White mineral oil (petroleum)

Endpoint summary

Additional information

Justification for Read Across

The complex and variable composition of UVCB substances means that it is not possible to define precisely their physico-chemical, toxicological and environmental properties, but they will fall into a range, defined by the properties, and amounts present, of the individual hydrocarbon constituents. To take account of the variable composition, hazard properties are determined using a ‘worst case’ approach, except where specified. Where data do not exist for highly refined base oils, a conservative read across is conducted to lubricant base oils. This read across is considered conservative since lubricant base oils are not as severely refined as highly refined base oils, but because compositional and physico-chemical data show that highly refined base oils are very similar to lubricating base oils, it is considered appropriate to read across from the lubricating base oils data to highly refined base oils.

 

In vitro and in vivo mutagenicity data indicate that highly refined base oils are not mutagens.

 

Genetic toxicity (In vitro)

The only in vitro genetic toxicity studies that have been reported on white oils have been either in abstracts or in an abbreviated form in publications written to demonstrate aspects other than the mutagenicity of white oils. The data are therefore, limited.  

 

In a key study, a modified Ames test was conducted on highly refined base oil (Klimisch score = 2, Exxon 2003a) in which the mutagenicity Index was calculated to be 0.1. No positive point was calculated nor was the substance found to be toxic. In a supporting standard OECD guideline reverse gene mutation assay in bacteria (Klimisch score = 1, McKee and Przygoda, 1987), Salmonella TA98 was exposed highly refined base oil at concentrations of 10, 25, 50, 100, 500, 1,000, and 10,000 µg/plate. Study authors reported that no mutagenic activity was detected at the test concentrations. In the same abstract the authors reported that Primol 185 elicited no evidence of mutagenic activity in an OECD guideline mouse lymphoma assay at test concentrations ranging from 50-1000 µg/ml. In an additional supporting, modified Ames test (Klimisch score = 2, Exxon 2003b), highly refined base oil was found not to produce positive points, nor was it found to be toxic. The mutagenicity index was reported to be 0.1.

 

In a supporting mammalian cell chromosome aberration assay (Klimisch score = 1, ARCO 1987j), Chinese hamster ovary cells were exposed to a lubricant base oil, 55/60 Pale Oil, sufficiently refined, IP 346 < 3% (batch TA288) at concentrations of 0.02, 0.04, 0.08, or 0.15 μL/mL, -S9, for 10 hours and 0.05, 0.1, 0.2, or 0.4 μL/mL, +S9, for 2 hours. Results from the chromosome aberration assay showed no significant structural or numerical aberrations in CHO cells at any dose level, with or without metabolic activation. Positive controls induced the appropriate response.

 

In a key mammalian cell gene mutation assay (Klimisch score = 2, Exxon 1985), mouse lymphoma L5178Y cells cultured in vitro were exposed to a highly refined base oil at concentrations of 0.5, 1, 5, 10, 50 μg/mL with metabolic activation and 5, 10, 50, 100, 500, 1000, μg/mL without metabolic activation for three hours. The dosing period was three hours followed by two day expression period for the test and control cultures. The highly refined base oil was found to be negative with and without metabolic activation. In a supporting, standard OECD guideline reverse gene mutation assay in mouse lymphoma cells (Klimisch score = 1, McKee and Przygoda, 1987), cells were exposed to acid-treated white mineral oil at concentrations of 0.5, 1.0, 5.0, 10, 50, 100, 500, and 1000 µg/plate. Study authors reported that no mutagenic activity was detected at the test concentrations. 

 

Genetic Toxicity (In Vivo)

No in vivo genetic toxicity studies have been reported for white oils, but such studies have been reported for lubricant base oils and as the basis for a worst case are summarised in this section.

 

In a key read-across from less refined lubricating base oils in vivo CD-1 mouse bone marrow micronucleus assay (Klimisch score = 1, McKee et al., 1990), male and female mice were given a single intraperitoneal injection of 5 different 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 significant.  All test samples and other doses were negative in this in vivo genetic assay; white oils would be expected to respond in a similar fashion.

 

Additional data support that HRBOs are not mutagens (Roy et al., 1988, API, 1982). This information is presented in the dossier.

Short description of key information:

In an in vitro modified Ames tests, highly refined base oils were found to be negative for mutagenicity (similar to OECD 471).

In an in vitro mammalian cell chromosome aberration assay, the sufficiently refined lubricant base oil 55/60 Pale Oil showed no significant aberrations at any dose level (OECD 473).

In an in vitro mammalian cell gene mutation assay, highly refined base oils were found to be not mutagenic (OECD 476).

In an in vivo CD-1 mouse bone marrow micronucleus assay on less refined paraffinic lubricant base oils, the micronucleus frequency was not found to be significant, and the materials were judged to be not mutagenic in in-vivo genetic toxicity assays (OECD 474).

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

Based on in vitro and in vivo mutagenicity data, highly refined base oils are not classified as mutagens under EU CLP Regulation (EC No. 1272/2008).