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Long-term toxicity to aquatic invertebrates

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Description of key information

NOEC: > 0.5 mg/L (development of the mud crab zoeae up to 18 d)
NOEC: 50 µg/L (estuarine copepod, 10 days, feeding and reproduction)
NOEC: 1 mg/L (development of sea urchin eggs)
NOEC: 0.6 mg/l (daphnia pulex, survival chronic exposition 42 to 90 days)

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater invertebrates:
0.6 mg/L
EC10, LC10 or NOEC for marine water invertebrates:
0.9 mg/L

Additional information

The following discussion is partly quoted from the EU RAR on naphthalene [EU RAR 2003]:

There are a lot of data available on aquatic invertebrates and a wide range of species has been tested. The majority of NOEC values resulting from long-term tests lie in the same range as for long-term toxicity to fish (0.6 -1 mg/L).

Geiger and Buikema (1982) exposed Daphnia pulex to naphthalene concentrations up to 0.6 mg/L (NOEC) in chronic toxicity tests. No significant effect was noted on moulting frequency, growth rate, production of total and live young, number of non-viable eggs, partial and full abortions, and whether or not abortions occurred prior to completion of embryonic development. However, daphnids lived significantly longer than did the controls. Falk-Peterson et al. (1982) exposed both sea urchin eggs (Strongylocentrotus droebachiensis) and copepod adults (Calanusfinmarchicus) to naphthalene concentrations of 0.4, 1.2 and 3.8 mg/L for up to 4 days. The normal development of sea urchin eggs and copepod survival were unaffected by concentrations of 0.4 or 1.2 mg/L. Laughlin and Neff (1979) exposed zoeae of the mud crab Rhithropanopeus harrisii to naphthalene concentrations up to 500 μg/L throughout larval development (up to 18 days). No significant effect of naphthalene exposure was observed. Berdugo et al. (1977) exposed copepods (Eurytemora affinis) to naphthalene concentrations of 1or 2 mg/L for 24 hours and found a significant reduction in ingestion rate. An exposure of 1 mg/L significantly reduced the total number of eggs produced by each female. Low levels of 14C-naphthalene (10 and 50 µg/L) over a period of 10 days had no significant effects on feeding or reproduction despite the high concentration of hydrocarbon accumulated (NOEC 50 µg/L, highest concentration tested). Ott et al. (1978) found significant reductions in the length of life, total numbers of nauplii produced and mean brood size of female copepods (Eurytemora affinis) exposed to 14 μg/L naphthalene for the duration of their adult life (up to 29 days). Saethre et al. (1984) exposed fertilised sea urchin (Strongylocentrotus droebachiensis) eggs to naphthalene concentrations of between 0.90 and 2.78 mg/L for 4 days. The lower exposure concentration had no effect on the survival of the eggs. The higher concentration killed all the eggs within 2 to 4 days. The test was performed in a static system and the authors noted rapid lost of naphthalene. Therefore, the nominal concentration of 1 mg/L naphthalene identified as NOEC for development of sea urchin eggs is used as supporting value only.

 

However, results based on nominal values do not take into account loss of the chemical during the test. These can be very variable depending on the test system employed. Saethre et al. (1984) noted that naphthalene was rapidly lost from solution with 80 to 90% lost over a 4-day period. The authors pointed out that this was probably due to evaporation from poorly sealed test beakers. Caldwell et al. (1977) found significant losses of 25 to 50% in flow-through systems. However, Ott et al. (1978) reported losses of less than 8% in a closed static system. Similar losses of 2 to 7% were found in flow-through systems over periods of up to 40 days (Moles et al., 1981). Like in the laboratory, naphthalene will also evaporate in the environment from compartments, thus showing a clear tendency to fade away (within hours to days). This would lead to a more or less rapid elimination of naphthalene out of the respective compartment and a decrease of potential biological impact. Low levels of naphthalene do not necessarily cause inhibition in organisms. In some instances increasing tolerance towards naphthalene was observed and even stimulation e.g. of growth or other parameters as compared to controls. This observation, however, may not necessarily be interpreted as “positive” or “beneficial” effects.

 

Behind this background, a NOEC for daphnia of 0.6 mg/l (Geiger and Buikema, 1982) is considered to be sufficiently low to cover aquatic invertebrates.

[EU RAR 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/]