Naphthalene

Long-term toxicity to fish

Description of key information

Depending on the aquatic organism and developmental state (selected) aquatic long-term  EC50/LC50/NOECs are:
0.12 mg/L (NOEC, juvenile pink salmon, 40 days exposure) [Moles etal. 1983]; 
0.37 mg/L (NOEC, coho salmon fry, exposure 40 days) [Moles et al. 1981];
0.11 – 0.12 mg/L (LC50, rainbow trout larval stage, exposed 20 minutes after fertilisation until 4 days post-hatching) [Black et al. 1983; Millemann et al. 1984];
0.02 mg/L (LC10, rainbow trout larval stage, exposed 20 minutes after fertilisation until 4 days post-hatching) [Black et al. 1983]
0.51 - 0.61 mg/L (LC50, largemouth bass, larval stage, exposed 2-4 hours post-spawning until 4 days post-hatch) [Black et al. 1983]; 
0.45 - 0.85 mg/L (MATC maximum acceptable toxicant concentration, fathead minnow, embryo-larval stage, exposure 30 days) [Graeve et al. 1982];

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

0.12 mg/L

Marine water fish

Marine water fish

Effect concentration:

0.4 mg/L

Additional information

There are a lot of data from long-term studies on fish available, and a wide range of species has been tested. Two 40-day juvenile tests with coho and pink salmon (Moles et al., 1981; Moles and Rice 1983, respectively) resulted in NOECs for growth of 0.37 mg/L (freshwater) and 0.12 mg/L (saltwater), respectively, both concentration measured.

In an embryo-larval study on fathead minnows, NOECs were found for survival to be 1.84 mg/L and for hatchability and fish length/weight to be 0.45 mg/L (de Graeve et al., 1982).

There was one group of investigators who found significantly lower long-term toxicity values in their ELS-studies that cannot be easily fitted into this scheme. One study derived LC50s of 0.11 mg/L and 0.51 mg/L for fish exposed from egg fertilisation through to 4 days post-hatching (rainbow trout and largemouth bass, respectively) (Black et al., 1983). The corresponding LC10 values were about 0.020 and 0.028 mg/L, respectively. These findings were based on the survival of the 4-day post-hatch fry, with the exposure having started at the earliest possible life-stage of a fertilised egg, the zygote, or very shortly thereafter. Thus, the test substance can act earlier and more intensively on the early development stages than common in standard chronic testing for aquatic toxicity. Therefore, for reasons of comparability, it is difficult to use these results in a conventional acute or chronic framework, as used when deciding on assessment factors or possibly on classification. The results obtained by Black et al. have also been called into question due to problems in reproducing the results in other laboratories. Therefore, in line with the EU risk assessment report for naphthalene (EU 2003), these findings are considered with caution and have not been used for deriving a PNEC and environmental classification.

A NOEC value of 0.12 mg/L for both freshwater and marine water fish is considered to be sufficiently low to cover freshwater and marine water fish, respectively.

[Note: On the other hand, there is apparently not an unequivocal rule in the OECD TG 210 of today (ELS test), which clearly explains when to start exposure (OECD 2013).]

References:

EU 2003: European Union Risk Assessment Report NAPHTHALENE [CAS No: 91-20-3; EINECS No: 202-049-5] RISK ASSESSMENT European Communities, 2003 [http://ecb.jrc.ec.europa.eu/esis/] OECD 2013: Fish, Early-life Stage Toxicity Test: "Conditions of Exposure - Duration: Section 18. The test should start as soon as possible after the eggs have been fertilised and preferably being immersed in the test solutions before cleavage of the blastodisc commences, or as close as possible after this stage. The test duration will depend upon the species used...."