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Toxicity to aquatic algae and cyanobacteria

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Description of key information

Relevant and reliable data that could be used for classification and PNEC for freshwater algae were retrieved for Pseudokirchneriella subcapitata. EC30 values, only, were available for Chlamydomonas reinhardtiiand therefore were not carried forward for hazard classification or PNEC derivation. For Pseudokirchneriella subcapitata (the more sensitive species), reported EC50s ranged from 95 - 486 µg Co/L and the EC10s ranged from 22.0 - 297 µg Co/L; variability is attributed to differences in the characteristics of the test waters. Values used for CSA are reported as geometric means of available data.

Relevant and reliable data that could be used for classification and PNEC for marine algae were retrieved for three different species: Champia parvula (seaweed), Skeletonema costatum (marine diatom), and Dunaliella tertiolecta (marine flagellate). The EC50s ranged from 24.1 µg Co/L for seaweed to 71314 µg Co/L for flagellate to 100,000 µg Co/L for marine diatom. EC10s ranged from 1.23 µg Co/L for seaweed to 590.3 µg Co/L for diatom and 11,961 µg Co/L for marine flagellate. Test results were obtained in experiments that followed international accepted guidance and were based on measured levels of dissolved cobalt as cobalt dichloride.

Key value for chemical safety assessment

EC50 for freshwater algae:
310.4 µg/L
EC50 for marine water algae:
24.1 µg/L
EC10 or NOEC for freshwater algae:
76.4 µg/L
EC10 or NOEC for marine water algae:
1.23 µg/L

Additional information

Freshwater:

From the database of cobalt toxicity to freshwater algae, NOEC/EC10 high quality values are reported for the Pseudokirchneriella subcapitata algae species (Heijerick et al 2007; OSU 2015). Tables showing the EC10 values of high quality that were used to derive the HC5 and aquatic freshwater PNEC are in the attached document, as well as below.

Table. High quality studies used for derivation of the freshwater aquatic EC50, and the HC5 and PNEC

 

Species

Endpoint

Value (mg Co/L)

OSU 2015

Raphidocelis subcapitata

Growth inhibition

EC50: 485.7

EC50: 397.1

EC50: 199.4

EC50: 146.4

EC50: 151.5

EC50: 95.2

EC10: 296.5

EC10: 148.3

EC10: 115.8

EC10: 62.7

EC10: 21.5

EC10: 38

OSU 2020

Raphidocelis subcapitata

Growth inhibition

EC50: 571.2

EC50: 803.7

EC50: 819.4

EC50: 585.5

EC10: 264.7

EC10: 317.4

EC10: 407.5

EC10: 226.2

Heijerick et al. 2007

Raphidocelis subcapitata

Growth inhibition

EC50: 144

EC10: 23

EC10: 30.3

EC10:38.2

EC10:30.2

EC10:38.9

EC10:92.6

EC10:40.2

EC10:70.2

EC10:59.6

EC10:64.6

EC10:105.1

EC10: 148

EC10:92.2

EC10:126.4

EC10:131.9

EC10:131

EC10:76.1

EC10:59.4

EC10:23

EC10:12.6

EC10: 205

EC10: 41

EC10: 36

EC10:101

EC10: 118

 

Marine:

From the database of cobalt toxicity to marine algae, 10 high quality NOEC and EC10 values are reported for three species. Toxicity values (EC10) range from 1.23 μg Co/L for growth of the marine algae, Champia parvula (CDI 2010m) to 11961 μg Co/L for growth of the marine flagellate, Dunaliella tertiolecta (CDI 2010l). The table below indicates the high quality EC10 values selected for derivation of HC5 and the marine aquatic PNEC:

Table. High quality studies used for derivation of the marine aquatic HC5 and PNEC

Key study

Species

Endpoint

Value (mg Co/L)

CDI, 2010k

Champia parvula (seaweed)

Cystocarp production

EC50: 24.1

EC10: 1.23

CDI, 2010m

Skeletonema costatum (marine diatom)

Growth rate

EC50: 100000

EC10: 590.3

CDI, 2010l

Dunaliella tertiolecta (marine flagellate)

Growth rate

EC50: 71314

EC10: 11961

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