spirodiclofen (ISO);3-(2,4-dichlorophenyl)-2-oxo-1-oxaspiro[4.5]dec-3-en-4-yl 2,2-dimethylbutyrate

Additional information on environmental fate and behaviour

Administrative data

Endpoint:

additional information on environmental fate and behaviour

Remarks:

Chemical Lifetime of spirodiclofen in the Troposphere

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Justification for type of information:

This experimental study report is reliable for use in the risk assessment as it has been conducted by a trusted laboratory, under GLP and following a recognised guideline relevant at the time of the study being conducted. This data has been deemed appropriate to use.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1998

Report date:

1998

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: Federal Biological Institute for Agriculture and Forestry, Braunschweig, FRG, part IV, 6-1

Version / remarks:

July 1990

Deviations:

not specified

GLP compliance:

yes (incl. QA statement)

Type of study / information:

Calculation of the Chemical Lifetime of spirodiclofen in the Troposphere

Test material

Test material information

1

Reference substance name:

3-(3,5-Dichlorophenyl)-2-oxo-1-oxaspiro[4.5]dec-3-en-4-yl 2,2-dimethylbutanoate

Cas Number:

148477-71-8

Molecular formula:

C21H24Cl2O4

IUPAC Name:

3-(3,5-Dichlorophenyl)-2-oxo-1-oxaspiro[4.5]dec-3-en-4-yl 2,2-dimethylbutanoate

Test material form:

solid: particulate/powder

Remarks:

white appearance

Results and discussion

Any other information on results incl. tables

The calculated overall OH reaction rate of 48.12 x 10^-12 [cm³/molecules sec] is mainly obtained by addition to the olefinic bond (k_add = 38.50 x 10^-12 [cm³/molecules sec]) and by hydrogen abstractions at several sites (k_{H-abs total} = 8.72 x 10^-12 [cm³/molecules sec]). Furthermore, a minor contribution was assumed by additions to the aromatic ring (k_ar = 0.91 x 10^-12 [cm³/molecules
sec]). Based on the before-mentioned calculated overall OH rate constant

⇒ a half-life of spirodiclofen in air of 2.67 hours corresponding to
⇒ a chemical lifetime of spirodiclofen in air of 3.9 hours

is assessed using a 12-hrs-day with 1.5 x 106 OH radicals/cm³

A more conservative assessment of the overall OH radical rate constant, i.e. only considering the half of estimated rates in case of assumed values in the modelling would result in a maximum chemical lifetime (τ) of spirodiclofen of less than 7 hours in the air. For the reaction of the olefinic bond with ozone in the troposphere a half-life of 13.1 hours corresponding to a chemical lifetime of 19 hours was assessed. The before-mentioned estimations do not consider any contribution of an attack by other radicals (i.e. by nitrate radicals). If the active ingredient will be applied during the early afternoon, as opposite to the early morning or to the late afternoon, it is to be expected that the chemical lifetime
will be shorter at that moment, as during the day the OH radical concentration may increase unto
5 x 10⁶ radicals/cm³ in the troposphere. On the other hand, the OH radical concentration in the night decreases to zero. However, the degradation via ozone is possible during the entire day, that is during day and night.

Applicant's summary and conclusion

Conclusions:

The chemical lifetime of spirodiclofen in the troposphere was calculated:
Half-life in air =2.67 hours.
Chemical lifetime in air =3.9 hours.

Executive summary:

The chemical lifetime of spirodiclofen in the air is assessed based on the calculation according to Atkinson by AOPWIN (version 1.87). A value of at the most 7 hours resulted, with respect to the OH radical reaction, only. In addition, a degradation via reaction with ozone is relevant during day and night. The chemical stability of spirodiclofen in air is not determined by an attack at one single site, but at different parts of the molecule. This should result in the formation of various primary radicals leading to secondary oxidation products, which can be eliminated from the air by wet and/or dry deposition. On account of the relatively short chemical lifetime of spirodiclofen in the air it is to be expected that the active ingredient can not be transported in gaseous phase over large distances nor accumulate in the air. This indicates that there should be no difference in the behaviour between spirodiclofen and other organic substances which are emitted into the air from natural sources (e.g. from soil or plants).