Sodium dichromate

Endpoint summary

Description of key information

Freshwater toxicity

Short-term toxicity data of chromium (VI) substances for freshwater organisms are available for three trophic levels: algae, aquatic invertebrates and fish. If only unreliable data were available, a weight-of-evidence approach was applied. The lowest acute effect value is the reliable 48-h EC50 of 0.03 mg Cr/L observed for the effect of potassium dichromate on the mobility of freshwater invertebrate Ceriodaphnia sp. (Dorn et al., 1987).

Long-term toxicity data of chromium (VI) substances for freshwater organisms are available for three trophic levels: algae, aquatic invertebrates and fish. If only unreliable data were available, a weight-of-evidence approach was applied. The lowest chronic effect value is the 72-h ErC10 of 0.01 mg Cr/L observed for the effect of potassium dichromate on the growth rate of freshwater algae Pseudokirchneriella subcapitata (Christensen and Nyholm, 1984).

In a 3-h respiration inhibition test with activated sewage sludge, a 3 h EC50 value of 28 mg Cr/L was derived for sodium dichromate as key value (Klecka and Landi, 1985).

 

Saltwater toxicity

Short-term toxicity data of chromium (VI) substances for saltwater organisms are available for three trophic levels: algae, aquatic invertebrates and fish. If only unreliable data were available, a weight-of-evidence approach was applied. The lowest acute effect value is the ErC50 of 0.341 mg Cr/L observed for the effect of potassium dichromate on the growth rate of marine diatom Thalassiosira pseudonana in brackish water (Riedel, 1984).

Long-term toxicity data of chromium (VI) substances for saltwater organisms are only available for one trophic level, i.e. invertebrates. The lowest chronic effect value is the NOEC of 0.0166 mg Cr/L observed for the effect of potassium dichromate on the reproduction of marine polychaete Neanthes arenaceodentata (Oshida and Word, 1982). Long-term toxicity data are not available for marine fish and marine algae/plants. The comparison of available data for the respective short-term toxicity to fish, invertebrates and algae and long-term toxicity to invertebrates indicates that saltwater organisms do not appear to be more sensitive than freshwater organisms. A similar conclusion was made in the EU RAR on chromates (ECB, 2005) based on the comparison of respective acute toxicity data in freshwater and saltwater.

Additional information

Acute toxicity

Freshwater

Acute freshwater toxicity data of chromium (VI) substances are available for three trophic levels (algae, invertebrates, fish).

Table: Overview of lowest (reliable) acute aquatic toxicity data for soluble chromium (VI) substances in freshwater:

Species	Parameter	Endpoint	Value (mg Cr/L)	Reference
Pimephales promelas	mortality	96 h LC50	26.1	Dorn et al., 1987
Ceriodaphnia sp.	mobility	48 h EC50	0.03	Dorn et al., 1987
Pseudokirchneriella subcapitata (prev. Selenastrum capricornutum)	growth rate	72 h ErC50	0.23	Christensen and Nyholm, 1984

 

In sum, three studies on the acute toxicity to fish, four studies on the acute toxicity to invertebrates and five studies on the toxicity to algae are available for soluble chromium (VI) substances in freshwater, which are summarised in respective endpoint summaries.

 

Saltwater

Acute saltwater toxicity data of chromium (VI) substances are available for three trophic levels (algae, invertebrates, fish).

Table: Overview of lowest (reliable) acute aquatic toxicity data for soluble chromium (VI) substances in saltwater:

Species	Parameter	Endpoint	Value (mg Cr/L)	Reference
Cyprinodon variegatus	mortality	96 h LC50	21.4	Dorn et al., 1987
Mysidopsis almyra	mortality	48 h LC50	5.13	Dorn et al., 1987
Thalassiosira pseudonana	growth rate	ErC50	0.341	Riedel, 1984*

* No reliable study is available for saltwater algae or aquatic plants

Altogether, two studies on the acute toxicity to fish, three studies on the acute toxicity to invertebrates and one study on the toxicity to algae are available for soluble chromium (VI) substances in marine water, which are summarised in respective endpoint summaries.

 

Long-term toxicity

Freshwater

Long-term freshwater toxicity data of chromium (VI) substances are available for three trophic levels (algae, invertebrates, fish).

Table: Overview of lowest (reliable) chronic aquatic toxicity data for soluble chromium (VI) substances in freshwater:

Species	Parameter	Endpoint	Value (mg Cr/L)	Reference
Oncorhynchus mykiss	wet weight	60 d NOEC	0.051	Sauter et al., 1976
Daphnia magna	reproduction	21 d NOEC	0.018	Kühn et al., 1989
Pseudokirchneriella subcapitata(prev. Selenastrum capricornutum)	growth rate	72 h ErC10	0.01	Christensen and Nyholm, 1984

 

Overall, two studies on the chronic toxicity to fish, four studies on the chronic toxicity to invertebrates and five studies on the toxicity to algae and aquatic plants are available for soluble chromium (VI) substances, which are summarised in respective endpoint summaries.

 

Saltwater

Long-term saltwater toxicity data of chromium (VI) substances are only available for one trophic level, i.e. invertebrates. Long-term toxicity data are not available for marine fish and algae/plants.

Table: Overview of lowest (reliable) chronic aquatic toxicity data for soluble chromium (VI) substances in saltwater:

Species	Parameter	Endpoint	Value (mg Cr/L)	Reference
Neanthes arenaceodentata	reproduction (brood size)	NOEC	0.0166	Oshida and Word, 1982

 

In sum, two studies on the chronic toxicity to invertebrates are available for soluble chromium (VI) substances, which are summarised in the respective endpoint summary.

 

Aquatic microorganisms

One study on the toxicity of soluble chromium (VI) substances to microorganisms is available, which is summarised in the respective endpoint summary. In a 3-h respiration inhibition test with activated sewage sludge according to OECD TG 209, a 3 h EC50 value of 28 mg Cr/L was derived.