Dichlobenil

Phototransformation in water

Link to relevant study record(s)

Reference

Endpoint:

phototransformation in water

Type of information:

experimental study

Adequacy of study:

key study

Study period:

January 1989 to February 1989

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Study type:

not specified

Qualifier:

according to guideline

Guideline:

EPA Guideline Subdivision N 161-2 (Photodegradation Studies in Water)

Deviations:

no

GLP compliance:

yes

Radiolabelling:

yes

Analytical method:

high-performance liquid chromatography

Details on sampling:

- Sampling intervals for the parent/transformation products: 0 hours, 1 day, 3 days, 7 days, 15 days and 21 days.
- Sampling method: At 0 hours five 1 mL samples were taken prior to filling the ampoules, at the remaining sampling times, one ampoule of the photolysis solution was taken from each of the four irradiated resevoirs and four from the dark controls. At sampling time 14 days, three more ampoules were taken from each irradiated resevoir for the isolation and identification of the degredation products. At sampling time 21 days, the remaining 16 ampoules from the irradiated resevoirs were also used for the identification of degradation products.
- Sample storage conditions before analysis: Samples were stored at 4 °C before analysis, and analysed within two days of sampling.

Light source:

Xenon lamp

Light spectrum: wavelength in nm:

340

Duration:

21 d

Temp.:

25 °C

Initial conc. measured:

5.749 mg/L

Dark controls:

yes

Remarks:

non-irradiated samples

Key result

DT50:

10.2 d

Test condition:

natural sunlight at 40 º Northern latitude (15.1 days of Xenon light assuming first-order reaction kinetics)

Transformation products:

yes

No.:

#1

No.:

#2

No.:

#3

No.:

#4

No.:

#5

No.:

#6

No.:

#7

No.:

#8

No.:

#9

No.:

#10

No.:

#11

No.:

#12

At sampling time 21 days, the total amount of [¹⁴C] in the irradiated solution was decreased to 95 % of the added [¹⁴C]. This loss is probably due to the disappearance of volatile degradation products when the ampoules are opened for analysis. In the dark controls, the test material remained stable. A [¹⁴C] balance of 99 % was found in these solutions, and the [¹⁴C] radioactivity was characterised as [¹⁴C]-dichlobenil. At sampling times 15 and 21 days, a degradation product was found which represented 14 and 17 % of the total [¹⁴C] radioactivity respectively. This compound was identified by MS 1H NMR and IR as #1 in the 'identity of degradation products' table. A mixture of polar compounds were also present at sampling times 15 and 21 days and represented 16 and 23 % of the total [¹⁴C] radioactivity respectively. Six of these compounds were identified by MS as #2 to #7 in the 'identity of degradation products' table above. Moreover, seven degradation products each present for less that 5 % of the [¹⁴C] radioactivity co-chromatographed on HPLC with the compounds #8 to #12 in the 'identity of degradation products' table above. The percentages at day 21 were 3, 1, 1, 2 and 4 % for compounds #8 to #12 respectively. The two other compounds could not be identified.

Conclusions:

Under the conditions of the test, the photodegradation of the test material in water was determined to be a half-life of 10.2 days of natural sunlight at 40 º Northern latitude.

Executive summary:

In a GLP compliant photodegradation in water study conducted in accordance with standardised guideline (EPA 161-2), the photodegradation of the test material was determined. Under the conditions of the test, the half-life of the test material in water is 10.2 days of natural sunlight at 40 º Northern latitude.

Description of key information

The half-life of the test material was determined to be 10.2 days according to study performed in line with EPA Guideline Subdivision N 161-2.

Key value for chemical safety assessment

Half-life in water:

10.2 d

Additional information

See 'Environmental Fate and Pathways' endpoint summary.