Naphthenic acids, zinc salts, basic

Endpoint summary

Description of key information

NAPHTHENIC ACIDS, ZINC SALTS, BASIC:

Only limited aquatic toxicity data are available for naphthenic acids, zinc salts, basic. Available short-term toxicity data seem to indicate that algae are the most sensitive trophic level since EC/LC50 for Daphnia magna and Dario rerio are above the respective OECD limit of 100 mg/L for acute toxicity tests. In a reliable study according to OECD 201, the ErC10 and ErC50 for effects of Naphthenic acids, zinc salts, basic on the growth rate of the freshwater alga Pseudokirchneriella subcapitata were determined with 1.09 mg/L and 3.62 mg/L, respectively. Available aquatic toxicity data are summarized in the following Table. Read-across to the assessment entities zinc cations and naphthenate anions is applied since the ions of the substance naphthenic acids, zinc salts, basic determine its fate and toxicity in the environment. Please refer to the endpoint summary of the respective assessment entityfor further details.

Trophic level	Species	Endpoint	Concentration	Reference	Reliability
fish	D. rerio	96-h LL50	> 100 mg/L	LAUS, 2006	4
crustacea	D. magna	48-h EL50	> 100 mg/L	LAUS, 2006	4
algae	P. subcapitata	72-h ErL50	3.6 mg/L	Ecosolutions, 2013	2
.	.	72-h NOErL	1 mg/L	.	.
.	.	72-h ErL10	1.1 mg/L	.	.

NAPHTHENIC ACIDS:

Reliable data available for algae, daphnia and fish seem to indicate a moderate potential for acute aquatic toxicity with the lowest LC/EC50 reported for fish with 5.62 mg/L. QSAR based estimates (Episuite, Ecosar V. 1.11) for the chronic toxicity of naphthenic acid to freshwater daphnids and saltwater mysids of 31.6 mg/L and 28.9 mg/L, and to freshwater and saltwater fish of 51.2 mg/L and 85.8 mg/L, respectively, and the fact that naphthenic acids are considered biodegradable and do not bioaccumulate indicate that chronic toxicity up to the OECD test limit for chronic toxicity of 10 mg/L is unlikely. Available aquatic toxicity data are summarized in the following Table.

Trophic level	Species	Endpoint	Concentration	Reference	Reliability
fish	P. promelas	96-h LC50	5.62 mg/L	HPVIS, 2010	1
crustacea	D. magna	48-h LC50	20 mg/L	HPVIS, 2010	1
algae	P. subcapitata	72-h ErC50	29.6 mg/L	HPVIS, 2010	1
.	.	72-h NOErC	7.38 mg/L	.	.

ZINC:

Freshwater

The short-term acute aquatic toxicity database for zinc covers 10 species (1 algae, 4 invertebrates and 5 fish species). A significant number of data is available at low and neutral/high pH. The reference values for the zinc ion that are used for the aquatic toxicity hazard assessment of zinc (Zn++) are:

- low pH: 413 µg Zn/l (based on single lowest value for Ceriodaphnia dubia)

- neutral/high pH: 137 µg Zn/l (based on single lowest value for Pseudokirchneriella subcapitata)

 

The 23 distinct chronic species ecotoxicity values available for 3 trophic levels (covering 8 different taxonomic groups) were used for the SSD with “species mean” NOEC values ranging from 19 to 530 µg/l. From these data, the following reference values for chronic zinc aquatic toxicity are derived:

- low pH: 82 µg Zn/l (Daphnia magna)

- high pH: 19 µg Zn/l (Pseudokircherniella subcapitata)

Marine

The marine zinc database with 39 species mean NOECs ranging from 5.6 to 900 µg/L are based on 48 NOEC values from 9 taxonomic groups covering three trophic levels.