Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:5:p1
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 5 (pt 1/5)
Character Range: 1598114–1601197

5                   Naphthalene

5.1              Compounds considered
Unlike Zn and As, which can occur in several forms in soil, naphthalene is a unique compound and only information relating to it was used in the derivation of the SQG values. Naphthalene (C10H8) is the smallest of the family of compounds collectively termed polycyclic aromatic hydrocarbons (PAHs). The chemical abstract service number for naphthalene is 91-20-3 (HSDB 2004).

5.2              Exposure pathway assessment
Selected physicochemical properties of naphthalene are:

Molecular weight:   128.17 (O'Neil 2001)
Log Kow    3.29 (US EPA 1982),
                   3.013.45 (Verschueren 1983),
                   3.30 (Hansch et al. 1995)
Log Koc    2.97 (US EPA 1982; GDCH 1992; Kenaga 1980)
Vapour pressure   0.087 mm Hg (US EPA 1982)
                   0.085 mm Hg at 25°C (Ambrose et al. 1975)
Aqueous solubility  31 mg/L at 25°C (Pearlman et al. 1984)
Henry's law constant 4.6 x 10-4 atm-m3/mol (US EPA 1982; Yaws et al. 1991)
                   4.4 x 10-4 atm-m3/mol (Shiu & Mackay 1997)
Half-life (in soil)  218 days (ATSDR 2005)
The minimum log Kow value at which biomagnification should be considered in the derivation of SQGs is 4 (Schedule B5b). As the reported log Kow values for naphthalene were below 4 and it has a relatively short half-life (see above), it is not considered a biomagnifying compound and the normal protection levels were used. Therefore only the direct toxicity exposure route was considered in the derivation of SQGs for naphthalene. The log Koc value for naphthalene is moderate (~3) and therefore there is only a moderate potential for naphthalene to be leached to groundwater or surface water. Soil quality guidelines to protect aquatic ecosystems were therefore not generated.

5.3              Toxicity data
Toxicity data for naphthalene was available for two plant species, eight species of soil invertebrates and four species of terrestrial vertebrates (Table 38). In total, there was data for 14 species that belonged to five taxonomic groups and thus this met the minimum data requirements recommended by the methodology to use the BurrliOZ SSD method (Campbell et al. 2000). Table 38 shows the geometric means of individual species used to derive the naphthalene SQGs. The raw toxicity data used to generate the species geometric means are presented in Appendix E.

In order to maximise the use of the available toxicity data, default conversion factors were used to permit the inter-conversion of NOEC, LOEC, EC50, EC30 and EC10 data (Table 30).

Table 38. Geometric means of the toxicity of naphthalene (expressed in terms of total naphthalene) to soil invertebrates, terrestrial vertebrates and plants.
Test species       Geometric mean (mg/kg)
Common name        Scientific name         NOEC or EC10  LOEC or EC30  EC50
Earthworm          Eisenia fetida          54            135           270
European rabbit    Oryctolagus cuniculus   2000          5000          10 000
House mouse        Mus musculus            407           1018          2036
Lettuce