Paraffin waxes and Hydrocarbon waxes

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Three in vitro gene mutation studies on a synthetic paraffin wax extract and one in vivo study on lubricant base oils were selected as key studies to support genetic toxicity data.  Overall, these studies demonstrate that the substances tested were not mutagenic.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

Additional information from genetic toxicity in vitro:

In vitro gene mutation studies

Three key studies (all with a Klimisch score=1) examined in vitro gene mutation of paraffin waxes (TNO, 2005a; TNA, 2005b; TNO, 2005c). A DMSO extract of Fischer-Tropsch synthetic paraffin wax (CAS No. 8002 -74 -2) was examined for mutagenic activity in the bacterial reverse mutation assay (TNO, 2005a). Salmonella typhimuriumstrains TA 1535, TA 1537, TA 98, TA 100 andEscherichia colistrain WP2uvrAwere incubated with the extract of the test substance at 62 to 5000 μg/plate in the absence and presence of a liver fraction of Aroclor 1254-induced rats (S9-mix) for metabolic activation. In both the absence and presence of metabolic activation, the extract of paraffin wax did not cause either a dose related or a more than two-fold increase in the mean number of revertant colonies compared to the negative control (DMSO). The extract of Fischer-Tropsch synthetic paraffin wax was judged to be not mutagenic under the conditions employed in this study.  Supporting data from other bacterial reverse mutation assays (BIBRA, 1993g; SafePharm Laboratories Limited, 2006a) also indicate that paraffin and hydrocarbon waxes are negative in the AMES test, both in the presence and absence of metabolic activation.

In a mouse lymphoma assay (TNO 2005b), L5178Y cells were exposed to 0.018 to 10 mmol/l of the extract for 4 hours with and without metabolic activation. In both the absence and presence of S9-mix, the extract of test substance was not cytotoxic to the L5178Y cells, and no relevant increase of the mutant frequency was observed at any dose level; therefore, the test substance was not judged to be mutagenic at the TK locus.

In a chromosomal aberration test (TNO 2005c), Chinese Hamster Ovary cells were exposed to the paraffin wax extract at concentrations ranging from 0.034 to 10 mmol/l. None of the extract concentrations analysed induced a statistically significant increase in the number of aberrant cells with or without metabolic activation at pulse or continuous exposures. Taken together, these studies indicate that the paraffin wax extract is not mutagenic under the assay conditions specified. Supporting data from in vitro chromosomal aberration tests conducted on human lymphocytes (Shell, 2006) indicate that paraffin and hydrocarbon waxes are non-clastogenic and non-aneugenic to human lymphocytes in vitro.

 

In vivo mouse micronucleus study

No in vivo genetic toxicity studies have been conducted with paraffin or hydrocarbon wax, but a key in vivo mouse micronucleus study (Klimisch score=1) performed on lubricant base oils was selected as a read-across study (McKee, 1990). In a CD-1 mouse bone marrow micronucleus assay, male and female mice were given a single intraperitoneal injection of 5 different solvent-extracted, dewaxed paraffin oils in corn oil vehicle at doses of 0, 1.0, 2.5, or 5.0 g/kg.  Bone marrow cells were harvested at 24, 48, and 72 hours post-dosing.  One animal did not survive to scheduled sacrifice, but there were no gross signs of toxicity.  The micronucleus frequency was significantly greater than the concurrent negative control in bone marrow cells of male mice given 5.0 g/kg at 48 hours post-dosing, but the negative control was unusually low in this instance, and therefore this result is not considered toxicologically significant. These data support the conclusion that the five mineral hydrocarbons tested were not clastogenic.

Justification for classification or non-classification

Paraffin and hydrocarbon waxes are not expected to be mutagenic in vitro or in vivo and therefore do not meet the EU classification criteria. The polycyclic aromatic compounds (PAC) in oil products are poorly bioavailable due to their physico-chemical properties (low water solubility and high molecular weight), making it unlikely that the genotoxic constituents can reach and cause damage to germ cells (Roy, 2007; Potter, 1999). Considering their poor bioavailability, oil products which have been classified as carcinogenic do not need to be classified as mutagenic unless there is clear evidence that germ cells are affected by exposure, consistent with EU CLP Regulation (EC No. 1272/2008).