Aluminium triisopropanolate

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

before 2011

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Remarks:

all relevant information in the publication is included in the summary

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

GLP compliance:

not specified

Remarks:

data published

Details on test solutions:

Aluminna obtained from the suplliers were used to produce suspensions in OECD algal medium. Stock suspensions were prepared in algal medium before each experiment (3, 6, 12, 24, 48, 96 and 196 mg/l) and kept at 4°C in refrigerator. Before use they were sonicated.

Test organisms (species):

other: scenedesmus sp and chlorella sp

Details on test organisms:

Isolated from VIT Lake, Vellore, Indoa. Soil water mixture samples were collected an srew-capped bottles. Bold Basal Medium was ued. Initial pH was 6.8.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

27°C

pH:

Initial pH 6.8

Nominal and measured concentrations:

3, 6, 12, 24, 48, 96 and 196 mg/L

Details on test conditions:

During 72 h growth experiments the exponential growth phase of algal cultures were used and exposed to various concentrations of the test substance under controlled conditions. it was insured that the cell concentration of the control culture (devoid of test substance) increased at least 16 times during 3 days. Algal biomass and total chlrorphyll were measured at 24, 48 and 72 h. The growth inhibition was was analyzed in batch cultures containing varying concentrations of alumina in suspensions. Erlenmeyer flasks containing medium with varied concentrations were inoculated with 1 ml of the freshly prepared algal suspension to maintain initial algal concentration of 10.000 cells/mL which was correlated with cell density as determined by cell counts (Neubauer hemocytometer). The flasks were the incubated for 72 h at 27°C, illuminated with cool white light (5000 lux). Algal growth was measured as an increase in absorbance at 680 nm determined using a spectrophotometer. The experiments in cluded a positive control (flask containing substance and medium, devoid of algal cells) and a negative control (flask containing algal cells and nutrient medium, devoid of substance). The neg controls indicated the algal growth profile inthe absence of substance. The absorbance values for positive controls were subtracted from the experimental values. Positive control OD values for different concentrations in algal growth medium are given as follows:

conc (mg/l) 3 6 12 24 48 96 192
OD 0.01 0.013 0.02 0.03 0.04 0.09 0.15

All experiments were carried out in triplicate and the mean value was reported.

Algal samples were collected at different time intervals such as initial 0h and at the end of the experiment 72h. Images were taken with Phase contrast microscope. All images were taken in 50 µm scale to get a clear picture of the algal cell.

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

100.4 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: Scenedesmus sp.

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

110.2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: Chlorella sp.

Details on results:

For Chlorella sp. the 72 h EC50 values for bulk alumina is 110.2 mg/L. A typical concentration-dependent inhibitory effect of alumina was observed. Total chlorophyll content of Chlorella sp. was significantly lower in the treated cells. A concentration-dependent decrease in the chlorophyll content was noted.
For Scenedesmus sp. the 72 h EC50 value was 100.4 mg/l. A concentration-dependent decrease in total chlorophyll content of Scenedesmus sp. was noted upon treating with the substance.

A comparative analysis of growth data of the two algal species revealed that Scenedesmus sp were more sensitive than Chlorella sp..

Reported statistics and error estimates:

Tests were performed in triplicate. EC50 values were computed. The EC50 values were calculated using EPA probit analyses (version 1.5). The level of significance was accepted at p=<0.05. EC and NOEC values are reported with mean value.

Conclusions:

A growth inhibitory effect of alumina was observed for both algal species: 72h EC50 value 110.2mg/L for Chlorella sp.; 100.4 mg/L for Scenedesmus sp.. A decrease in chlorophyll content was observed in the treated cells compared to the untreated ones.

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

GLP compliance:

no

Specific details on test material used for the study:

no data

Analytical monitoring:

no

Vehicle:

yes

Details on test solutions:

diluted in distilled water

Test organisms (species):

Stichococcus sp.

Details on test organisms:

TEST ORGANISM: Monoraphidium Monoraphidium dybowskii and Stichococcus sp.
- Source: from slightly acidified Swedish lakes
- Age of inoculum (at test initiation):
- Method of cultivation: grown in erlenmeyer flasks (at 25 °C and continuous light 100 uE/m2s), reinoculated once weekly --> exponentially growing

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

10 d

Remarks on exposure duration:

10-12 days

pH:

tests at pH 5.0, 5.5 and 6.0

Nominal and measured concentrations:

0, 0.10, 0.18, 0.32, 0.56, 1.00 and 1.80 mg/L as Al,

Details on test conditions:

TEST SYSTEM
- Test vessel: Erlenmeyer flask
- Aeration: no data
- Initial cells density: 10E7 cells/L
- Control end cells density: ca 10E9 (taken from figure in the publication)
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3

GROWTH MEDIUM
- Standard medium used: no data

TEST MEDIUM / WATER PARAMETERS: similar to growth medium

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: particle counter (Coulter counter)
- Other: cell size of living cells

Duration:

12 d

Dose descriptor:

EC50

Effect conc.:

1.1 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Basis for effect:

growth rate

Remarks on result:

other: for Monoraphidium dybowskii

Duration:

10 d

Dose descriptor:

EC50

Effect conc.:

0.54 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Basis for effect:

growth rate

Remarks on result:

other: for Stichococcus sp

Duration:

12 d

Dose descriptor:

NOEC

Effect conc.:

0.04 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Basis for effect:

growth rate

Remarks on result:

other: for Monoraphidium dybowskii

Duration:

10 d

Dose descriptor:

NOEC

Effect conc.:

0.23 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Basis for effect:

growth rate

Remarks on result:

other: for Stichococcus sp

Duration:

12 d

Dose descriptor:

NOEC

Effect conc.:

0.1 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Basis for effect:

other: cell decomposition

Remarks on result:

other: for both algae species

Conclusions:

The EC50 for growth rate in both algae species tested is 0.54-1.1 mg/L
The NOEC is 0.04-0.23 mg/L

Reference 3

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

GLP compliance:

not specified

Remarks:

data published

Specific details on test material used for the study:

AlCl3x6H2O, Ajax Finechem, Univar, AR grade)

Analytical monitoring:

yes

Vehicle:

yes

Remarks:

seawater

Details on test solutions:

Bioassay test solutions werde prepared in triplicate using filtered seawater with nutrients added and incubated for 72h at 21°C in 12:12 h light/dark cycle.Cells were harvested from cultures in their exp growth phase (5-6d) and rinsed 3 times in seawter using centrifugation to remove residual culture media. Initial algal coonc were 2x10exp4 cells/mL to 4x10exp4 cells/mL for C. closterium and 2x10exp3 to 4x10exp3 cells/mL for the other species. Flasks were shaken manually twice a day and positioned randomly to account for light and temperature gradients. The algal conc was measured daily using flow cytometry. Growth rate was calculated as the slope of the linear regression of log10 algal cell conc vs time and was used in deriving the chronic effect value for algal growth inhibition. The test was acceptable if the control growth rate was >1 doubling/d and the control growth rate coeefeicient of variation was <10%, and the inhib conc, 50% (IC50) for the copper reference test was within 2SD of the mean.

Test organisms (species):

other: Ceratoneis closterium (formerly Nitzschia closterium), Minutocellus polymorphus, Dunaliella tertiolecta, Tetraselmis sp.

Details on test organisms:

The C. closterium cells were gently homogenized to reduce clumping of cells priot to counting. Inspection of cells under the microscope before and after homogenizing confirmed no damage to cells and reduced clumping. Homogenization was not needed for the other species.

Test type:

static

Water media type:

saltwater

Total exposure duration:

72 h

Test temperature:

21°C

pH:

8.2

Dissolved oxygen:

100 % saturation (±4% SD)

Nominal and measured concentrations:

10-100000µg Al/L nominal

Reference substance (positive control):

yes

Remarks:

CuSO4x5H2O

Duration:

72 h

Dose descriptor:

IC10

Effect conc.:

1 400 µg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element (total fraction)

Basis for effect:

growth rate

Remarks on result:

other: Dunaliella tertiolecta

Duration:

72 h

Dose descriptor:

IC50

Effect conc.:

1 100 µg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element (dissolved fraction)

Basis for effect:

growth rate

Remarks on result:

other: Dunaliella tertiolecta

Duration:

72 h

Dose descriptor:

IC10

Effect conc.:

18 µg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element (total fraction)

Basis for effect:

growth rate

Remarks on result:

other: Ceratoneis closterium

Duration:

72 h

Dose descriptor:

IC10

Effect conc.:

690 µg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element (total fraction)

Basis for effect:

growth rate

Remarks on result:

other: Minutocellus polymorphus

Duration:

72 h

Dose descriptor:

IC10

Effect conc.:

3 200 µg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element (total fraction)

Basis for effect:

growth rate

Remarks on result:

other: Tetraselmis sp.

Duration:

72 h

Dose descriptor:

IC10

Effect conc.:

1 300 µg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element (dissolved fraction)

Basis for effect:

growth rate

Remarks on result:

other: Tetraselmis sp.

Details on results:

The toxicity of Al to the chronic growth rate of marine microalgae as quantified by the IC10 was species specific, with greater effects on diatoms relative to green algae. The microalgal species ranked in sensitivity to Al as follows: C. closterium ) > M. polymorphus > D. teriolecta > Tetraselmis sp.
Toxicity appears to be more strongly related to dossolved Al with potential contributions from particulate Al at total concentations of <100µg/L.
For D tertiolecta, there was a sharp drop in algal growth tae above 890 µg total Al/L. Growth rate reached 50% of the control where dissolved Al reached a max of 1700 µg/L and total Al conc exceeded 4000 µg/L. This region of the the concentration-response curve was dominated by particulate Al and there was little change in dssolved Al conc with increasing total Al concentration. Growth rate eclined further to 30% of control when total Al reached 43000 µg/L. Growth rates showed the best relationship with total Al, suggesting that a combination or particulate and dissolved forms contribute to toxicity.

Reported statistics and error estimates:

Concnentration-response curves were constructed using the biological effect as a funtion of the measure Al conc data from the bioassay. The IC50 for each organisms was determined by nonlinear regression using R package drc (2.3-0). The package uses log-logistic and Weibull models. The 95% confidence limits on the toxicity values were genrated using the delta method of estimating the asmptotic standard error and the approp t-distribution.

Conclusions:

In the present study, IC10 and IC50 for Dunaliella tertiolecta are 1400 and 4200 µg Al/L for total Al concentration. For dissolved Al conc, IC10 and IC50 for Dunaliella tertiolecta are 960 and 1100 µg Al/L. The studies showed that dissolved forms of Al dominate below approx 500 µg/L.. Above 1000 µg/L particulate Al hydroxide becomes increasingly dominant. Thus, the authors conclude that Dunaliella tertiolecta was affected by a combination of dissolved and particulate Al species.
In conclusion, the derived IC values are above the water solubility of the relevant Al species in the frame of the experimental conditions.

Reference 4

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1980

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study without detailed documentation

Qualifier:

no guideline followed

Principles of method if other than guideline:

The concentration of the algal suspension is measured turbidimetrically and expressed by the extinction of the primary light of the monochromatic radiation at 578 nm for a layer of 10 mm thickness. The concentration at which the inhibitory action of the test material begins is present in that dilution from a series of dilutions of the test material having, at the end of the test period, a mean extinction value that is ≥ 3% below the mean value of the extinction value for non-toxic dilutions of the test cultures.

GLP compliance:

no

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
Aluminium triisopropylate immediately hydrolyses to isopropanol and Al3+ species in contact with moisture or water as shown in the hydrolysis study in this dossier. Hence, isopropanol is the species present in aqueous media and thus the ideal surrogate for assessing toxicity to aquatic species posed by the organic moiety of the reference substance.

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

Before preparing the test cultures neutralize the test material solution having a known content in sterile double-distilled water to be tested by using the minimum volume of acid or alkaline solution.

From this test material solution, prepare dilutions with varying volume ratios using sterile double-distilled water. These dilutions each contain 1 part v/v of test material solution in 2E0 to 2E14 parts v/v mixture. When preparing the two parallel dilution series in 300-ml Erlenmeyer flasks proceed as follows: the first flask of each dilution series contains 80 ml of test material solution at the start. Starting from this flask, prepare subsequent dilutions using a constant dilution ratio of 40 ml preliminary test material dilution + 40 ml double-distilled water. So each flask will first contain 40 ml liquid.

Then, complete each flask from the dilution series to be inoculated to the rated value of 50 ml by adding 5 ml each of stock solution I and 5 ml each of the algal suspension of the preliminary culture having a known adjusted extinction value.

Test organisms (species):

Scenedesmus quadricauda

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

7 d

Hardness:

not reported

Test temperature:

27 ºC

pH:

not reported

Dissolved oxygen:

not reported

Salinity:

freshwater

Nominal and measured concentrations:

2 E0 to 2E 14 parts v/v mixtures

Details on test conditions:

Following inoculation, the extinction value of the monochromatic radiation at 578 nm for a 10-mm layer of the algal suspension of the test cultures will correspond to the extinction value of the Formazin standard suspension TE/F/578 nm = 20.

While shaking the contents, transfer from each flask of the inoculated dilution series 10 ml into three Kapsenberg culture tubes (18 x 180 mm), from each flask of the non-inoculated dilution series into one Kapsenberg tube each and stopper culture tubes with metal caps. Keep the filled culture tubes from the dilution series on a white surface protected against daylight and exposed to constant lighting by luminescent warm white tubes at 60 cm distance from each other, at 27ºC and a relative humidity of 50% for 7 days and shake once each day.

Measure the extinction of the monochromatic radiation at 578 mm in a 10-mm layer of the cell suspension from each test culture.

Nutrient solution 1 (for stock and preliminary cultures)
Dissolve in double-distilled water:
496 mg sodium nitrate, NaNO3
39 mg dipotassium hydrogen phosphate, K2HPO4 anhydrous
75 mg magnesium sulphate, MgSO4.7 H2O
36 mg calcium chloride, CaCl2.2 H2O
40 mg sodium metasilicate, Na2SiO3
58 mg sodium carbonate Na2CO3, anhydrous
3 mg citric acid C6H8O7.H2O
3 mg iron (III) citrate C6H5FeO7.5 H2O
10 mg disodium salt of ethylene diamine tetracetic acid, C10H14N2Na2O8.2 H2O

Add 10 ml of the trace elements operating solution, complete to 1 litre with double-distilled water and adjust pH to 7.0 using the minimum of Na2CO3 solution.

Stock solution I (for test cultures)
Dissolve in double-distilled water:
248 mg sodium nitrate, NaNO3
19.5 mg disodium hydrogen phosphate, K2HPO4, anhydrous
750 mg magnesium sulphate, MgSO4.7 H2O
360 mg calcium chloride, CaCl2.2 H2O
30 mg iron (III) citrate C6H5FeO7.5 H2O.

Add 10 ml of the trace elements operating solution, complete to 1 liter with double -distilled water and adjust pH to 7.0 using the minimum of Na2CO3 solution.

Stock solution II (trace elements)
Dissolve in double-distilled water:
2.86 g boric acid, H3BO3
1.81 g manganese (II) chloride, MnCl2 . 4 H2O
220 mg zinc sulphate, ZnSO4.7 H2O
80 mg copper (II) sulphate, CuSO4.5 H2O
24 mg sodium molybdate, Na2MoO4.2 H2O
40 mg cobalt (II) chloride, CoCl2.6 H2O

Complete solution with double distilled water to 1 liter in a volumetric flask.

Operating solution of trace elements
Complete 4 ml of stock solution II with double-distilled water to 100 ml in a volumetric flask.

Reference substance (positive control):

no

Duration:

7 d

Dose descriptor:

other: Toxicity threshold

Effect conc.:

1 800 mg/L

Nominal / measured:

not specified

Conc. based on:

test mat.

Basis for effect:

other: mean extinction value

Details on results:

For evalution of the toxicological findings at the end of the test period, the mean value (A) of the extinction is calculated for all test cultures that are free from both toxic influence and stimulation of growth except for those having extinction values outside a standard deviation of <3% and also, the mean value (B) of the extinction for those test cultures having the lowest toxic test material concentration within the dilution series.

For mathematical evaluation, (a) (highest non-toxic test material concentration) is plotted against (A) and (b) (lowest toxic test material concentration) against (B) as coordinates. After having entered (A - 3%), the test material concentration at which the inhibitory action (c) begins may be obtained from the regression line between (a;A) and (b;B) if a negative deviation of the mean extinction by a 3% difference against the mean extinction value of all test cultures having a non-toxic and non-stimulating test material concentration is used as an indicator of the beginning of inhibitory action.

Validity criteria fulfilled:

not applicable

Conclusions:

The toxicity threshold (EC3) for 2 -propanol is 1800 mg/l in this published study.

Executive summary:

Aluminium triisopropylate immediately hydrolyses to isopropanol and Al3+ species in contact with moisture or water as shown in the hydrolysis study in this dossier. Hence, isopropanol is the organic species present in aqueous media and thus the ideal surrogate for assessing toxicity to aquatic species posed by the organic moiety of the reference substance.

The toxicity threshold for 2-propanol has been publsihed being 1800 mg/l and thus isopropanol is of low toxicological concern to green algae.

Reference 5

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

before 2016

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

in this summary only the results for P. Tricormutum were included

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

GLP compliance:

not specified

Remarks:

data published

Specific details on test material used for the study:

The test conditions were choosen to allow the examination of Aluminium species under non-acidic marine water conditions.
Substance of interest was Aluminium hydroxide by from Aluminium chloride under more alkaline conditions.

Analytical monitoring:

yes

Details on test solutions:

Al stock solutions (1 and 10 g Al/L) were prepared on the day of toxicity test initiation by the addition of aluminium chloride to sodiumhydroxide solution, to couteract the pH decrease in spiked test solutions cause by aluminium hydrolysis. Al test solutions (10-10000 µg Al/L nominal) were prepared in polycarbonate containers by adding appropriate aliquots of the stock solution to the natural filtered seawater. Nitrate and phisphate were added to ensure that the diatoms were not nutirient limited. Tests were conducted in natural seawater supplemented with low levels of nitrate and phosphate rather than in growth media to ensure toxicity results wew as environmentally relevant as possible. The pH of the test solution was measured and adjusted to obtain a pH of 8.2±0.05.

Test organisms (species):

Phaeodactylum tricornutum

Details on test organisms:

Diatoms were obtained from the CSIRO Collection of living Microalgae, Marine and Atmospheric Research, Hobart, Australia. P. tricornatum Bohlin (strain CS-29/4) were cultured in f/2 growth medium (half strength f medium, Guillard and Ryther). All cultures were maintained in a temperature-controlled room at 21°C on a 12:12 hrs light:dark cycle and transferred into fresh media weekly. Cultures of P. tricornutum were axenic.

Test type:

static

Water media type:

saltwater

Remarks:

Natural seawater from a rock platform (Cronulla, NSW, Australia).

Total exposure duration:

72 h

Test temperature:

21°C

pH:

8.2±0.05

Details on test conditions:

The chronic toxicity of Al to P.tricornutum was determined using 72-h population growth-rate inhibition bioassay. Asay was carried out in Erlenmeyer flasks, coated with a silanising solution to reduce adsorption of aluminium to the flask walls. For the bioassay, five different treatments (10-10000 µg Al/L) and control were preopared in triplicate. Cells in the exponential growth phase were washed 3 times with seawater by centrifuging to remove residual culture media. Flasks were inoculated, covered with transparent lids, placed randomly in a growth cabinet and incubated for 72 h at 21°C. Test flasks were shaken manually and randomly re-positioned twice daily. Algal cell density was measured every 24 h for 72 h using flow cytometry. The population growth rate was the slope derived from a linear regression of log10 cell density versus time(h). Growth rates for treatment flasks were expressed as a percentage of the control growth rate. Tests were considered valid if population growth rates in the control treatmnent exceed 1doubling/day, if the percent coefficient of variation was less than 10% and if pH changes were <1 unit over the 72-h incubation period.
Aluminium species, operationally defined by size fractionation of dissolved and precipated forms, was monitored of the 72-h bioassays. Dissolved aluminium was defined as that which passed through a 0.025µm filter and included truly soluble species and low molecular weight aluminium complexes. Dossiolved aluminium which passed through a 0.45µm filter included colloidal as well as low molecular weight aluminium complexes. The term total aluminium refers to aluminium in all forms.

Reference substance (positive control):

yes

Remarks:

copper salt (CUSO4x5H2O; AR grade, Ajax Finechem, Australia)

Duration:

72 h

Dose descriptor:

IC10

Effect conc.:

2 100 µg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element (total fraction)

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

IC50

Effect conc.:

> 9 500 µg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element (total fraction)

Basis for effect:

growth rate

Details on results:

Diatom control growth rate was acceptable with a value of 1.5±0.09 doublings/day for P. tricornutum, the percent coefficient of variation <10%. Changes in pH were minimal and changes not exceeding 0.3 pH units by 72 h. The sensitivity of the diatom to aluminium over 72 h, at the initial cell density of 10exp3 cel/mL as shown as an attachment. The results are the combination of 3 separate bioassays pooled together and IC50 and IC10 values were calculated using time-averaged total and dissolved (<0.45 µm) AL concentrations to account for changes in aluminium size fractionation over the duration of the bioassay. Effect concentrations based on the initial measured total aluminium were not significantly different (p>0.05) from those based on time-averaged concentrations.
Growth rate inhibition was initially observed at somewhat higher concentration for P. tricornutum (500 µg/L) and the concentration range was relatively narrow (spanning only one order of magnitude). For P. tricornutum growth rate reached 60% of the control when dissolved aluminium reached a maximum of ca. 1000 µg/l and total aluminium exceeded ca. 4000 µg/L. Growth rate the declined to further to 20% of the control when total aluminium reached ca. 9000µg/L. For P. tricornutum the concentration-response relationship for total and dissolved (<0.45 µm) Al concentrations follwed the same shape but deviated above 500 µg/l where aluminium starts to precipate, decreasing the proportion of dissolved aluminium in the total aluminium pool.

Results with reference substance (positive control):

Copper reference test demonstrated that the diatom culture exhibited similar sensitivity throughout testing and was consistent with previous copper exposure asssays.

Reported statistics and error estimates:

IC10 and IC50 values (the AL conc to reduce growth rate by 10% and 50%, respectively, after 72 h compared to the control) were calculated using linear interpolation of pooled data from indiv bioassay ()ToxCalc 5.0.23C, Tidepool Scientific Software). The data were tested for normality using Kolmogorov D test (p>0.01) and equal variances using Bartlett's test (p>0.01). Effect concentrations were based on measured dissolved (<0.45 µm) and total aluminium concentrations based on time averaged measured dissolved (<0.45 µm) and total aluminium. Time-averaged aluminium conc were calculated by averaging aluminium conc measured at 24h intervals over the bioassay, assuming linear change between each time point. For the initial cell density experiments, algal growth in the aluminium treatment was expressed as a percentage of the control. After the data had been tested for equal variances using the Bartlett's test (p>0.05), a Tukey-Kramer multiple comparison test was used to determine which initial cell densities had significantly (p<0.05) different growth rates.

In this summary the results for P. tricornutum were included. Two other marine diatom species (C. Closterium and M polymorphus) proved to be more sensitive to aluminium toxicy. This was related to the high silica amount in the cell wall of those species. In addition toxicity was dependent on the initial cell concentration for these two species and not for P. tricornutum. Toxicity of C Closterium (IC50 807 ug/L) was mainly determied by dissolved aluminium, while for M polymorphus (IC50 1370 ug/L) by both dissolved and precipiated aluminium.

The mechanism of toxicity for precipitated and dissolved aluminium differs and was not further investigated. Permeability of the cell wall was shown not to be of influence on aluminium toxicity.

Conclusions:

72h IC10 for P. tricornutum was 2100 (2000-2000) µg/L and IC50 was >9500 µg/L. Toxicity to this diatom was due predominantly to precipitated aluminium under the test conditions.

Description of key information

Aluminium tri-isopropanolate dissociates instantaneously when exposed to water forming isopropanol and soluble aluminium(III) species. Therefore the effects of both hydrolysis products are considered most relevant to assess the toxicity of aluminium tri-isopropanolate.

For Chlorella sp. the 72 h EC50 values for bulk alumina is 110.2 mg/L. For Scenedesmus sp. the 72 h EC50 values was 100.4 mg/l. A concentration-dependent decrease in total chlorophyll content was observed in both species (Sadiq 2011).

The EC50 for growth rate in fresh water species Monoraphidium dybowskii and Stichococcus sp. is 0.54-1.1 mg/L. The NOEC is 0.04-0.23 mg/L (Claesson 1988).

The toxicity of Al to the chronic growth rate of marine microalgae was assessed with IC10 values between 18 and 3200 µg Al/L. The microalgal species ranked in sensitivity to Al as follows: C. closterium > M. polymorphus > D. teriolecta > Tetraselmis sp. Toxicity appears to be more strongly related to dissolved Al with potential contributions from particulate Al at total concentrations of <100 µg/L (Golding 2015). 72h IC10 for P. tricornutum (marine species) was 2100 (2000-2000) µg/L and IC50 was >9500 µg/L.  Toxicity to this diatom was due predominantly to precipitated aluminium under the test conditions (Gillmore 2016).

The toxicity threshold for 2-propanol for Scenedesmus quadricauda (green algea) by a cell multiplication inhibition test during 7 days (Bringmann 1980).

Key value for chemical safety assessment

EC50 for freshwater algae:

0.54 mg/L

EC10 or NOEC for freshwater algae:

40 µg/L

EC10 or NOEC for marine water algae:

18 µg/L

Additional information

Aluminium triisopropanolate reacts instantaneously with water to form isopropanol and Al3+ species. The resulting pH being weakly alkaline indicates according to Langmuir et al. 2004 that Al3+ species formed are mainly Al(OH)4-, Al(OH)3 and Al(OH)2+ at pH 8.5.

Thus, aluminium tri-isopropanolate is abiotically degradable and forms isopropanol being rapidly biodegradable as shown in a publication Bbyridie (1979).

Hence, both isopropanol and aluminium species will be present in aqueous media. Based on its toxicity, aluminium species seem to represent a worst case surrogate for assessing toxicity to aquatic species exposed to the substance, aluminium tri-isopropanolate.