most soils. The highest rates were found for the three loamy soils (Topper, Geerlig, Westerdijk) the Meijer "problem" soil and the Vellekoop greenhouse soil. In these soils, the highest concentrations of methyl isothiocyanate were already measured at the first sampling, 0.1 d after addition ofmetham-sodium. In the other humic and sandy soils, with lower pH, the highest concentrations of methyl isothiocyanate were measured at the second and third sampling, 0.3 and 1 d respectively after application of the metham-sodium. In the Odoorn soil maximum, concentration was measured after 4 d, which Indicated a slow transformation for part of the metham-sodium.The maximum amount of methyl isothiocyanate measured in the incubation flasks depends on the ratio between the rates of formation and transformation of methyl isothiocyanate in the soils.Therefore, the extent to which metham-sodium was transformed to methyl isothiocyanate was estimated wherein the amounts of methyl isothio'cyanate on each sampling time were plotted on a logarithmic scale against time. The amounts of methyl isothiocyanate produced were estimated by linear back extrapolation and found to be more than 90%(90-98) of the amount that could theoretically be produced.The percentage degradation of test chemicalMetam-sodiumin soil was determined to be >90% in 0.1 days (2.4 hrs). The major transformation of the test chemical was determined to bemethyl isothiocyanate and the amounts of methyl isothiocyanate produced were estimated by linear back extrapolation and found to be more than 90%(90-98) of the amount that could theoretically be produced.Thus, based on percentage degradation, it is concluded that the chemicalMetam-sodiumis not persistent in the soil environment and the exposure risk to soil dwelling animals is moderate to low.

Additional information

Various experimental studies for the target chemical Metam-sodium (CAS No. 137-42-8) were reviewed for the biodegradation in soil end point which are summarized as below:

 

In an experimental key study from peer reviewed journal (J.H. Smelt, et. al; 1989), biodegradation experiment in soil was conducted for determining the half-life of the chemical Metam-sodium (CAS no. 137-42-8).Soils for the transformation studies were collected from: a) field trials, b) "problem" fields, c) greenhouses and d) fields with loamy soils. If possible, untreated soil was collected from a spot outside (50-100 m) the trial, in the same field or from an adjacent field. This was done for the Lelystad, Oosternijkerk, Vredepeel and Creil fields. For the Smilde trial field, no untreated soil was available. The six greenhouse soils were chosen for sampling because frequent application of high rates of metham-sodium (up to 600 kg/ha) could have induced microbial adaptation, resulting in enhanced transformation. Three heavier loam soils were collected in the young polder East Flevoland. At each location, soil sample was collected from 15 sites (0-20 cm layer).The total mass of soil sample was mired thoroughly and then stored in a moist condition in partly open plastic bags at a temperature range of 10-15⁰C in the dark. Incubation of the soil started 2-8 weeks after the collection of soil sample. Glass flask (300 ml) was used as a test vessel for the study. The test vessel glass flask was stoppered with Mininert gas sampling valves. Metham-sodium(3.75 mg) was added to two flasks in 1 cm3 of a diluted aqueous solution of the trade product Amonam GC (a.i., 510 g/litre).This dose is equivalent to 2.12 mg methyl isothiocyanate at complete conversion. The flasks were placed in the dark in a water bath at 15 (± 0.2) "C and were occasionally shaken to ensure quick equilibration of methyl isothiocyanate between the gas, water and solid phases. From 0.1 d on, up to 15 d the headspace of the flasks was sampled after increasing intervals by withdrawing a 0.1-0.5 ml sample with a 1 ml gas syringe.At the sampling times the remaining masses of methyl isothiocyanate were calculated. The masses were expressed as a fraction{%)of the dose of methyl isothiocyanate, or of the theoretical dose for the flasks to which metham-sodium had been added. The soils were extracted with ethyl acetate (100 ml) and water (50 ml) by shaking for 2 h on a reciprocating shaker. Part of the supernatant organic layer was pipetted off and dried with anhydrous sodium sulphate. Recovery for each soil type was calculated from the amounts extracted from two flasks after incubation for 0.1-0.2 d. Recovery for all soils ranged from93-102%of the dose. No corrections were made for this recovery. Headspace samples (0.1-0.5 ml) were injected directly into the gas chromatograph. At each sampling time, two samples were taken, which always gave similar results (mean difference 3 % of the mean concentration).Methyl isothiocyanate was determined to be the transformation product of the test chemical Metam-sodium. Thus, concentrations of methyl isothiocyanate in the ethyl acetate extracts and in the headspace samples were measured with a Pye Unicam GCV gas chromatograph equipped with a flame photometer detector, operated in the sulphur mode (394 nm filter). The glass column (length 1.4 m; inner diameter 4 mm) was packed with 3% Carbowax 20 M on Chromosorb W AW-DMCS, particle size 0.15-0.18 mm. At a carrier gas (nitrogen) flow rate of 60 ml min~* and a column temperature of 110 °C, the retention time of methyl isothiocyanate was 1 min. The temperatures of injector and detector were 150 and 210°C .respectively. Concentrations in the extracts and headspace samples were calculated with the external standard method, based on peak heights or integrated peak areas obtained with 3 pi injections of standard solutions of methyl isothiocyanate (99.8%)in ethyl acetate(0.1-10mg/litre).The transformation of metham-sodium to methyl isothiocyanate at 15°C was very fast in most soils. The highest rates were found for the three loamy soils (Topper, Geerlig, Westerdijk) the Meijer "problem" soil and the Vellekoop greenhouse soil. In these soils, the highest concentrations of methyl isothiocyanate were already measured at the first sampling, 0.1 d after addition of metham-sodium. In the other humic and sandy soils, with lower pH, the highest concentrations of methyl isothiocyanate were measured at the second and third sampling, 0.3 and 1 d respectively after application of the metham-sodium. In the Odoorn soil maximum, concentration was measured after 4 d, which Indicated a slow transformation for part of the metham-sodium. The maximum amount of methyl isothiocyanate measured in the incubation flasks depends on the ratio between the rates of formation and transformation of methyl isothiocyanate in the soils. Therefore, the extent to which metham-sodium was transformed to methyl isothiocyanate was estimated wherein the amounts of methyl isothio'cyanate on each sampling time were plotted on a logarithmic scale against time. The amounts of methyl isothiocyanate produced were estimated by linear back extrapolation and found to be more than 90%(90-98) of the amount that could theoretically be produced.The percentage degradation of test chemical Metam-sodium in soil was determined to be >90% in 0.1 days (2.4 hrs). The major transformation of the test chemical was determined to bemethyl isothiocyanate and the amounts of methyl isothiocyanate produced were estimated by linear back extrapolation and found to be more than 90%(90-98) of the amount that could theoretically be produced. Thus, based on percentage degradation, it is concluded that the chemicalMetam-sodiumis not persistent in the soil environment and the exposure risk to soil dwelling animals is moderate to low.

Another biodegradation study in soil was carried out for determining the half-life or percentage degradation of the test chemical Metam-sodium (CAS no. 137-42-8) (Stephen B. Pruett, et. al; 2001).The percentage degradation of test chemical Metam-sodium in soil was determined to be92% in less than 12 days. Transformation product of chemical Metam-sodium was determined to be methylisothiocyanate (MITC) and H2S, respectively. Depending on soil moisture and soil composition, substantial amount of Metam-sodium may remain in the soil for 12 days or more, respectively. Based on this, it is concluded that the chemical Metam-sodium is not persistent in the soil environment and the exposure risk to soil dwelling animals is moderate to low.

 

In a supporting study from authoritative database (HSDB and PubChem, 2017), biodegradation experiment in soil was carried out for determining the half-life of the test chemical Metam-sodium (CAS no. 137-42-8).The half-life period of Metam-sodiumin soil was determined to be ranges from 0.23 min to 4 days, respectively. Based on this half-life value of chemical Metam-sodium, it is concluded that the chemical Metam-sodium is not persistent in the soil environment and the exposure risk to soil dwelling animals is moderate to low.

 

For the target chemical Metam-sodium (CAS no. 137-42-8) from authoritative database (Agricultural Research Service (ARS) Pesticide Properties Database, 1995 and Pesticide Properties in the Environment, 2012), biodegradation study in soil was carried out for determining the half-life of the test chemical Metam-sodium (CAS no. 137-42-8).The half-life period of Metam-sodium in soil was determined to be ranges from 5 to 7 days, respectively. Based on this half-life value of chemical Metam-sodium, it is concluded that the chemical Metam-sodium is not persistent in the soil environment and the exposure risk to soil dwelling animals is moderate to low.

 

Additional biodegradation study from secondary source (IUCLID dataset, 2000) in soil was carried out for determining the half-life of the test chemical Metam-sodium (CAS no. 137-42-8).The study was performed according to other method EPA/FIFRA 162–1at a temperature of 28°C, respectively. Test chemical used for the study was in the form of radiolabel 14C–sodium–monomethyldithiocarbamate. Initial test substance concentration used for the study was 125.7 mg/l. The properties of the soil includes clay 1.2%, silt 7%, sand 91.8%, organic carbon content 0.2%, pH 6.9 and CEC of the soil was6.5 meq/100 g soil dry weight, respectively. 6.5 meq/100 g soil dry weight. The half-life period ofMetam-sodiumin soil was determined to be 23 min, respectively. Based on this half-life value of chemical Metam-sodium, it is concluded that the chemical Metam-sodium is not persistent in the soil environment and the exposure risk to soil dwelling animals is moderate to low.

 

In a supporting study, biodegradation experiment in soil was carried out for determining the half-life of the test chemical Metam-sodium (CAS no. 137-42-8) (HSDB, PubChem and Pesticide Properties Database, 2017).The half-life period of Metam-sodium in soil was determined to be 7 days. Based on this half-life value of chemical Metam-sodium, it is concluded that the chemical Metam-sodium is not persistent in the soil environment and the exposure risk to soil dwelling animals is moderate to low.

 

In an another study from authoritative database (AGRITOX - Plant Protection Phentopharmaceuticals Database, 2012), biodegradation experiment in soil was carried out under aerobic conditions for 21 days for determining the percentage degradation of the chemical Metam-sodium (CAS no. 137-42-8).The percentage degradation of test chemical Metam-sodium in soil was determined to be in the range 45.96 – 86.25% in 21 days. The transformation of the product of the test chemical was determined to be methylisothiocyanate (MITC). The max. metabolite i.e methylisothiocyanate 82.9% was obtained in 1-2 days.Based on this, it is concluded that the chemical Metam-sodium is not persistent in the soil environment and the exposure risk to soil dwelling animals is moderate to low.

 

On the basis of above results for target chemical Metam-sodium (from peer reviewed journal, secondary source and authoritative databases), it can be concluded that the test substance Metam-sodium is not persistent in the soil environment and therefore the exposure risk to soil dwelling animals is moderate to low.