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EC number: 219-110-7 | CAS number: 2362-14-3
- Life Cycle description
- Uses advised against
- Endpoint summary
- Appearance / physical state / colour
- Melting point / freezing point
- Boiling point
- Density
- Particle size distribution (Granulometry)
- Vapour pressure
- Partition coefficient
- Water solubility
- Solubility in organic solvents / fat solubility
- Surface tension
- Flash point
- Auto flammability
- Flammability
- Explosiveness
- Oxidising properties
- Oxidation reduction potential
- Stability in organic solvents and identity of relevant degradation products
- Storage stability and reactivity towards container material
- Stability: thermal, sunlight, metals
- pH
- Dissociation constant
- Viscosity
- Additional physico-chemical information
- Additional physico-chemical properties of nanomaterials
- Nanomaterial agglomeration / aggregation
- Nanomaterial crystalline phase
- Nanomaterial crystallite and grain size
- Nanomaterial aspect ratio / shape
- Nanomaterial specific surface area
- Nanomaterial Zeta potential
- Nanomaterial surface chemistry
- Nanomaterial dustiness
- Nanomaterial porosity
- Nanomaterial pour density
- Nanomaterial photocatalytic activity
- Nanomaterial radical formation potential
- Nanomaterial catalytic activity
- Endpoint summary
- Stability
- Biodegradation
- Bioaccumulation
- Transport and distribution
- Environmental data
- Additional information on environmental fate and behaviour
- Ecotoxicological Summary
- Aquatic toxicity
- Endpoint summary
- Short-term toxicity to fish
- Long-term toxicity to fish
- Short-term toxicity to aquatic invertebrates
- Long-term toxicity to aquatic invertebrates
- Toxicity to aquatic algae and cyanobacteria
- Toxicity to aquatic plants other than algae
- Toxicity to microorganisms
- Endocrine disrupter testing in aquatic vertebrates – in vivo
- Toxicity to other aquatic organisms
- Sediment toxicity
- Terrestrial toxicity
- Biological effects monitoring
- Biotransformation and kinetics
- Additional ecotoxological information
- Toxicological Summary
- Toxicokinetics, metabolism and distribution
- Acute Toxicity
- Irritation / corrosion
- Sensitisation
- Repeated dose toxicity
- Genetic toxicity
- Carcinogenicity
- Toxicity to reproduction
- Specific investigations
- Exposure related observations in humans
- Toxic effects on livestock and pets
- Additional toxicological data
Toxicity to aquatic algae and cyanobacteria
Administrative data
Link to relevant study record(s)
- Endpoint:
- toxicity to aquatic algae and cyanobacteria
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- guideline study
- Qualifier:
- according to guideline
- Guideline:
- EPA OPPTS 850.5400 (Algal Toxicity, Tiers I and II) (January 2012)
- Deviations:
- no
- GLP compliance:
- yes
- Analytical monitoring:
- yes
- Details on sampling:
- Collected from each replicate test vessel at the start and end of the test.
- Vehicle:
- yes
- Details on test solutions:
- Water used for acclimation of test organisms and for all toxicity testing was sterile freshwater AAP medium (U.S. EPA, 1978) at a pH of 7.5 ± 0.1 (the pH was adjusted with NaOH). The vehicle used was dimethylformamide (DMF).
A series of solutions were prepared by bringing 0.0377, 0.0754, 0.1509, 0.3018 and 0.6038 g of test substance to 50 mL of dimethylformamide in volumetric flasks. The solutions were shaken vigorously until the test substance dissolved. Test solutions were prepared by combining 0.050 mL of each stock solution and dilution water in 500 mL volumetric flasks. A stability blank sample was set up at 1200 µg/L and placed among the test vessels. No algae were inoculated into the stability blank. - Test organisms (species):
- Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)
- Details on test organisms:
- Algae used for the test: Selenastrum capricornutum, UTEX 1648.
The culture was transferred to sterile enriched media identical to media used for this test and maintained at test conditions for at least 14 days before the definitive test. During the 14-day acclimation period, the culture was actively growing in at least 2 subcultures prior to the start of the toxicity test. The subsample of algae used to inoculate media at the start of the definitive test came from a seven day old culture. Identification of the culture organisms, which are also referred to as Raphidocelis subcapitata, was verified using an appropriate taxonomic key. - Test type:
- static
- Water media type:
- freshwater
- Limit test:
- no
- Total exposure duration:
- 96 h
- Post exposure observation period:
- none
- Test temperature:
- 24.3 to 24.7 °C
- pH:
- 7.2 to 7.3 (initial); 7.8 to 9.4 (termination)
- Nominal and measured concentrations:
- Nominal: 0 (control and solvent control), 75, 150, 300, 600 and 1200 µg/L
Mean Measured: ND (none detected; control and solvent control), 81, 161, 297, 595 and 1165 µg/L - Details on test conditions:
- A range-finding test was conducted under static conditions with a control, a solvent control, and five concentrations of DMBPC: 0.0, 0.99, 9.9, 100, 500 and 1200 µg/L. At the conclusion of the test, the number of cells/mL in the test vessels equalled the following percent of the number of cells/mL in the control vessels: 0.99 g/L = 81 %; 9.9 µg /L = 79 %; 100 µg/L = 83 %; 500 µg/L = 64 %; and 1200 µg/L = 45 %.
The definitive toxicity test was conducted at 24 ± 2°C with five concentrations of test substance, a control, and a solvent control (0.10 mL/L dimethylformamide). A series of solutions were prepared by bringing 0.0377, 0.0754, 0.1509, 0.3018 and 0.6038 g of test substance to 50 mL of dimethylformamide in volumetric flasks. The solutions were shaken vigorously until the test substance dissolved.
These stock solutions were used to prepare the nominal test solutions by transferring the appropriate amount of stock solution into DMF. Water quality measurements were made, analytical samples were collected and each solution was subdivided into three clear glass 250 mL Erlenmeyer flasks. The flasks were inoculated with approximately 10 000 algal cells/mL and capped with inverted glass beakers. Test vessels were randomly arranged on a rotary shaker adjusted to approximately 100 rpm in an incubator during the test (a random numbers table was used to select the location for each vessel). A 24 hour light and 0 hour dark photoperiod was automatically maintained with cool-white fluorescent lights that provided a light intensity of approximately 380 to 400 footcandles.
The number of algal cells/mL in each test vessel and the occurrence of relative size differences, unusual cell shapes, colours, flocculations, adherence of cells to test containers, or aggregation of cells was determined visually by means of direct microscopic examination with a haemocytometer at 24, 48, 72, and 96 hours.
Temperature of the incubator was measured and recorded daily and the temperature in a representative vessel of water incubated with the test vessels was continuously recorded. The pH of test solutions was measured and recorded in each test solution prior to distribution to the test vessels at the start of the test and in each test vessel at the end of the test.
A 0.5 mL aliquot of test media from each test vessel where growth was maximally inhibited (1200 µg/L nominal DMBPC concentration) was combined in a 250 mL flask with 100 mL of fresh media to determine whether toxic effects were algicidal or algistatic. This culture was incubated under test conditions for 48 hours. - Reference substance (positive control):
- no
- Duration:
- 96 h
- Dose descriptor:
- EC50
- Effect conc.:
- > 1 165 µg/L
- Nominal / measured:
- meas. (arithm. mean)
- Conc. based on:
- act. ingr.
- Basis for effect:
- cell number
- Remarks on result:
- other: 95 % CL = 1029 to >1165 µg/L
- Duration:
- 96 h
- Dose descriptor:
- EC90
- Effect conc.:
- > 1 165 µg/L
- Nominal / measured:
- meas. (arithm. mean)
- Conc. based on:
- act. ingr.
- Basis for effect:
- cell number
- Remarks on result:
- other: 95 % CL = 1094 to >1165 µg/L
- Duration:
- 96 h
- Dose descriptor:
- EC50
- Effect conc.:
- > 1 165 µg/L
- Nominal / measured:
- meas. (arithm. mean)
- Conc. based on:
- act. ingr.
- Basis for effect:
- growth rate
- Remarks on result:
- other: 95 % CL > 1165 µg/L
- Duration:
- 96 h
- Dose descriptor:
- EC90
- Effect conc.:
- > 1 165 µg/L
- Nominal / measured:
- meas. (arithm. mean)
- Conc. based on:
- act. ingr.
- Basis for effect:
- growth rate
- Remarks on result:
- other: 95 % CL .1165 µg/L
- Duration:
- 96 h
- Dose descriptor:
- EC50
- Effect conc.:
- 1 141 µg/L
- Nominal / measured:
- meas. (arithm. mean)
- Conc. based on:
- act. ingr.
- Basis for effect:
- other: area under the curve
- Remarks on result:
- other: 95 % CL = 837 to >1165 µg/L
- Duration:
- 96 h
- Dose descriptor:
- EC90
- Effect conc.:
- > 1 165 µg/L
- Nominal / measured:
- meas. (arithm. mean)
- Conc. based on:
- act. ingr.
- Basis for effect:
- other: area under the curve
- Remarks on result:
- other: 95 % CL > 1165 µg/L
- Duration:
- 96 h
- Dose descriptor:
- NOEC
- Effect conc.:
- 595 µg/L
- Nominal / measured:
- meas. (arithm. mean)
- Conc. based on:
- act. ingr.
- Basis for effect:
- cell number
- Duration:
- 96 h
- Dose descriptor:
- NOEC
- Effect conc.:
- 161 µg/L
- Nominal / measured:
- meas. (arithm. mean)
- Conc. based on:
- act. ingr.
- Basis for effect:
- other: area under the curve
- Details on results:
- Insoluble material was not observed during the test.
The initial measured concentrations ranged from 97 to 108 % of the nominal concentrations and the final measured concentrations were 57 to 76 % of the nominal concentrations.
The algal population grew well, resulting in an average of 4 173 000 cells/mL in the control after 96 hours. No effects (relative size differences, unusual cell shapes, colours, flocculations, adherence of cells to test containers, or aggregation of cells) were noted during the test. Water quality throughout the test was within acceptable limits. The incubator temperature ranged from 24.3 to 24.7 °C. The pH was not affected by the test substance.
Exposure of Selenastrum capricornutum to DMBPC for 96 hours resulted in an EC50 greater than 1165 µg/L when calculated using the number of cells/mL or the average specific growth rate, and 1141 µg/L when calculated using the area under the growth curve. The 96 hour NOEC is 595 µg/L DMBPC when determined using the number of cells/mL or the average specific growth rate, at 161 µg/L when determined using the area under the growth curve.
At the conclusion of the definitive toxicity test, a 0.5 mL aliquot of test media from each test vessel where growth was maximally inhibited (the 1200 g/L) was combined with 100 mL of fresh media in a 250 mL flask. This culture was incubated under test conditions for 48 hours. During this period the number of algal cells increased from an initial calculated concentration of approximately 36 000 cells/mL to 676 000 cells/mL, indicated that any toxic effect at this concentration was algistatic rather than algicidal. - Reported statistics and error estimates:
- The average specific growth rate was calculated as the natural log of the number of cells/mL at time t1 minus the natural log of the number of cells/mL at time t0 divided by the exposure period. The area under the growth curve was calculated as:
Area = (N1 - N0) / 2) x [(t1 + (N1 + N2 - 2N0) / 2)] x [(t2 - t1) + (Nn - 1 + Nn - 2N0) / 2] x (tn - tn - 1);
where: N0 = nominal number of cells/mL at time t0, N1 = measured number of cells/mL at time t1, Nn = measured number of cells/mL at time tn, t1 = time of first measurement after the beginning of the test and tn = time of nth measurement after the beginning of the test.
The EC10, EC50 and EC90 values were calculated using a weighted least squares non linear regression technique when warranted.
The no observed effect concentration (NOEC) was determined using a one-way analysis of variance (ANOVA) and Bonferroni’s test (TOXSTAT 3.3). The effective concentrations and NOECs were determined using the initial measured concentrations of DMBPC and the number of cells/mL, average specific growth rate, and area under the growth curve. Treatment data were compared to pooled control and solvent control data for the determination of the NOECs (mean control and solvent control data were never significantly different). - Validity criteria fulfilled:
- yes
- Conclusions:
- Under the conditions of this study, the 96 hour ErC50 was > 1165 µg/L. The 96 hour NOEC was 595 µg/L DMBPC when determined using the number of cells/mL or the average specific growth rate.
- Executive summary:
The toxicity potential of the test material to freshwater algae was investigated in accordance with the standardised guideline EPA OPPTS 850.5400 under GLP conditions.
The definitive toxicity test was conducted at 24 ± 2°C with five concentrations of test substance, a control, and a solvent control (0.10 mL/L dimethylformamide). Nominal concentrations were 0 (control and solvent control), 75, 150, 300, 600 and 1200 µg/L. Each solution was subdivided into three clear glass 250 mL Erlenmeyer flasks. The flasks were inoculated with approximately 10 000 algal cells/mL and capped with inverted glass beakers. Test vessels were randomly arranged on a rotary shaker adjusted to approximately 100 rpm in an incubator.
The number of algal cells/mL in each test vessel and the occurrence of relative size differences, unusual cell shapes, colours, flocculations, adherence of cells to test containers, or aggregation of cells was determined visually by means of direct microscopic examination with a haemocytometer at 24, 48, 72, and 96 hours.
A 0.5 mL aliquot of test media from each test vessel where growth was maximally inhibited (1200 µg/L nominal DMBPC concentration) was combined in a 250 mL flask with 100 mL of fresh media to determine whether toxic effects were algicidal or algistatic. This culture was incubated under test conditions for 48 hours.
Insoluble material was not observed during the test. The initial measured concentrations ranged from 97 to 108 % of the nominal concentrations and the final measured concentrations were 57 to 76 % of the nominal concentrations.
The algal population grew well, resulting in an average of 4 173 000 cells/mL in the control after 96 hours. No effects were noted during the test. The 0.5 mL aliquot that was incubated for a further 48 hours indicated that any toxic effect at this concentration was algistatic rather than algicidal.
Exposure of algae to DMBPC for 96 hours resulted in a median effective concentration (EC50) that was greater than 1165 µg/L (the highest tested concentration and reported water solubility limit) when calculated using the number of cells/mL or the average specific growth rate, and 1141 µg/L when calculated using the area under the growth curve. The 96 hour no observed effect concentration (NOEC) is 595 µg/L DMBPC when determined using the number of cells/mL or the average specific growth rate, and 161 µg/L when determined using the area under the growth curve.
Reference
Effective concentrations (EC10, EC50 and EC90 values) from the toxicity test with DMBPC and the freshwater alga, Selenastrum capricornutum
Duration | Endpoint | Effect conc. (microg/L) | Nominal/ Measured | Conc. Based on (nominal, a.i., test material) | Basis for Effect | 95% CL (microg/L) |
48 hours | EC10 | 178 | measured | a.i. | Cell number | <81 to 505 |
48 hours | EC50 | >1165 | measured | a.i. | Cell number | 800 to >1165 |
48 hours | EC90 | >1165 | measured | a.i. | Cell number | >1165 |
72 hours | EC10 | -- | measured | a.i. | Cell number | -- |
72 hours | EC50 | 530 | measured | a.i. | Cell number | 248 to 1130 |
72 hours | EC90 | >1165 | measured | a.i. | Cell number | 947 to >1165 |
96 hours | EC10 | -- | measured | a.i. | Cell number | -- |
96 hours | EC50 | >1165 | measured | a.i. | Cell number | 1029 to >1165 |
96 hours | EC90 | >1165 | measured | a.i. | Cell number | 1094 to >1165 |
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48 hours | EC10 | >1165 | measured | a.i. | Growth rate | -- |
48 hours | EC50 | >1165 | measured | a.i. | Growth rate | >1165 |
48 hours | EC90 | >1165 | measured | a.i. | Growth rate | >1165 |
72 hours | EC10 | >1165 | measured | a.i. | Growth rate | -- |
72 hours | EC50 | >1165 | measured | a.i. | Growth rate | >1165 |
72 hours | EC90 | >1165 | measured | a.i. | Growth rate | >1165 |
96 hours | EC10 | >1165 | measured | a.i. | Growth rate | -- |
96 hours | EC50 | >1165 | measured | a.i. | Growth rate | >1165 |
96 hours | EC90 | >1165 | measured | a.i. | Growth rate | >1165 |
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48 hours | EC10 | -- | measured | a.i. | AUC | -- |
48 hours | EC50 | >1165 | measured | a.i. | AUC | 930 to >1165 |
48 hours | EC90 | >1165 | measured | a.i. | AUC | >1165 |
72 hours | EC10 | -- | measured | a.i. | AUC | -- |
72 hours | EC50 | 653 | measured | a.i. | AUC | 360 to >1165 |
72 hours | EC90 | >1165 | measured | a.i. | AUC | >1165 |
96 hours | EC10 | -- | measured | a.i. | AUC | -- |
96 hours | EC50 | 1141 | measured | a.i. | AUC | 837 to >1165 |
96 hours | EC90 | >1165 | measured | a.i. | AUC | >1165 |
AUC = Area under the curve |
Measured concentrations of DMBPC in test media during the toxicity test with the freshwater alga, Selenastrum capricornutum.
Nominal Concentration of DMBPC (microg/L) | Measured Concentrations of DMBPC | |||
0 Hour | % Recovery | 96 Hours | % Recovery | |
Test Media Samples | ||||
Control | ND | -- | ND | -- |
Solvent Control | ND | -- | ND | -- |
75 | 81 | 108 | 43 | 57 |
150 | 161 | 107 | 98 | 65 |
300 | 297 | 99 | 228 | 76 |
600 | 595 | 99 | 435 | 73 |
1200 | 1165 | 97 | 900 | 75 |
Laboratory Control Sample | ||||
300 | 311 | 104 | 317 | 106 |
Matrix Spike Blank | ||||
300 | -- | -- | 285 | 95 |
-- | -- | 277 | 92 | |
Stability Blank | ||||
1200 | 1181 | 98 | 1036 | 86 |
Blank | ||||
0 | ND | -- | ND | -- |
ND = none detected at or above 8.0 microg/L, the limit of detection. |
Cell growth data from the toxicity test with DMBPC and the freshwater alga, Selenastrum capricornutum.
Initial Measured Concentration of DMBPC (microg/L) | Rep | Number of Cells per Milliliter | ||||
Hour of Exposure | ||||||
0 | 24 | 48 | 72 | 96 | ||
Control | 1 | 10,000 | 37,000 | 174,000 | 1,290,000 | 4,920,000 |
2 | 10,000 | 36,000 | 150,000 | 2,020,000 | 3,740,000 | |
3 | 10,000 | 29,000 | 170,000 | 1,220,000 | 3,860,000 | |
Mean | 10,000 | 34,000 | 165,000 | 1,510,000 | 4,173,000 | |
Solvent Control | 1 | 10,000 | 34,000 | 136,000 | 880,000 | 4,420,000 |
2 | 10,000 | 45,000 | 130,000 | 700,000 | 4,820,000 | |
3 | 10,000 | 35,000 | 156,000 | 960,000 | 4,880,000 | |
mean | 10,000 | 38,000 | 141,000 | 847,000 | 4,707,000 | |
% control | 100 | 112 | 85 | 56 | 113 | |
81 | 1 | 10,000 | 43,000 | 146,000 | 840,000 | 5,360,000 |
2 | 10,000 | 31,000 | 188,000 | 860,000 | 3,220,000 | |
3 | 10,000 | 23,000 | 140,000 | 720,000 | 4,100,000 | |
mean | 10,000 | 32,000 | 158,000 | 807,000 | 4,227,000 | |
% control | 100 | 94 | 96 | 53 | 101 | |
161 | 1 | 10,000 | 24,000 | 146,000 | 772,000 | 4,640,000 |
2 | 10,000 | 47,000 | 142,000 | 1,260,000 | 4,720,000 | |
3 | 10,000 | 36,000 | 150,000 | 720,000 | 4,400,000 | |
mean | 10,000 | 36,000 | 146,000 | 917,000 | 4,587,000 | |
% control | 100 | 106 | 88 | 61 | 110 | |
297 | 1 | 10,000 | 26,000 | 124,000 | 720,000 | 3,440,000 |
2 | 10,000 | 49,000 | 126,000 | 780,000 | 3,760,000 | |
3 | 10,000 | 47,000 | 150,000 | 940,000 | 3,720,000 | |
mean | 10,000 | 41,000 | 133,000 | 813,000 | 3,640,000 | |
% control | 100 | 121 | 81 | 54 | 87 | |
595 | 1 | 10,000 | 36,000 | 100,000 | 448,000 | 3,820,000 |
2 | 10,000 | 43,000 | 116,000 | 830,000 | 4,660,000 | |
3 | 10,000 | 40,000 | 66,000 | 430,000 | 3,640,000 | |
mean | 10,000 | 40,000 | 94,000 | 569,000 | 4,040,000 | |
% control | 100 | 118 | 57 | 38 | 97 | |
1165 | 1 | 10,000 | 24,000 | 82,000 | 304,000 | 2,280,000 |
2 | 10,000 | 23,000 | 98,000 | 356,000 | 2,860,000 | |
3 | 10,000 | 25,000 | 76,000 | 294,000 | 2,140,000 | |
mean | 10,000 | 24,000 | 85,000 | 318,000 | 2,427,000 | |
% control | 100 | 71 | 52 | 21 | 58 | |
Rep = Replicate |
Average specific growth rate from the toxicity test with DMBPC and the freshwater alga, Selenastrum capricornutum.
Measured Concentration of DMBPC (microg/L) |
| Average Specific Growth Rate | |||
Hour of Exposure | |||||
24 | 48 | 72 | 96 | ||
Control | mean | 0.051 | 0.058 | 0.069 | 0.063 |
Solvent Control | mean | 0.055 | 0.055 | 0.062 | 0.064 |
% control | 108 | 95 | 90 | 102 | |
81 | mean | 0.048 | 0.057 | 0.061 | 0.063 |
% control | 94 | 98 | 88 | 100 | |
161 | mean | 0.051 | 0.056 | 0.062 | 0.064 |
% control | 100 | 97 | 90 | 102 | |
297 | mean | 0.057 | 0.054 | 0.061 | 0.061 |
% control | 112 | 93 | 88 | 97 | |
595 | mean | 0.057 | 0.046 | 0.056 | 0.062 |
% control | 112 | 79 | 81 | 98 | |
1165 | mean | 0.037 | 0.045 | 0.048 | 0.057 |
% control | 73 | 78 | 70 | 90 |
Limit of detection was 8.0 microg/L
Area under the growth curve from the toxicity test with DMBPC and the freshwater alga, Selenastrum capricornutum.
Measured Concentration of DMBPC (microg/L) |
| Area Under the Growth Curve | |||
Hour of Exposure | |||||
24 | 48 | 72 | 96 | ||
Control | mean | 288,000 | 2,436,000 | 22,296,000 | 90,252,000 |
Solvent Control | mean | 336,000 | 2,244,000 | 14,100,000 | 80,268,000 |
% control | 117 | 92 | 63 | 89 | |
81 | mean | 264,000 | 2,304,000 | 13,644,000 | 73,812,000 |
% control | 92 | 95 | 61 | 82 | |
161 | mean | 312,000 | 2,256,000 | 14,772,000 | 80,580,000 |
% control | 108 | 93 | 60 | 89 | |
297 | mean | 372,000 | 2,220,000 | 13,332,000 | 66,528,000 |
% control | 129 | 91 | 60 | 74 | |
595 | mean | 360,000 | 1,728,000 | 9,440,000 | 64,512,000 |
% control | 125 | 71 | 42 | 71 | |
1165 | mean | 168,000 | 1,236,000 | 5,832,000 | 38,532,000 |
% control | 58 | 51 | 26 | 43 |
Description of key information
Under the conditions of this study, the 96 hour ErC50 was > 1165 µg/L. The 96 hour NOEC was 595 µg/L DMBPC when determined using the number of cells/mL or the average specific growth rate.
Key value for chemical safety assessment
- EC10 or NOEC for freshwater algae:
- 595 µg/L
Additional information
The toxicity potential of the test material to freshwater algae was investigated in accordance with the standardised guideline EPA OPPTS 850.5400 under GLP conditions. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).
The definitive toxicity test was conducted at 24 ± 2°C with five concentrations of test substance, a control, and a solvent control (0.10 mL/L dimethylformamide). Nominal concentrations were 0 (control and solvent control), 75, 150, 300, 600 and 1200 µg/L. Each solution was subdivided into three clear glass 250 mL Erlenmeyer flasks. The flasks were inoculated with approximately 10 000 algal cells/mL and capped with inverted glass beakers. Test vessels were randomly arranged on a rotary shaker adjusted to approximately 100 rpm in an incubator.
The number of algal cells/mL in each test vessel and the occurrence of relative size differences, unusual cell shapes, colours, flocculations, adherence of cells to test containers, or aggregation of cells was determined visually by means of direct microscopic examination with a haemocytometer at 24, 48, 72, and 96 hours.
A 0.5 mL aliquot of test media from each test vessel where growth was maximally inhibited (1200 µg/L nominal DMBPC concentration) was combined in a 250 mL flask with 100 mL of fresh media to determine whether toxic effects were algicidal or algistatic. This culture was incubated under test conditions for 48 hours.
Insoluble material was not observed during the test. The initial measured concentrations ranged from 97 to 108 % of the nominal concentrations and the final measured concentrations were 57 to 76 % of the nominal concentrations.
The algal population grew well, resulting in an average of 4 173 000 cells/mL in the control after 96 hours. No effects were noted during the test. The 0.5 mL aliquot that was incubated for a further 48 hours indicated that any toxic effect at this concentration was algistatic rather than algicidal.
Exposure of algae to DMBPC for 96 hours resulted in a median effective concentration (EC50) that was greater than 1165 µg/L (the highest tested concentration and reported water solubility limit) when calculated using the number of cells/mL or the average specific growth rate, and 1141 µg/L when calculated using the area under the growth curve. The 96 hour no observed effect concentration (NOEC) is 595 µg/L DMBPC when determined using the number of cells/mL or the average specific growth rate, and 161 µg/L when determined using the area under the growth curve.
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