ALFERROCK

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:

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

Adequacy of study:

key study

Justification for type of information:

For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

>= 10.02 mg/L

Nominal / measured:

not specified

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: 95 % CI = 10.00–10.04

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

>= 10.9 mg/L

Nominal / measured:

not specified

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95 % CI = 9.40–12.70

Results with reference substance (positive control):

Various other toxicants were used as control, e.g. formaldehyde: EC50 = 6.61 mg/L and K2Cr2O7: EC50 = 0.78 mg/L. Both measured in Erlenmayer falsks on the basis of growth inhibition.

Reported statistics and error estimates:

Inhibition values were calculated from three parallels according to the standard ISO 8692 (1989). EC values were calculated from the sigmoidal concentration–inhibition curves fitted by probit analysis using the maximum-likelihood method (Finney, 1964), and the confidence limits were calculated using the equation from Fieller (Weber, 1980).

Validity criteria fulfilled:

not applicable

Remarks:

Non-guideline study, but scientifically robust result, published in peer-reviewed article.

Conclusions:

Several metals were tested and for AlCl3 the following results were obtained from the Erlenmyer flask assays:
Algal growth rate ErC50 = 10.90 mg/L
Biomass integral of the growth curve EbC50 = 10.02 mg/L

Executive summary:

In a 72-hour toxicity study, the cultures of Desmodesmus subspicatus were exposed to aluminium chloride (AlCl₃) at nominal concentrations not further detailed, under static conditions in accordance with OECD test guideline 201. The EC₅₀ value based on biomass and growth rate were 10.02 and 10.90 mg/L, respectively.

No abnormalities were noted.

This toxicity study is classified as acceptable and satisfies the guideline requirements for an algal toxicity study.

Results synopsis

Test organism: Desmodesmus subspicatus

Test type: Static

72-hr EC₅₀: 10.9 mg/L (95 % CI: 9.40 to 12.7 mg/L)

Endpoint(s) effected: Growth rate

This information is used in a read-across approach in the assessment of the target substance. For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

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

Adequacy of study:

supporting study

Justification for type of information:

For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Vehicle:

no

Duration:

4 d

Dose descriptor:

other: EC30

Effect conc.:

ca. 800 µg/L

Nominal / measured:

nominal

Conc. based on:

dissolved

Basis for effect:

growth rate

Remarks on result:

other: at pH 4.3 for monomeric Al

Duration:

4 d

Dose descriptor:

other: EC30

Effect conc.:

ca. 660 µg/L

Nominal / measured:

nominal

Conc. based on:

dissolved

Basis for effect:

growth rate

Remarks on result:

other: at pH 4.6 for monomeric Al

Duration:

4 d

Dose descriptor:

other: EC30

Effect conc.:

ca. 410 µg/L

Nominal / measured:

nominal

Conc. based on:

dissolved

Basis for effect:

growth rate

Remarks on result:

other: at pH 4.8 for monomeric Al

Duration:

4 d

Dose descriptor:

other: EC30

Effect conc.:

ca. 90 µg/L

Nominal / measured:

nominal

Conc. based on:

dissolved

Basis for effect:

growth rate

Remarks on result:

other: at pH 5.0 for monomeric Al

Key result

Duration:

4 d

Dose descriptor:

other: EC30

Effect conc.:

ca. 7 µg/L

Nominal / measured:

nominal

Conc. based on:

dissolved

Basis for effect:

growth rate

Remarks on result:

other: at pH 6.0 for monomeric Al

Details on results:

The sensitivity of algal growth to inorganic monomeric Al (Al-mono) was determined over the pH range of 4.3 to 6.0 in buffered media. Inhibition of algal growth by Al-mono was slight at pH 4.3 or 4.6 but increased markedly at pH ≥ 5.

Reported statistics and error estimates:

The effects of Al on algal growth were determined by comparing the areas under the growth curves for the various cultures (cell numbers vs. time over 4 d), and EC30 values were determined for different pH values. Statistical analysis of the experiments run at different pH values (one-way ANOVA) indicated that pH per se had no demonstrable effect on algal growth in the pH range from 4.5 to 6.0 (p = 0.05; Bartlett’s test).

The influence of pH in the range of 4.5 to 6.0 without the addition of aluminium on alga growth rate was tested and found to be negligible.

Validity criteria fulfilled:

not applicable

Remarks:

Non-guideline study, but scientifically robust result published in peer-reviewed article.

Conclusions:

The influence of aluminium on algal growth was studied in Chlorella pyrenoidosa. The study revealed that the observed effect (growth inhibition) depends on the pH value of the growth media. EC30 (Al3+) values ranged from 70 nM (pH 6.0) to 10 µM (pH 4.5). For systems at a given pH, containing only inorganic monomeric Al, aluminium bioavailability varies predictably as a function of the free Al3+ concentration. However, aluminium concentrations inhibiting growth by 30 % (EC30) increased markedly from 3 µg/L to 50 µg/L as the pH was decreased from 6 to 5.

Executive summary:

A 96h study was performed to determine the influence of aluminium on the growth of the unicellular alga Chlorella pyrenoidosa. Initially, a cell inoculum was transferred into fresh algal assay procedure growth medium under constant temperature (22 °C) and light conditions (115 µE/m²/s) and grown under constant bubbling with filtered air in Teflon containers (1-2 L). The bioassay exposure media, containing neither phosphate nor trace metals, covered the pH range 4.3 to 6. At time zero algae were washed and resuspended at a cell density of ca. 10E+05 cells per mL. The effects of aluminium on algal growth were determined by comparing the areas under the growth curves for the various cultures and EC30 values were determined for different pH values. The algal density was determined using an electronic particle counter. The test was performed at various pH (4.4–6.0) and Al concentrations measuring algal growth with a total length of 4 days.

This information is used in a read-across approach in the assessment of the target substance. For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.

Description of key information

Toxicity of "Neutralisation and reduction products of bauxite residue from refinement process" to aquatic algae and cyanobacteria can be elicited by aluminium ions released from the material during dissolution. EC30 (72-h) values (Al3+) ranged from 70 nM (pH 6.0) to 10 µM (pH 4.5). The influence of aluminium on the growth of the alga Chlorella pyrenoidosa was expressed as EC30, increasing markedly from 3 µg/L to 50 µg/L as the pH is decreased from 6 to 5. This test was not conducted in accordance with standard test guidelines.
The following inhibitory concentrations were determined describing adverse effects of aluminium against Desmodesmus subspicatus in standard tests (test duration 72h): Algal growth rate ErC50 = 10.90 mg/L; biomass integral of the growth curve EbC50 = 10.02 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:

10.9 mg/L

Additional information

The 72h study by Eisenträger et al. was performed to measure algal growth-inhibition with Desmodesmus subspicatus in photometric and fluorometric assays in accordance with strandard guidelines for several metals including aluminium. The following results were obtained: Algal growth rate E_rC₅₀ = 10.90 mg/L; biomass integral of the growth curve E_bC₅₀ = 10.02 mg/L; endpoint measurement E_eC₅₀ = 12.87 mg/L.

The 96h study by Parent et al. measured the influence of aluminium on the growth of the alga Chlorella pyrenoidosa. Effects were reported as 30 % inhibitory concentrations (EC₃₀) and values for aluminium increased markedly from 3 µg/L to 50 µg/L as the pH is decreased from 6 to 5. The study revealed that the observed adverse effect (growth inhibition) depends on the pH value of the growth media. EC₃₀ values for aluminium (Al³⁺) values ranged over more than two orders of magnitude from 70 nM (pH 6.0) to 10 µM (pH 4.5).

The presented studies show that adverse effects on algae exposed to aluminium is strongly dependent on pH and temperature.

The effect values reported by Eisenträger et al. will be forwarded to the risk assessment as these are the only "standard values" regarding exposure duration (72h) and effect level (ErC50) available.