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Toxicity to aquatic algae and cyanobacteria

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Description of key information

This test was conducted in accordance with the OECD test guideline 201 and with GLP compliance, so it can be considered reliable without restrictions. Test results shows the ErC50 - 72h to algae is 48 mg/l and a NOECr = 18 mg/l.

Key value for chemical safety assessment

EC50 for freshwater algae:
48 mg/L
EC10 or NOEC for freshwater algae:
18 mg/L

Additional information

The aim of the study was to determine the concentrations of SULPHAMIDIC ACID inhibiting the average specific growth rate (μ) and yield (y) of the freshwater alga Desmodesmus subspicatus in a 72-hour static test.

SULPHAMIDIC ACID was tested in nominal concentrations 18; 27; 40; 60 and 90 mg/l. 

On the basis of the results, it is concluded that the test substance inhibited:

-        50 % of the average specific growth rate of the alga Desmodesmus subspicatus, at an effective concentration (ErC50) 48.0 mg/l after 72 – hour exposure (95 % confidential limit:47.0 – 49.2mg/l);

-        10 % of the average specific growth rate of the alga Desmodesmus subspicatus, at an effective concentration (ErC10) 29.5 mg/l after 72 – hour exposure (95 % confidential limit:28.6 – 30.3mg/l).

 On the basis of the results, it is also deduced that the test substance inhibited:

-        50 % of the yield of the alga Desmodesmus subspicatus,at an effective concentration (EyC50) 33.8 mg/l after 72 – hour exposure (95 % confidential limit:32.6 – 35.2mg/l);

-        10 % of the yield of the alga Desmodesmus subspicatus, at an effective concentration (EyC10) 13.3 mg/l after 72 – hour exposure (95 % confidential limit:11.5 – 14.9mg/l).

Also “no observed effect concentrations” for average specific rate and yield were determined:

72 – hour NOErC was calculated at 18 mg/l and 72 – hour NOEyC was also determined at a value 18 mg/l.

As it follows from results discussed above the test substance showed higher toxicity on the response variable “yield” than in comparison with “average specific growth rate”. This fact is also generally confirmed by OECD Guideline № 201.

From the results obtained in this study it can also be stated that inhibition of growth recorded has mainly been caused due to acidic properties of the test substance in defined test solutions in which the pH values decreased with an increment of a test substance concentration. The highest leap of the mean inhibition for both response variable (specific growth rate and yield) was measured between nominal concentrations 40 mg/l and 60 mg/l with corresponding average pH values of both test solutions (7.14 and 4.56). For the response variable - specific growth rate, it was an increase of inhibition from 16.1% to 90 %. For the response variable - yield, it was measured as an increase of inhibition from 55.6 % to 99.5 %. A difference between both average pH values of both border concentrations equaled approximately 2.58 and in terms of both boundary concentrations the difference was by 20 mg/l. This increment of concentrations caused a substantial decrease of the pH value, which resulted in a rapid alga inhibition of specific growth rate and biomass yield, incompatible with algae survival.

Based on the ecotoxicity results on sulphamidic acid, on the one hand, hazard assessment is in fact hazard assessment of acidity (H+ ions). But on the other hand, we can expect, as in most of other mineral acids (e.g. sulphuric acid), that residual anion has no toxicity in green alga Desmodesmus subspicatus at environmentally relevant strong acid concentrations.