Phosphorodithioic acid, mixed O,O-bis(iso-Bu and pentyl) esters, zinc salts

Long-term toxicity to aquatic invertebrates

Administrative data

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

24 July 2009 - 30 May 2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Report date:

2010

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 211 (Daphnia magna Reproduction Test)

Deviations:

yes

Remarks:

Deviations and amendments to the study did not negatively impacts the integrity or quality of the data

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.20 (Daphnia magna Reproduction Test)

Deviations:

yes

Remarks:

Deviations and amendments to the study did not negatively impacts the integrity or quality of the data

GLP compliance:

yes (incl. QA statement)

Remarks:

Inspected and issued by The Standards council of Canada (SCC) and the certificate expires on 7/17/2013

Test material

Test material information

Constituent 1

Reference substance name:

Phosphorodithioic acid, mixed O,O-bis(1,3-dimethylbutyl and iso-Pr) esters, zinc salts

EC Number:

283-392-8

EC Name:

Phosphorodithioic acid, mixed O,O-bis(1,3-dimethylbutyl and iso-Pr) esters, zinc salts

Cas Number:

84605-29-8

IUPAC Name:

Phosphorodithioic acid, mixed O,O-bis(1,3-dimethylbutyl and iso-Pr) esters, zinc salts

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
PHYSICO-CHEMICAL PROPERTIES
- Melting point: liquid at room temperature
- Boiling point: decomposes before boiling
- Vapour pressure: 0.0069 Pa at 25 deg. C
- Henry's law constant (for volatie substances): no data
- Water solubility (under test conditions): 2764 ppm at 22 deg. C
- Solubility in organic solvents: no data
- log Pow: 0.56
- pKa: no data
- Base or acid catalysis of test material: no data
- UV absorption: no data
- Stability of test material at room temperature: stable
- pH dependance on stability: hydrolytically stable at pH 4 and 7 for 5 days at 50 deg. C (OECD 111, Tier 1 preliminary study)

OTHER PROPERTIES (if relevant for this endpoint)
- Toxicity to microorganisms: EC50 > 10,000 mg/L (OECD 209)
-Ready Biodegradability: 1.5% in 28 d (OECD 301B)

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Nominal loading rates: 0.05, 0.1, 0.2, 0.4 and 0.8 mg/L prepared from 100 mg/L WAF. Measured loading rates 0.04, 0.06, 0.13, 0.26, and 0.53 mg/L.

- Sampling method: Water samples were taken from the control and each test group for quantitative analysis. Samples of the fresh initial test preparations and final test preparations were taken on Days 0, 2, 4, 7, 911, 14, 16, 18, and 21.

- Sample storage conditions before analysis: Samples were stored refrigerated at 2 to 8 degrees C until analysis. Prior to analysis, samples were warmed to room temperature and vigorously shaken. All reportable study samples were analyzed within 142 days of submission.

Test solutions

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)

- Method: 100 mg/L WAF prepared based on ASTM document “Standard Practice for Aquatic Toxicity Testing of Lubricants: Sample Preparation and Results Interpretation”

- Eluate: No.

- Differential loading: the 100 mg/L WAF was then serially diluted to give further nominal loading rates

- Controls: Negative control of laboratory water and WAF control

- Chemical name of vehicle (organic solvent, emulsifier or dispersant): none

-Evidence of undissolved material (e.g. precipitate, surface film, etc): Not observed.

Test organisms

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Water Flea
- Strain/clone: None stated.
- Justification for species other than prescribed by test guideline: NA.
- Source: in house culture; original culture was obtained from Aquatic Biosystems in August 2006 and Identified by Vittor and Associates.
- Age of parental stock (mean and range, SD): Test neonates came from organisms cultured in Daphnia culture water for approximately 4 weeks. The test was initiated with < 24 hour old neonates

- Feeding during test
- Food type: Algae (Pseudokirchneriella subcapitata and Chlorella sp.) and Yeast Cereal Trout Chow (YCT)
- Amount: At water changes, 0.5 mL each of the algae and YCT. Feeding was at a level of approximately 0.276 mg carbon/daphnid at each feeding.
- Frequency: At water changes

ACCLIMATION
- Acclimation period: Test neonates came from organisms cultured in Daphnia culture water for approximately 4 weeks.
- Acclimation conditions (same as test or not): None stated.
- Type and amount of food: Prior to the test the daphnid cultures were fed 2 mL of each green algae and YCT.
- Feeding frequency: None stated.
- Health during acclimation (any mortality observed): 5.2% mortality in 7 days preceding test

QUARANTINE (wild caught)
- Duration: NA
- Health/mortality: NA

METHOD FOR PREPARATION AND COLLECTION OF EARLY INSTARS OR OTHER LIFE STAGES:
Moderately hard reconstituted water was used for culturing the daphnids and as the control/dilution water.

Study design

Test type:

other: Static-renewal. Water changed every Monday, Wednesday and Friday on Days 2, 4, 7, 9, 11, 14, 16, 18, and 21

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Post exposure observation period:

N/A

Test conditions

Hardness:

In the range of 96 to 108 in controls and 92 to 104 in the highest test concentration.

Test temperature:

Temperature was maintained at approximately 20 degrees C throughout the test.

pH:

7.7 to 8.1, no treatment related differences for pH.

Dissolved oxygen:

Dissolved oxygen ranged from 8.4 to 9.2 mg/L; no treatment related differences for oxygen concentration

Salinity:

Not applicable for freshwater test.

Nominal and measured concentrations:

Nominal Range of test concentrations: Lab Control, WAF Control, 0.05, 0.1, 0.2, 0.4, 0.8 mg/L
Measured range of test concentrations: 0.04, 006, 0.13, 0.26, 0.53

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Type (delete if not applicable): The test vessels had lids to prevent evaporation
- Material, size, headspace, fill volume: Each replicate test vessel consisted of 120 mL of test solution in a 125 mL glass jar
- Aeration: The test vessels were not aerated.
- Type of flow-through (e.g. peristaltic or proportional diluter):
- Renewal rate of test solution (frequency/flow rate): The test preparations were renewed 3 times per week on Monday, Wednesday and Friday on Days 2, 4, 7, 9, 11, 14, 16, and 18.
- No. of organisms per vessel: 1
- No. of vessels per concentration (replicates): 10
- No. of vessels per control (replicates): 10
- No. of vessels per vehicle control (replicates): NA
- Biomass loading rate: NDA.

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Moderately hard reconstituted water was used for culturing the daphnids and as the control and dilution water. The reconstituted water had hardness measurements from 96 to 108 mg/L as CaCO3.
- Total organic carbon: NDA.
- Particulate matter: NDA.
- Metals: NDA.
- Pesticides: NDA.
- Chlorine: NDA.
- Alkalinity: NDA.
- Ca/mg ratio: NDA.
- Conductivity: NDA.
- Culture medium different from test medium: No.
- Intervals of water quality measurement: Dissolved Oxygen, temperature, pH and conductivity were measured at test initiation and in new solutions prior to a water change. Dissolved oxygen, termperature and pH were measured in the old solutions following a water change. Hardness was measured at the start of weeks 1 and 2, at the start of a renewal period in the controls, and in the highest test loading rate.

OTHER TEST CONDITIONS
- Adjustment of pH:
- Photoperiod: photoperiod of 16 hours light and 8 hours darkness
- Light intensity: 75.2 to 91.8 fc

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
TEST CONCENTRATIONS
- Spacing factor for test concentrations:
- Justification for using less concentrations than requested by guideline:
- Range finding study
- Test concentrations: 0, 0.06, 0.12, 0.6, 1.2, 6 and 12 mg/L
- Results used to determine the conditions for the definitive study: Based on the results of an OECD 202 48 hour range finding test, made from dilutions of a 100 mg/L water accommodated fraction, there was no observed immobilization up to the 0.6 mg/L loading rate. At the 1.2 mg/L nominal test concentration there was 5% immobilization, at 6 mg/L 80% immobilization, and at 12 mg/L 100% immobilization. Additional range finding tests showed some toxicity at the 1 mg/L loading rate. Based on these preliminary results, the definitive test was conducted using nominal loading rates of 0, 0.5, 0.1, 0.2, 0.4 and 0.8 mg/L prepared from dilutions of a 100 mg/L WAF. A negative control containing dilution water only was tested along with a WAF control.

Reference substance (positive control):

yes

Remarks:

A reference item test using zinc sulphate heptahydrate was conducted as a separate study to assess the relative sensitivity of the test organisms and the precision of the data produced by the laboratory. The reference item test was conducted within two w

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

21 d

Dose descriptor:

IC50

Effect conc.:

> 0.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Effect concentrations 2

Duration:

21 d

Dose descriptor:

IC50

Effect conc.:

> 0.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth

Effect concentrations 3

Duration:

21 d

Dose descriptor:

IC50

Effect conc.:

> 0.53 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

reproduction

Effect concentrations 4

Duration:

21 d

Dose descriptor:

IC50

Effect conc.:

> 0.53 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

growth

Effect concentrations 5

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

0.4 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Effect concentrations 6

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

0.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth

Effect concentrations 7

Duration:

21 d

Dose descriptor:

LOEC

Effect conc.:

0.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Effect concentrations 8

Duration:

21 d

Dose descriptor:

LOEC

Effect conc.:

> 0.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth

Details on results:

- Mortality of parent animals: At test completion, there was < 10% mortality observed in all treatments.

- No. of offspring produced per day per female: The mean number of neonates produced were as follows:

Lab Control: 83.2

WAF Control: 87

0.05 (mg/L): 64.9

0.1 (mg/L): 70.2

0.2(mg/L): 73.7

0.4 (mg/L): 73.2

0.8 (mg/L): 68.9

- Body length and weight of parent animals: The mean length of adult daphnids at test completion ranged from 3.7 to 3.8 mm in controls and from 3.6 to 3.7 mm in test solutions. The mean weight of adult daphnids at test completion ranged from 0.45 to 0.54 mg in controls and from 0.47 to 0.52 mg in test solutions.

- Type and number of morphological abnormalities: No.

- Type and number of behavioural abnormalities: No.

- Time to first brood release or time to hatch: 9 days was the minimum time to first brood for the control as well as all test concentrations.

- Egg development time: NDA

- Brood size: NDA

- Time to sexual maturity: NDA

- Type and magnitude of biochemical changes: NDA

- Other biological observations: NDA

- Effect concentrations exceeding solubility of substance in test medium: No.

Results with reference substance (positive control):

- Results with reference substance valid? The 48 hour LC50 (95% confidence limits) for the reference item test was 0.40 mg Zn2+/L (0.19 to 0.6 mg/L). This value was within the acceptable range of + 2 SD of previous tests conducted and indicates that the test organisms responded normally to the reference item.

Reported statistics and error estimates:

The total number of offspring per parent animal was calculated for each replicate. The means and associated standard deviations are reported for all endpoints, which are calculated based on both the nominal concentrations and the measured concentrations. The mean measured concentrations of the test item were calculated by a time weighted mean. The NOEC and LOEC values for reproductive output, length, and weight were determined by ANOVA. Two sample t-tests were performed comparing the lab and WAF controls for reproduction, weight, and length. There were no significant differences between the controls using analysis of variance and thus all statistical analyses were performed using the WAF control. All IC50 values are presented as “greater than” values since none of the endpoints measured showed a >50% effect. Statistical analyses were performed using the statistical program CETIS.

Any other information on results incl. tables

Table I: Test Item Results

Nominal Loading Rate / Measured Concentration (mg/L)
	Surviving Adults (%)	Mean # Neonates	Mean Length (mm)	Mean Weight (mg)
Lab Control	100	83.2	3.7	0.45
WAF Control	100	87.0	3.8	0.54
0.05 / 0.04	90	64.9	3.7	0.52
0.1 / 0.06	100	70.2	3.7	0.49
0.2 / 0.13	90	73.7	3.7	0.47
0.4 / 0.26	100	73.2	3.6	0.48
0.8 / 0.53	100	68.9	3.7	0.52

Justification for Read Across from Analogue EC 283-392-8 

 

Common Manufacturing Process: The test substance (EC 270-608-0) and the analogue (EC 283-392-8) are produced under a common manufacturing process in which a phosphorodithioic acid ester intermediate, (RO)₂PS₂H,is produced by the reaction of phosphorus pentasulfide with a mixture of two alcohols of a similar class - branched alcohols containing C4 and C5 carbons (test substance) and C3 and C6 carbons (analogue ). The intermediate is neutralized with zinc oxide to produce the final multicomponent substance.The reaction is performed in the presence of a highly refined base oil which accounts for 8 – 10 % of the final products. 

 

Impurities: The level of impurities in the submission substance and the analogue is minimal (0.09 % wt and < 0.15% wt, respectively). Impurities have been identified as residual, unreacted alcohols from the production of the phosphorodithioic acid ester intermediates (isobutyl alcohol and pentyl alcohol isomers in the submission substance and isopropyl and 1,3-dimethylbutyl alcohols in the analogue).

 

Same Chemical Category: The submission substance (EC 270-608-0) and the analogue (EC 283-392-8), generically referred to as ZDDPs, have been shown to have sufficient structural similarities to be included in the Zinc Dialkydithiophosphate Category (ZDDPs) in the United States Environmental Protection Agency High Production Volume (HPV) Chemical Challenge Program.

Structural Similarity: The primary feature accounting for the similarity of the test substance (EC 270-608-0) and the analogue (EC 283-392-8) is the common organometallic core structure consisting of a central zinc metal bonded to four alkyldithiophosphate esters (ligands) by coordinate covalent bonds -Zn[(S₂P(OR)₂]_2. Structural variations between the test substance and the analogue are related to the alkyl (R) groups of the alkyldithiophosphate ligands.

 

Both substances contain a distribution of several different zinc dialkyldithiophosphates (ZDDPs).  The type and distribution of the zinc dialkyldithiophosphates is determined by the alcohol mixture and charge ratios of the alcohols used in the manufacturing process.

 

The test substance (EC 270-608-0) is a mixture of ZDDPs containing isobutyldithiophosphate ligands, pentyldithiophosphate ligands, and mixtures containing both isobutyldithiophosphate and isomeric pentyldithiophosphate ligands resulting in a multicomponent substance with a molecular weight range of 548 – 604 (for monomers).            

 

The analogue (EC 283-392-8) is a multicomponent mixture of ZDDPs containing all isobutyl dithiophosphate ligands, all pentyl dithiophosphates ligands and ZDDPs containing both isobutyl and isomeric pentyl dithiophosphates with a molecular weight range of 492 – 660 (for monomer).

 

Tanimoto Fingerprint (ToxMatch Version 1.06 software) gives a similarity index greater than 0.8 (values range from 0, no similarity to 1, identical). Peer reviewed literature indicates that values greater than 0.6 are significantly similar.  DSSTox similarity was 80% between the submission substance and the analogue.

Similarity of Physicochemical Properties: In addition to the structural similarities, similar physicochemical properties further support the justification for read across from the analogue. Both the test substance and analogue have similar physical states, densities and the same order of magnitude of vapour pressures and partition coefficients (logPow). Both were determined to be hydrolytically stable at pH 4, 7 and 9 in an OECD 111 preliminary hydrolysis study.

 

In evaluating the evidence for read across, significant consideration was given to water solubility. Water solubility studies conducted on the test substance and the analogue show the lower molecular weight ZDDP monomers are preferrentially dissolved in water with solubility decreasing with increasing alkyl chain lengths (molecular weights) of the alkyldithiophosphate ligands.  In this respect, the water soluble composition of the test substance (EC 270-608-0) and the analogue (EC 283-392-8) are considered to be sufficiently close to reasonably expect a similar mode of action and toxicological effects in aquatic toxicity studies. The slightly lower molecular weight of the water solubles in the analogue would represent the “worst case” with respect to bioavailability and potential for toxicity.

 

 

                            Data Matrix for Read Across from Analogue                                       

Property	Submission Substance (Target)	Analogue       (Data Source)
EC	270-608-0	283-392-8
CAS	68457-79-4	84605-29-8
Chemical Name	Phosphorodithioic acid, mixed O,O-bis(iso-Bu and pentyl) esters, zinc salts	Phosphorodithioic acid, mixed O,O-bis(1,3-dimethylbutyl and iso-Pr) esters, zinc salts
Physical	Viscous liquid	Viscous liquid
Boiling Point	Decomposes before boiling	Decomposes before boiling
Density @ 15.6 deg. C  (ASTM D4052)	1.17 mg/L	1.2 mg/L
Vapour Pressure @ 25 C   ( EU Method A.4)	0.0025 Pa	0.0069 Pa
Water Solubility @ 22 deg. C (OECD 105)	1658 mg/L	2764 mg/L
Identity of water soluble components (% = GC area %)	ZDDPs containing 76% isobutyl (C4) dithiophosphate ligands + 24% containing mixed isobutyl (C4) and pentyl (C5) dithiophosphate ligands	ZDDP containing 95% isopropyl (C3) dithiophosphate ligands + 5% containing mixed isopropyl and 1,3 -dimethylbutyl dithiophosphate ligand
Average molecular weight of water solubles (weighted average based on GC peak area %)	562	500.4
Partition Coefficient, logPow (OECD 107)	0.69	0.56
Hydrolysis as a function of pH (OECD 111, Tier 1 preliminary study at pH 4,7 and 9)	Hydrolytically stable at pH 4, 7 and 9	Hydrolytically stable at pH 4, 7 and 9

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The 21 day IC50s based on nominal loading rates for length, weight, and neonate production were all >0.8 mg/L. Based on measured test item concentration the IC50s were all >0.53 mg/L. The NOECs were 0.4 mg/L nominal for reproduction and 0.8 mg/L nominal for both daphnid length and daphnid weight. The LOECs were 0.8 mg/L nominal for reproduction and >0.8 mg/L nominal for daphnid length and daphnid weight.

Executive summary:

Introduction. A study was performed to assess the effect of the test material on the reproduction of Daphnia magna over a 21-day period. The method followed that described in the OECD Guidelines for Testing of Chemicals No 211 (1 998)"Daphnia magna, Reproduction Test". 

Methods.

Based on the results of an acute range finding test, the definitive static renewal 21 day test assessed the effect of the test material on daphnids over a 21 day period by observing survival, growth, and reproduction under controlled conditions to the following nominal loading rates: 0, 0.05, 0.1, 0.2, 0.4 and 0.8 mg/L prepared from dilutions of a 100 mg/L WAF. The test dispersions were renewed 3 times per week.  Survival, reproduction, and growth were recorded. The Daphnia were fed daily with an algal and YCT suspension.

Results.

The measured concentrations of test material differed by greater than 20% from the start of some exposure periods to the end, and therefore time-weighted means were calculated for each of the concentrations. The 21 day IC50s for neonate production, adult daphnid length and adult daphnid weight were > 0.8 mg/L based on nominal loading rates and >0.53 mg/L based on measured concentrations. The NOECs were 0.4 mg/L nominal (0.26 mg/L measured) for reproduction and 0.8 mg/L nominal (0.53 measured) for both daphnid length and daphnid weight, the latter being the highest level tested. The LOECs were 0.8 mg/L nominal for reproduction and >0.8 mg/L nominal for daphnid length and weight. Measured concentrations were calculated using the time weighted mean method.