Dichloroacetyl chloride

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

effects on growth of green algae

Type of information:

(Q)SAR

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

1. SOFTWARE
EpiWin

2. MODEL (incl. version number)
ECOSAR v1.11 Class-specific Estimations

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
CAS 79-36-7

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
- Defined endpoint: Yes
- Unambiguous algorithm: Yes
- Defined domain of applicability: Yes
- Appropriate measures of goodness-of-fit and robustness and predictivity: Yes
- Mechanistic interpretation: No

5. APPLICABILITY DOMAIN
- Descriptor domain: organic substances, acid halides
- Structural domain: organic substances, acid halides
- Mechanistic domain: no
- Similarity with analogues in the training set: unknown

6. ADEQUACY OF THE RESULT
considered to be sufficient as WoE as support of the results of the read across source substance.

Principles of method if other than guideline:

QSAR

GLP compliance:

no

Test organisms (species):

not specified

Key result

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

1 454.81

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

not specified

Remarks on result:

other: QSAR Acid Halides

Validity criteria fulfilled:

not applicable

Conclusions:

96h-EC50= 1454.810 Acid Halides

Executive summary:

The Epiwin QSAR calculation (acid halides) confirms that DCAC is not acute toxic to algae (96-h EC50: 1455 mg/L).

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The non-GLP study with good documentation was performed according to ASTM E1218-04.

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH


1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The target substance DCAC hydrolyses within short time to the source substance and HCl, read across is considered relevant, justified and conservative when using the data from the source substance as they are, i.e., without further assesment factor.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The target substance DCAC hydrolyses within short time to the source substance and HCl, read across is considered relevant, justified and conservative when using the data from the source substance as they are, i.e., without further assesment factor.

3. ANALOGUE APPROACH JUSTIFICATION
The target substance DCAC hydrolyses within short time to the source substance and HCl, read across is considered relevant, justified and conservative when using the data from the source substance as they are, i.e., without further assesment factor.

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

other: ASTM E1218-04

GLP compliance:

not specified

Remarks:

The data source is a publication

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Control, highest and lowest concentration
- Sample storage conditions before analysis: maximum 14 days at 4°C. Shipped on ice.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The highest concentration was prepared in dilution water and further diluted to obtain the lower concentrations
- Controls: dilution water
- Evidence of undissolved material (e.g. precipitate, surface film, etc): not reported

Test organisms (species):

other: Isochysis galbana (clone T-ISO)

Details on test organisms:

TEST ORGANISM
- Common name: Isochysis galbana
- Strain: clone T-ISO
- Source (laboratory, culture collection): University of Texas Algal Culture, University of Texas, Austin, Texas.
- Method of cultivation: The growth media and culture conditions for this species were those described in Appendix A3 of ASTM (American Society of Testing and Materials) Designation E 1218-04 (ASTM, 2006).

Test type:

static

Water media type:

brackish water

Limit test:

no

Total exposure duration:

72 h

Test temperature:

average temperature 25.2 C with a range of 24.9-25.5 C

pH:

The 72-h acute I. galbana growth data generated in this test indicates a relatively strong relationship between the low pH of the highest dichloroacetic acid treatmentsand reduced population growth. There was complete lack of population growth at the highest test concentration of 418 mg/l (pH = 2.86) and very reduced growth at a dichloroacetic acid concentration of 209 mg/l (pH = 5.37).

Nominal and measured concentrations:

Nominal: Control, 418, 209, 105, 52.3, 26.2 mg/L (the lowest concentration was calculated from the information that the four highest concentrations were 418, 209, 104.5 and 52.3 mg/L and 5 concentrations were set up).
Since the recoveries were >= 88 % of the nominal concentrations, the biological data were based on nominal concentrations.

Details on test conditions:

TEST SYSTEM
- Test vessel: 250 mL Erlenmeyer flasks
- Material, size, headspace, fill volume: 100 mL
- Renewal rate of test solution (frequency/flow rate): static
- Initial cells density: 1-2 x 10.000 cells/mL
- Control end cells density: > 1x10E6 cells/mL
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4

GROWTH MEDIUM
- Standard medium used: yes, ASTM f/2 Culture media (Appendix A3 of ASTM designation E 1218-04; ASTM, 2006)
- Algal testing protocols followed the method given in “Short-term Methods for Estimating the Chronic Toxicity of Effluents and Receiving Water to Freshwater Organisms” (USEPA, 2002). The only variations from the EPA manual are the use of a saltwater algal species (I. galbana (clone T-ISO) and a corresponding saltwater algal growth media (ASTM, 2006)). Individual compounds were added to previously prepared algal media (f/2). The algal growth media was prepared by the addition of f/2 micro and macro nutrients to salinity adjusted Wye River, MD water after vacuum filtration through a 0.45 mm glass fiber filter.

TEST MEDIUM / WATER PARAMETERS
- Culture medium different from test medium: no
- Intervals of water quality measurement: start and end of exposure

OTHER TEST CONDITIONS
- Sterile test conditions: yes/no
- Adjustment of pH: no
- Photoperiod: 24 h/day
- Light intensity and quality: 360- 440 foot candles, “Cool white” fluorescent lighting
- Salinity (for marine algae): 20 permille

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: [counting chamber; electronic particle counter; fluorimeter; spectrophotometer; colorimeter]
- Chlorophyll measurement:
- Other:

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 0.5

Reference substance (positive control):

not specified

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

39.9 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

148.2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

52.3 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Details on results:

- Exponential growth in the control (for algal test): not reported
- Observation of abnormalities (for algal test): not reported
- Any stimulation of growth found in any treatment: no
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: No, recoveries were > 88% of nominal
- Effect concentrations exceeding solubility of substance in test medium: no

Chemical stability tests indicate that dichloroacetic acid is stable. The 72-h acute I. galbana growth data generated in this test indicates a relatively strong relationship between the low pH of the highest dichloroacetic acid treatments and reduced population growth. There was complete lack of population growth at the highest test concentration of 418 mg/L (pH = 2.86) and very reduced growth at a dichloroacetic acid concentration of 209 mg/L (pH = 5.37). The statistical analysis also indicates reduced algal growth at 104.5 mg/L dichloroacetic acid with a test solution pH of 6.55. The 72-h EC50 for I. galbana exposed to dichloroacetic acid was 148.2 mg/L and the EC10 was calculated to be 39.9 mg/L.

Validity criteria fulfilled:

not specified

Executive summary:

In the publication from Fisher et al (2014) the toxicity of DCA on the unicellular algae Isochysis galbana (clone T-ISO) was investigated in brackish water. The test was performed according to ASTM E1218-04. The pH was not adjusted. In total 5 concentrations were tested. Nominal: Control, 26.2, 52.3, 104.5, 209 and 418 mg/L (the lowest concentration was calculated from the information that the four highest concentrations were 52.3, 104.5, 209 and 418 mg/L and 5 concentrations were set up). The test was performed for 72 hours. Chemical stability tests indicate that dichloroacetic acid is stable. The 72-h acute I. galbana growth data generated in this test indicates a relatively strong relationship between the low pH of the highest dichloroacetic acid treatments and reduced population growth. There was complete lack of population growth at the highest test concentration of 418 mg/L (pH = 2.86)and very reduced growth at a dichloroacetic acid concentration of 209 mg/L (pH = 5.37). The statistical analysis also indicates reduced algal growth at 104.5 mg/L dichloroacetic acid with a test solution pH of 6.55 (LOEC). The NOEC was 52.3 mg/L. The 72-h EC50 for I. galbana exposed to dichloroacetic acid was 148.2 mg/L and the EC10 was calculated to be 39.9 mg/L.The data were based on cell number. Typically, this endpoint is more sensitive than the evaluation based on growth rate. Furthermore, the pH was not adjusted and it could be speculated that the decreased pH might have affected the algae growth. Therefore, these values are considered worst case data.

The EC50 and EC10 are considered relevant and reliable for the risk assessment.

 

 

Since the target substance DCAC has a higher molecular weight when compared to the source substance and hydrolyses within short time to the source substance read across is considered relevant, justified and conservative when using the data from the source substance as they are, i.e., without further assesment factor.

 

 

Key value for chemical safety assessment

EC50 for marine water algae:

148.2 mg/L

EC10 or NOEC for freshwater algae:

1 485 mg/L

EC10 or NOEC for marine water algae:

39.9 mg/L

Additional information

When getting in contact with water, DCAC hydrolyses very fast to DCA and HCl. Data for DCA added as read across data (DCA as source) demonstrate that DCA is not toxic to aquatic algae (72h-EC50 148.2 mg/L, see below).  Hence, it must be concluded that DCAC is also not toxic to aquatic algae. This is supported by QSAR analysis (i.e, the QSRR resulted in a 96 h-EC50 of 1455 mg/L and is hence >> 100 mg/L).

 In the publication from Fisher et al (2014) the toxicity of DCA on the unicellular algae Isochysis galbana (clone T. iso) was investigated in brackish water. The test was performed according to ASTM E1218-04. The pH was not adjusted. In total 5 concentrations were tested. Nominal: Control, 26.2, 52.3, 104.5, 209 and 418 mg/L (the lowest concentration was calculated from the information that the four highest concentrations were 52.3, 104.5, 209 and 418 mg/L and 5 concentrations were set up). The test was performed for 72 hours. Chemical stability tests indicate that dichloroacetic acid is stable. The 72-h acute I. galbana growth data generated in this test indicates a relatively strong relationship between the low pH of the highest dichloroacetic acid treatments and reduced population growth. There was complete lack of population growth at the highest test concentration of 418 mg/L (pH = 2.86)and very reduced growth at a dichloroacetic acid concentration of 209 mg/L (pH = 5.37). The statistical analysis also indicates reduced algal growth at 104.5 mg/L dichloroacetic acid with a test solution pH of 6.55 (LOEC). The NOEC was 52.3 mg/L. The 72-h EC50 for I. galbana exposed to dichloroacetic acid was 148.2 mg/L and the EC10 was calculated to be 39.9 mg/L.The data were based on cell number. Typically, this endpoint is more sensitive than the evaluation based on growth rate. Furthermore, the pH was not adjusted and it could be speculated that the decreased pH might have affected the algae growth. Therefore, these values are considered worst case data.

The EC50 and EC10 are considered relevant and reliable for the risk assessment.

 

 In the non-GLP study from the Umweltbundesamt (1982), the growth inhibition of DCA on Desmodesmus subspicatus (reported as Scenedesmus subspicatus) was determined according to Bringmann and Kühn, 1980. In total 11 concentrations (spacing factor 2) were set up in 300 mL Erlenmeyer flasks filled with 50 mL test solution. The test flasks were set up in triplicate. The test was performed with continuous illumination at 27°C. The algae were re-suspended once a day by gentle shaking. Seven days after start of the exposure the optical density of the cultures was determined at 578 nm. The EC3 was determined to be 1485 mg/L. This EC3 result will be used as EC10 for the risk assessment for freshwater algae.

 

For the risk assessment the EC10 of 39.9 mg/L and the EC50 of 148.2 mg/L will be used for marine algae and the EC10 of 1485 mg/L for freshwater algae.

 

The lack of algae toxicity is supported by QSAR analysis for DCAC, i.e., a 96h-EC50 of 1455 mg/L was calculated for DCAC.

 

Since the target substance DCAC has a higher molecular weight when compared to the source substance DCA and hydrolyses within short time to the source substance DCA read across is considered relevant, justified and conservative when using the data from the source substance as they are, i.e., without further assesment factor.