Reaction products of dimethyl phosphonate with 2-alkyl-2-alkylpropanediol and alkanediol

Endpoint summary

Description of key information

Fish: Based on mean measured test concentrations and mortality data, the 96-hourLC50 was determined to be > 87 mg/L. The no-mortality concentration was 87 mg/L and the no-observed effect concentration was 48 mg/L (OECD 203, OPPTS 850.1075 and ASTM E729-96).

 

Aquatic invertebrates: Based on mean measured WAF loading rates and immobility data, the EL50 was determined to be 30 mg/L (OECD 202, OPPTS 850.1010 and ASTM E729-96).

 

Algae: Based on nominal loading rates, the 72-hour ErL50 value for growth rate was determined to be 40 mg/L loading rate WAF and the NOELR value based for growth rate was determined to be 6.1 mg/L loading rate WAF (OECD 201, EU Method C.3 and ASTM E 1218-04).

 

Microorganisms: An inhibitory dose response effect was not observed for the treatment groups and calculation of an EC50 value is not possible for the test item as a stimulatory dose response was observed (OECD 209).

Additional information

Fish

The key study was conducted according to procedures outlined in the OECD Guidelines for Testing of Chemicals, Guideline 203Fish, Acute Toxicity Test (adopted 17 July 1992); U.S. Environmental Protection Agency Series 850 - Ecological Effects Test Guidelines, OPPTS Number 850.1075Fish Acute Toxicity Test, Freshwater and Marine(1996) and ASTM Standard E729-96Standard Guide for Conducting Acute Toxicity Tests on Test Materials with Fishes,Macroinvertebrates and Amphibians (1996).

Due to potentially poor aqueous solubility and complex nature of the test item, testing was done using water accommodated fractions (WAF). Fathead minnows were exposed to five WAF loading rates of test item and a negative control (dilution water) for 96 hours under static conditions. Two replicate test chambers were maintained in each treatment and control group, with 7 fish in each test chamber, for a total of 14 fish per loading rate. Nominal WAF loading rates were selected in consultation with the Sponsor based on the results of exploratory range finding toxicity data. For this test loading rates means the total amount of test item added to the dilution water volume to achieve the respective WAF solutions. Nominal test item WAF loading rates selected were 6.3, 13, 25, 50 and 100 mg /L. Mean measured test concentrations were determined from samples of test water collected from each treatment and control group at test initiation, at the approximate mid-point of the test and at test termination. Juvenile fathead minnows were impartially assigned to exposure chambers at test initiation. Observations of mortality and other signs of toxicity were made approximately 2, 24, 48, 72 and 96 hours after test initiation. Cumulative percent mortality observed in the treatment groups was used to determine LC50 values at 24, 48, 72 and 96 hours. The no-mortality concentration and the no-observed-effect concentration (NOEC) were determined by visual interpretation of the mortality and biological observation data.

Based on mean measured test concentrations and mortality data, the 96-hour LC50 was determined to be > 87 mg/L. The no-mortality concentration was 87 mg/L and the no-observed effect concentration was 48 mg/L.

Daphnia magna

The key study was conducted in accordance with OECD Guidelines for Testing of Chemicals, Guideline 202 Daphnia sp., Acute Immobilization Test (adopted 13 April 2004); U.S. Environmental Protection Agency Series 850 - Ecological Effects Test Guidelines (draft), OPPTS Number 850.1010 Aquatic Invertebrate Acute Toxicity Test, Freshwater Daphnids and ASTM Standard E 729-96: Standard Guide for Conducting Acute Toxicity Tests on Test Materials with Fishes, Macroinvertebrates, and Amphibians.

Due to low aqueous solubility of the test item, testing was done using water accommodated fraction solutions (WAF). Daphnids were exposed to five WAF loading rates of test item and a negative control (dilution water) for 48 hours under static conditions. Two replicate test chambers were maintained in each treatment and control group, with 10 daphnids in each test chamber, for a total of 20 daphnids per loading rate. Nominal WAF loading rates were selected in consultation with the Sponsor based on the results of exploratory range-finding toxicity data. For this test, loading rates means the total amount of test item added to the dilution water volume to achieve the respective WAF solutions. Nominal test item WAF loading rates selected were 13, 25, 50, 100 and 200 mg/L. Test concentrations were measured in samples of test water collected from the batches of test solution prepared for each treatment and control group at the beginning of the test and from each test chamber at 48 hours (± 1 hour) to determine concentrations of the test substance. Results of the analyses were used to calculate mean measured test concentrations. Neonate daphnids < 24-hours old were impartially assigned to exposure chambers at test initiation. Observations of immobility and other signs of toxicity were made approximately 18, 24 and 48 hours after test initiation. Cumulative percent immobility observed in the treatment groups was used to determine EL50 values at 24 and 48-hour intervals.

Based on nominal WAF loading rates and immobility data, the EL50 was determined to be 71 mg/L. The no-immobility loading rate was 13 mg/L and the no-observed effect loading rate was 13 mg/L. Based on mean measured WAF loading rates and immobility data, the EL50 was determined to be 30 mg/L. The no-immobility loading rate was 8.9 mg/L and the no-observed effect loading rate was 8.9 mg/L.

Algae

The key study was conducted in accordance with OECD 201 Freshwater Alga and Cyanobacteria, Growth Inhibition Test (adopted 23 March 2006; revised 28 July 2011); EU Method C.3 Algal Inhibition Test (1992) and ASTM E 1218-04 Standard Guide for Conducting Static Toxicity Tests with Microalgae (2012).

The green alga (Raphidocelis subcapitata) was exposed to five test concentrations and a negative control (culture medium) under static conditions for 72 hours. Six replicate test chambers in the control group and three replicate test chambers in each treatment group were maintained. Due to the low solubility of the test item, test solutions were prepared as water accommodated fractions (WAFs) and test concentrations are based upon the loading rate for each test solution. Nominal loading rates were selected in consultation with the Sponsor and were based upon results of exploratory range finding toxicity tests and preliminary analytical results. A range-finding test conducted with nominal WAF loading rates of 2.0, 20, and 200 mg/L, and yielded 2, 38, and 100 % inhibition of mean cell density after 72 hours of exposure, respectively, relative to the mean negative control response. Nominal loading rates selected for the definitive test were 1.9, 6.1, 20, 63, and 200 mg/L. Samples of test medium were collected from each treatment and control group at the beginning of the test and at test termination for analytical verification of the test concentrations. At test initiation an inoculum of the algal cells was added to each test chamber to achieve a nominal concentration of approximately 10,000 Raphidocelis cells/mL. Samples were collected from each replicate test chamber at approximately 24-hour intervals during the test to determine cell densities, which were used to calculate yield and growth rates. Growth rates and yields were used to calculate percent inhibition values relative to the control at the 0-72 hour exposure interval. EL50 and ErL50 values (i.e., the theoretical concentrations that would produce a 50% reduction in cell density and growth rate, respectively) were calculated, when possible, at 72 hours of exposure. In addition, the EyL50 value (i.e., the theoretical concentrations that would produce a 50 % reduction in yield) was calculated, at 72 hours of exposure. The no-observed-effect-level (NOEL) was determined at 72 hours through statistical evaluation of cell density, growth rate and yield data.

 

The 72-hour EL50, ErL50 and EyL50 values for cell density, growth rate and yield were determined to be 37, 40, and 28 mg/L, respectively. The 72-hour NOEL values for cell density, growth rate and yield were determined to be 6.1 mg/L, for all three endpoints, and were determined based on evaluation of the dose-response. The introduction of test item to the test medium reduced the pH substantially in the nominal 63 and 200 mg/L treatment groups. Adverse effects observed in these treatments may have been caused by the decline in pH, however, since the addition of the test substance caused the decline in pH they were considered to be treatment related effects.

Inhibition of sewage sludge micro-organisms

The potential effect of test item on activated sludge microorganisms maintained in an aerobic environment was assessed by the Activated Sludge Respiration Inhibition Test Method (OECD Guideline 209).

 

The test contained control, reference and treatment groups. The control replicates were used to determine the background respiration rate of the sludge and were not dosed with the test or reference substance. The reference group was dosed with 3, 5-dichlorophenol, a known inhibitor of respiration, at concentrations of 3, 15 and 50 mg/L. The treatment group was dosed with test item at concentrations of 10, 100, and 1000 mg/L. The 1000 mg/L treatment was tested in triplicate. An abiotic control was dosed with the test substance at a concentration of 1000 mg/L to discriminate between abiotic uptake by the test substance and microbial respiration. After an exposure period of three hours, the respiration rates of the test solutions were measured using an YSI Model 5000 Dissolved Oxygen Meter.

Respiration rates in the two controls were 27.04 and 29.08 mg O2/L/hr. Both controls had respiration rates above or equal to 26.53 mg O2/L/hr, which is the low limit based on the validity criteria for mixtures with 1.33 g dry weight of suspended solids per liter. The coefficient of variation of the two control respiration rates was 5.14%, and was within the 30% limit established for the test. The validity of the test was further supported by the results from the 3, 5-dichlorophenol reference group, which resulted in an EC50 value of 15.00 mg/L, with 95 percent confidence limits of 3 mg/L and 50 mg/L. The EC50 for the reference substance was within the 2 to 25 mg/L range considered acceptable for the test.

An inhibitory dose response effect was not observed for the treatment groups. The EC50 value calculation is not possible for the test item as a stimulatory dose response was observed. The abiotic treatment mixture dosed with 1000 mg/L of test item had a respiration rate of 0.3 mg O2/L/hr showing there was no significant uptake or release of oxygen resulting from abiotic reactions of the test substance.