Hydrocarbons, C11-C12, isoalkanes, <2% aromatics

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

April 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: This robust summary has a reliability rating of 1 because the study followed a standard guideline, followed GLP, and was conducted without deviations that would invalidate the study.

Qualifier:

according to guideline

Guideline:

OECD Guideline 211 (Daphnia magna Reproduction Test)

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Analytical measurements were taken to confirm test material presence in test solutions and absence in control. Samples were taken from each test (0.1 and 1.0 mg/l loading) and control solution on Days 0, 7, 14, and 20 and the corresponding old solutions (three individual replicates) on Days 1, 8, 15 and 21. For the 0.1 mg/l treatment analysis was not continued after day 1 as no hydrocarbons were detected in this loading.

Vehicle:

no

Details on test solutions:

Individual WAFs were prepared for each loading rate by adding the appropriate amount of the test substance to the dilution water in glass aspirator bottles using glass/stainless steel syringes. The test substances were added by volume as the amounts added were too small to determine gravimetrically. The vessels were sealed with foil-covered stoppers. The solutions were mixed with Teflon®-coated stirbars on magnetic stirplates. The vortex was set at plus minus 10% of the static liquid depth. The solutions mixed for 24 hours (±2 hours) at test temperature (20°±1°C). At the end of mixing, the solutions were allowed to settle for 1 to 2 hours (±30 minutes). At the end of the settling period, the solutions will be removed from the mixing vessels through the outlet at the bottom of the vessels and placed into ten replicate chambers.

Test chambers were completely filled with the appropriate solution. Treatments were prepared and renewed at 24-hour (±2 hour) intervals. Renewals were performed by transferring each parent daphnid, via plastic pipette, to fresh solution. The volume of medium transferred was minimized.

Test organisms (species):

Daphnia magna

Details on test organisms:

Test organisms were cultured at the test facility. The original culture was supplied by Aquatic Biosystems, Inc., Fort Collins, Colorado, USA and received at the test facility on 11 April 2002.
Stock cultures of eight to ten daphnids were kept in 1-liter glass culture beakers with approximately 800 mL of reconstituted water (study dilution water). The culture chamber was maintained at 20±2ºC under a 16 hour light: 8 hour dark photoperiod (10 – 20 footcandles, 108 – 215 lux, 15 - 20 µE*m-2*s-1). Two sets of Day 0 cultures were started at least five days a week. The neonates were less than 24 hours old and came from a day 12-18 culture which experienced less than an estimated 10% neonate mortality and less than or equal to 20% adult mortality.

Stock cultures of Daphnia magna were fed Pseudokirchneriella subcapitata (approximately 4.5 – 6.0 E5 cells/mL). They were also fed 25 µL/L of Vita-chem mixed on a magnetic stir plate with reconstituted water prior to feeding with algae. The culture was fed every other day, or more frequently as needed, based on observed algal clearing. Cultures were transferred every other day, with exceptions on holidays or weekends when staff was not present. The brood stock health was evaluated and any mortality, production of males or ephippia was documented as well as any mitigation procedures.

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Post exposure observation period:

None

Hardness:

The hardness of the dilution water during the study was 168 mg/L as CaCO3.

Test temperature:

20.8 to 21.4 degrees C for test substance systems.
21.0 to 21.5 degrees C for control systems.

pH:

7.42 to 8.29 for test substance systems.
7.55 to 8.17 for control systems.

Dissolved oxygen:

7.38 to 8.79 mg/L for test substance systems.
7.26 to 8.5 mg/L for control systems.

Nominal and measured concentrations:

Nominal loading rates were control, 0.1 and 1 mg/L.

Details on test conditions:

Ten replicates per treatment were tested. One <24 hour old daphnid was added to each replicate. The adults were transferred to fresh solution daily.The test chambers were 130-mL clear glass containers sealed with PTFE-lined screw type caps to minimize contamination, evaporation and/or volatilization. All test chambers were completely filled with test solution (no headspace). A separate set of test chambers was used on a rotating basis for renewals. Feed was first added to each test chamber. Test chambers were filled with the appropriate amount of vehicle/dilution water. The adult Daphnia magna from the old test solution were transferred to the vehicle/dilution water using a glass pipette.
Diurnal light: approximately 16 hours light and 8 hours dark. Daylight intensity ranged from approximately 103-133 lux during full daylight periods of the study.

Reference substance (positive control):

no

Key result

Duration:

21 d

Dose descriptor:

NOELR

Effect conc.:

> 1 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks:

The test substance also showed no effects based on growth at 1 mg/L.

Details on results:

The following are the endpoint results for the control and test solutions:
Adult Neonates Adult
Group Immobilization per Ave. Length
(nominal) (%) Adult (mm)
Control 10 147 4.7
0.1 mg/l 0 138 4.7
1 mg/l 20 143 4.7

The control daphnids released their first brood between days 7 and 10. The coefficient of variation (cv) for control fecundity was 16%, the guideline indicates that the cv for control reproduction in a “well run” study should be ≤25%. The test was considered acceptable as less than 20% of control organisms were immobilized and mean reproduction in the controls exceeded 60 young per adult.

Results with reference substance (positive control):

None used

Reported statistics and error estimates:

Chronic toxicity results are expressed as a reduction of reproductive output in the treatment groups compared to the control group. The No Observed Effect Loading Rate (NOELR) was the highest loading rate that did not exhibit a statistical difference in reproductive output from the control group. This endpoint was also calculated for adult growth and survival.
The T-test with Bonferroni adjustment (Bland, 1995) were used to determine the NOELR values for reproduction and growth. Fisher’s Exact Test (Finney, 1948, Pearson and Hartley, 1962) was used to determine the NOELR values for survival. Both types of calculations were performed using TOXSTAT (WEST Inc. and Gulley 1994) software.

Validity criteria fulfilled:

yes

Conclusions:

The test substance showed no effects on survival, reproduction, or length at nominal concentrations of 1 and 0.1 mg/L, respectively. Therefore, the 21-Day No Observed Effect Loading Rate (NOELR) is > 1 mg/l for these endpoints based upon nominal loading rates.

Executive summary:

The test substance showed no effects on survival, reproduction, or length at nominal concentrations of 1 and 0.1 mg/L, respectively. Therefore, the 21-Day No Observed Effect Loading Rate (NOELR) is > 1 mg/l for these endpoints based upon nominal loading rates.

Reference 2

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

February to March 2004

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: This robust summary has a reliability rating of 1 because the study followed a standard guideline, followed GLP, and was conducted without deviations that would invalidate the study.

Qualifier:

according to guideline

Guideline:

OECD Guideline 211 (Daphnia magna Reproduction Test)

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Analytical measurements were taken to confirm test material presence in test solutions and absence in control. Samples were taken from each test and control solution on Days 0, 7, 14, and 20 and the corresponding old solutions (three individual replicates) on Days 1, 8, 15 and 21, unless complete mortality occurred prior to the sampling event. Twenty-four samples from each group were analyzed during the twenty-one day study.

Vehicle:

no

Details on test solutions:

The exposure solutions were generated by aerating the test substance alone in a closed system using air stones at an air flow rate of 45 +/-5 cc/min. The vapor generated of the test substance from the aeration procedure flowed into aspirator bottles and bubbled through vehicle/dilution medium (reconstituted water). The test substance saturated vapor passed through air stones near the bottom of the aspirator bottles providing maximum contact between the test substance in the vapor phase and the vehicle/dilution medium. The systems were allowed to aerate/equilibrate for one day prior to preparing the exposure solutions for the first time. Ten replicates per treatment were tested.

Test organisms (species):

Daphnia magna

Details on test organisms:

Test organisms were cultured at the test facility. The original culture was supplied by Aquatic Biosystems, Inc., Fort Collins, Colorado, USA and received at the test facility on 11 April 2002.
For the test, eight adult daphnids were kept in 1-liter glass culture beakers with approximately 800 mL of reconstituted water (study vehicle/dilution water). The culture chamber was maintained at 20 ± 1 degrees C under a 16 hour light 8 hour dark photoperiod (10 - 20 foot/candles, 108 - 215 Lux). Day 0 cultures were started daily (at least five days per week) using eight <24 hour old neonates from culture beakers between 12 and 18 days old, exhibiting ≤20% adult mortality. Cultures were transferred to fresh reconstituted water on regular intervals to ensure that ≤24 hour old neonates are available for studies and to start new cultures.
Cultures of Daphnia magna were fed Pseudokirchneriella subcapitata (approximately 4.5 x 105 cells/mL) and 4.0 mL of a yeast / salmon starter / wheat grass (YTC) mixture per 800 mL daily (five days per week at a minimum). YTC and algae were supplied by Aquatic Biosystems, Inc., Fort Collins, Colorado, USA.

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Post exposure observation period:

None

Hardness:

The hardness of the dilution water during the study was 150 mg/L as CaCO3.

Test temperature:

19.2 to 19.9 degrees C for test substance systems.
19.2 to 19.9 degrees C for control systems.

pH:

8.0 to 8.6 for test substance systems.
8.0 to 8.6 for control systems.

Dissolved oxygen:

7.8 to 9.2 mg/L for test substance systems.
7.9 to 9.1 mg/L for control systems.

Nominal and measured concentrations:

Nominal loading rates were control, 0.020, and 0.040 mg/L, which measured 0.0, 0.011, and 0.015 mg/L.

Details on test conditions:

Ten replicates per treatment were tested. One <24 hour old daphnid was added to each replicate. The adults were transferred to fresh solution daily. The test chambers were 125 mL capacity clear glass bottles containing approximately 125 mL of solution (no headspace). The test chambers were closed with foil lined screw type lids to minimize contamination, evaporation, and/or volatilization. A separate set of test chambers was used on a rotating basis for renewals. Feed was first added to each test chamber. Test chambers were filled with the appropriate amount of vehicle/dilution water. The adult Daphnia magna from the old test solution were transferred to the vehicle/dilution water using a glass pipette.
Diurnal light: approximately 16 hours light and 8 hours dark. Daylight intensity ranged from approximately 16 to 19 µE•m-2•s-1 during full daylight periods of the study.

Reference substance (positive control):

no

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

0.011 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks:

The test substance also showed no effects based on growth at 0.011 mg/L.

Details on results:

The following are the endpoint results for the control and test solutions:
Adult Neonates Adult
Group Group Immobilization per Ave. Length
(nominal) (meas.) (%) Adult (mm)
Control 0.0 µg/L 0 119 4.6
20 µg/L 11 µg/L 0 125 4.5
40 µg/L 15 µg/L 100 n/a n/a

The control daphnids released their first brood between days 7 and 10. The coefficient of variation (cv) for control fecundity was 16%, the guideline indicates that the cv for control reproduction in a “well run” study should be ≤25%. The test was considered acceptable as less than 20% of control organisms were immobilized and mean reproduction in the controls exceeded 60 young per adult.

Results with reference substance (positive control):

None used

Reported statistics and error estimates:

The chronic survival and reproduction NOEC for each test substance was based on empirical observation. The length NOEC was determined using the Bonferroni t-test using TOXSTAT software.

Validity criteria fulfilled:

yes

Conclusions:

The test substance showed no effects on survival, reproduction, or length at nominal and measured concentrations of 0.020 and 0.011mg/L, respectively. Therefore, the 21-Day No Observed Effect Loading Rate (NOELR) and No Observed Effect Concentration (NOEC) values are 0.020 and 0.011 mg/L, respectively, for these endpoints based upon nominal loading rates and measured (geometric means) concentrations.

Executive summary:

The test substance showed no effects on survival, reproduction, or length at nominal and measured concentrations of 0.020 and 0.011mg/L, respectively. Therefore, the 21-Day No Observed Effect Loading Rate (NOELR) and No Observed Effect Concentration (NOEC) values are 0.020 and 0.011 mg/L, respectively, for these endpoints based upon nominal loading rates and measured (geometric means) concentrations. The next highest loading rate and concentration tested, 0.040 and 0.015 mg/L, respectively, produced 100% immobilization of the adults exposed.

Reference 3

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

August - September 1998

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: This robust summary has a reliability rating of 1 because the study followed a standard guideline, followed GLP guidelines, and was conducted without deviations that would invalidate the study.

Qualifier:

according to guideline

Guideline:

OECD Guideline 211 (Daphnia magna Reproduction Test)

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Samples for analysis of new and old test solutions and controls were taken on days 1, 2, 3, 7, 10, 14, 17, and 21.

Vehicle:

no

Details on test solutions:

The water accommodated fraction (WAF) of the test material was prepared by stirring the test material in the exposure solution for approximately 2 days with a 1 to 2.5 hour settling period, after which the aqueous phase was removed and added to the test system. An equilibration study was conducted over a period of 96 hours prior to the definitive study to determine the approximate length of time needed to stir the test substance in the test media to acheive a saturated solution. Results suggested that a stirring period of approximately 2 days would be sufficient to reach equilibrium. The stirring period to develop WAFs used through the study ranged from 44.5 to 47 hours.

Test organisms (species):

Daphnia magna

Details on test organisms:

Organisms used in the test were from a laboratory culture were less than 24 hour old. The source of the culture was from Zeneca Brixham Laboratory from I.R.Ch.A., France.

Test type:

semi-static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

21 d

Post exposure observation period:

None

Hardness:

164 to 172 mg/L CaCO3

Test temperature:

19.9 to 20.5 degrees C

pH:

8.1 to 8.9

Dissolved oxygen:

6.3 to 9.1 mg/L

Nominal and measured concentrations:

The nominal treatment levels of the test substance included a control and 1000 mg/L, which measured <0.002 (the limit of detection) and 0.013 mg/L, respectively. The measured data represent the mean test substance concentration of samples taken from new and 24-hour old treatment solutions from days 1, 2, 3, 7, 10, 14, 17, and 21. The mean concentration of the test substance in new and old WAFs was 0.016 and 0.010 mg/L, respectively. The percent decrease in concentration of test material in solution from new to old WAFs on the sampling days ranged from 13 to 63%.

Details on test conditions:

The study was conducted in closed test systems that were renewed daily during the study. The test systems used were 150 ml glass Erlenmeyer flasks that were completely filled with media so as not to leave any headspace. The control and treatment level were each evaluated in 10 replicate test systems. One organism, less than 24 hours old, was added to each control and treatment solution flasks and were fed each day of the study. The feed was chlorella vulgaris at a rate of 0.3 mg carbon/daphnid/day. This rate was greater than that suggested in the OECD guideline (0.2 mg carbon/daphnid/day) because the test vessels were larger than specified by the guideline (50 to 100 ml). Light intensity was 485 lux.

Reference substance (positive control):

no

Key result

Duration:

21 d

Dose descriptor:

EL50

Effect conc.:

> 1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

immobilisation

Key result

Duration:

21 d

Dose descriptor:

NOELR

Effect conc.:

< 1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Details on results:

Adult immobility: control - 0%; 1 mg/L - 10%
Total live young produced: control - 1453; 1 mg/L - 1122
Mean number of live young produced per surviving adult: control - 145; 1 mg/L - 124
Mean number of dead young produced per surviving adult: control - 0.2; 1 mg/L - 13

Reduction in fecundity in 1 mg/L treatment relative to control:
Brood 1 - 34%
Brood 2 - 28%
Brood 3 - 13%
Brood 4 - 3%
Brood 5 - 1.9%

Reported statistics and error estimates:

The significance of differences in the mean number of live young produced by adults in 21 days between the control and treatment solutions was assessed using a two-sample T-test.

Validity criteria fulfilled:

yes

Remarks:

The results show that survival of the adult control daphnids (100%) and the mean number of living offspring produced per surviving control parent (145) fulfilled the test validity criteria of >/= 80% and >/= 60 young/daphnia.

Conclusions:

During the 21-day study, the adult daphnids exposed to the test substance at a loading rate of 1 mg/L produced significantly fewer (<0.05) live offspring per adult than the adult daphnids in the control media. Therefore, the 21-day NOELR for reproduction was <1 mg/L. There was 10% immobility of parents in the treatment solution, therefore the EL50 can be reported as >1 mg/L.

Executive summary:

During the 21-day study, the adult daphnids exposed to the test substance at a loading rate of 1 mg/L produced significantly fewer (<0.05) live offspring per adult than the adult daphnids in the control media. Therefore, the 21-day NOELR for reproduction was <1 mg/L. There was also a greater number of dead offspring produced by the daphnids exposed to the test substance compared with those in the control. There was 10% immobility of parents in the treatment solution, therefore the EL50 can be reported as >1 mg/L.

Reference 4

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

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

Adequacy of study:

key study

Study period:

August - September 1998

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: This robust summary has a reliability rating of 1 because the study followed a standard guideline, followed GLP guidelines, and was conducted without deviations that would invalidate the study.

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

according to guideline

Guideline:

OECD Guideline 211 (Daphnia magna Reproduction Test)

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Samples for analysis of new and old test solutions and controls were taken on days 1, 2, 3, 7, 10, 14, 17, and 21.

Vehicle:

no

Details on test solutions:

The water accommodated fraction (WAF) of the test material was prepared by stirring the test material in the exposure solution for approximately 2 days with a 1 to 3 hour settling period, after which the aqueous phase was removed and added to the test system. An equilibration study was conducted over a period of 96 hours prior to the definitive study to determine the approximate length of time needed to stir the test substance in the test media to acheive a saturated solution. Results suggested that a stirring period of approximately 2 days would be sufficient to reach equilibrium. The stirring period to develop WAFs used through the study ranged from 44.5 to 46.5 hours.

Test organisms (species):

Daphnia magna

Details on test organisms:

Organisms used in the test were from a laboratory culture were less than 24 hour old. The source of the culture was from Zeneca Brixham Laboratory from I.R.Ch.A., France.

Test type:

semi-static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

21 d

Post exposure observation period:

None

Hardness:

154 to 170 mg/L CaCO3

Test temperature:

20.1 to 20.5 degrees C

pH:

8.3 to 9.0

Dissolved oxygen:

7.8 to 9.1 mg/L

Nominal and measured concentrations:

The nominal treatment levels of the test substance included a control and 1000 mg/L, which measured <0.002 (the limit of detection, with the exception of the day 10 control sample, which measured 0.003 mg/L) and 0.036 mg/L, respectively. The measured data represent the mean test substance concentration of samples taken from new and 24-hour old treatment solutions from days 1, 2, 3, 7, 10, 14, 17, and 21. The mean concentration of the test substance in new and old WAFs was 0.047 and 0.025 mg/L, respectively. The percent decrease in concentration of test material in solution from new to old WAFs on the sampling days ranged from 41 to 54%.

Details on test conditions:

The study was conducted in closed test systems that were renewed daily during the study. The test systems used were 150 ml glass Erlenmeyer flasks that were completely filled with media so as not to leave any headspace. The control and treatment level were each evaluated in 10 replicate test systems. One organism, less than 24 hours old, was added to each control and treatment solution flasks and were fed each day of the study. The feed was chlorella vulgaris at a rate of 0.3 mg carbon/daphnid/day. This rate was greater than that suggested in the OECD guideline (0.2 mg carbon/daphnid/day) because the test vessels were larger than specified by the guideline (50 to 100 ml). Light intensity was 505 lux.

Reference substance (positive control):

no

Key result

Duration:

21 d

Dose descriptor:

EL50

Effect conc.:

> 1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

immobilisation

Key result

Duration:

21 d

Dose descriptor:

NOELR

Effect conc.:

< 1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Details on results:

Adult immobility: control - 10%; 1 mg/L - 10%
Total live young produced: control - 1245; 1 mg/L - 841
Mean number of live young produced per surviving adult: control - 138; 1 mg/L - 93
Mean number of dead young produced per surviving adult: control - 0; 1 mg/L - 13

Reduction in fecundity in 1 mg/L treatment relative to control:
Brood 1 - 88%
Brood 2 - 73%
Brood 3 - 39%
Brood 4 - ca.0%
Brood 5 - (-46%) the treatment solution produced a greater number of live young (31) than the control (16 live young)

Reported statistics and error estimates:

The significance of differences in the mean number of live young produced by adults in 21 days between the control and treatment solutions was assessed using a two-sample T-test.

Validity criteria fulfilled:

yes

Remarks:

The results show that survival of the adult control daphnids (90%) and the mean number of living offspring produced per surviving control parent (138) fulfilled the test validity criteria of >/= 80% and >/= 60 young/daphnia.

Conclusions:

During the 21-day study, the adult daphnids exposed to the test substance at a loading rate of 1 mg/L produced significantly fewer (<0.05) live offspring per adult than the adult daphnids in the control media. Therefore, the 21-day NOELR for reproduction was <1 mg/L. There was 10% immobility of parents in the treatment solution, which was equivalent to the control mortality, therefore the EL50 can be reported as >1 mg/L.

Executive summary:

During the 21-day study, the adult daphnids exposed to the test substance at a loading rate of 1 mg/L produced significantly fewer (<0.05) live offspring per adult than the adult daphnids in the control media. Therefore, the 21-day NOELR for reproduction was <1 mg/L. There was also a greater number of dead offspring produced by the daphnids exposed to the test substance compared with those in the control. There was 10% immobility of parents in the treatment solution, which was equivalent to the control mortality, therefore the EL50 can be reported as >1 mg/L.

Description of key information

There is data available for this substance. Additionally, key data is available for the structural analogue, Hyd C10-C12, isoalkanes, <2% arom. The data is read across to this substance based on analogue read across and a discussion and report on the read across strategy is provided as an attachment in IUCLID Section 13. Key and weight-of-evidence information is summarised below:

Hyd C10-C12, isoalkanes, <2% arom exposure of Daphnia magna during the 21-day study at a loading rate of 1 mg/L produced significantly fewer (<0.05) live offspring per adult than the adult daphnids in the control media.

Hyd C11-C12, isoalkanes, <2% arom showed no effects on survival, reproduction, or length of Daphnia magna at nominal concentrations of 1 and 0.1 mg/L, respectively.

Hyd C11-C12, isoalkanes, <2% arom showed no effects on survival, reproduction, or length of Daphnia magna at nominal and measured concentrations of 0.020 and 0.011mg/L, respectively.

Hyd C11-C12, isoalkanes, <2% arom exposure of Daphnia magna during the 21-day study at a loading rate of 1 mg/L produced significantly fewer (<0.05) live offspring per adult than the adult daphnids in the control media.

Additional information

During the 21-day study, the adult daphnids exposed to Hyd C10-C12, isoalkanes, <2% arom at a loading rate of 1 mg/L produced significantly fewer (<0.05) live offspring per adult than the adult daphnids in the control media. Therefore, the 21-day NOELR for reproduction was <1 mg/L. There was also a greater number of dead offspring produced by the daphnids exposed to the test substance compared with those in the control. There was 10% immobility of parents in the treatment solution, which was equivalent to the control mortality, therefore the EL50 can be reported as >1 mg/L.

Hyd C10-C12, isoalkanes, <2% arom showed no effects on survival, reproduction, or length at nominal and measured concentrations of 0.026 and 0.025 mg/L, respectively. Therefore, the 21-Day No Observed Effect Loading Rate (NOELR) and No Observed Effect Concentration (NOEC) values are 0.026 and 0.025 mg/L, respectively, for these endpoints based upon nominal loading rates and measured (geometric means) concentrations. The next highest loading rate and concentration tested, 0.085 and 0.050 mg/L, respectively, produced 100% immobilization of the adults exposed.

Hyd C11-C12, isoalkanes, <2% arom showed no effects on survival, reproduction, or length at nominal concentrations of 1 and 0.1 mg/L, respectively. Therefore, the 21-Day No Observed Effect Loading Rate (NOELR) is > 1 mg/l for these endpoints based upon nominal loading rates.

Hyd C11-C12, isoalkanes, <2% arom showed no effects on survival, reproduction, or length at nominal and measured concentrations of 0.020 and 0.011mg/L, respectively. Therefore, the 21-Day No Observed Effect Loading Rate (NOELR) and No Observed Effect Concentration (NOEC) values are 0.020 and 0.011 mg/L, respectively, for these endpoints based upon nominal loading rates and measured (geometric means) concentrations. The next highest loading rate and concentration tested, 0.040 and 0.015 mg/L, respectively, produced 100% immobilization of the adults exposed.

During the 21-day study, the adult daphnids exposed to Hyd C11-C12, isoalkanes, <2% arom at a loading rate of 1 mg/L produced significantly fewer (<0.05) live offspring per adult than the adult daphnids in the control media. Therefore, the 21-day NOELR for reproduction was <1 mg/L. There was also a greater number of dead offspring produced by the daphnids exposed to the test substance compared with those in the control. There was 10% immobility of parents in the treatment solution, therefore the EL50 can be reported as >1 mg/L.