Naphthalene

Toxicity to soil macroorganisms except arthropods

Description of key information

LC50(14 d): approx. 150 mg/kg soil dw (Eisenia fetida, OECD 207; mono-methylnaphthalenes, structure analogy) / LC50: 4.67 mg/cm2 (Eisenia fetida, EEC guideline 79/831, Rev.3; naphthalene) 

Key value for chemical safety assessment

Short-term EC50 or LC50 for soil macroorganisms:

150 mg/kg soil dw

Additional information

There is only very limited information available on toxicity of naphthalene to soil macroorganisms. Neuhauser et al. (1986) performed a contact test with Eisenia fetida. A naphthalene LC50 value for of 4.67 mg/ cm² for earthworms has been determined in this study, which strictly followed the EEC guideline 79/831, Rev.3.

A reliable guideline 14d short-term study was focused on mortality of Eisenia fetida in the presence of the structure-related methylnaphthalenes (technical isomer mixture) (BioChem 1992) and resulted in a NOEC and LOEC of 100 and 200 mg/kg soil dw, respectively. The LC50 has been estimated as arithmetic mean between these experimental results.

According to Column 2 of REACH Annexes IX and X (standard information requirements for substances manufactured or imported in quantities of 100 tonnes per year or more and 1,000 tonnes per year or more) of Regulation (EC) No 1907/2006, studies on effects on terrestrial organisms do not need to be conducted if direct and indirect exposure of the soil compartment is unlikely and in the absence of toxicity data for soil organisms, the equilibrium partitioning method may be applied to assess the hazard to soil organisms.

The use pattern of naphthalene limits the risk for direct or indirect exposure of the soil compartment. Unlike pesticides e.g., naphthalene is not intentionally released into the environment. Production, handling and use, in most cases take place in closed systems with very low releases to the environment and with low probability of any significant release to the environment from products.

According to the European Risk Assessment Report on naphthalene [EU RAR], results of toxicity testing for terrestrial organisms are limited and only short-term tests have been carried out. The PNEC for the terrestrial compartment has therefore been calculated in this report using the equilibrium partitioning method in the Technical Guidance document. The PNEC for soil has been calculated to be 53.3 μg/kg using the PNEC calculated for freshwater. It has been suggested that naphthalene might have an effect on soil organisms exposed through the air and water in soil. The equilibrium partition approach assumes that exposure occurs through the water alone. In the absence of data on naphthalene toxicity to terrestrial organisms, information on 1,4-dichlorobenzene has been examined in the risk assessment of that substance. Although there are structural differences the physical properties of naphthalene and 1,4-dichlorbenzene are similar, with 1,4-dichlorbenzene having a lower boiling point and higher vapour pressure. A set of short-term terrestrial toxicity tests are available for 1,4-dichlorobenzene, which give a PNEC of 85 μg/kg wet weight using an assessment factor of 1,000. The equilibrium partitioning approach gives a value of 160 μg/kg from the aquatic PNEC, which is derived using a factor of ten on a data set of three long-term tests. Longer term testing on soil organisms might be expected to result in an increase in the PNEC from this calculation route. On the basis of these data, there is no indication of extra toxicity to soil organisms through uptake from solids or air. The same can be expected for naphthalene, and therefore the equilibrium partitioning PNEC has been considered to be trustworthy.

Against this background and according to Regulation (EC) No 1907/2006 performance of further studies on effects of naphthalene on terrestrial organisms is considered to be unnecessary.

 

[EU RAR]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/]