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The available reliable ecotoxicity data about the effect of arsenic on aquatic organisms are based on dissolved elemental arsenic concentrations. Reliable chronic NOEC and EC10 values were identified for 27 freshwater species and 11 marine species. The reliable data were based on tests with inorganic As(III) and As(V) substances.

The available data do not allow a conclusion regarding the As source or the effect of specific water parameters, including hardness, pH, phosphate level, on the toxicity of arsenic to aquatic organisms. All reliable bounded NOEC and EC10 values were taken forward to the derivation of the PNEC according to the statistical extrapolation approach. In case several data were available for one species, the lowest NOEC or EC10 value for the relevant endpoints (e.g. growth rate for algae) is selected.

The most sensitive chronic NOEC/EC10 -values for arsenic toxicity to the 27 freshwater species covered that were selected for the PNEC derivation are shown below:

Test organism

Taxonomic group

Endpoint

NOEC/EC10 (µg As/L)

Achnanthidium minutissimum

Alga

Growth rate

122.1

Asellus aquaticus

Isopod

Mortality

97.3

Botryococcus braunii

Alga

Growth rate

749.2

Brachionus patulus

Rotifer

Mortality

1500.0

Ceriodaphnia dubia

Crustacea

Reproduction

793.0

Chironomus riparius

Insect

Reproduction

629.3

Chlorella sp.

Alga

Growth rate

6403.0

Closterium aciculare

Alga

Growth rate

4.6

Cyclopoids taxa 1

Copepod

Mortality

2670.0

Cyclopoids taxa 2

Copepod

Mortality

40.0

Daphnia magna

Crustacea

Reproduction

633.0

Gammarus pseudolimnaeus

Amphipod

Mortality

88.0

Gammarus pulex

Crustacea

Mortality

380.0

Harpactoid taxa

Copepod

Mortality

130.0

Hyalella azteca

Amphipod

Growth (weight)

200.8

Hydropsiche pellucidula

Mayfly

Mortality

98.0

Jordanella floridae

Fish

Growth (weight)

2130.0

Lemna minor

Plant

Growth rate (number of fronds)

938.0

Lermna disperma

Plant

Growth (surface area)

292.0

Monoraphidium arcuatum

Alga

Growth rate

71.2

Navicula sp.

Alga

Growth rate

149.8

Oncorhynchus mykiss

Fish

Development (abnormalities)

234.0

Pediastrum duplex

Alga

Growth rate

4.6

Pimephales promelas

Fish

Growth (weight)

2130

Scenedesmus actus

Alga

Growth rate

50.1

Staurastrum paradoxum

Alga

Growth rate

670.4

Wolffia arrhiza

Plant

Growth rate (number of fronds)

192.0

No-effect levels for arsenic toxicity to freshwater were situated between 4.6 µg As/L and 6403 µg As/L, i.e., a difference of a factor of 1391 between the most and least sensitive species. The most sensitive species appeared to be the algae Closterium acculare and Pediastrum duplex, the least sensitive species of the data set was for another alga, i.e. Chlorella sp.

The most sensitive chronic NOEC/EC10 -values for arsenic toxicity to the 11 marine species covered that were selected for the PNEC derivation are shown below:

Test organism

Taxonomic group

Endpoint

NOEC/EC10(µg As/L)

Americamysis bahia

Crustacea

Mortality

631

Fucus serratus

Macroalga

Growth (length)

18.7

Lytechinus variegatus

Echinoderm

Mortality

120

Macrocystis pyrifera

Macroalga

Growth & development

40

Paracentrotus lividus

Echinoderm

Development

56

Penaeus indicus

Crustacea

Growth

13.2

Platichthys stellatus

Fish

Growth (length & weight)

312

Skeletonema costatum

Alga

Growth rate

32.6

Crassostrea angulata

Mollusc

Development

23.6

Crassostrea gigas

Mollusc

Development

73.1

Champia parvula

Macroalga

Reproduction

60

No-effect levels for dissolved arsenic were situated between 13.2 µg As/L and 631 µg As/L, i.e., a difference of a factor of 48 between the most and least sensitive species. The crustacean Penaeus indicus was the most sensitive trophic level. The least sensitive species was observed for another crustacean, i.e. the mysid Americamysis bahia.

Relevant information on acute toxicity of arsenic to standard fish species, invertebrates and algae were retained for classification purposes when tests were in line with accepted standard testing guidelines. An overview of the critical data is given hereunder:

  • For fish, the lowest reliable data point for arsenic, added to the test medium as sodium arsenate, was put forward for hazard assessment purposes: 96h-LC50of 12600 µg As/L for the fish P. promelas.
  • For invertebrates, the following lowest reliable data point for sodium arsenate (test organism: D. magna) was put forward for hazard assessment purposes: 48h-LC50of 1500 µg As/L for the cladoceran D. magna.
  • For algae, two reliable acute data points, representing the most sensitive strain of Chlorella sp. were available for hazard assessment purposes. The lowest value of those two data points was 25200 µg As/L and is considered as a reliable acute toxicity value for hazard assessment purposes. No reliable EC50-values were reported for other relevant algal species.

The identified long-term data for standard species (and trophic levels) that are considered for classification purposes, revealed a chronic ERV of 234 µg As/L. An overview of the most sensitive freshwater species-specific NOEC/EC10-values for arsenic used for chronic ERV derivation is shown below:

Test organism

Taxonomic group

Endpoint

NOEC/EC10 (µg As/L)

Ceriodaphnia dubia

Crustacea

Reproduction

793.0

Chlorella sp.

Alga

Growth rate

6403.0

Daphnia magna

Crustacea

Reproduction

633.0

Lemna minor

Plant

Growth rate (number of fronds)

938.0

Oncorhynchus mykiss

Fish

Development (abnormalities)

234.0

Pimephales promelas

Fish

Growth (weight)

2130