Perchloric acid

Toxicity to aquatic algae and cyanobacteria

Description of key information

By analogy with sodium perchlorate, neutralised solution of perchloric acid is not harmful to algae with a 72hErC50 > 357 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:

357 mg/L

EC10 or NOEC for freshwater algae:

357 mg/L

Additional information

No data on perchloric acid is available for this endpoint. However, a reliable unpublished key study is available for sodium perchlorate (Tiebaud H., 1998), which is used in a read-across approach (See the endpoint study summary "Aquatic toxicity" for the read-across justification).

The results are recalculated in perchloric acid to be expressed in concentration of perchloric acid for the derivation of its PNEC and the determination of its classification.

The determination of the growth inhibition of the freshwater algae Pseudokirchneriella subcapitata exposed to the test substance Sodium Perchlorate for a duration of 72 hours was performed following the method C3 described in Directive 92/69/EEC of the European Commission and in the guideline 201 of the OECD.

Algae were exposed to a range of concentrations of Sodium Perchlorate dissolved in dilution water. The toxic effect measured during the assay was the inhibition of cellular multiplication over a time period of 72 hours.

The study was performed using 100ml glass Erlenmeyer flasks stoppered with cotton wool wrapped in sterilized gauze, containing 50 ml of test solution inoculated with an algal suspension so that the initial cell concentration was equal to 1x104cells/ml. Test flasks were incubated at 23 ±1.5 oC continuously shaken and constantly exposed to a light intensity of between 6000 and 6900 lux. The algal concentration was measured daily. Analytical chemistry and physico-chemical measurements were carried out at the beginning and the end of the test.

The results were the following:

-      72h EbC50 (biomass) > 435.7 mg/L of NaClO4 (corresponding to 357 mg/l of HClO4)

-      72h EbC10 (biomass) = 150 mg/L of NaClO4 (corresponding to 123 mg/l of HClO4)

-      NOEC (biomass, determined using a statistical analytical method Dunnett test) = 145.7 mg/L of NaClO4 (corresponding to 119 mg/l of HClO4)

-      72h ErC50 (growth rate) > 435.7 mg/L of NaClO4 (corresponding to 357 mg/l of HClO4)

-      72h ErC10 (growth rate) > 435.7 mg/L of NaClO4 (corresponding to 357 mg/l of HClO4)

-      NOEC (growth rate, determined using a statistical analytical method Dunnett test) = 86.9 mg/L of NaClO4 (corresponding to 71 mg/l of HClO4)

The appearance of the test solutions was visually checked at the beginning and at the end of the test. Solutions were found to be clear, colourless. No precipitation was observed at the end of the test.

Microscopic observation confirmed that the algae appeared normal at the end of the test in comparison to the control; the normal form of the unicellular algae is a crescent shaped cell with an average length of 5 -10 µm.

During the test, the control pH varied by 0.19 units.

The validity criteria of the study were respected; the increase in cell density (R), measured in the control solution between the end and the beginning of the test, was greater than a factor of 16 (R = 280); the final concentrations of Sodium Perchlorate were maintained within the designated limit of 80% of the initial concentration in non-inoculated flasks.

The study was performed according to the principles of Good Laboratory Practice (GLP) as described by OECD.